PDA

View Full Version : Is Life Inevitable ?



Selfsim
2012-May-28, 06:58 AM
This thread has been spawned by a sub-topic of discussion in the recent S&T Evidence and Belief (http://www.bautforum.com/showthread.php/132352-Evidence-and-belief) thread.

To get the ball rolling, I would like to pose the question:

"What theoretical bases underpin the firmer speculative conclusion that a second emergence of life might be inevitable elsewhere within the observable universe ?"

In more detail:

Are the assumptions made along the way, actually applicable to biological systems, or are they a hang-over from a backdrop of Classical Astrophysical principles, and established Physical Laws ? Are such principles and Laws, an appropriate basis for extrapolation and coming to firmer speculative outlooks, which invariably involve conclusions such as 'likely'?

I wonder .. ??

Comments welcome.

Regards

Perikles
2012-May-28, 08:57 AM
... that a second emergence of life might be inevitable elsewhere within the observable universe ?Not wishing to highjack the thread with semantic quibbles before it even starts, but what do you mean by "might be inevitable "? Surely, all we can do is calculate a probability which might be very nearly 1. But until we have direct evidence, it will never be exactly 1. Or am I missing the point?

Selfsim
2012-May-28, 09:39 AM
Not wishing to highjack the thread with semantic quibbles before it even starts, but what do you mean by "might be inevitable "? Surely, all we can do is calculate a probability which might be very nearly 1. But until we have direct evidence, it will never be exactly 1. Or am I missing the point?Hi Perikles;
Hmmm ... what are the steps and assumptions leading to: 'a probability which might be very nearly 1' ?

The phrase 'might be inevitable' is what I'd call speculator 'speak' for isolating the possibility that exo-life is inevitable, without overtly stating that it is inevitable.

What I'm trying to tackle is: what is the basis in theory, underpinning the common view that exo-life is 'likely'. I've seen 'likely' used just about everywhere at BAUT when referring to exo-life, and I'd like to understand what is the valid theoretical basis for coming to this (albeit, speculative) conclusion ?
I'd appreciate it if someone who uses the 'likely' term, could explain from first principles, why they see it as 'likely' in theory, and see if the rationale is valid from a biology perspective.

Regards

mutleyeng
2012-May-28, 12:08 PM
Does it matter to you if somebody having a likely conclusion also concedes it to be speculative, or is it only if they assert it as a truth?

Paul Wally
2012-May-28, 01:13 PM
To get the ball rolling, I would like to pose the question:

"What theoretical bases underpin the firmer speculative conclusion that a second emergence of life might be inevitable elsewhere within the observable universe ?"



I would like to cut out all the redundant adjectives. The so-called "speculative" part is contained in the tentative "theoretical bases" not the "conclusion". The conclusion follows as an implication of theory, whatever the disputed theory/theories may be in this particular case. So I would pose a different question:
"What must the process of the emergence of life be like for life to be unlikely/likely elsewhere within the observable universe ? "

So, in my opinion, the discussion should be about different theories and how different theories have different implications for the likelihood of life elsewhere.


Are the assumptions made along the way, actually applicable to biological systems, or are they a hang-over from a backdrop of Classical Astrophysical principles, and established Physical Laws ?

The assumptions are actually applicable to pre-biological systems in order to explain how biological systems can emerge from pre-biological systems. Astrophysics and the laws of physics do not prevent the emergence of complexity. In fact chaos is a possibility implicit in classical deterministic systems like the very simple 3-body setup. The mathematical problem is to find out how life-like phenomena can emerge within such systems, and at the moment I see no reason why that must be impossible. It's just a question of solving the problem.




Are such principles and Laws, an appropriate basis for extrapolation and coming to firmer speculative outlooks, which invariably involve conclusions such as 'likely'?

I think you've got the scientific process all mixed up here. The "principles and laws" are built into your theory, whatever your theory may be. The uncertainty is in the theory not the conclusions. It's a premise-conclusion relation where the conclusion follows by implication from the premise. So from my perspective, I just cannot make sense of this notion of "appropriate basis". Our most well-supported theories are not absolutely certain, so I don't know what would make a theory an "appropriate basis"? "Appropriate" is a bit of a vague notion by which to appraise scientific theories, don't you think?

Hlafordlaes
2012-May-28, 01:38 PM
We'll never have certainty until we have proof. My bet, of a whopping $1, is we'll find life right here in around Sol.

It's like being stuck in a valley and wondering what the other side of the mountain looks like. Well, just like this side, only more so.

filrabat
2012-May-28, 11:38 PM
I don't have the link with me, but I do recall that under the right conditions, life MIGHT be inevitable. As evidence, scientists point to the multiple impacts and catastrophes that almost wiped out life here on Earth.

I'm not even close to being an expert (my degrees are in business and humanities fields), but I would think that if a planet was born under ideal (for life-forming) conditions*, then life will pretty much evolve inevitably. This is especially so given that life's essentials are composed of the most common chemical elements in the universe.

*Right orbital distance for liquid water
*Right size and mass for
-gravity to hold a Nitrogen/Oxygen atmosphere
- sufficient vulcanism for atomospheric creation and to keep it
- sufficient water to lubricate rock, which can easily lead to..
- plate tectonics
- right amount of iron/cobalt in the core + right rotation speed, meaning...
- right strength of planetary magnetic field

As you can see, conditions have to be exactly right for an Earth-complexity ecosystem to form. IMO, once all those conditions are met, then life is pretty much inevitable or close to it.

mike alexander
2012-May-28, 11:41 PM
Having seen all those definitions of life for a very long time, it seems to me that a basic property of life is the ability to distinguish self from nonself. Lipid bilayers are self-assembling and require no specific information from a molecule such as DNA or RNA.

transreality
2012-May-28, 11:48 PM
Surely the fundamental basis for an expectation that life occurs elsewhere is that the earth/solar system has no special conditions that distinguish it from many of the other similar environments in the universe. Life requires a Sun for energy, other stars are suns like ours. Life, as we know it arises on a planet; we know there are other planets around other stars. We can detect other elements in the universe, they are distributed in roughly the same amounts and proportions that we observe them locally. There is no reason to expect then that potential habitats for life are uncommon.


Then there is the timescale evidence. the Earth formed 4.3 billion years ago, we have fossil data for life from 3.4 billion years. That is, roughly as early as we can expect that surface of the earth was cool enough for liquid water to pool, life arose. That suggests that Life evolves readily in suitable environments. It is not unreasonable that the earth could have sat vacant for billions of years, waiting for the rare spark of life, in which case we would not draw this conclusion, but the evidence we have suggests otherwise.


And then there is the sheer number of potential habitats that astronomy suggests exists in terms of other stars. This would seem to overwhelm even the probabilities if life, or liquid water habitats, are exceedingly unlikely (not that there is any evidence of that) given the volume of the universe.

Colin Robinson
2012-May-29, 12:58 AM
I would like to cut out all the redundant adjectives. The so-called "speculative" part is contained in the tentative "theoretical bases" not the "conclusion". The conclusion follows as an implication of theory, whatever the disputed theory/theories may be in this particular case. So I would pose a different question:
"What must the process of the emergence of life be like for life to be unlikely/likely elsewhere within the observable universe ? "

Yes! This is a much more neutral way of expressing the scientific issue.

"What must the process of the emergence of life be like for life to be unlikely"

If it is a process of atoms and molecules milling about randomly, until a huge self-replicating molecule forms by chance, then the probability of it happening on any particular planet could be very very low. I think that is essentially what Jacques Monod meant when he said: "The universe was not pregnant with life... Our number came up in the Monte Carlo game."

"What must the process of the emergence of life be like for life to be likely"

If it results from chemical systems being impelled in a particular direction by the laws of thermodynamics... E.g. In an environment where there are molecules of hydrogen and molecules of carbon dioxide, thermodynamics favors the formation of chemical systems in which the carbon dioxide gets hydrogenated, as happens in the reductive Krebs cycle.

If that is the way life emerges, there would be a very high probability of it happening on any planet which has

* molecules of hydrogen and molecules of carbon dioxide (or, perhaps, a different mix of molecules with a similar thermodynamic character) and
* conditions favorable to active chemistry (e.g. a liquid solvent, minerals with catalytic properties).

This is the argument of James Trefil, Harold Morowitz and Eric Smith in their article The Origin of Life (http://www.americanscientist.org/issues/feature/2009/2/the-origin-of-life/1
).

whimsyfree
2012-May-29, 02:29 AM
This thread has been spawned by a sub-topic of discussion in the recent S&T Evidence and Belief (http://www.bautforum.com/showthread.php/132352-Evidence-and-belief) thread.

To get the ball rolling, I would like to pose the question:

"What theoretical bases underpin the firmer speculative conclusion that a second emergence of life might be inevitable elsewhere within the observable universe ?"


That conclusion can't be right because you can apply it iteratively to prove that the number of times life emerges is unbounded. If it's here then it's inevitable somewhere else. If it's here and somewhere else then it's inevitable in one of the other places, and so on.

Selfsim
2012-May-29, 03:48 AM
Ok, so where to start ? ...

So far, the specifics I was after, have been presented by filrabat in post #7, mike alexander in post #8, Transreality in post #9, Perikles (partially) in post #2. Thanks kindly for those posts, folks ! Paul and Colin’s changes, I don’t think impact very much where I’m going with all this. I’m more concerned about the nature of the arguments, than any perceived biases in the wording of my question .. after all, it was just a question. Thanks to all others adding commentary, as well.

So, with the specific physical evidence presented in posts #7 and #9, there is a common underlying scientific theme which seems to ultimately rely on the traditional determinable structures of Classical Physics. An example of such a ‘structure’, which enables Classical Physics to produce determinable outcomes, might be the theoretical symmetries in the dynamic equations which facilitate for example, the determination of the orbit of a planet, or the calculation of the surface temperature of a planet, based on the laws of thermodynamics, and planet’s distance from its host star.

But do these symmetries, which certainly do produce valid results in these two examples, operate in the case of say biological evolution ? Do they also operate in the steady-state functioning of a biological organism ? If not, then why do we point to the evidence cited, (eg: in posts#7 and #9), and draw inference from them, when talking about the possibility of emergence of life on exo-planets ... and make speculative conclusions such as ‘likely’, or ‘inevitable’ ?

In order to explain the point more deeply, I’d like to reference a recent paper entitled: "No entailing laws, but enablement in the evolution of the biosphere", (http://arxiv.org/pdf/1201.2069v1.pdf) by G. Longo, M. Montevil and Stuart Kauffman, (released onto arXiv on Jan 10th, 2012), which provides an interesting theoretical argument for the inappropriateness of Classical Physical reductionist thinking, when it comes to explaining the evolutionary natural selection process, and ultimately, the emergence of life as well:


Biological evolution is a complex blend of ever changing structural stability, variability and emergence of new phenotypes, niches, ecosystems. We wish to argue that the evolution of life marks the end of a physics world view of law entailed dynamics. Our considerations depend upon discussing the variability of the very ”contexts of life”: the interactions between organisms, biological niches and ecosystems. These are ever changing, intrinsically indeterminate and even unprestatable: we do not know ahead of time the "niches" which constitute the boundary conditions on selection.

The analysis covers how Classical Physics is able to reach predictable conclusions in typical physical phenomena, (like orbital mechanics, thermodynamics etc), and the authors then argue that such methods are not applicable to biological systems. They then explain why employing these traditional approaches, is inappropriate for predicting the outcomes of biological systems, shaped by Darwinian evolution. They argue that it is more appropriate to view them from a Complex Adaptive Systems perspective, which encompasses the randomness intrinsic in all biologically evolving systems.

Whilst this paper includes some rather obscurely used terminology, like: ‘becoming of the biosphere’, ‘entailment’, and even invokes ‘Kantian wholes’, (which normally sets off alarm bells with me), the paper is co-authored by Stuart Kauffman, a relative authority on the topic .. (even if I do find his language ‘flowery’ and difficult to comprehend at times).

Also, I find the key arguments resulting in a non-inevitability outlook on the emergence of life, to be very much relevant to the discussion.

The principles which legitimise the use of Classical Physical principles, lies in the commonly overlooked bases of Symmetry (see Sections 6 and 7 of the paper).

Their overall conclusion is:


If we are right in our conclusion, the strong reductionist dream of a theory that entails the full becoming of the universe is wrong. With life, we reach the end of a physics worldview that has dominated us since Newton. Yet the biosphere is magnificent in its enabled, radically emergent becoming, the most complex system we know of in the universe. If no law entails this becoming, then our belief that such entailing law is a necessary condition for the emergence of highly organized integrated complex systems is wrong.

I notice the implication and acknowledgement that such a belief exists, and that it is also commonly shared … (a point I have also experienced in certain conversations on such topics).

Even if they haven’t presented a clear alternative, their arguments certainly cause one to think again about the assumptions we typically skim over, (due to familiarity with Classical Physics in the Astrophysics domain), which may very well not be an applicable basis from which to draw inferences, when it it comes to discussions about the inevitability of exo-life emergence in the observable universe

Regards

Van Rijn
2012-May-29, 06:48 AM
Also, I find the key arguments resulting in a non-inevitability outlook on the emergence of life, to be very much relevant to the discussion.


Where did the article discuss that? I'll admit to doing a fair bit of scanning, there definitely was flowery language, repetition, and arguments that were at best unclear, but it appeared to me to be more about the difficulty of predicting the development of an ecosystem given biological evolution. I don't see where it made an argument about abiogenesis, however.

Van Rijn
2012-May-29, 08:03 AM
What I'm trying to tackle is: what is the basis in theory, underpinning the common view that exo-life is 'likely'. I've seen 'likely' used just about everywhere at BAUT when referring to exo-life, and I'd like to understand what is the valid theoretical basis for coming to this (albeit, speculative) conclusion ?


As an introductory note, I don't assume exolife is inevitable, though I think a similar statement could have been made about exoplanets before they were detected.

But as for your question, let's turn it around: What would make exo-life unlikely? Not whether it is rare or common, but if there are any other examples in the visible universe.

Two possibilities I can think of (1) there is something physically unique about this part of the universe or (2) there is something incredibly improbable about the formation of life. But what's the evidence for these things? (And it should be something better than Hoyle's argument (http://en.wikipedia.org/wiki/Hoyle%27s_fallacy)).

I am willing to consider the possibility that there might be something unique about this bit of universe, or there might be some extreme improbability issue, but I don't see a good reason to assume it.

Selfsim
2012-May-29, 08:53 AM
Also, I find the key arguments resulting in a non-inevitability outlook on the emergence of life, to be very much relevant to the discussion.Where did the article discuss that? I'll admit to doing a fair bit of scanning, there definitely was flowery language, repetition, and arguments that were at best unclear, but it appeared to me to be more about the difficulty of predicting the development of an ecosystem given biological evolution. I don't see where it made an argument about abiogenesis, however.Hi Van Rijn;
Well as far as my read is concerned, I can't find any explicit statements about abiogenesis. However, their conclusion makes a pretty generalised 'swipe' at it:

If we are right in our conclusion, the strong reductionist dream of a theory that entails the full becoming of the universe is wrong.So, presumably, the emergence of life is part of: 'the full becoming of the universe' ? If so, then the 'strong reductionist dream' of a theory of abiogenesis, is wrong also (according to them, that is) ... (ie: if their conclusion is right also ...).

Yet the biosphere is magnificent in its enabled, radically emergent becoming, the most complex system we know of in the universe. Well, 'radically emergent' suggests that its emergence is atypical (compared with what determistic theories providing predictatibility give us).

If no law entails this becoming, then our belief that such entailing law is a necessary condition for the emergence of highly organized integrated complex systems is wrong.If a governing law is absent, then what would lead one to the conclusion that 'emergence of highly integrated complex systems' (such as life), would be inevitable ?

Not that I buy into something as wobbly as this final conclusion. (I'd require a lot more detail than just that bunch of 'floweriness').
However, as I stated, I do think their reasons for coming to this conclusion, seem relevant and of interest, to the discussion.

Regards

Selfsim
2012-May-29, 10:46 AM
As an introductory note, I don't assume exolife is inevitable, though I think a similar statement could have been made about exoplanets before they were detected.Neptune was predicted before exo-planets were discovered. The same laws enabling the prediction of Neptune, were key in concluding the existence of exo-planets. The point being made in this paper, is that those laws cannot be used to predict the trajectories of features about organisms or their phenotype variations, or evolutionary shaping of lifeforms and possibly, life emergence (the latter being purely speculative).

Frankly, I don't see any connection between 'a similar statement being made about exoplanets before they were detected' and the prediction of a planet using those laws. The remote observations, and the laws, resulted in the declaration of 'existence' of exo-planets and Neptune. Once the correct remote exo-planet observations were made, exoplanet existence, (and Neptune's), was inevitable.
As I have explained many, many, many times over, in as many posts, remote detection of life over light year distances by observation, (other than a chance discovery, SETI detection or ET visitation), is not practically feasible until, at least, a local exo-life discovery is caused by the deliberate act of local exploration.

The existence of life on earth does not imply the existence of life elsewhere. As a result, in the absence of a law which 'entails the becoming of life' (in Longo et al speak), how does exo-life become 'inevitable', or 'likely'? (A rhetorical question here .. I note that you've already stated that you don't assume exolife is inevitable ... its more for the readers of this thread. :) )


But as for your question, let's turn it around: What would make exo-life unlikely? Not whether it is rare or common, but if there are any other examples in the visible universe.

Two possibilities I can think of (1) there is something physically unique about this part of the universe or (2) there is something incredibly improbable about the formation of life. But what's the evidence for these things? (And it should be something better than Hoyle's argument (http://en.wikipedia.org/wiki/Hoyle%27s_fallacy)).Well, life has never been resynthesised from scratch, nor has any second emergence ever been discovered. That would make its emergence pretty unique from amongst the available evidence, eh ?
Life itself may well be an emergent phenomenon having complexity, non-linearity and chaotic physical behaviours at play. This might mean that its emergence is not inevitable and it also doesn't require there to be anything unique about this part of the universe, or its applicable laws, either.
This behaviour stands well and truly distinct from pure randomness as well. Fred Hoyle may not have been aware of complex adaptive behaviour phenomena, when he formulated his statement.


I am willing to consider the possibility that there might be something unique about this bit of universe, or there might be some extreme improbability issue, but I don't see a good reason to assume it.I agree.

Colin Robinson
2012-May-29, 01:41 PM
Whilst this paper includes some rather obscurely used terminology, like: ‘becoming of the biosphere’, ‘entailment’, and even invokes ‘Kantian wholes’, (which normally sets off alarm bells with me), the paper is co-authored by Stuart Kauffman, a relative authority on the topic ..

Are you aware that in his book At Home in the Universe (http://www.amazon.com/dp/0195111303/ref=rdr_ext_tmb), Stuart Kauffman puts forward a hypothesis where the emergence of life is indeed "near inevitable", a phrase he uses on page 147?

The article you've quoted argues that biology is different from physics, in that specific lines of evolution (what sort of organism evolves into what) are not predictable as trajectories of planets are predictable. An interesting question... but it is not the same question as whether emergence of some sort of life is likely or unlikely to occur at multiple sites in the universe.

Paul Wally
2012-May-29, 07:57 PM
The analysis covers how Classical Physics is able to reach predictable conclusions in typical physical phenomena, (like orbital mechanics, thermodynamics etc), and the authors then argue that such methods are not applicable to biological systems. They then explain why employing these traditional approaches, is inappropriate for predicting the outcomes of biological systems, shaped by Darwinian evolution. They argue that it is more appropriate to view them from a Complex Adaptive Systems perspective, which encompasses the randomness intrinsic in all biologically evolving systems.

Whilst this paper includes some rather obscurely used terminology, like: ‘becoming of the biosphere’, ‘entailment’, and even invokes ‘Kantian wholes’, (which normally sets off alarm bells with me), the paper is co-authored by Stuart Kauffman, a relative authority on the topic .. (even if I do find his language ‘flowery’ and difficult to comprehend at times).


In the paper you referenced, the concepts of biological evolution are essential to their argument, so how does it then have implications for pre-biotic environments where biological evolution doesn't exist? For example the following statement on p.7 is based on an analysis of biological evolution:



Thereby, this is our main thesis, the very phase space of evolution changes in unprestatable ways. (My underline)

Since there is no biological evolution in the pre-biotic environment this doesn't apply there.

I think this next paragraph on p.13 nicely captures the central idea of the paper:


The circularity “of the definitions” applies, instead, when it is impossible to prestate the phase
space, so the very novel interaction (including the “boundary conditions” in the niche and the
biological dynamics) co-defines new observables. The circularity then radically differs from the
one in the definition, since it is at the meta-theoretical (meta-linguistic) level: which are the
observables and variables to put in the equations? It is not just within prestatable yet circular
equations within the theory (ordinary recursion and extended non—linear dynamics), but in the
ever changing observables, the phenotypes and the biological functions in a circularly co-specified
niche. From this follows our statement that, mathematically and logically, no law entails the
evolution of the biosphere. (My underline)

In a pre-biological environment there can be no identification and categorical distinctions like "phenotype", "biological functions" and "niche", therefore the "ever changing observables" defined on these categories have no meaning in the pre-biological environment. In order to apply this theory to abiogenesis, we will have to see whether analogous arguments could be applied to the categories of observables in that environment. I didn't see any such argument presented in the paper though.

Another point that I'd like to make is that this paper is an example of a typical emergence-argument requiring an hierarchical distinction between an autonomous biological level and the fundamental physical level, the argument is that the higher level cannot be reduced to the lower level. However, in the pre-biological environment there is no biological level yet, so this whole hierarchical distinction doesn't apply also.


Also, I find the key arguments resulting in a non-inevitability outlook on the emergence of life, to be very much relevant to the discussion.

The paper had nothing to say about inevitability/ non-inevitability of the emergence of life. It may, in your opinion, have said that we can't predict it, but that's not the same as saying it's not inevitable.

MaDeR
2012-May-29, 09:08 PM
If I understanded this hard-to-read prose, presented claim is in short "The more unpredictable it is, the less probable it is to start existing". Not only it sounds unconvincing, it is non sequitur.

profloater
2012-May-29, 10:39 PM
In a both trivial and significant experiment a pile of paper clips will form chains and it seems molecules will form amino acids and the like. It does seem life is very likely but intelligent life or even complex life forms are more difficult. It seems we needed a fortuitous sequence of disasters to evolve. Whilst big brain life in a useful body has proved so successful here it is clearly not an easy path from bacteria upwords. Yet while basic life would be an amazing discovery outside Earth, we really want to know if self aware and intelligent life exists for long enough to be discovered. It is interesting to speculate whether intelligent life could follow a different route such as Hoyle's "black cloud" or perhaps distributed like telepathic ants. Which route would produce a long term stable growth as compared to our own competitive and self destructive variety?

swampyankee
2012-May-29, 11:13 PM
This thread has been spawned by a sub-topic of discussion in the recent S&T Evidence and Belief (http://www.bautforum.com/showthread.php/132352-Evidence-and-belief) thread.

To get the ball rolling, I would like to pose the question:

"What theoretical bases underpin the firmer speculative conclusion that a second emergence of life might be inevitable elsewhere within the observable universe ?"

In more detail:

Are the assumptions made along the way, actually applicable to biological systems, or are they a hang-over from a backdrop of Classical Astrophysical principles, and established Physical Laws ? Are such principles and Laws, an appropriate basis for extrapolation and coming to firmer speculative outlooks, which invariably involve conclusions such as 'likely'?

I wonder .. ??

Comments welcome.

Regards

I'm trying to parse the highlighted sentence, and I can't be entirely sure my interpretation is coincident with the intended meaning of the author.

More briefly, I'm confused. I think the highlighted sentence means "Do current studies, using currently understood science, show that there is a 100% chance that life has arisen in other parts of the Universe?" To that, I answer "mu (http://en.wikipedia.org/wiki/Mu_%28negative%29#Signifying_.22unasking.22_the_qu estion_or_similar)."

transreality
2012-May-29, 11:41 PM
If rather than the inevitability of life, we were discussing the inevitability of intelligent bipedal multicellular creatures that functionally resemble man, then the warnings of Loglo etal raised by Selfsim would be relevant. We should not even be prescriptive over the specific chemistry involved in life as we have no idea about the contingent steps in out own evolution. This is Stephen J Goulds warning that if the tape of life was played over again, the outcome would be completely different and unpredictable. But evolution does not apply until life has already arisen.

The 'niche' of life, though, is to employ an abundance of energy to build a structural complexity from simple molecules. Much as the niche of chemistry builds molecules from simple particles. Semantic determinism aside, but why, given the prerequesites, would Life be any less inevitable than Chemistry since they both seem to have relation to entropy (if I am using the correct term)?

Selfsim
2012-May-30, 12:30 AM
Ok, so Paul, Colin and MaDeR (and all);

I need to make it perfectly clear again, that I recognise that paper is not specifically addressing abiogenesis.

It does express the argument that there exist, relevant major biological systems, distinguishable in nature, which are observed to behave in ways which exclude them from the classical strong reductionist principles, which have traditionally enabled us to distil physical laws, which enable mathematical formulae to be written, which are then typically used to make predictions about classical system behaviours.

The purpose of presenting the paper, was to highlight the key part of this argument, which is discussed in the Sections on Symmetry and phase trajectories.


Also, I find the key arguments resulting in a non-inevitability outlook on the emergence of life, to be very much relevant to the discussion.As described in my post #15, the Longo conclusion covered "the universe". As this includes life (and, presumably abiogenesis processes), my statement above is consistent with their (admittedly, fairly wobbly), generalised conclusion. Frankly, I'm not really very interested in defending what was admittedly, not immediately obvious from those words, with regards to specifically, life emergence.

The Symmetry arguments, I find, are more interesting when forming generalised hypotheses about the likelihood, (or otherwise), of exo-life. How do these arguments effect our thinking when predicting exo-life 'possibilities', and thence: 'likelihood or 'unlikelihood' ? What role do physical Symmetry assumptions play in all this ? Have they become so ingrained that we forget to check for their validity, before forming views about exo-life likelihood (or otherwise) ?

Re: post #22:
Hi transreality;

Semantic determinism aside, but why, given the prerequesites, would Life be any less inevitable than Chemistry since they both seem to have relation to entropy (if I am using the correct term)?What are the 'prerequisites', and how can we know whether the assumptions underpinning them are valid, (in order to arrive at implications relating to 'inevitability') ?
An 'equivalent', (in complexity terms), pre-biotic environment, might equally explain the complexity which persists to the present-day (??)

Regards

KABOOM
2012-May-30, 12:59 AM
The current best thinking in science suggests that the Universe arose out of "nothing" due to random quantum fluctuations (or something to that effect). Couldn't the same thought process from this paper deem the formation our our universe to be equally improbable? No evidence that a similar phenomena has happened before or since (not that the concept of "before" has meaning since there was no "time" until the BB started)

All of this seems to weigh heavily on the deeming of events that are currently impossible to quantify (i.e., the likelihood of quantum fluctuations creating a universe out of nothing, or exolife being spawned out of raw chchemical ingredients) being ascribed an exceedingly low probability. Not sure why that should be the case.

Paul Wally
2012-May-30, 01:14 AM
The Symmetry arguments, I find, are more interesting when forming generalised hypotheses about the likelihood, (or otherwise), of exo-life. How do these arguments effect our thinking when predicting exo-life 'possibilities', and thence: 'likelihood or 'unlikelihood' ? What role do physical Symmetry assumptions play in all this ? Have they become so ingrained that we forget to check for their validity, before forming views about exo-life likelihood (or otherwise) ?

Ok, very well. This looks more reasonable. I'll have to look into these symmetry assumptions to see whether they have any implications in terms of likelihoods. Longo et al. did mention the concept of ergodicity, which is also relevant. Do note however that likelihood implications are different from predictability implications, and if I understood correctly, the Longo et al paper talked about predictability ("prestatability of the phase space") and not likelihoods.


An 'equivalent', (in complexity terms), pre-biotic environment, might equally explain the complexity which persists to the present-day (??)

Would you care to explain what that means?

Selfsim
2012-May-30, 06:15 AM
An 'equivalent', (in complexity terms), pre-biotic environment, might equally explain the complexity which persists to the present-day (??)
Would you care to explain what that means?Well, what I'm trying to say here, (even though I'm trying to steer away from the uncertainty of abiogenesis), is that there seems to be an implied assumption that pre-biotic chemical reactions might be dominated by equilibrium thermodynamic behaviours, where the driving forces are balanced so no state changes occur, unless the system is acted upon externally. In such equilibrium thermodynamics, any subsequent state changes, can be predicted by formula calculations.

However there is an entire class of non-equilibrium thermodynamical chemical systems, which result in non-linear chemical 'oscillators' (eg: the Belousov-Zhabotinsky reaction (http://en.wikipedia.org/wiki/Belousov-Zhabotinsky_reaction)). The macroscopic behaviours of these reactions also mimic the growth patterns of certain amoeba colonies at different spatial and temporal scales (see the Wiki article).

We view evolution as a distinct dynamic process which we normally think of as only pertaining to life from self-replicating cells onwards, but the process itself, clearly exists in inert chemical reactions as well.

So, how might this class of non-linear, far from equilibrium, naturally oscillating chemical phenomena, have influenced the formation pre-biotic chemistry ? How prevalent (or uncommon) might such a class of reactions have been, in pre-biotic environments ? Could it have influenced what eventually became life? What effect would such a process have on the predictability of the emergence of complex life elsewhere? More specifically, what effect might it have on the predictability of the phase trajectory assumptions mentioned in the Longo paper ?
(Some rhetorical questions here .. hopefully only to demonstrate that unexpected outcomes are at least quite possible, when it comes to certain chemical environments).

These reactions represent an example of what I was referring to in post #16 when I responded to Van Rijn:

Life itself may well be an emergent phenomenon having complexity, non-linearity and chaotic physical behaviours at play. This might mean that its emergence is not inevitable and it also doesn't require there to be anything unique about this part of the universe, or its applicable laws, either.(Replace 'inevitable' with 'predictable', to suit personal tastes ..).

Just a thought, anyway.

Regards

transreality
2012-May-30, 07:28 AM
Re: post #22:
Hi transreality;
What are the 'prerequisites', and how can we know whether the assumptions underpinning them are valid, (in order to arrive at implications relating to 'inevitability') ?
An 'equivalent', (in complexity terms), pre-biotic environment, might equally explain the complexity which persists to the present-day (??)



Just as chemistry itself has a prerequesite temperature range and abundance of raw material, so no doubt, with life. So Life will not form in a vaccuum.
Not sure what you mean by 'explain the complexity which persists to the present-day', since we seem to be in the realm of the hypothetical anyway. But if there was an equally complex environment from a similar but seperate pre-biotic environment, and if it showed self replication and evolution we could easily call it Life. If it didn't have those characteristics, and also was capable of turning the local chemistry into a complex or stable system more efficiently than life, then that is something we should readily detect in the laboratory.

Selfsim
2012-May-30, 11:48 AM
We view evolution as a distinct dynamic process which we normally think of as only pertaining to life from self-replicating cells onwards, but the process itself, clearly exists in inert chemical reactions as well.I should add that it is difficult to express the level of abstraction where Belousov-Zhabotinsky reactions, cell growth and evolutionary processes, might begin to look similar (as I mention above). Cell differentiation, chemotaxis and programmed cell death, are examples of phases and states involved in the cell life cycle. Elements of evolution might be: reproduction, mutation, recombination and selection.

Evolutionary algorithms seem to be employing concepts discovered at cellular and sub-cellular functional levels, as changes at these scales also influence evolutionary progress, just as much as those coming from external environmental influences.

This really is the domain of complexity modelling, and where it seems, breakthroughs about the functional synergies between non-linear chemical reactions, cellular functions and evolution, are likely to begin to appear.

Perhaps this is where Longo et al, are foreseeing the 'replacement' for the assumed 'law of becoming' as coming from ?

Colin Robinson
2012-May-30, 09:52 PM
Well, what I'm trying to say here, (even though I'm trying to steer away from the uncertainty of abiogenesis),

I thought this thread was all about reasons for thinking abiogenesis is certain or uncertain. If you want to steer away from this question, maybe you should start another thread?


is that there seems to be an implied assumption that pre-biotic chemical reactions might be dominated by equilibrium thermodynamic behaviours, where the driving forces are balanced so no state changes occur, unless the system is acted upon externally. In such equilibrium thermodynamics, any subsequent state changes, can be predicted by formula calculations.

Such an "implied assumption" may have been there once. However, recent work on abiogenesis takes energy gradients and energy flows to be a basic ingredient in the process. Such a gradient is the state of affairs opposite to equilibrium. I'd suggest (once again) that you have a look at James Trefil et al The Origin of Life (http://www.americanscientist.org/issues/feature/2009/2/the-origin-of-life/1) in the journal American Scientist.

Selfsim
2012-May-30, 10:33 PM
I thought this thread was all about reasons for thinking abiogenesis is certain or uncertain. If you want to steer away from this question, maybe you should start another thread?The details of the abiogenesis process are speculative, and hence are uncertain. Inferences drawn from the general principles, or concepts, of abiogenesis, (as opposed to the details), resulting in conclusions of inevitability, require that certain physical assumptions such as symmetry, be valid. If non-linear chemistry is conceptually possible in the abiogenesis process, then the outcomes of abiogenesis are far from predictable (or certain).

This seems to be where Paul and myself have agreed on this as a boundary. (Not that I can predict we'll stay within that boundary, however).

The principles, (or concepts), are less subject to opinion, than the details.




is that there seems to be an implied assumption that pre-biotic chemical reactions might be dominated by equilibrium thermodynamic behaviours, where the driving forces are balanced so no state changes occur, unless the system is acted upon externally. In such equilibrium thermodynamics, any subsequent state changes, can be predicted by formula calculations.Such an "implied assumption" may have been there once. However, recent work on abiogenesis takes energy gradients and energy flows to be a basic ingredient in the process. Such a gradient is the state of affairs opposite to equilibrium. I'd suggest (once again) that you have a look at James Trefil et al The Origin of Life (http://www.americanscientist.org/issues/feature/2009/2/the-origin-of-life/1) in the journal American Scientist.Ok .. I'll have a read and get back shortly. As a precursor, the question is already set in my mind as to whether the assumptions of symmetry get thrown out when incorporating such gradients. What is the impact on predictability ?

More later.

syzygy42
2012-Jun-01, 12:29 AM
Above and beyond specific chemical reactions, there are some purely theoretical based on the underlying structure of the chemical network. Kauffman's autocatalytic sets, mentioned above, is one such example, but there are many others. Unfortunately, as Athel Cornish-Bowden points out, most of the researchers in the field have been academic loners, rarely citing each other's work. An excellent review of the history of this subject area is From L'Homme Machine to metabolic closure: Steps towards understanding life by Letelier, Cardenas and Cornish-Bowden (http://www.sciencedirect.com/science/article/pii/S0022519311003389).

In brief, these authors give a short history of the underlying metaphors used to develop and frame our understanding of how life works: from late 18th century of a mechanical understanding (think clock), through molecular biology, and finally to systems biology. One central theme underlying almost all of the various "modern" theories is that of metabolic closure, i.e. all of the essential components of an organism are required for the synthesis of all of the other essential components and itself. This self-referential property of living systems is to my mind the thorniest problem confronting theoretical biology (shades of GEB).

The following is a brief synopsis of several theories being bandied about. One of the problems with reading the different authors is that a coherent language of this subject has yet to evolve. Thus, the authors use different words for the same concept and the same words for different concepts. Often these words are different from how biologists use them. This is not meant as a critisism of the authors, since they come from very diverse backgrounds.

(M,R) systems - This theory was developed by Robert Rosen, a mathematician who had a life-long interest in biology. As a graduate student, he and Nicolas Rashevsky developed an approach they referred to as relational biology emphasizing topology over molecular details. From this, Rosen went on to develop his (M,R) systems theory. His theory was developed within the mathematical confines of category theory and was thus beyond the comprehension of most biologists. Recently, Cornish-Bowden and coworkers have translated the essential arguments into set theory

Originally, the "M" stood for metabolism and the "R" stood for repair. Since these words have specific meanings in current molecular biology, C-B has suggested replacement as a more appropriate word that is closer to the underlying meaning within the system. Metabolism is represented as a mapping of substrates to products in the broadest sense, i.e. every molecule within a living organism is a product of metabolism. A subset of these products act as catalysts that are responsible for all of the reactions (mappings). Replacement is more abstract. It is a subset of catalysts that are required for the replacement of catalysts lost due to degradation, inactivation, or dilution because of growth.

Translation of these concepts to biological systems is a daunting task since even the simplest extant systems are extremely complex. A few toy models have been developed to aid in the understanding of these concepts. Regardless, one key aspect from the study of these systems is that they are not hierarchical. Hierarchy is important for understanding subsystems (e.g., gene expression), but for origin of life theories, one can never lose sight of the properties of the whole system.

Autopoiesis - This theory has a rather circuitous route of development. The original theory was developed by Humberto Maturana in the late 1960s and early 1970s. It was developed from using cybernetics to understand the functioning of the brain (modelled after a computer) and an attempt to model the Chilean economy. Maturana came to the conclusion that the brain/computer metaphor was seriously flawed due to the strict input -> output nature of the computer metaphor. Instead, he hypothesized that systems involved in perception/response were always active and constituted a continuous loop. Although different in origin, autopoiesis has many of the same concepts and properties as (M,R) systems.

The chemoton - This is a system of a model organism proposed by Tibor Ganti and published mostly in Hungarian, though an English book was published in 2003, The Principles of Life (Oxford Univ Press). This model provides an outline of a fully functional cell with the incorporation of metabolic, informational, and structural systems. I have not read the book, but Letelier et al. point out that catalytic cycles are a major feature this model.

The hypercycle - Extant organisms have large genomes that specify enzymes that replicate and repair the genome. Obviously, early in the development of life, the enzymes and genomes were much smaller and simpler. The problem with this is that replicating a genome of a decent size requires a low enough error rate to avoid error catastrophy. Maynard Smith and Szathmary coined this Eigen's paradox. Manferd Eigen and Peter Schuster proposed a hypercycle to deal with this problem. This cycle consists of a set of RNA molecules each specifying the synthesis of an enzyme that replicated an RNA molecule different from the one that encoded it. Their analysis suggested that different hypercycle quasispecies could occupy the same space and evolve by Darwinian selection.

Autocatalytic sets - Freeman Dyson and Stuart Kauffman asked the question of what properties were necessary for self organization. Kauffman has pursued this line of reasoning since the mid 1980s. He has always used quirky terms, and in his book The Origins of Order, he refers to this self organization as the Fourth Law of Thermodynamics. I read the book when it first came out, and if one looks more at his arguments than his language, there are many interesting concepts to be examined, from cellular automata to rugged landscapes to gradients in morphogenesis. The basic concept of autocatalytic sets is one of metabolic closure where each metabolite is synthesized by another metabolite in the system. His basic argument is that given enough variety in molecules, some of them will catalyze the formation of other molecules, which in turn catalyze more molecules. From this variety, an autocatalytic set can (will?) emerge and "replicate" itself from the available materials.

Recently Hordijk and Steel have developed Reflexive autocatalytic sets (RAF) to provide a more solid foundation for studying autocatalytic sets. One important contribution is the development of an algorithm to generate these sets, making them amenable to analysis on a computer.

Metabiology - A relative latecomer (not mentioned in this review) is Gregory Chaitin, a mathematician, recently published a book, "Proving Darwin: Making Biology Mathematical". It's on my reading list, but from what I can gather it is about studies that grew out of evolution of LISP programs. Could be an interesting read.

None of the above models are complete and each have their deficiencies/problems as outlined in more detail in the review. Yet, each has contributed valuable concepts and ideas. I must admit that I have been strongly influenced by the writings of Cornish-Bowden. I first encountered his work in basic biochemistry and learned Metabolic Control Analysis from his writings (along with a bunch of others). I look forward to getting the new edition of his textbook, Fundamentals of Enzyme Kinetics, which is now affordable ($63 as opposed to the previous edition at ~$500).

For those who want to read more, the bibliography of the Letelier et al. paper is extensive. For those not familiar with finding non-paywalled papers, Google Scholar is a great resource with links to ungated pdf versions, plus a whole lot more.

Obviously, there is much more on the wet bench side of things along with more specific proposals involving biochemical and organic reactions.

Cheers

Paul Wally
2012-Jun-01, 02:59 PM
Well, what I'm trying to say here, (even though I'm trying to steer away from the uncertainty of abiogenesis), is that there seems to be an implied assumption that pre-biotic chemical reactions might be dominated by equilibrium thermodynamic behaviours, where the driving forces are balanced so no state changes occur, unless the system is acted upon externally. In such equilibrium thermodynamics, any subsequent state changes, can be predicted by formula calculations.

I would limit my assumptions to fundamental physics and chemistry until/if it becomes necessary to revise those assumptions. Thermodynamics (equilibrium and non-equilibrium) I take to be defined on macroscopic observables like temperature, pressure, entropy (correct me if I'm wrong). So what happens now is that non-equilibrium thermodynamics cannot be explained by equilibrium thermodynamics. I think both macroscopic classes of phenomena still follow from the same underlying physical and chemical mechanisms, it's just that for the non-equilibrium phenomena it becomes difficult to develop a macroscopic phenomenological theory of the behaviour.


However there is an entire class of non-equilibrium thermodynamical chemical systems, which result in non-linear chemical 'oscillators' (eg: the Belousov-Zhabotinsky reaction (http://en.wikipedia.org/wiki/Belousov-Zhabotinsky_reaction)). The macroscopic behaviours of these reactions also mimic the growth patterns of certain amoeba colonies at different spatial and temporal scales (see the Wiki article).

I had a look at this article and also at some non-equilibrium stuff. What caught my attention was the computer simulation depicted on the side. The fact that it can be simulated suggests that we know the microscopic mechanisms responsible for these kinds of phenomena, we just don't know exactly how to predict it in an analytical way.



We view evolution as a distinct dynamic process which we normally think of as only pertaining to life from self-replicating cells onwards, but the process itself, clearly exists in inert chemical reactions as well.

I would define self-replication and evolvability as minimum requirements for biological evolution. The Belousov-Zhabotinsky reaction is an example of complex pattern formation, but is there anything identifiable as self-replication in there? If there is, then that would be very interesting.


So, how might this class of non-linear, far from equilibrium, naturally oscillating chemical phenomena, have influenced the formation pre-biotic chemistry ? How prevalent (or uncommon) might such a class of reactions have been, in pre-biotic environments ? Could it have influenced what eventually became life? What effect would such a process have on the predictability of the emergence of complex life elsewhere? More specifically, what effect might it have on the predictability of the phase trajectory assumptions mentioned in the Longo paper ?
(Some rhetorical questions here .. hopefully only to demonstrate that unexpected outcomes are at least quite possible, when it comes to certain chemical environments).

That similar kinds of phenomena are found in different physical scenarios and simple computer simulations, suggests to me that it shouldn't be uncommon, but more rigorous proof is of course required. I do want to add though, that unexpected outcomes we find in pure mathematics also even though we have the rules or axioms of the system clearly defined.

Selfsim
2012-Jun-01, 10:25 PM
I think both macroscopic classes of phenomena still follow from the same underlying physical and chemical mechanisms, it's just that for the non-equilibrium phenomena it becomes difficult to develop a macroscopic phenomenological theory of the behaviour.I think the main point behind such phenomena is that we know such reactions will produce a kind of pattern, but we can't predict the exact shapes.

Along the same lines, the question which some of the theories in syzygy42's post are attempting to grapple with is: "Can nature's ability to turn simplicity into complexity in such an unpredictable way, explain why life exists ?"


I had a look at this article and also at some non-equilibrium stuff. What caught my attention was the computer simulation depicted on the side. The fact that it can be simulated suggests that we know the microscopic mechanisms responsible for these kinds of phenomena, we just don't know exactly how to predict it in an analytical way.Meaning that the phenomenon itself, is inherently unpredictable, at certain scales.

The big question is: "At which scales ?"

Unless there is direct empirical evidence at the exo-planetary scale, attempts at phenomenological theories will have no predictive validity in the physical universe … ie: inherently unpredictable … not 'likely'.


I would define self-replication and evolvability as minimum requirements for biological evolution. The Belousov-Zhabotinsky reaction is an example of complex pattern formation, but is there anything identifiable as self-replication in there? If there is, then that would be very interesting.
Well, I think the patterns exhibit fractal dimensionality. (A fractal being generated by simple rules repeated over and over again .. recursive in nature .. incorporating feedback, and self-similarity). Where, and when, a particular self-similar feature will recur, (or even if it recurs), is unpredictable.

What if life on Earth is one instance of such a feature ? The next instance would be unpredictable, and not necessarily inevitable, until we have evidence of the scales of self-similarity, both spatially and temporally.


That similar kinds of phenomena are found in different physical scenarios and simple computer simulations, suggests to me that it shouldn't be uncommon, but more rigorous proof is of course required. I do want to add though, that unexpected outcomes we find in pure mathematics also even though we have the rules or axioms of the system clearly defined.There is plenty of evidence that such processes in nature are common.
The unexpected outcomes (seemingly, in spite of the rules and axioms we use to describe them), is the nature of Chaos. It all somehow fits into the Standard Physical (and Chemical) Laws. It can fit into those laws without necessarily being predictable. As a matter of fact, there is plenty of abundant evidence that many natural systems do exactly this. Predictability and inevitability are scale dependent. The concept of the "Infinite Universe" is the only theoretical basis I can think of, which would make all this inevitable (and the observable universe isn't infinite).

Regards

Selfsim
2012-Jun-02, 12:22 AM
Such an "implied assumption" may have been there once. However, recent work on abiogenesis takes energy gradients and energy flows to be a basic ingredient in the process. Such a gradient is the state of affairs opposite to equilibrium. I'd suggest (once again) that you have a look at James Trefil et al The Origin of Life (http://www.americanscientist.org/issues/feature/2009/2/the-origin-of-life/1) in the journal American Scientist.Ok .. I'll have a read and get back shortly. As a precursor, the question is already set in my mind as to whether the assumptions of symmetry get thrown out when incorporating such gradients. What is the impact on predictability ?

More later.
As promised, I've had a read through this article.
Overall, I find that its probably almost exactly what Longo et al are saying is the very kind of formulaic, reductionist thinking, which they criticise as being inappropriate as far biology reasoning is concerned. (Note this statement is my attempt at coming from the Longo perspective .. but is not an attempt at pushing my own personal views).

I also notice that it appeared in April 2009, whereas the Longo et al paper was dated Jan 2012 (~3 years later).

I must admit that I also feel very uncomfortable with statements such as:

Current research into this foundational question now centers on the fact that the chemical substrate of living systems is much more complex than that of simple physical systems that have been examined so far. One important new direction of research involves the development of small-molecule catalysts in increasingly complex cooperative networks. The hope is that when a full theory is available, we will see the formation of life as an inevitable outcome of basic thermodynamics, like the freezing of ice cubes or the formation of magnets.Sort of putting the cart before the horse, isn't this ?

Ie: .. why is there a hope from the outset that: "we will see the formation of life as an inevitable outcome of basic thermodynamics" ???
By their own words, this seems to be a classic case of building a story based on a reductionist world view, then propping it up by carefully contrived lab experiments, then calling it a 'theory'?


In a larger sense, however, the future of the experimental program associated with the Metabolism First philosophy is tied to the development of the appropriate theory, guided by experimental results. The hope is that the interplay of theory and experiment, so familiar to historians of science, will produce a theory that illuminates the physical principles that led to the development of life and, hence, give us the ability to re-create life in our laboratories.Well, with such a heavily biased motivating influence behind the development of such a 'theory', about the only way it could be accepted, would be if it did re-create life in the laboratories !

Notice how a philosophy is deliberately tied to the development of an 'appropriate theory' ?!!

Does no-one else see how biased this approach is ? Where are the steps for ensuring that they don't just end up with the answer they were looking for all along ? Seems to me, these have been deliberately excluded ...

More back-to-front (circular) reasoning:

Assuming the experimental and theoretical programs outlined above work out well, our picture of life as a robust, inevitable outcome of certain geochemical processes will be on firm footing. Who knows? Maybe then someone will write a book titled Necessity, Not Chance.Once again, their 'picture of life' shall be reinforced by the story and evidence they deliberately select ??
Then, the story they're creating is for the purpose of writing books, eh ?
(As distinct from an attempt at investigative science ?).

Honestly, this entire article (and, perhaps, their 'research' program(?) ), is based on just what they say its based on ... ie: "our picture of life as a robust, inevitable outcome of certain geochemical processes".

I can now see why Longo et al are writing papers like they have ! (Not that theirs is necessarily much different, mind you).
And this piece of literature also reinforces Letelier/Cardenas/Cornish-Bowden's assertions that: 'most of the researchers in the field have been academic loners, rarely citing each other's work', (as outlined in syzygy42's post #31).

Still, the content of what they present, in isolation, seems quite sound, so I'd regard the Trefil et al article, as yet another one to add to the Letelier list, presented by syzygy42.

… Gee, all these 'theories' … and no way to distinguish a preferred one over any of the others, (other than via a philosophically based worldview), eh ?

.. What we need is some empirical evidence … you know, like a local exo-life discovery ?! :)

Selfsim
2012-Jun-02, 12:42 AM
Above and beyond specific chemical reactions there are some purely theoretical based on the underlying structure of the chemical network. Kauffman's autocatalytic sets, mentioned above, is one such example, but there are many others …. {big snip} …
… From L'Homme Machine to metabolic closure: Steps towards understanding life (http://www.sciencedirect.com/science/article/pii/S0022519311003389)

(M,R) systems … Autopoiesis … The chemoton … The hypercycle … Autocatalytic sets … Metabiology …

None of the above models are complete and each have their deficiencies/problems as outlined in more detail in the review.Hi syzygy;

… A very useful article … capturing a broad spectrum of the ideas being worked on.

Many thanks for the 'heads-up'. :)

Certainly highlights the unpredictability of exo-life issue, especially if the present theoretical status is undecided on which variant of these, reflects the as yet, undiscovered reality.


One central theme underlying almost all of the various "modern" theories is that of metabolic closure, i.e. all of the essential components of an organism are required for the synthesis of all of the other essential components and itself. This self-referential property of living systems is to my mind the thorniest problem confronting theoretical biology (shades of GEB).
.. and I'm not sure whether any of these theories is ultimately ever going to crack that problem ..
In the meantime, the whole decision landscape is dominated by philosophically based opinion … which is certainly no scientific basis for assuming 'inevitability'.

Cheers

Paul Wally
2012-Jun-02, 03:41 AM
Unless there is direct empirical evidence at the exo-planetary scale, attempts at phenomenological theories will have no predictive validity in the physical universe … ie: inherently unpredictable … not 'likely'.


The three concepts that you're using: "inherentness", "unpredictability" and "likelihood", do not necessarily go together. In other words, a phenomenon can be unpredictable without being inherently unpredictable, and a phenomenon can be inherently unpredictable and yet be highly likely. In this case its possible that the emergence of life is inherently unpredictable and yet highly likely. You see, unpredictability just means that it's random, not that it's necessarily unlikely. Anyway, to get back to "inherent unpredictability" claim; since we don't yet understand the process of how life emerges how is it that you can know that the emergence of life is inherently unpredictable? Maybe it isn't, and we just don't know it yet.



Well, I think the patterns exhibit fractal dimensionality. (A fractal being generated by simple rules repeated over and over again .. recursive in nature .. incorporating feedback, and self-similarity). Where, and when, a particular self-similar feature will recur, (or even if it recurs), is unpredictable.

Fractal patterns are not exactly what I mean by self-replication. With self-replication I mean something making an exact copy of itself, and not a smaller copy of itself still attached to itself. The copy must also be capable of making a copy of itself, and so forth. Self-replication then leads to population growth. Now, if there is some variability in the self-replication process, that makes for variety in the population and that's where natural selection starts coming into the picture. So, in this understanding, biological evolution cannot start before there is both self-replication and variability.


What if life on Earth is one instance of such a feature ?

Life on Earth is one instance of a very general kind of phenomenon, that is self-replication and evolvability, but I wouldn't call these "features" really. A feature is something unique, whereas this phenomenon is of a more general kind.


The next instance would be unpredictable, and not necessarily inevitable, until we have evidence of the scales of self-similarity, both spatially and temporally.

I don't think there is much that needs to be similar, other than the minimum requirements of self-replication and evolvability. Evolution takes care of the rest. I'm not sure I understand what you mean by "evidence of the scales of self-similarity"; what would such evidence look like?


There is plenty of evidence that such processes in nature are common.

Now if such processes are common in nature, why would the emergence of life be uncommon, or am I missing something here?


The unexpected outcomes (seemingly, in spite of the rules and axioms we use to describe them), is the nature of Chaos.

Well, without the rules and axioms there is no chaos theory and thus no "nature of Chaos" to talk about. Chaos is a mathematical concept.


It all somehow fits into the Standard Physical (and Chemical) Laws. It can fit into those laws without necessarily being predictable.

Chaos doesn't just somehow fit, it follows as an implicit possibility of these laws.


Predictability and inevitability are scale dependent.
Could you please provide an example illustrating the meaning of the above statement?


The concept of the "Infinite Universe" is the only theoretical basis I can think of, which would make all this inevitable (and the observable universe isn't infinite).

... hence exolife is not inevitable? But what does this conclusion mean? Suppose we knew for a fact that the universe is teeming with life, how would the concept of "non-inevitability of life" apply in that case?

Selfsim
2012-Jun-03, 01:23 AM
Unless there is direct empirical evidence at the exo-planetary scale, attempts at phenomenological theories will have no predictive validity in the physical universe … ie: inherently unpredictable … not 'likely'.Anyway, to get back to "inherent unpredictability" claim; since we don't yet understand the process of how life emerges how is it that you can know that the emergence of life is inherently unpredictable? Maybe it isn't, and we just don't know it yet.
i) We don't know the process of how life emerges.
ii) The theory is incomplete. (In this case, lacking in physical evidence).
iii) Prediction requires a theory.
iv) Predictability is not implied.



I would define self-replication and evolvability as minimum requirements for biological evolution. The Belousov-Zhabotinsky reaction is an example of complex pattern formation, but is there anything identifiable as self-replication in there? If there is, then that would be very interesting.
Well, I think the patterns exhibit fractal dimensionality. (A fractal being generated by simple rules repeated over and over again .. recursive in nature .. incorporating feedback, and self-similarity). Where, and when, a particular self-similar feature will recur, (or even if it recurs), is unpredictable. Fractal patterns are not exactly what I mean by self-replication. With self-replication I mean something making an exact copy of itself, and not a smaller copy of itself still attached to itself. The copy must also be capable of making a copy of itself, and so forth.A fractal pattern can form as a result of self-replication. In fractals, interestingly, many sequences of output points of an iterative process, do not converge to a finite quantity, and 'escape' to infinity. (I don't know for sure, but I think there may be more that do this, than converge, depending on the fractal expression, and assuming a large, but finite bounded iteration space .. a bit like the observable universe space, but I am not certain of this .. its an interesting question, though). So, if life on Earth were to represent the set of non-escaping sequences resulting from a starting point, then there would be many (more?) escaping sequences resulting from the overall interative process .. and they may not result in viable lifeforms.
This is really pure conjecture/fantasy, (and only for illustrative purposes .. to get the feeling for the permutation space outside of life-as-we-know-it), but if the pattern of life distribution throughout the universe is generated by a natural iterative process, then non-viable outcomes would also result. The question remains .. what is the scale of the boundary which might separate viable and non viable outcomes … and we don't know this. Thinking of it all in fractal terms at least forces us to think simultaneously, about both sides of the 'likely/unlikely' biological coin, maintaining some semblance of balance about this, as well as reminding us about the detailed unpredictability over-riding it all.



Well, I think the patterns exhibit fractal dimensionality. (A fractal being generated by simple rules repeated over and over again .. recursive in nature .. incorporating feedback, and self-similarity). Where, and when, a particular self-similar feature will recur, (or even if it recurs), is unpredictable.

What if life on Earth is one instance of such a feature ? The next instance would be unpredictable, and not necessarily inevitable, until we have evidence of the scales of self-similarity, both spatially and temporally.Life on Earth is one instance of a very general kind of phenomenon, that is self-replication and evolvability, but I wouldn't call these "features" really. A feature is something unique, whereas this phenomenon is of a more general kind. .. and can be abstracted and found to mimic non-linear recursion .. along with all its implications. I think this is a more fundamental, generalised natural process than say, self-replication or evolvability, (which is specific to the progress of biology), as it can be applied in more fundamentally based, (inorganic), processes such as fusion in a star, coelescence of gases and dust, accretion, etc.


I don't think there is much that needs to be similar, other than the minimum requirements of self-replication and evolvability. Evolution takes care of the rest. I'm not sure I understand what you mean by "evidence of the scales of self-similarity"; what would such evidence look like?Other instances of exo-life at measurable spatial distances and temporal scales.


Now if such processes are common in nature, why would the emergence of life be uncommon, or am I missing something here?I'm not sure it would be uncommon. (I'm not saying this .. there's no direct evidence). But thinking about it from this paradigm, at least follows roughly one established by biological behaviours. Following my fractal 'fantasy' above, I wonder how many sets are discarded (or escape) in a finite 'run' of say a Mandelbrot Set algorithm ? (They're usually the coloured pixels, I think .. ?)


Well, without the rules and axioms there is no chaos theory and thus no "nature of Chaos" to talk about. Chaos is a mathematical concept.I've seen you mention this elsewhere. Chaos is intrinsic in nature. Mathematics is the language used to model it. 'Tis not a purely theoretical abstraction emerging from some mathematical formula, which has no physical significance !


Chaos doesn't just somehow fit, it follows as an implicit possibility of these laws.I'd say Chaos is an explicit outcome of natural laws which results in unpredictability at certain scales.



Predictability and inevitability are scale dependent.
Could you please provide an example illustrating the meaning of the above statement?Lets see, now ... hmm .. how about ...

i) Death of any human being is inevitable on a scale of say, five hundred years. Death of any human being is not inevitable on a scale of say, one month.

ii) The orbital period of Halley's comet over the last 3 centuries, can be predicted to be between 75 and 76 years. Over the last 2250 years however, its period can be predicted to be between 74 and 79 years.



The concept of the "Infinite Universe" is the only theoretical basis I can think of, which would make all this inevitable (and the observable universe isn't infinite).... hence exolife is not inevitable? Nope ... that's a different statement .. and its not what I'm saying. Inevitability is unknown. (What I'm saying may have come across ambiguously, due to this text medium ??)


The concept of the "Infinite Universe" is the only theoretical basis I can think of, which would make all this inevitable (and the observable universe isn't infinite).But what does this conclusion mean? Suppose we knew for a fact that the universe is teeming with life, how would the concept of "non-inevitability of life" apply in that case?The point is: we don't know this.

Regards

Hlafordlaes
2012-Jun-03, 02:36 AM
Barring mythical causes, that abiogenesis happened either implies that it happens, or that it was a singularity. I think it happens. There is no indication that the physics and chemistry on our planet is rare or exceptional, containing as it does that mix of elements and conditions one might expect from known planetary formation. To argue it as a singularity seems to imply we need to find something authentically special about local conditions, doesn't it?

IOW, if nature tries the same experiment with the same or similar soup elsewhere, why should we expect different results? Is nature crazy?

Selfsim
2012-Jun-03, 04:50 AM
Barring mythical causes, that abiogenesis happened either implies that it happens, or that it was a singularity. I think it happens.It must have happened. How else could life exist ? Whether we call the event 'abiogenesis' or, 'a singularity', is just semantics.


There is no indication that the physics and chemistry on our planet is rare or exceptional, containing as it does that mix of elements and conditions one might expect from known planetary formation. To argue it as a singularity seems to imply we need to find something authentically special about local conditions, doesn't it?Ignoring any particular meaning associated with the term 'singularity' (see above comment), ….. No !…. Not at all !

What could be said is that it could be a perfectly natural outcome .. with absolutely nothing special about local conditions, needing to be shown.

For example, try on:
"It just happened to have happened here .. and we showed up later, to notice that it happened here". (The Anthropic Principle).

The perspective you mention (which should be equally valid, although not necessary), is caused by a strong interpretation of the Copernican Principle, (or more broadly .. the Cosmological Principle) .. but, "it ain't the only Principle in town" !

IOW, if nature tries the same experiment with the same or similar soup elsewhere, why should we expect different results? Is nature crazy?Whilst there is no compelling evidence to suggest that abiogenesis is necessarily a Chaotic phenomenon, it is equally possible that if it was, no two outcomes would necessarily be the same because either:

i) no two initial (pre-abiogenesis) conditions might be identical or;
ii) we have no way of knowing what those precise original (pre-abiogenesis) conditions were, and hence we have no way of knowing that a another re-run of the same process would necessarily result in a viable emergent lifeform.

This is Chaos Theory's 'sensitive dependence on initial conditions', and is the basic conclusion of Edward Lorenz's (http://en.wikipedia.org/wiki/Edward_Lorenz) work on non-linear dynamics, (and has mathematical proof underpinning it): even if one knows the initial conditions quite precisely, the error in specifying the initial condition rapidly grows, so that after even a short time, one cannot predict the details of the outcome. And any of these 'details', could easily be critical for life to become viable (or non-viable).

I have no particular interest in pushing the idea, because there is no physical evidence that the abiogenesis event ever happened this way, but it certainly is possible in theory, and many presently functioning biological systems, (and Evolution), behave in just this way. The 'unknown' status of (i) how metabolic closure occurs and; (ii) the self-referential property of living systems, allows for this possibility in abiogenesis theory.

If it is possible in theory, then 'predictability' and 'inevitability' are not necessarily assured. Personally, I'd still say both of these aspects are still 'unknown', (for all the above reasons).

Regards

Colin Robinson
2012-Jun-03, 04:55 AM
Barring mythical causes, that abiogenesis happened either implies that it happens, or that it was a singularity. I think it happens. There is no indication that the physics and chemistry on our planet is rare or exceptional, containing as it does that mix of elements and conditions one might expect from known planetary formation. To argue it as a singularity seems to imply we need to find something authentically special about local conditions, doesn't it?

IOW, if nature tries the same experiment with the same or similar soup elsewhere, why should we expect different results? Is nature crazy?

Whether the results would be different or not, is not necessarily an either/or question.

When water vapour condenses into snow crystals, every crystal is different, though they are also structurally similar. The process that led to abiogenesis was presumably more complex than crystallization of snow. Perhaps that means greater diversity of possible results?

Isn't it conceivable that "soups" on other worlds might result in intricate chemical systems and physical structures which we will find difficult to classify either as living or as non-living?

Colin Robinson
2012-Jun-03, 05:26 AM
This is Chaos Theory's 'sensitive dependence on initial conditions', and is the basic conclusion of Edward Lorenz's (http://en.wikipedia.org/wiki/Edward_Lorenz) work on non-linear dynamics, (and has mathematical proof underpinning it): even if one knows the initial conditions quite precisely, the error in specifying the initial condition rapidly grows, so that after even a short time, one cannot predict the details of the outcome.

Edward Lorenz was a meteorologist.

No doubt he was right that some of the details of meteorological systems can't be predicted much in advance. But does that mean all bets are off, that nothing can be said about what is likely to happen?

E.g. It may be impossible to predict exactly when and where the next tropical cyclone is going to form. On the other hand, it has long been known that tropical cyclones tend to form at a particular range of latitudes (which is why they are called "tropical", after all) and at particular times of year…

Selfsim
2012-Jun-03, 06:16 AM
Edward Lorenz was a meteorologist.

No doubt he was right that some of the details of meteorological systems can't be predicted much in advance. But does that mean all bets are off, that nothing can be said about what is likely to happen? What Lorenz was, or wasn't, is not relevant. What he, and many others discovered in theory, is.

Unpredictability at certain scales in non-linear Chaotic Systems in nature, is a mathematical certainty.


E.g. It may be impossible to predict exactly when and where the next tropical cyclone is going to form. On the other hand, it has long been known that tropical cyclones tend to form at a particular range of latitudes (which is why they are called "tropical", after all) and at particular times of year…As I have said numerous times in this thread, (and provided examples thereof), the unpredictability in these systems is spatially and temporally scale dependent. You have cited yet another example.

Regards

Colin Robinson
2012-Jun-03, 07:16 AM
What Lorenz was, or wasn't, is not relevant. What he, and many others discovered in theory, is.

It's relevant because meteorological systems are the classical chaotic systems. If chaos theory is applicable to abiogenesis, that means the processes involved in abiogenesis are in some ways comparable to meteorological processes.


As I have said numerous times in this thread, (and provided examples thereof), the unpredictability in these systems is spatially and temporally scale dependent. You have cited yet another example.

The point I'm interested in is this...

Does a chaotic model of abiogenesis necessarily contradict the hypotheses of Stuart Kauffman and Christian de Duve and James Trefil, all of whom have argued for abiogenesis being a high-probability process?

My example -- formation of tropical cyclones -- suggests to me that a chaotic model does not necessarily contradict their hypotheses.

Selfsim
2012-Jun-03, 08:39 AM
The point I'm interested in is this...

Does a chaotic model of abiogenesis necessarily contradict the hypotheses of Stuart Kauffman and Christian de Duve and James Trefil, all of whom have argued for abiogenesis being a high-probability process?

My example -- formation of tropical cyclones -- suggests to me that a chaotic model does not necessarily contradict their hypotheses.

Ok, as an example, so a quick overview summary of Trefil's hypothesis follows:

We believe this early version of metabolism consisted of a series of simple chemical reactions running without the aid of complex enzymes, via the catalytic action of networks of small molecules, perhaps aided by naturally occurring minerals. If the network generated its own constituents—if it was recursive—it could serve as the core of a self-amplifying chemical system subject to selection. We propose that such a system arose and that much of that early core remains as the universal part of modern biochemistry, the reaction sequences shared by all living beings. Further elaborations would have been added to it as cells formed and came under RNA control, and as organisms specialized as participants in more complex ecosystems.From my read of that, all of the basic fundamentals of Chaos are incorporated. In his pursuit of closing the thermodynamic pathway, by suggesting the citric acid cycle as a fundamental, (etc), he drills down, (in true reductionist form), to the molecular levels, in order to find a level where he can come up with a hypothetical step-by-step rationale, leading towards what looks like a pre-determined outcome .. ie: an inevitable metabolism first outcome.

As Longo (and Kauffman) argue in their paper however, this approach is very formulaic, whereas what they propose, is less so. Frankly, I think Kauffman is backing both horses. I concur that Kauffman has written extensively from the view which ultimately concludes an inevitable life resultant, following a non-linear, complex systems route. However, I do think that his thinking (relating to inevitability of life), is a purely philosophically based pre-conceived interpretation, which ignores the reality of unpredictability inherent in Chaos Theory. And all this, even though Kauffman is more focused on biological Systems Complexity, (which encompasses Chaos principles, and self-assembly). I mentioned somewhere else, (in response to Cougar, somewhere), that I find Kauffman tends to spend a lot less time on falsification of his hypotheses, than verification, and this is where I was coming from .. ie: the exclusion of the unpredictability component introduced by Chaos inherent in Complexity.

All this comes down to the scales at which one thinks unpredictability and predictability operate in the process.

Also, I think syzgy42's comment about the unknown part of metabolic closure, being 'one of the thorniest problems', might be right on the mark ... and may account for what I think, is some inconsistency in each of these hypotheses.

I haven't looked at de Duve's material from this perspective yet. Have you posted any de Duve links in this thread ? (Apologies if I missed it).

Regards

Colin Robinson
2012-Jun-03, 10:50 AM
Ok, as an example, so a quick overview summary of Trefil's hypothesis follows:
From my read of that, all of the basic fundamentals of Chaos are incorporated. In his pursuit of closing the thermodynamic pathway, by suggesting the citric acid cycle as a fundamental, (etc), he drills down, (in true reductionist form), to the molecular levels, in order to find a level where he can come up with a hypothetical step-by-step rationale, leading towards what looks like a pre-determined outcome .. ie: an inevitable metabolism first outcome.

Re Trefil's suggestion that the citric acid cycle or something like it was a very early, thermodynamically favored precursor to metabolism...

In November 2009, a few months after the Trefil article was published, Marcelo Guzman published laboratory results which showed that most (at least) of the steps in the reductive citric acid cycle (aka the reductive Krebs cycle) can indeed take place with the help of mineral catalysts instead of enzymes.

Summary of Guzman's results in Astrobiology Magazine… (http://www.astrobio.net/exclusive/3359/shallow-origins)

"Guzman and Martin tried to chemically replicate the Krebs cycle – that is, without enzymes playing a role. They experimented with the semi-conducting mineral zinc sulfide as the catalyst. But iron, cadmium and manganese can also be used, says Guzman. Using a “colloidal suspension” (a chemical mixture in which a solid is suspended in a liquid) of zinc sulfide and sodium sulfide and exposing it to UV light, the research team was able to reproduce about 70 percent of the cycle."


As Longo (and Kauffman) argue in their paper however, this approach is very formulaic, whereas what they propose, is less so.

Have you forgotten that Longo's paper is about evolution not abiogenesis? Or, when you say "As Longo (and Kauffman) argue", do you mean something like "it can be argued, by extending Longo's and Kauffman's argument back from the sphere of evolution to the sphere of abiogenesis"?


All this comes down to the scales at which one thinks unpredictability and predictability operate in the process.

Yes, this seems like a crucial question.


I haven't looked at de Duve's material from this perspective yet. Have you posted any de Duve links in this thread ? (Apologies if I missed it).

No, I don't think I have posted anything by de Duve. So here is something now...

Christian de Duve, "The Beginnings of Life on Earth" in American Scientist (http://www.americanscientist.org/issues/id.864,y.0,no.,content.true,page.1,css.print/issue.aspx)

Regards

Paul Wally
2012-Jun-03, 04:17 PM
i) We don't know the process of how life emerges.
ii) The theory is incomplete. (In this case, lacking in physical evidence).
iii) Prediction requires a theory.
iv) Predictability is not implied.

I asked how you can know the emergence of life is "inherently unpredictable", with emphasis on "inherently". It may just be unpredictable because we don't yet have
a complete theory, as you say in ii), but that is not a sufficient basis for making the much stronger claim of "inherent unpredictability". What is the theoretical basis for your claim that the emergence of life is inherently unpredictable, given certain conditions?

Just to clarify the concept of "prediction"; there are two interpretations I can think of:
1) Temporal prediction, i.e. predicting the evolution of a process in time.
2) Theoretical prediction, i.e. a theory makes a statement that is not yet empirically confirmed, e.g. General Relativity predicting the bending of starlight near the sun.

It is mainly prediction (2) that is relevant here in the sense that we want a theory "predicting" what the necessary conditions for the emergence of life is. But this is not the same as predicting how any particular process is going to evolve in real time as a function of time. This ties in with what Colin said about tropical cyclones. We cannot predict the emergence of cyclones in real time, but we can theoretically predict the necessary conditions for the emergence of cyclones based on our theoretical understanding of atmospheric dynamics. The same kind of thinking applies to emergence of life where we could have theoretical prediction of emergence of the general phenomenon of life as opposed to predicting the evolution of particular lifeforms as a function of time.



Quote Originally Posted by Paul Wally
I don't think there is much that needs to be similar, other than the minimum requirements of self-replication and evolvability. Evolution takes care of the rest. I'm not sure I understand what you mean by "evidence of the scales of self-similarity"; what would such evidence look like?


Quote Originally Posted by Selfsim
Other instances of exo-life at measurable spatial distances and temporal scales.


That is just too vague. What does "evidence of the scales of self-similarity" in particular look like? You make these vague general statements and they're subject to multiple interpretations, so please clarify.


I've seen you mention this elsewhere. Chaos is intrinsic in nature. Mathematics is the language used to model it. 'Tis not a purely theoretical abstraction emerging from some mathematical formula, which has no physical significance !

Chaos, like circles and parabolas, is a purely mathematical concept. Like circles and parabolas are used to model real world phenomena, so chaos is also used to model real world phenomena. You've got the whole thing backwards.


I'd say Chaos is an explicit outcome of natural laws which results in unpredictability at certain scales.

The natural laws are mathematical formulations of how we think nature behaves in general. Chaos follows implicitly from certain mathematical models based on these formulations. Absolutely no empirical data is required for mathematical equations to imply chaos, i.e. no explicit input is required. The chaotic behaviour follows implicitly from the equations and the equations only; that's the beauty of mathematics!


Lets see, now ... hmm .. how about ...

i) Death of any human being is inevitable on a scale of say, five hundred years. Death of any human being is not inevitable on a scale of say, one month.

ii) The orbital period of Halley's comet over the last 3 centuries, can be predicted to be between 75 and 76 years. Over the last 2250 years however, its period can be predicted to be between 74 and 79 years.

These are examples of temporal prediction. How does your "scale -dependence" concept apply to theoretical predictions (as I explained above)?



Nope ... that's a different statement .. and its not what I'm saying. Inevitability is unknown. (What I'm saying may have come across ambiguously, due to this text medium ??)
Inherent unpredictability is unknown too. Just because we don't know, that doesn't mean we can automatically assume inherent unpredictability.

Selfsim
2012-Jun-05, 09:03 PM
I asked how you can know the emergence of life is "inherently unpredictable", with emphasis on "inherently". It may just be unpredictable because we don't yet have a complete theory, as you say in ii), but that is not a sufficient basis for making the much stronger claim of "inherent unpredictability". What is the theoretical basis for your claim that the emergence of life is inherently unpredictable, given certain conditions?Paul, I never said that that the emergence of life is inherently unpredictable. What I said was:

Unless there is direct empirical evidence at the exo-planetary scale, attempts at phenomenological theories will have no predictive validity in the physical universe … ie: inherently unpredictable … not 'likely'. ... meaning that the theories themselves, would be incapable of delivering predictions .. which would make them inherently incapable of making predictions. Perhaps I should have said "inherently unpredictive" (??) Science cannot determine whether the emergence of life is able to be predicted, or not. Having made this statement, so long as a class of natural phenomena exists, for which we do have evidence supporting unpredictability, (and it forms part of the incomplete abiogenesis theories), unpredictability cannot be ruled out .. but following this line of argument, basically leads back to a status of 'unknown', as predictability coming from certain purely deterministically based rationale can also not be ruled out, for the same reasons. It should be noted that the chemistry cited in most abiogenesis hypotheses is complex and dependent on a very large number of variables, which do lead to dynamic phase states, which can easily behave chaotically.

Unpredictability may be ruled out however, if philosophical bias is driving the theory .. ie: if the emergence of life is believed to be determinable, from the outset, but this would not be coming from scientific argument.

One thought I've been playing around with lately is that I'm thinking that we can never know in detail, those "certain conditions" you mention above, from Earth's history. If the environment plays a role in the abiogenesis of life, then the abiogenesis is also subject to the same unpredictability in the detail of that environment. No amount of data would allow us to 'postdict' the details of that environment backwards over evolutionary timescales. Given this is the case, then its influence on the details proposed by theories of abiogenesis, is also unpredictable over the same timescale. Fossil records also do not contain the kinds of details, which may be of significance.


Just to clarify the concept of "prediction"; there are two interpretations I can think of:
1) Temporal prediction, i.e. predicting the evolution of a process in time.
2) Theoretical prediction, i.e. a theory makes a statement that is not yet empirically confirmed, e.g. General Relativity predicting the bending of starlight near the sun.

It is mainly prediction (2) that is relevant here in the sense that we want a theory "predicting" what the necessary conditions for the emergence of life is. If this is the agenda behind the development of an abiogenesis 'theory', then it has started out under an unjustifiable premise (and it seems, a philosophically based agenda). The details of the conditions for the emergence of life are unknown, and unpredictable. So how can one come up with a theory which attempts to predict from an unknowable initial condition ?


But this is not the same as predicting how any particular process is going to evolve in real time as a function of time. This ties in with what Colin said about tropical cyclones. We cannot predict the emergence of cyclones in real time, but we can theoretically predict the necessary conditions for the emergence of cyclones based on our theoretical understanding of atmospheric dynamics.But you can't predict where, or when, other variables may trigger those 'necessary' conditions ... no matter how much data you accumulate. This is the Butterfly Effect ... if a critical state occurs, the slightest variation in the steady-state 'necessary' conditions may or may not trigger the cyclone. And that trigger (or catalyst) itself, cannot be predicted. Neither can the occurrence of the 'necessary' conditions we know of, so at the scales which matter (of interest), what predictive capability does such a cyclone theory have ?
That cyclones are seasonal and tend to be localised within approximate geographical zones, might also represent the self-similar spatial and temporal scale issues at work. (Yet another example of them, actually). But we only know this happens, because of observational evidence .. not theoretical.
The same kind of thinking applies to emergence of life where we could have theoretical prediction of emergence of the general phenomenon of life as opposed to predicting the evolution of particular lifeforms as a function of time. Why does 'the same kind of thinking apply to the emergence of life' ?


I don't think there is much that needs to be similar, other than the minimum requirements of self-replication and evolvability. Evolution takes care of the rest. I'm not sure I understand what you mean by "evidence of the scales of self-similarity"; what would such evidence look like?
Other instances of exo-life at measurable spatial distances and temporal scales.
That is just too vague. What does "evidence of the scales of self-similarity" in particular look like? You make these vague general statements and they're subject to multiple interpretations, so please clarify.Instances of replication (other than Earth) of known biological processes - eg similarity with: the citric cycle for metabolism, enzymatic or mineralogic catalysis, polynucleotide molecules used by Earth-life, glycolysis (or similar) using the same or similar enzymes as earth-life in similar sequences, similar molecular chirality as Earth-life, similar amino acid synthesis aligning with our 'standard' genetic code etc. How specific does it have to get in order to satisfy your definition of not 'vague' ?
Similarity with any one of these details would become a valid data point which could perhaps contribute towards giving more weight to certain abiogenesis theories.



I've seen you mention this elsewhere. Chaos is intrinsic in nature. Mathematics is the language used to model it. 'Tis not a purely theoretical abstraction emerging from some mathematical formula, which has no physical significance !Chaos, like circles and parabolas, is a purely mathematical concept. Like circles and parabolas are used to model real world phenomena, so chaos is also used to model real world phenomena. You've got the whole thing backwards.

I'd say Chaos is an explicit outcome of natural laws which results in unpredictability at certain scales.
The natural laws are mathematical formulations of how we think nature behaves in general. Chaos follows implicitly from certain mathematical models based on these formulations.
Absolutely no empirical data is required for mathematical equations to imply chaos, i.e. no explicit input is required. The chaotic behaviour follows implicitly from the equations and the equations only; that's the beauty of mathematics! 'Backwards' you reckon eh ?
Admittedly, the whole point of physics is to replace what is happening in the real world, with something that may not actually be happening, but what we can make sense of (ie: theoretical models). Some parts of these models can be confirmed to accurately mimic reality via real-world measurements. As it turns out, some chaos models have been originally developed from real-life observational data (eg: meteorological<=>Lorenz models). Lorenz started out with a simplified model for thermal fluid convection but it was then demonstrated that these were the equations of motion of a waterwheel. The waterwheel was built, and demonstrated convincingly the reality of the chaos phenomenon. The subsequent discoveries about sensitivity to initial conditions, then came from mathematical analysis of those models, but the original data, (ie: before it was mapped into deterministic mathematical formulae), came originally from real-world observational measurements of the phenomena and was confirmed in the lab by the waterwheel behaviours.

Having said this, the mathematics of chaos theory is deterministic, but in mathematically modelled chaos systems, as it turns out, determinism is one of the things which doesn't map in the opposite direction .. ie: back across to the real-world.

In general, this is not so surprising ... for example, the failure of the deterministic components to map back into the macroscopic real world behaviours is exhibited in quantum mechanics ... (like the two slit experiments). So here, we have other real-world examples of the same non-mappability of deterministic functions.

Anyway, when there is chaos, it is also clear that we definitely can't say that the model outcomes are deterministic, in spite of them being generated by formulae which describe a deterministic model. The solutions to a chaos model, highlight that even deterministic models can result in unpredictability .. which is the big lesson from mathematically described, deterministic Chaos Theory.

Determinism cannot be said to be fundamentally embedded in reality. It comes from the way we connect the dots .. ie: the decisions we make and the questions we ask .. all of which, is external to maths and physics however, it all nonetheless, ends up embedded within the descriptions and tools we use.


These are examples of temporal prediction. How does your "scale -dependence" concept apply to theoretical predictions (as I explained above)? Well, in the cyclone example, I suppose there are geographical constraints imposed by the theoretical improbability of 'cyclone forming conditions' developing outside 'the tropics'. This would be an example of a spatial scale boundary, delineating between where self-similar cyclones probably form, and where they probably don't form. But the 'probability' in this statement represents randomness, and is based on prior measurements ... not from the determinism of the mathematical theory.

So if one were to zoom inside a cyclone, it would be unlikely to find another cyclone, and if one zoomed back from a single cyclone, one wouldn't necessarily find another one .. so, the 'zoom' scale makes a difference ... a spatial scale pattern dependence.

Overall, the only way I can see that an abiogenesis theory can produce predictability, (and perhaps, lead to a conclusion of the 'inevitability' other geneses), is for such a theory to have either demonstrated the emergence of life in the lab (from scratch), or for an exo-life discovery to demonstrate in detail, the key biological details, such as those I mention above. 'Predictability' arrived at through theoretical correlations with exo-environments is insufficient, due to the non mappability of deterministic chaos model outcomes, into the real-world.

Regards

Paul Wally
2012-Jun-06, 01:47 AM
Paul, I never said that that the emergence of life is inherently unpredictable. What I said was:
Unless there is direct empirical evidence at the exo-planetary scale, attempts at phenomenological theories will have no predictive validity in the physical universe … ie: inherently unpredictable … not 'likely'.
... meaning that the theories themselves, would be incapable of delivering predictions .. which would make them inherently incapable of making predictions.

Even this doesn't make sense, and it comes down to the same question: How do you know when a theory is inherently incapable of making predictions? There's no such thing as "predictive validity" anyway; theories make predictions, that's what makes them useful. Well, of course, the theory can make wrong predictions but that can happen to even the most well supported theories. I maintain, however, that the whole point of a theory of abiogenesis is for necessary conditions for the emergence of life to be derived from that theory, i.e. we should be able to derive from that theory that an environment must at least have certain general characteristics in order for the emergence of life to be likely in that environment.



One thought I've been playing around with lately is that I'm thinking that we can never know in detail, those "certain conditions" you mention above, from Earth's history. If the environment plays a role in the abiogenesis of life, then the abiogenesis is also subject to the same unpredictability in the detail of that environment. No amount of data would allow us to 'postdict' the details of that environment backwards over evolutionary timescales. Given this is the case, then its influence on the details proposed by theories of abiogenesis, is also unpredictable over the same timescale. Fossil records also do not contain the kinds of details, which may be of significance.

It is because of these very difficulties in acquiring evidence, that I'm proposing the mathematical,theoretical and computational route to solving the problem of abiogenesis. I think it's a much better strategy to first solve the problem theoretically, and then to test the theory against experimental and observational evidence as they come in over time, than to attempt to make something out of the little bits and pieces of scattered evidence that we may find.



If this is the agenda behind the development of an abiogenesis 'theory', then it has started out under an unjustifiable premise (and it seems, a philosophically based agenda). The details of the conditions for the emergence of life are unknown, and unpredictable.

A theory doesn't need an agenda or a justified premise to get started. It only needs to be consistent with known evidence and make testable predictions. And when it starts making wrong predictions, we go back to the drawing board.


So how can one come up with a theory which attempts to predict from an unknowable initial condition ?

A general theory of abiogenesis should answer the question of what the initial conditions must have been like for life to have emerged on Earth. So the initial conditions are implied by the theory as an explanation of how life could have emerged. The same general theory could then be used to predict other possible conditions for the emergence of life. At the moment we don't even have a theory like this, i.e. we cannot yet explain how life emerges. The problem is not yet solved. Once we have such a theory or theories they can then be tested against whatever evidence we can find and against laboratory experiments.



But you can't predict where, or when, other variables may trigger those 'necessary' conditions ... no matter how much data you accumulate. This is the Butterfly Effect ... if a critical state occurs, the slightest variation in the steady-state 'necessary' conditions may or may not trigger the cyclone. And that trigger (or catalyst) itself, cannot be predicted. Neither can the occurrence of the 'necessary' conditions we know of, so at the scales which matter (of interest), what predictive capability does such a cyclone theory have ?
That cyclones are seasonal and tend to be localised within approximate geographical zones, might also represent the self-similar spatial and temporal scale issues at work. (Yet another example of them, actually). But we only know this happens, because of observational evidence .. not theoretical.Why does 'the same kind of thinking apply to the emergence of life' ?

And it's not the "when" and "where" type of prediction I'm talking about, as I already tried to make clear. In the example of tropical cyclones a theoretical prediction would mean predicting what kinds of conditions are conducive to the formation of tropical cyclones. So it would essentially mean explaining why tropical cyclones occur in those particular geographical zones and also explaining why they occur at those particular parts of the year. What I meant then, in the case of life, is that the same kind of theory should be developed for explaining the emergence of life, i.e. predicting what kinds of conditions are conducive to the formation of life.



Instances of replication (other than Earth) of known biological processes - eg similarity with: the citric cycle for metabolism, enzymatic or mineralogic catalysis, polynucleotide molecules used by Earth-life, glycolysis (or similar) using the same or similar enzymes as earth-life in similar sequences, similar molecular chirality as Earth-life, similar amino acid synthesis aligning with our 'standard' genetic code etc. How specific does it have to get in order to satisfy your definition of not 'vague' ?
Similarity with any one of these details would become a valid data point which could perhaps contribute towards giving more weight to certain abiogenesis theories.

But alien biochemistries might be completely different from Earth-life biochemistries. Why this narrow requirement? I find this view quite strange.
I'd say instances of any self-replication on planets other than Earth would be a major discovery, and that's why I'm arguing for a more general theory of abiogenesis.


As it turns out, some chaos models have been originally developed from real-life observational data (eg: meteorological<=>Lorenz models). Lorenz started out with a simplified model for thermal fluid convection but it was then demonstrated that these were the equations of motion of a waterwheel. The waterwheel was built, and demonstrated convincingly the reality of the chaos phenomenon.

Sure, and we can "demonstrate convincingly" certain geometric properties of circles and triangles with a ruler and compass. My point is though that chaos follows logically from simple mathematical rules, and these simple mathematical rules are sufficient to generate the phenomenon of chaos and make it available for study, all this independent of any physical experimental investigations.


Having said this, the mathematics of chaos theory is deterministic, but in mathematically modelled chaos systems, as it turns out, determinism is one of the things which doesn't map in the opposite direction .. ie: back across to the real-world.

One could develop stochastic models of chaos also - bring in some random variables and distribution functions and then do some mathematical investigations on that. You talk about chaos as if real-world chaos has some unknown mysterious properties that we don't already know about in mathematics. Chaotic phenomena in the real world can be explained from already known laws of physics such that there is no need to postulate unknowable processes. Anyway, even if there are unknowables, how are you going to prove their existence?



Overall, the only way I can see that an abiogenesis theory can produce predictability, (and perhaps, lead to a conclusion of the 'inevitability' other geneses), is for such a theory to have either demonstrated the emergence of life in the lab (from scratch), or for an exo-life discovery to demonstrate in detail, the key biological details, such as those I mention above. 'Predictability' arrived at through theoretical correlations with exo-environments is insufficient, due to the non mappability of deterministic chaos model outcomes, into the real-world.

Mathematically or computationally demonstrating the emergence of self-replication and evolvability in complex systems would be a big step forward and a step closer towards a general theory of abiogenesis. Developing theories to test is a much better strategy in my opinion. Deterministic chaos model outcomes will obviously be non-mappable if you're trying to do one-one mappings of model dynamics to world-dynamics, but the point is to look at the general structural similarities between the model and the real world phenomenon.

Selfsim
2012-Jun-08, 06:54 AM
Even this doesn't make sense, and it comes down to the same question: How do you know when a theory is inherently incapable of making predictions? There's no such thing as "predictive validity" …
…{snip}...
we should be able to derive from that theory that an environment must at least have certain general characteristics in order for the emergence of life to be likely in that environment.
We know that:

i) The choices made in studying particular observables, determine the preservation of invariants and symmetries in an intended theory. These invariants and symmetries then form the backdrop where phenomena being analysed are accommodated. Prediction from such a theory is then credible, but because of the parameter choices originally made. You are making exactly such a choice, by deliberately selecting (in your own words): 'general characteristics in order for the emergence of life to be likely in that environment. What about other characteristics and variables which still may influence the outcome in a non-deterministic way, but have been excluded ?

ii) Mathematical determinism necessary for prediction, is not a default in the physical world .. the double slit experiment (for example), shows that if light strictly behaved as particles, an interference pattern wouldn't be predictable.

iii) Small variations in initial conditions lead to wildly unpredictable results from deterministic formula which, when applied in nature, to weather systems and waterwheels, result in observable macro-scale unpredictability over longer terms of study.

iv) There is presently no real world evidence which necessarily leads to an inevitable outcome of self replication in metabolism first, or RNA first abiogenesis models.

v) The main presently proposed abiogenesis processes involve feedback mechanisms and highly complex interactions of components. Non-linearity is evident early on at the molecular levels (as a matter of fact, these theories depend on it).

vi) All real world systems in nature, are non-linear*and are irreversible. As a result, the evolution theories of biology (including abiogenesis theory phases) also fit within such a backdrop. The details of the originating environmental conditions resulting in abiogenesis are also untraceable, due to irreversibility.

vii) Feedback in non-linear environmental systems, results in chaotic behaviours. Abiogenesis theories are thus subject to chaotic behaviours in pre-biotic environments. Such behaviours shape the outcome of abiogenesis in unpredictable ways.

* For example back to fundamentals: if a molecule in a solid (or liquid) is attracted away from its position, then the forces from neighbouring molecules act to restore that position - there is a negative feedback effect, the displacement is no longer linear. Any time that we have a system that has limits, minimum or maximum settings, then we have a nonlinear system. Populations of animals are limited by food, space or predators; trignometrical functions are limited, elastic stretching is limited, pendulum swings are limited. All aspects of our perceived reality are, at root, nonlinear - none are completely unrestrained. Feedback can also be positive but the main point is that the output behaviours of just about any naturally occurring system influenced by neighbouring elements, is a function of its own behaviours and is hence non-linear.


It is because of these very difficulties in acquiring evidence, that I'm proposing the mathematical,theoretical and computational route to solving the problem of abiogenesis. I think it's a much better strategy to first solve the problem theoretically, and then to test the theory against experimental and observational evidence as they come in over time, than to attempt to make something out of the little bits and pieces of scattered evidence that we may find.I assert that the choices of which approaches to take, and which variables to study in your outlined method, will impose a deterministic outcome where one may not exist.
Another instance of a separate life emergence, or lab synthesis are THE tests for any abiogenesis theory. Until this happens, there is no reason for assuming the inevitability of exo-life emergence from ultimately unknowable, non-linear, unpredictable (over the majority of timescales), environmental conditions.


A theory doesn't need an agenda or a justified premise to get started. It only needs to be consistent with known evidence and make testable predictions. And when it starts making wrong predictions, we go back to the drawing board.And abiogenesis 'theories' (and their so-called predictive capabilities), are still on the drawing board .. and will stay there, until someone can either; reproduce life from a scratch, or another emergence is found which demonstrates the dominance of predictability, (in order to solidify prior assumptions in the theories).

A general theory of abiogenesis should answer the question of what the initial conditions must have been like for life to have emerged on Earth. So the initial conditions are implied by the theory as an explanation of how life could have emerged.The detail of the initial conditions is not traceable no matter how much evidence turns up. There is no way we could ever conclude from the theory you propose what the initial conditions must have been for life to have emerged on Earth. There is no evidence that generalised conditions you focus on, are sufficient to catalyse the emergence of life but more importantly, there is no reason to assume that these are sufficient for predictability, or inevitability.
I'll take your use of the term 'like', above, as now referring to a tentative hypothesis, rather than a scientific theory, (which asserts and predicts).

The same general theory could then be used to predict other possible conditions for the emergence of life. I disagree … for the reasons outlined above.

At the moment we don't even have a theory like this, i.e. we cannot yet explain how life emerges. The problem is not yet solved. Once we have such a theory or theories they can then be tested against whatever evidence we can find and against laboratory experiments. Until the straw-man is tested, it will have no real-world predictive capabilities, either.


And it's not the "when" and "where" type of prediction I'm talking about, as I already tried to make clear. In the example of tropical cyclones a theoretical prediction would mean predicting what kinds of conditions are conducive to the formation of tropical cyclones. So it would essentially mean explaining why tropical cyclones occur in those particular geographical zones and also explaining why they occur at those particular parts of the year. This IS 'the when' !! (See the latter emboldened phrase).

What I meant then, in the case of life, is that the same kind of theory should be developed for explaining the emergence of life, i.e. predicting what kinds of conditions are conducive to the formation of life. It seems we're now talking about an opinion of what should be developed, seemingly, in order to satisfy a requirement of predictability ?


But alien biochemistries might be completely different from Earth-life biochemistries. Why this narrow requirement? I find this view quite strange.The search for exo-life is, by necessity, modelled on Earth-life. There is only one model of Earth-life. Certain selected elements of that model, seem to now be being excluded, in order to meet the need of predictability (??)

I'd say instances of any self-replication on planets other than Earth would be a major discovery, and that's why I'm arguing for a more general theory of abiogenesis.So, an imagined discovery in the indeterminate future, now seems to be being used to justify the generalisation of the 'theory'(??)

Sure, and we can "demonstrate convincingly" certain geometric properties of circles and triangles with a ruler and compass. My point is though that chaos follows logically from simple mathematical rules, and these simple mathematical rules are sufficient to generate the phenomenon of chaos and make it available for study, all this independent of any physical experimental investigations. It can be. But the application of mathematical chaos in physics is demonstrated, and seems to play a role in these 'theories'. These 'theories', then somehow, end up attempting to 'predict' the emergence of life (??) And yet, the big lesson from the mathematical analysis of chaos, is that prediction is not possible, as the mathematical determinism behind the formulae resulting in chaos, does not map into the real world without empirical evidence.


One could develop stochastic models of chaos also - bring in some random variables and distribution functions and then do some mathematical investigations on that. You talk about chaos as if real-world chaos has some unknown mysterious properties that we don't already know about in mathematics. Chaotic phenomena in the real world can be explained from already known laws of physics such that there is no need to postulate unknowable processes. Anyway, even if there are unknowables, how are you going to prove their existence? Chaos encompasses randomness. There are no mysterious properties in chaos. The mathematical models have eliminated any of what you call 'mystery'. Real-world observation and experiment, define the Laws of nature ..which include chaotic phenomena .. ie: it exists !


Mathematically or computationally demonstrating the emergence of self-replication and evolvability in complex systems would be a big step forward and a step closer towards a general theory of abiogenesis. Developing theories to test is a much better strategy in my opinion. Deterministic chaos model outcomes will obviously be non-mappable if you're trying to do one-one mappings of model dynamics to world-dynamics, but the point is to look at the general structural similarities between the model and the real world phenomenon.That's what physics is all about. The mappings require empirical evidence, and observation.

Paul Wally
2012-Jun-08, 02:03 PM
Well Selfsim, the strawman in this instance is your persistent insinuation that mathematical modelling necessarily implies determinism. Chaos, non-linearity and randomness are all modelled mathematically.


Prediction from such a theory is then credible, but because of the parameter choices originally made. You are making exactly such a choice, by deliberately selecting (in your own words): 'general characteristics in order for the emergence of life to be likely in that environment. What about other characteristics and variables which still may influence the outcome in a non-deterministic way, but have been excluded ?

I'm not making any choice of parameters. I'm just saying what a theory of abiogenesis should be able to do if it is to be of any use as a theory. The nonlinear phenomena, you're mentioning are explainable in terms of already known physics and already known nonlinear equations. Why can't the emergence of life be explained in a similar way?


There is no way we could ever conclude from the theory you propose what the initial conditions must have been for life to have emerged on Earth. There is no evidence that generalised conditions you focus on, are sufficient to catalyse the emergence of life but more importantly, there is no reason to assume that these are sufficient for predictability, or inevitability.

Why is there no way? How do you know there is no way? We know the necessary conditions for the emergence of tropical cyclones, and the physics is not even that complicated, why must the emergence of life be treated differently?


The search for exo-life is, by necessity, modelled on Earth-life. There is only one model of Earth-life. Certain selected elements of that model, seem to now be being excluded, in order to meet the need of predictability (??)

Actually, my view is completely opposite. If it's modelled on Earth-life, that would narrow down the possibilities. A more general theory would include Earth life as one particular instance. In actuallity, it is your view that excludes possibilities.


Chaos encompasses randomness. There are no mysterious properties in chaos. The mathematical models have eliminated any of what you call 'mystery'. Real-world observation and experiment, define the Laws of nature ..which include chaotic phenomena .. ie: it exists !

... and yet your assertions imply that there are these unknowable things.

Again, allow me to clarify what the problem of abiogenesis is:
If we live in a universe working according to the known laws of nature, how does life emerge in such a universe? So this means, based on what we already know, how is the emergence of life implied?.

This is the reason why I see it as more of a theoretical problem than an empirical problem. We can follow your empirical route, but all you'll find are singular instances. With mathematics we can work with whole spaces of possibility, and nothing still prevents us from testing those possibilities against available evidence.

Gomar
2012-Jun-27, 04:13 PM
I think life is indeed inevitable; just like judgment day.
If one planet (Earth) has so many life forms, insects, amoeba, plants, animals, trees, birds, hominids, germs,
fish, etc. then logic follows so should any planet that is capable of sustaining life. The planet cant be too close or
too far from its star; has water, air, ... and abra cadabra you get life!

96% of all species that ever existed on Earth are extinct; whether because of meteorites, climate change, volcanoes,
or whatever, but life still exists. Now, if intelligent life is inevitable, that's the true question. Only hominids have
produced pyramids, writing, math, computers, space ships; thus, only hominids are capable of evolving intelligence.

MaDeR
2012-Sep-24, 03:16 PM
the immense delay between life first appearing on Earth and the emergence of complex life points to another, very different explanation for why we have yet to discover aliens.
Reasons why multi-celluar life started so late are known. In fact, multi-celluar life started almost as soon as it could (access to large energy source). Oxygenating entire planet took a little while. First saturating oceans and their bottom, rusting iron (banded iron formation (http://en.wikipedia.org/wiki/Banded_iron_formation)) and anything else on land, once oceanic sink no longer existed. Only after rusting whole world level of oxygen in air could start grow to significant percentage, killing anything live, unprotected and not evolved to deal with this nasty, extremely reactive and deadly gas. Thus Great Oxygenation Event (http://en.wikipedia.org/wiki/Great_oxygenation_event).

Other planets have different environment. For example oxygenating could took tens, not hundred milions of years - or never happened. History of our planet cannot be any indicator of anything that happens out there. We can only know that one particular way is possible - our history - and can theorize about countless other ways that may or may not work.

Of course, some folks think that not only our way is only one possible way, but also this way is completely inprobable. This stance is for me untenable and I see it as justification of their predetermined beliefs.

Githyanki
2012-Sep-24, 05:48 PM
We don't have enough information as of now to answer your question. If life is a natural-process then yes, given time. If it's a strange-accident then no.

Zo0tie
2012-Oct-07, 04:47 AM
This thread has been spawned by a sub-topic of discussion in the recent S&T Evidence and Belief (http://www.bautforum.com/showthread.php/132352-Evidence-and-belief) thread.

To get the ball rolling, I would like to pose the question:

"What theoretical bases underpin the firmer speculative conclusion that a second emergence of life might be inevitable elsewhere within the observable universe ?"

In more detail:

Are the assumptions made along the way, actually applicable to biological systems, or are they a hang-over from a backdrop of Classical Astrophysical principles, and established Physical Laws ? Are such principles and Laws, an appropriate basis for extrapolation and coming to firmer speculative outlooks, which invariably involve conclusions such as 'likely'?

I wonder .. ??

Comments welcome.

Regards

Life can be defined as a mechanism for reversing the tendency of a system to go towards disorder by the the use of an energy gradient that passes through the system to replicate self organizing ordered forms. The energy flow absorbs the disorder and halts or reverses the entropic accumulation within the system for a period of time. In low energy systems, such as frigid planets or moons order can be maintained without the need for entropic reversal for billions of years. Crystals on Pluto will no doubt last for a long time because there is little erosive energy to reduce them to powder. On worlds with a high energy flux self replication of ordered chemical states can rebuild complexity through the exploitation of the energy gradient and available material resources. If there is too much of an energy gradient or if there is insufficient resources for chemical interaction self replication can not occur and the system uniformly trends towards maximal disorder. The balance between too much and too little energy gradient and available resources to start and maintain self replication is what defines the earth. Note that this does not specifically call for any particular type of chemical basis or type of energy gradient.

MRFTest
2012-Oct-15, 09:01 PM
Universe is a place so so vast, that we can't even imagine it. We can't understand its distances. We are talking here about an unknown place, where life can exist in so many ways, that we are just one of them. And, as here on Earth there are some evil forces (murder, rapper, bad people, etc), it's "logic" to assume that life out there may also be evil or something horrible, it's a possibility.

So, in a way or another (good or bad), life may be evolving right now, in a distant world, in a distant galaxy, in a cold or a hot place, with a chemistry so different than ours, that we can't picture it.

My conclusion is: as here on Earth there are no two same dogs, there are no two same cats, nor flies, nor fish, nor delphins, nor sharks... there are not two identical human beings... although we are taking into account the same species. So, to a cosmic level: there are no two identical plantes, two identical galaxies, two identical life forms. I'm quite sure that life out there is something completely different than all we know.

Colin Robinson
2012-Oct-16, 02:55 AM
Universe is a place so so vast, that we can't even imagine it. We can't understand its distances. We are talking here about an unknown place, where life can exist in so many ways, that we are just one of them. And, as here on Earth there are some evil forces (murder, rapper, bad people, etc), it's "logic" to assume that life out there may also be evil or something horrible, it's a possibility.

So, in a way or another (good or bad), life may be evolving right now, in a distant world, in a distant galaxy, in a cold or a hot place, with a chemistry so different than ours, that we can't picture it.

My conclusion is: as here on Earth there are no two same dogs, there are no two same cats, nor flies, nor fish, nor delphins, nor sharks... there are not two identical human beings... although we are taking into account the same species. So, to a cosmic level: there are no two identical plantes, two identical galaxies, two identical life forms. I'm quite sure that life out there is something completely different than all we know.

Do you mean completely different, in the literal sense of "completely"?

Or do you mean very different?

It's true that no two planets are identical, yet don't planets have similarities too? E.g. the underlying laws of gravity are the same on different planets, even though gravity at the surface may be quite different...

By your own analogy, I would expect life on another planet to be very different, yes, but not completely different...

Selfsim
2012-Oct-16, 03:04 AM
By your own analogy, I would expect life on another planet to be very different, yes, but not completely different... .. or maybe completely absent(?)
Why not completely different, or completely absent?

agingjb
2012-Oct-16, 08:07 AM
If we observe phenomena, and there is any case for calling those phenomena "life", then there would have be some describable parallels between them and our own biosphere. Such parallels might range from tenuous generalities to chemical specifics.

I would say that it is not altogether useless to speculate, a little, beforehand, on how we might think about those parallels, allowing for the likelihood of surprise; clearly others disagree.

MRFTest
2012-Oct-16, 10:58 AM
Do you mean completely different, in the literal sense of "completely"?

Or do you mean very different?

It's true that no two planets are identical, yet don't planets have similarities too? E.g. the underlying laws of gravity are the same on different planets, even though gravity at the surface may be quite different...

By your own analogy, I would expect life on another planet to be very different, yes, but not completely different...

Take into account Titán, Saturn's moon. If some kind of bacteria is living there, it's based on methane, a whole new chemistry, and it's "near" us.


.. or maybe completely absent(?)
Why not completely different, or completely absent?

It has to be different, because every planet that we know, every star, every galaxy... every thing in the Cosmos, is unique, there are not two identical entities, so then, we are unique as human race. So, other life forms, must be different. Similar? I don't think so. Different? yes, completely. Maybe there's life inside Neptune or Jupiter, something like Carl Sagan explained. Something living in a gas giant? why not? searching liquid water in another planets just because it's the only way that life could be present, is ridiculous. We have to be opened-mind.

Selfsim
2012-Oct-16, 08:50 PM
It has to be different, because every planet that we know, every star, every galaxy... every thing in the Cosmos, is unique, there are not two identical entities, so then, we are unique as human race. So, other life forms, must be different. Similar? I don't think so. Different? yes, completely. Maybe there's life inside Neptune or Jupiter, something like Carl Sagan explained. Something living in a gas giant? why not? searching liquid water in another planets just because it's the only way that life could be present, is ridiculous. We have to be opened-mind.Welcome to CQX, MRFTest (and welcome to the notorious "If … Then … Else … Likely" Forum!) :p :)

You've made some pretty sweeping generalisations there.

I'd suggest introducing the concept of scale into a discussion about likeness/uniqueness. Both are also dependent on the observer's perspective and frame of reference. For eg: all known living things use polymers to perform four basic functions (replication, heritability, catalysis and energy utilisation (metabolism); all known life uses the same polymer polynucleotide (DNA or RNA) for storing species information, all known life duplicates this molecule; the DNA is synthesised by the same four nucleosides; all known life catalyse chemical reactions based on enzymatic catalysis, etc, etc ...

Note that each of the underlined terms above, is invariably derived from our models of how organic chemistry (on Earth) functions. (This is what I mean by 'frame of reference'). At normal everyday scales and in general terms, it is reasonable to say that all humans have noses .. there are exceptions of course, but there are good reasons to expect all humans to have something which performs the function of a nose). This does not exclude how some other discovery from elsewhere might function, and an appropriate model would have to be developed to analyse that, should it not be able to be resolved using our best Earth-based models.

Even though it may have appeared that I argue for uniqueness, randomness and therefore unpredictability at certain scales, I'm still operating within the scope of scientific principles and terms of reference. The main issue is our human expectations in thinking that all things are able to be predicted from our everyday, constrained-by-necessity perspectives. ('Constrained' in an astronomical scales sense, that is).

Science constructs generalised theories to explain phenomena beyond our everyday scales, but biology functions at everyday scales, so a generalised, universal, theoretically based abiogenesis model, is speculative until we can draw parallels from at least another non-terrestrially dwelling lifeform observable at 'everyday' scales, or perhaps one synthesised-from-scratch. Biology modelling is empirically based … which differs, (with subtlety), from the theoretical, classical Astrophysics approach .. and this aspect is frequently overlooked in Astronomy based Life fora discussions.

Whilst I'm 'with you', to a certain degree, about the speculation that 'where there's water … there's life', I wouldn't label it as strongly as 'ridiculous' .. perhaps more like; 'necessarily highly constrained' and perhaps, 'uniquely specifc to Earth' …. who knows(??)' … it is an ongoing investigation exploring a hypothesis, which posits a 'universal life' theoretical model.

Cheers

MRFTest
2012-Oct-16, 11:16 PM
Whilst I'm 'with you', to a certain degree, about the speculation that 'where there's water … there's life', I wouldn't label it as strongly as 'ridiculous' .. perhaps more like; 'necessarily highly constrained' and perhaps, 'uniquely specifc to Earth' …. who knows(??)' … it is an ongoing investigation exploring a hypothesis, which posits a 'universal life' theoretical model.Cheers

Thanks for the warm welcome :)

I'm sorry if I was not clear, but what I meant to say was that thinking in "water = life" as the ONLY formula to find extraterrestial life, is to be closed-mind. I know about the DNA, and all that... but let me ask you this: what about if the life-form out there is based in something that we can't even imagine? What if it doesn't use DNA at all? Maybe it's something completely new for us. Maybe it's incredible huge... or incredible small... who knows?

Searching a planet in the habitable zone with liquid water on its surface, would give us great hope in finding a life form similar to us (that's what we are looking for, don't we?)... but, for me, this is not mandatory for life to develop. Life might find its way in a cold world, in a hot one, who knows? maybe in an asteroid... Universe is soooo vast....

And another thing that I posted in "Gliese 581g" topic:
Does anybody consider that life out there could be... hostile? Why do we always assume that extraterrestial life is more intelligent and peaceful? here on Earth, there are/was several evil forces, human beings that are considered by me like "black and evil force" (aka, Hitler, dictatorships, a murderers, etc), so... should we expect some kind of paralelism? could be there some evil/hostile life forms?

So, without evidences, I'd like to consider both possibilities (peaceful and hostile life-forms). Of course everybody would like to find some beautiful, peaceful and innofensive life out there... but Aliens -in a sort way- or a much worse, unimaginable life-form might exist somewhere.

Colin Robinson
2012-Oct-17, 12:09 AM
Take into account Titán, Saturn's moon. If some kind of bacteria is living there, it's based on methane, a whole new chemistry, and it's "near" us.

True, though there are chemical similarities between Titan and Earth, and meteorological similarities too. Both places have lots of carbon compounds, for instance... Not to mention rivers and lakes, although the ones on Earth don't consist of methane or ethane.

Whether Titan seems weird or familiar depends on how you look at it. I'd expect organisms there to be likewise... quite different to Earth life in some ways, quite similar in others...


It has to be different, because every planet that we know, every star, every galaxy... every thing in the Cosmos, is unique, there are not two identical entities, so then, we are unique as human race. So, other life forms, must be different. Similar? I don't think so. Different? yes, completely. Maybe there's life inside Neptune or Jupiter, something like Carl Sagan explained. Something living in a gas giant? why not?

I agree that's a valid question to ask.

One argument against life in the atmosphere of Jupiter, (mentioned in the Wikipedia page: Jupiter (http://en.wikipedia.org/wiki/Jupiter#Possibility_of_life)) is that
* there is strong vertical gas circulation.
* temperatures are very different at different levels, and the deeper levels are hot enough to break down complex molecules.


searching liquid water in another planets just because it's the only way that life could be present, is ridiculous. We have to be opened-mind.

Yes, I agree.

Selfsim
2012-Oct-17, 01:22 AM
... but let me ask you this: what about if the life-form out there is based in something that we can't even imagine? What if it doesn't use DNA at all? Maybe it's something completely new for us. Maybe it's incredible huge... or incredible small... who knows? .. or there is no life form out there at all? (All possibilities have equal weighting in the light of zero data).

My answer is … 'don't know' … 'wait and see' .. the outcome(s) depend entirely on the nature of the finding.


Searching a planet in the habitable zone with liquid water on its surface, would give us great hope in finding a life form similar to us (that's what we are looking for, don't we?)… What, hope? … I don't think we need to search a planet in order to come up with that particular hope!

but, for me, this is not mandatory for life to develop. Life might find its way in a cold world, in a hot one, who knows? maybe in an asteroid... Universe is soooo vast….The vastness of the universe means nothing, without a discovery somewhere else.


… So, without evidences, I'd like to consider both possibilities (peaceful and hostile life-forms). Without evidence, what is there to consider which can further science?

Of course everybody would like to find some beautiful, peaceful and innofensive life out there…but Aliens -in a sort way- or a much worse, unimaginable life-form might exist somewhere. [/B]Well, looks to me that you've managed to imagine it .. even though you say its unimaginable!
.. A first for humankind?
… Just kidding .. :) … methinks you're not alone in imaging this kind of thing ...

Colin Robinson
2012-Oct-17, 02:53 AM
.. or there is no life form out there at all? (All possibilities have equal weighting in the light of zero data).

My answer is … 'don't know' … 'wait and see' .. the outcome(s) depend entirely on the nature of the finding.

What, hope? … I don't think we need to search a planet in order to come up with that particular hope!
The vastness of the universe means nothing, without a discovery somewhere else.

Without evidence, what is there to consider which can further science?
Well, looks to me that you've managed to imagine it .. even though you say its unimaginable!
.. A first for humankind?
… Just kidding .. :) … methinks you're not alone in imaging this kind of thing ...

To sum up your argument, Selfsim:

There is zero data about life beyond Earth, no point in speculating about it without data, and nothing to do except wait and see...

What, then, do you think is the point of having a forum called "Life in Space" at all?

Selfsim
2012-Oct-17, 06:09 AM
To sum up your argument, Selfsim:

There is zero data about life beyond Earth, no point in speculating about it without data, and nothing to do except wait and see...

What, then, do you think is the point of having a forum called "Life in Space" at all?Well, there's plenty of interesting scientific research about life to discuss, which would contribute far more knowledge to the community than mere wild, romanticised opinion-based speculation ... (and that's just for starters).

Noclevername
2012-Oct-17, 06:57 AM
Well, there's plenty of interesting scientific research about life to discuss, which would contribute far more knowledge to the community than mere wild, romanticised opinion-based speculation ... (and that's just for starters).

Which would necessarily make this thread "Life On Earth", and completely missing the point.

Labelling any speculation you don't care for as "wild" and "romanticized" merely shows that you don't get what this thread is here for.

Selfsim
2012-Oct-17, 09:28 AM
Which would necessarily make this thread "Life On Earth", and completely missing the point.

Labelling any speculation you don't care for as "wild" and "romanticized" merely shows that you don't get what this thread is here for.This thread is here because I put it here.

What are you on about?

This thread is querying the theoretical bases which appear to lead to a speculative conclusion that a second emergence elsewhere, is inevitable. Further, I explicitly asked whether any assumptions were applicable to biological systems ....


"What theoretical bases underpin the firmer speculative conclusion that a second emergence of life might be inevitable elsewhere within the observable universe ?"

... Are the assumptions made along the way, actually applicable to biological systems ...

Are you now saying that scientific research is completely irrelevant to the conclusion that a second emergence elsewhere is inevitable??

MRFTest
2012-Oct-17, 10:59 AM
There is zero data about life beyond Earth

As you may know, there have been some weird "incidents" in history.

In 1977, we have received the famous "WOW Signal". It's considered by many, as the only "proof" that there's life out there. But... since we haven't been able to receive that signal again, there's much skepticism to a certain degree. Personally and honestly, I really don't know about it. It could have been generated by an alien life form, but since we don't know the exact origin, we can't track it. The only thing we know for sure, is that it came for outer space. From which planet? was a spaceship? from where? questions that we may never be able to clarify...

Another episode: http://www.dailymail.co.uk/sciencetech/article-1316538/Gliese-581g-mystery-Scientist-spotted-mysterious-pulse-light-direction-newEarth-planet-year.html

Are these signals the definitive proof that we are not alone?

Colin Robinson
2012-Oct-17, 11:54 AM
Well, there's plenty of interesting scientific research about life to discuss, which would contribute far more knowledge to the community than mere wild, romanticised opinion-based speculation ... (and that's just for starters).

Why don't you give us an example of the interesting scientific research which is relevant to this thread and this forum?

Noclevername
2012-Oct-17, 12:18 PM
This thread is here because I put it here.

What are you on about?

This thread is querying the theoretical bases which appear to lead to a speculative conclusion that a second emergence elsewhere, is inevitable. Further, I explicitly asked whether any assumptions were applicable to biological systems ....



You ask for speculation, on a subject that by its very nature requires imaginitive thinking, then call it "wild" and "romanticized". Make up your mind.


Are you now saying that scientific research is completely irrelevant to the conclusion that a second emergence elsewhere is inevitable??

Don't put words in my mouth. I said exactly what I said, nothing more, nothing less.


ETA: I think that maybe the whole Life In Space section just isn't right for you, since you seem to have problems accepting astrobiology.

ETA More: You know what, just forget I said anything. There's just no way this discussion can end well. There's just a fundamental disconnent in our thinking about science.

Colin Robinson
2012-Oct-17, 09:25 PM
As you may know, there have been some weird "incidents" in history.

In 1977, we have received the famous "WOW Signal". It's considered by many, as the only "proof" that there's life out there. But... since we haven't been able to receive that signal again, there's much skepticism to a certain degree. Personally and honestly, I really don't know about it. It could have been generated by an alien life form, but since we don't know the exact origin, we can't track it. The only thing we know for sure, is that it came for outer space. From which planet? was a spaceship? from where? questions that we may never be able to clarify...

Another episode: http://www.dailymail.co.uk/sciencetech/article-1316538/Gliese-581g-mystery-Scientist-spotted-mysterious-pulse-light-direction-newEarth-planet-year.html

Are these signals the definitive proof that we are not alone?

Actually when I used the words "zero data" in the post you quote, that was meant as a summary of someone else's argument. I would say that there is still not enough data...

The report you've quote describes the apparent pulse of light as "suspicious". Are "suspicious" and "definitive" the same thing?

That Daily Mail report is perhaps slightly misleading in one respect. It says that Bathal "picked up the odd signal in December 2008, long before it was announced that the star Gliese 581 has habitable planets in orbit around it."

Actually people have been interested in possibility of life in the Gliese 581 system ever since discovery of Gliese 581C in 2007. See the WP entry for Gliese 581 (http://en.wikipedia.org/wiki/Gliese_581).

Colin Robinson
2012-Oct-17, 09:27 PM
As you may know, there have been some weird "incidents" in history.

In 1977, we have received the famous "WOW Signal". It's considered by many, as the only "proof" that there's life out there. But... since we haven't been able to receive that signal again, there's much skepticism to a certain degree. Personally and honestly, I really don't know about it. It could have been generated by an alien life form, but since we don't know the exact origin, we can't track it. The only thing we know for sure, is that it came for outer space. From which planet? was a spaceship? from where? questions that we may never be able to clarify...

Another episode: http://www.dailymail.co.uk/sciencetech/article-1316538/Gliese-581g-mystery-Scientist-spotted-mysterious-pulse-light-direction-newEarth-planet-year.html

Are these signals the definitive proof that we are not alone?

Actually when I used the words "zero data" in the post you quote, that was meant as a summary of someone else's argument. I would say that there is still not enough data...

The report you've quote describes the apparent pulse of light as "suspicious". Are "suspicious" and "definitive" the same thing?

That Daily Mail report is perhaps slightly misleading in one respect. It says that Bhathal "picked up the odd signal in December 2008, long before it was announced that the star Gliese 581 has habitable planets in orbit around it."

Actually people have been interested in possibility of life in the Gliese 581 system ever since discovery of Gliese 581C in 2007. See the WP entry for Gliese 581 (http://en.wikipedia.org/wiki/Gliese_581).

transreality
2012-Oct-17, 10:40 PM
.. or there is no life form out there at all? (All possibilities have equal weighting in the light of zero data).

My answer is … 'don't know' … 'wait and see' .. the outcome(s) depend entirely on the nature of the finding.

The vastness of the universe means nothing, without a discovery somewhere else.

Without evidence, what is there to consider which can further science?
...


To advance the hypothesis that life on earth is unique, would require some support as to why life would be unique to earth, surely. To be any use at all. Do you see any characteristics that were present on earth (3.4 bya) that for some reason could be considered to unique to our solar system. If no evidence for such characteristics exist, then what is the basis for your hypothesis? How is it useful, scientifically.

Selfsim
2012-Oct-18, 03:33 AM
To advance the hypothesis that life on earth is unique, would require some support as to why life would be unique to earth, surely. To be any use at all.In theory, such a hypothesis stands on an equal footing with: 'life on earth is not unique'. Both can be shown to be either falsifiable or verifiable (respectively) and theoretically, as 'Earth-like' life tests exist. Both are therefore valid hypotheses, (technically speaking).


Do you see any characteristics that were present on earth (3.4 bya) that for some reason could be considered to unique to our solar system. If no evidence for such characteristics exist, then what is the basis for your hypothesis? How is it useful, scientifically.It is not possible for us to know precisely all of the micro-environmental conditions on the Earth, at the scale relevant to the first molecular assemblage of say, a DNA molecule. Such precise detail cannot be comprehensively retraced from the geological record. Paradoxically, it can be said that it is equally possible that the eventual self-replicating outcome of pre-biotic life, might be critically dependent on just these precise conditions. (That is speculation .. but it is just as 'possible' as it not being critically dependent on these micro environmental conditions.. the 'evidence' for this may be that we have not yet succeeded in creating such functionality (in the lab) from fundamental life chemical constituents)*. Any of the 'gateway' steps through which pre-biotic life passed, which were critical to life emerging, may also have been subject to the same sensitivities and hence, uncertainty. Or even maybe, they had almost no relevance to progression through these gateway steps, (in the hitherto unknown pre-biotic sequence) … we simply have no idea at this level of scale detail. We still aren't even certain about the limits of our life-model combinations, which actually do result in life, throughout time - which could easily be of similar orders of magnitude, as the numbers of micro-environments throughout time, in the observable universe!)

The above factors impact both hypotheses in the same way … ie: not just the: 'life on Earth is unique' hypothesis.

The scientific value of recognising this, might be a realisation that this dilemma may only have very few known methods of resolution. For example: (i) recreation of self-replication from scratch, in the lab or; (ii) chance discoveries within a practically reachable search radius (from Earth), brought on purely by the act of local exploration or; (iii) a recognition that complexity modelling at micro-scales, might yield improved visibility of some constraints on 'origin' questions and; (iv) computing infrastructure development, in order to run chaos/complexity simulations as more data becomes available. Emphasis on local planet/moons exploration, accompanied by Earth-like life biological tests, would be seen as being consistent within this paradigm, and would evidently become the emerging priority, as far as space programs are concerned.

Coming to terms with the implications that in this particular area, classical determinism may not lead to any greater insights than simple, pure chance discoveries, I think, represents a huge step forward in thinking. Achieving critical mass of thinking in this domain, likewise. The potential onflowing benefits of such recognition, won't come about by dwelling on human speculative anticipation alone.

*Note, I am not saying that an absence of evidence, becomes proof of the evidence of absence. In speculative parlance however, this concept balances out the temptation to think that we actually do have evidence at an appropriate scale, (which we don't).

PS: To give a snapshot (of no particular intended scientific repute), about possible uniqueness trends, this article (http://www.universetoday.com/98006/extreme-solar-systems-why-arent-we-finding-other-planetary-systems-like-our-own/) appeared the other day:
There are several theories about the formation of the large planets in our outer solar system which involves the planets moving and migrating inward and outward during the formation process. But why didn’t the inner planets, including Earth, move in closer, too? “We don’t know why this didn’t happen in our solar system,” Ragozzine said, but added that KOI-500 will “become a touchstone for future theories that will attempt to describe how compact planetary systems form. Learning about these systems will inspire a new generation of theories to explain why our solar system turned out so differently.” … which serves as a reminder that an awareness of uniqueness is not as necessarily as unanticipated in scientific circles, as some enthusiasts might sometimes intimate. What happens if we can't find any Earth-like Solar Systems at the appropriate scale levels, which might be capable of giving rise to 'believed' pre-biotic, (or even post-biotic), chemical environments? Does this mean anything as far as exo-life is concerned?

transreality
2012-Oct-18, 10:45 PM
repeat deleted

transreality
2012-Oct-18, 10:49 PM
In theory, such a hypothesis stands on an equal footing with: 'life on earth is not unique'. Both can be shown to be either falsifiable or verifiable (respectively) and theoretically, as 'Earth-like' life tests exist. Both are therefore valid hypotheses, (technically speaking).

yet only one flies in the face of the copernician principle.



It is not possible for us to know precisely all of the micro-environmental conditions on the Earth, at the scale relevant to the first molecular assemblage of say, a DNA molecule. Such precise detail cannot be comprehensively retraced from the geological record. Paradoxically, it can be said that it is equally possible that the eventual self-replicating outcome of pre-biotic life, might be critically dependent on just these precise conditions. (That is speculation .. but it is just as 'possible' as it not being critically dependent on these micro environmental conditions.. the 'evidence' for this may be that we have not yet succeeded in creating such functionality (in the lab) from fundamental life chemical constituents)*. Any of the 'gateway' steps through which pre-biotic life passed, which were critical to life emerging, may also have been subject to the same sensitivities and hence, uncertainty. Or even maybe, they had almost no relevance to progression through these gateway steps, (in the hitherto unknown pre-biotic sequence) … we simply have no idea at this level of scale detail. We still aren't even certain about the limits of our life-model combinations, which actually do result in life, throughout time - which could easily be of similar orders of magnitude, as the numbers of micro-environments throughout time, in the observable universe!)).


If 'we simply have no idea' why in the face of the certainty that is has happened, are you arbitarily assigning a difficulty that renders the process astronomically unlikely, other than sheer personal incredulity that such a complex set of steps could occur at all.




The above factors impact both hypotheses in the same way … ie: not just the: 'life on Earth is unique' hypothesis.

The scientific value of recognising this, might be a realisation that this dilemma may only have very few known methods of resolution. For example: (i) recreation of self-replication from scratch, in the lab or; (ii) chance discoveries within a practically reachable search radius (from Earth), brought on purely by the act of local exploration or; (iii) a recognition that complexity modelling at micro-scales, might yield improved visibility of some constraints on 'origin' questions and; (iv) computing infrastructure development, in order to run chaos/complexity simulations as more data becomes available. Emphasis on local planet/moons exploration, accompanied by Earth-like life biological tests, would be seen as being consistent within this paradigm, and would evidently become the emerging priority, as far as space programs are concerned.

Coming to terms with the implications that in this particular area, classical determinism may not lead to any greater insights than simple, pure chance discoveries, I think, represents a huge step forward in thinking. Achieving critical mass of thinking in this domain, likewise. The potential onflowing benefits of such recognition, won't come about by dwelling on human speculative anticipation alone.

*Note, I am not saying that an absence of evidence, becomes proof of the evidence of absence. In speculative parlance however, this concept balances out the temptation to think that we actually do have evidence at an appropriate scale, (which we don't).

PS: To give a snapshot (of no particular intended scientific repute), about possible uniqueness trends, this article (http://www.universetoday.com/98006/extreme-solar-systems-why-arent-we-finding-other-planetary-systems-like-our-own/) appeared the other day: … which serves as a reminder that an awareness of uniqueness is not as necessarily as unanticipated in scientific circles, as some enthusiasts might sometimes intimate. What happens if we can't find any Earth-like Solar Systems at the appropriate scale levels, which might be capable of giving rise to 'believed' pre-biotic, (or even post-biotic), chemical environments? Does this mean anything as far as exo-life is concerned?


Yet the search for an earth like system is driving the planetary search. While it is true that technical methods couldn't detect a solar system, they can detect other systems that find out that 1) other planets certainly do exist 2) our system is not necessarily typical. This is turn has directly lead to investigations into why our system is not typical, or how it evolved into its current state, thinking about the stability of the planetary configuration, explaining the earths impact history, and recently the discovery of an earth-size world around one of our nearest neighbours. Deciding that our solar system was so unique that only unanticipated chance discoveries in space science unguided by any principles could be expected to yield results, and it would therefore pointless to fund any 'speculative' projects would not have got us where we are now.

The Murchison meteorite has simple organic molecules, the less energetic amino acid combinations. DNA uses some of these simple amino acids, but it also uses more complex amino acids that we know form in terrestrial environments. Would you speculate that Earth is the only place in the universe that can form complex amino acids?

Selfsim
2012-Oct-19, 06:02 AM
yet only one flies in the face of the copernician principle.Not so.
… Only so, if the Copernican Principle is inappropriately taken out of context and applied at inappropriate scales (ie:molecular biological), where the myriad of permutations occur. (More discussion on this is here (http://cosmoquest.org/forum/showthread.php/136559-Alien-invasion-scenario-s?p=2043603#post2043603)).


If 'we simply have no idea' why in the face of the certainty that is has happened, are you arbitarily assigning a difficulty that renders the process astronomically unlikely, other than sheer personal incredulity that such a complex set of steps could occur at all.This is not personal incredulity .. it comes from Evolutionary Molecular Biology, Organic Chemistry, Chaos and Complexity Theories. (I am also not claiming that abiogenesis necessarily actually works this way, either. I have posted numerous examples showing that this is quite a typical process for certain classes of organic chemical reactions). If it is typical for classes of organic chemistry, then on what basis should this chaotic behaviour be excluded from consideration in the speculative abiogenesis topic?
Whilst I realise that abiogenesis is 'pre-Evolution', (ie: as far as the emergence process is modelled), more and more research evidence is also showing that Evolution's natural selection process, also operates to 'select' the right molecules for certain functions.

All I'm saying is that by considering where such combinatorial permutations, sensitivities to perturbations, and accompanying responses arise in similar organic chemistry, a different credible perspective arises, which casts some doubt on the idea that deterministic, predictable outcomes must occur in the presence of Earth-like environments and water (for eg). If one doesn't have an understanding of Chaos Theory, Organic and Inorganic Chemistry and Classical Astrophysics areas, one simply won't recognise the significance. It is very rare that such knowledge comes together when discussing this topic. To label such as 'personal incredulity' is well, .. y'know … unjustifiably 'dismissive'.


Yet the search for an earth like system is driving the planetary search. While it is true that technical methods couldn't detect a solar system, they can detect other systems that find out that 1) other planets certainly do exist 2) our system is not necessarily typical. This is turn has directly lead to investigations into why our system is not typical, or how it evolved into its current state, thinking about the stability of the planetary configuration, explaining the earths impact history, and recently the discovery of an earth-size world around one of our nearest neighbours. Deciding that our solar system was so unique that only unanticipated chance discoveries in space science unguided by any principles could be expected to yield results, and it would therefore pointless to fund any 'speculative' projects would not have got us where we are now.Sure … see this is my point … all of what I suggest, is guided by scientific principles. It just seems that no-one here, seems to recognise those particular branches of science from where it comes! The funding already happens, because it is already recognised as legitimate science. The only incredulity I have, is related to the responses the topic seems to garner around here! There seems to be a lot of time spent on 'story' development here, rather than pursuit of legitimate scientific knowledge of other areas, which are applicable to the realities about 'life in space'! Oh well, 'to each his own', I guess ...


The Murchison meteorite has simple organic molecules, the less energetic amino acid combinations. DNA uses some of these simple amino acids, but it also uses more complex amino acids that we know form in terrestrial environments. Would you speculate that Earth is the only place in the universe that can form complex amino acids?No. It doesn't just stop with the presence of complex amino acid molecules though!
The trivialisation of the huge gap in understanding between knowledge of the molecular structure of DNA, and its behaviours under certain conditions is just, well .. <achem .. (throat clearing)>, well y'know .. gross, uninformed over-simplification of something which is extremely complex and full of unknowns .. and all glosses over the equally complex topic of just how a DNA molecule might have formed in the first place.
Gee, amino acids have also been found floating in space!
This stuff might be in lots of exotic places .. but what does that mean? (Not much, really …)

MarianoRF
2012-Oct-20, 01:46 AM
In theory, such a hypothesis stands on an equal footing with: 'life on earth is not unique'. Both can be shown to be either falsifiable or verifiable (respectively) and theoretically, as 'Earth-like' life tests exist. Both are therefore valid hypotheses, (technically speaking)

For me, life on Earth is unique. In the Cosmos, every thing is unique. You won't find two or more identical worlds. So, following this idea, I'd say that we are surronded by infinte worlds and galaxies, all of them unique. And in many of those galaxies, including our Milky Way, life may be present in millons of planets. The problem is the distance, the vastness of the Cosmos doesn't allow us to travel, neither to make contact.

ZunarJ5
2012-Oct-20, 03:32 AM
I have to say Selfsim, I admire your dogged and often vehement devotion to pure science. I have read a number of your posts throughout these boards and the consistency with which you adhere to the purest skepticism of science is as perfect as the presentation is vocal. Its fascinating.

For example, your first sentence in the quote below rings out as absolutely true to me.


Sure … see this is my point … all of what I suggest, is guided by scientific principles. It just seems that no-one here, seems to recognise those particular branches of science from where it comes! The funding already happens, because it is already recognised as legitimate science. The only incredulity I have, is related to the responses the topic seems to garner around here! There seems to be a lot of time spent on 'story' development here, rather than pursuit of legitimate scientific knowledge of other areas, which are applicable to the realities about 'life in space'! Oh well, 'to each his own', I guess ...

My question to you though, and it addresses the OP to a certain extent as well, is this; In a subject where such dismissive skepticism is so strongly backed by science that it allows one to present the argument you have been presenting, isn't it nearly impossible to have a meaningful exploration without spending some time on so called 'story' development?

Imaginitive speculation can be a boon to discovery.

Colin Robinson
2012-Oct-20, 07:26 AM
It is not possible for us to know precisely all of the micro-environmental conditions on the Earth, at the scale relevant to the first molecular assemblage of say, a DNA molecule. Such precise detail cannot be comprehensively retraced from the geological record. Paradoxically, it can be said that it is equally possible that the eventual self-replicating outcome of pre-biotic life, might be critically dependent on just these precise conditions. (That is speculation .. but it is just as 'possible' as it not being critically dependent on these micro environmental conditions..

I appreciate that you've acknowledged that you are speculating here, just like the rest of us...


...if the Copernican Principle is inappropriately taken out of context and applied at inappropriate scales (ie:molecular biological), where the myriad of permutations occur... This is not personal incredulity .. it comes from Evolutionary Molecular Biology, Organic Chemistry, Chaos and Complexity Theories. (I am also not claiming that abiogenesis necessarily actually works this way, either. I have posted numerous examples showing that this is quite a typical process for certain classes of organic chemical reactions). If it is typical for classes of organic chemistry, then on what basis should this chaotic behaviour be excluded from consideration in the speculative abiogenesis topic?

In chaos theory, the "butterfly effect" magnifies the consequences of small random perturbations. On the other hand, doesn't chaos theory also recognize "attractors", which can reduce the consequences of small random perturbations?

Can you give us a reason for thinking the butterfly effect is more relevant to the topic of this thread than the effects of attractors?

Selfsim
2012-Oct-20, 08:25 AM
My question to you though, and it addresses the OP to a certain extent as well, is this; In a subject where such dismissive skepticism is so strongly backed by science that it allows one to present the argument you have been presenting, isn't it nearly impossible to have a meaningful exploration without spending some time on so called 'story' development?

Imaginitive speculation can be a boon to discovery.Hi ZunarJ5;

Speculation in the hands of researchers following a rigorous process, is one thing ..... speculation for the purposes of sci-fi development however, is another matter entirely.

Selfsim
2012-Oct-20, 09:14 AM
I appreciate that you've acknowledged that you are speculating here, just like the rest of us...'When in Rome' ....


In chaos theory, the "butterfly effect" magnifies the consequences of small random perturbations. On the other hand, doesn't chaos theory also recognize "attractors", which can reduce the consequences of small random perturbations?

Can you give us a reason for thinking the butterfly effect is more relevant to the topic of this thread than the effects of attractors?In the context of where I've raised it, small errors made in our estimates of Earth's initial pre-biotic environmental conditions, could lead to an entirely different outcome in a different 'run' or 'trial' (second emergence), should the emergence process itself, involve non-linearities. This would compromise our ability to predict a second emergence.

Sensitivity to small changes in initial conditions, could also lead to different outcomes also, one of which could easily be 'no-life'. No-one is saying this is the way emergence operates. The behaviour is however, very common in nature and in biological systems (the majority behaviour, in fact).

It has long been known that the weather is subject to such sensitivity to initial conditions, which results in its unpredictability over comparatively tiny timeframes, (when compared with geological time). Such sensitivity is responsible for unpredictable outcomes. What I am saying is, that all this unpredictability is certainly 'possible'. So, how does one eliminate such a 'possibility' from consideration, in order to conclude that an 'Earth-like' environment would necessarily result in Earth-like life?

There is evidence that life processes themselves, rely on certain components arranging themsleves so that they are precariously balanced at critical points and without this happening, life functions would not be possible. Perturbations influencing these criticality points can easily upset this 'balancing act'.

The presence of possible attractors is just another class of system behaviour ... which might also be 'possible' in the context of life emergence.... but so what? So how would one then eliminate certain classes of attractors from consideration in the emergence scenario? ... Ie: the same question exists ... and so on.

We simply do not know. So if we do not know, in the face of all this, how can we possibly predict that exo-life is 'likely'?

Colin Robinson
2012-Oct-20, 10:09 PM
Sensitivity to small changes in initial conditions, could also lead to different outcomes also, one of which could easily be 'no-life'. No-one is saying this is the way emergence operates. The behaviour is however, very common in nature and in biological systems (the majority behaviour, in fact).

It has long been known that the weather is subject to such sensitivity to initial conditions, which results in its unpredictability over comparatively tiny timeframes, (when compared with geological time). Such sensitivity is responsible for unpredictable outcomes. What I am saying is, that all this unpredictability is certainly 'possible'. So, how does one eliminate such a 'possibility' from consideration, in order to conclude that an 'Earth-like' environment would necessarily result in Earth-like life?

You've mentioned two categories of possible outcomes, "no life" and "Earth-like life".

There is another category of possible outcomes: another Earth-like planet might produce life that is not Earth-like, in the sense that it uses a different set of catalytic molecules.

This (as I understand it) is Stuart Kauffman's position. He argues that a huge number of organic molecules have catalytic properties, and the emergence of complex self-catalysing systems is indeed likely wherever chemical activity and diversity has reached a certain level.

What is unpredictable is exactly which catalytic molecules the systems will include.


The presence of possible attractors is just another class of system behaviour ... which might also be 'possible' in the context of life emergence.... but so what? So how would one then eliminate certain classes of attractors from consideration in the emergence scenario? ...

Maybe the question to consider is what classes of attractors would the overall system eventually eliminate, and what classes of attractors would it favor?

MarianoRF
2012-Oct-20, 11:43 PM
This (as I understand it) is Stuart Kauffman's position. He argues that a huge number of organic molecules have catalytic properties, and the emergence of complex self-catalysing systems is indeed likely wherever chemical activity and diversity has reached a certain level.

What is unpredictable is exactly which catalytic molecules the systems will include.

I agree with this vision. Life out there, is completely different than all we know, just because there are not two identical planets, then, not two identical life chemistry. And, bear in mind that life out there, could be something completely unpredictable and unimaginable. Take for example, Titan, where life might be present. If this is true, that life is based on methane and acetylene.

Colin Robinson
2012-Oct-21, 03:55 AM
I agree with this vision. Life out there, is completely different than all we know, just because there are not two identical planets, then, not two identical life chemistry. And, bear in mind that life out there, could be something completely unpredictable and unimaginable. Take for example, Titan, where life might be present. If this is true, that life is based on methane and acetylene.

Even so, some characteristics of life beyond Earth may be predictable.

For instance, a number of scientists, including David Grinspoon and Chris McKay, have predicted that life on Titan, if it exists, would consume acetylene plus hydrogen (or ethane plus hydrogen) and produce methane.

Their reasoning (as I understand it) is this...

According the laws of thermodynamics, a living thing needs a energy source to keep functioning, just like a machine needs an energy source to keep functioning. Life (as often defined) is a special sort of chemical system, therefore its logical source of energy is chemical energy. We certainly know of organisms that can utilize other forms of energy, e.g. plants using sunlight, but even they do so by first converting the light energy into chemical energy (in the form of sugars).

So these scientists considered the question: Are there sources of chemical energy on Titan, and if so, what are they?

headrush
2012-Oct-21, 09:17 AM
For me, life on Earth is unique. In the Cosmos, every thing is unique. You won't find two or more identical worlds. So, following this idea, I'd say that we are surronded by infinte worlds and galaxies, all of them unique. And in many of those galaxies, including our Milky Way, life may be present in millons of planets. The problem is the distance, the vastness of the Cosmos doesn't allow us to travel, neither to make contact.

I don't think you can use the word unique quite so liberally. Exactly because of the size of the observable universe, we will probably never be able to quantify whether there are identical forms of life elsewhere.

Unique is a binary term, something is either unique or it's not. You can't be almost unique, or more unique.

Maybe you mean individual ?

Selfsim
2012-Oct-21, 09:46 AM
You've mentioned two categories of possible outcomes, "no life" and "Earth-like life".

There is another category of possible outcomes: another Earth-like planet might produce life that is not Earth-like, in the sense that it uses a different set of catalytic molecules.

This (as I understand it) is Stuart Kauffman's position. He argues that a huge number of organic molecules have catalytic properties, and the emergence of complex self-catalysing systems is indeed likely wherever chemical activity and diversity has reached a certain level. ... and yet none of these other self-catalysing alternative chemistries, appears to have ever resulted in another lifeform on Earth ... in spite of the supposed 'likelihood' that it would have!
Of all the different chemically identical polymers which could have possibly supported catalysis on Earth, (differing in say, for eg; chirality), and the thousands of thermodynamically equivalent possible glycolysis, and core metabolic pathways ... and all other molecules capable of transporting energy within a cell on Earth, we somehow ended up with just one ... and only one, specific set of these, common to all life .... with no exceptions ever found. I'd say this makes Kauffman's inference pretty well moot, wouldn't you?

What was the outcome of all the other 'trials', which presumably, were just equally as possible as eachother here on Earth? If those other 'possibiliities' are worthy of any 'weight' as far as consideration as concerned, where is the evidence of even a single alternative lifeform here on Earth that they would have led to? If there was evidence of these, then presumably, we'd then have some justifiable basis for saying that alternative chemistries do actually result in life? ... But alas, there is no evidence ever found anywhere of this speculative phenomenon.

(I think we may have just discovered the basis for eliminating some of the other attractors in your application of the concept, eh? .. If so, then we're back to only two ... 'life' and 'no life' ... phew! .. makes it a lot simpler, thank goodness!)


What is unpredictable is exactly which catalytic molecules the systems will include.Nope ... what is unpredictable, is whether speculated alternative chemical systems would result in 'life', or not .. elsewhere.
They certainly couldn't be said to 'inevitably' result in life!


Maybe the question to consider is what classes of attractors would the overall system eventually eliminate, and what classes of attractors would it favor?Well, at a guess, if you base the answer on evidence, the answer would be: (a) eliminates all but two ('life' and 'no-life') and; (b) favours two ('life' and 'no-life') ... which, in turn, leads to a third alternative ... 'unknown'.

Selfsim
2012-Oct-21, 10:03 AM
For instance, a number of scientists, including David Grinspoon and Chris McKay, have predicted that life on Titan, if it exists, would consume acetylene plus hydrogen (or ethane plus hydrogen) and produce methane. Well I suppose at least McKay admits that his 'predictions' are wrong, more often than they are right ...

Colin Robinson
2012-Oct-21, 10:52 AM
This (as I understand it) is Stuart Kauffman's position. He argues that a huge number of organic molecules have catalytic properties, and the emergence of complex self-catalysing systems is indeed likely wherever chemical activity and diversity has reached a certain level.... and yet none of these other self-catalysing alternative chemistries, appears to have ever resulted in another lifeform on Earth ... in spite of the supposed 'likelihood' that it would have!

As I think I mentioned, Kauffman's theory is that emergence of a complex self-catalysing system requires a certain level of chemical diversity...

Once it emerges, it reduces the chemical diversity. Why? Because it transforms stuff different from itself into stuff like itself. That is what "self-catalysing" means.

The reduced chemical diversity means that the emergence of a different unrelated self-catalysing system on the same planet becomes less probable.

It's what they call a "phase transition".

Colin Robinson
2012-Oct-21, 10:54 AM
Well I suppose at least McKay admits that his 'predictions' are wrong, more often than they are right ...

Argumentum ad hominem.

MarianoRF
2012-Oct-21, 02:54 PM
Even so, some characteristics of life beyond Earth may be predictable.

For instance, a number of scientists, including David Grinspoon and Chris McKay, have predicted that life on Titan, if it exists, would consume acetylene plus hydrogen (or ethane plus hydrogen) and produce methane.

Their reasoning (as I understand it) is this...

According the laws of thermodynamics, a living thing needs a energy source to keep functioning, just like a machine needs an energy source to keep functioning. Life (as often defined) is a special sort of chemical system, therefore its logical source of energy is chemical energy. We certainly know of organisms that can utilize other forms of energy, e.g. plants using sunlight, but even they do so by first converting the light energy into chemical energy (in the form of sugars).

So these scientists considered the question: Are there sources of chemical energy on Titan, and if so, what are they?

Good point, and very interesting one. I'm afraid that we won't be able to answer the question "what are they" in a short time. More missions to Titan are required, and several months of study. Personally, I think that some kind of bacteria might be present, because of its rare enviornment: http://scienceray.com/technology/nasa-discovers-that-life-forms-could-be-breathing-hydrogen-on-titan/

But... who knows... we need more missions!!


I don't think you can use the word unique quite so liberally. Exactly because of the size of the observable universe, we will probably never be able to quantify whether there are identical forms of life elsewhere.

Unique is a binary term, something is either unique or it's not. You can't be almost unique, or more unique.

Maybe you mean individual ?

I mean, unique in all senses. Tell me, how do you imagine some kind of life out there? I agree that life itself requires energy to self-develop and maintain, like an engine requires fuel in order to function. But, what kind of energy do you imagine? What kind of life are we talking about: simple (microbacterian) or complex (living organisms)? do they need food? do they fly? can they talk? or it's just something completely different? Maybe, Aliens could exist, who knows. I don't know if they will have acid for blood, but could be something like that: different than our life, unique.

Paul Wally
2012-Oct-21, 05:01 PM
In theory, such a hypothesis stands on an equal footing with: 'life on earth is not unique'. Both can be shown to be either falsifiable or verifiable (respectively) and theoretically, as 'Earth-like' life tests exist. Both are therefore valid hypotheses, (technically speaking).

No, they are not on equal footing. That life is unique to Earth is not verifiable. It is however, falsifiable, but only in considering the implications of the more useful hypothesis that life is not unique to Earth. The latter hypothesis is also fruitful in the sense that it inspires us to come up with testable hypotheses about specific life on specific planets. We can design our payload instruments based on hypothesised life and what we expect to observe if such life exists or doesn't exist. The same cannot be said of the former hypothesis, because it doesn't specify what it is that we must be looking for.

Can you provide us with possible tests or experiments for the hypothesis that life is unique to Earth?

Selfsim
2012-Oct-21, 08:18 PM
Argumentum ad hominem.No … not if its going by his own words on the topic. (http://www.youtube.com/watch?v=xlIj-BtYWn4)

- See the 29:50 mark, where McKay proudly points out just how often he is wrong ….
I've published many papers which have proven to be dead wrong.

A professional 'wrong' publishing machine(??), he seems to be, (by his own word).

Van Rijn
2012-Oct-21, 09:09 PM
... and yet none of these other self-catalysing alternative chemistries, appears to have ever resulted in another lifeform on Earth


How did you determine that?

All we have are fossil records and what we can determine from currently existing life. Fossilization is more the exception than the rule, so we'll likely never know about most of the life that has existed on Earth. Even when there are fossils, little can be determined directly about biochemistry, so generally fossils are compared to currently existing life. A second, or even multiple abiogenesis events can't be ruled out on Earth.

transreality
2012-Oct-21, 09:43 PM
This is not personal incredulity .. it comes from Evolutionary Molecular Biology, Organic Chemistry, Chaos and Complexity Theories. (I am also not claiming that abiogenesis necessarily actually works this way, either. I have posted numerous examples showing that this is quite a typical process for certain classes of organic chemical reactions). If it is typical for classes of organic chemistry, then on what basis should this chaotic behaviour be excluded from consideration in the speculative abiogenesis topic?
Whilst I realise that abiogenesis is 'pre-Evolution', (ie: as far as the emergence process is modelled), more and more research evidence is also showing that Evolution's natural selection process, also operates to 'select' the right molecules for certain functions.

All I'm saying is that by considering where such combinatorial permutations, sensitivities to perturbations, and accompanying responses arise in similar organic chemistry, a different credible perspective arises, which casts some doubt on the idea that deterministic, predictable outcomes must occur in the presence of Earth-like environments and water (for eg). If one doesn't have an understanding of Chaos Theory, Organic and Inorganic Chemistry and Classical Astrophysics areas, one simply won't recognise the significance. It is very rare that such knowledge comes together when discussing this topic. To label such as 'personal incredulity' is well, .. y'know … unjustifiably 'dismissive'.



I am sure you are familiar with the creationist argument that says that life as it appears is intrinsically unlikely, so many combinations required, like the odds of a particular draw of cards from the deck etc, so it must have been designed just so. The problem with the argument is that it doesn't recognise that life as we see is the result of a large set of stacked contingent events in evolution and history. If the events had different results then what we would see before us would not be 'no-life', instead what we would see is 'different life'. The likelihood of permutations, peturbations, variations would not necessarily lead to life exactly as we recognise it here, but with the variety of molecules, the availability of energy, the existance of mixing environments, then something is going to develop emergent complexity comparable to our biosphere. Does it act is such a way that we could call it life, who knows, certainly we are in the realm of speculation in trying to predict the characteristics of possible alien life analogs, but it is not unreasonable to expect such complexity to arise, as opposed to potentially life bearing enironments remain sterile and inert in some low energy configuration of abundant pre-biotic molecules.

Colin Robinson
2012-Oct-21, 09:45 PM
No … not if its going by his own words on the topic. (http://www.youtube.com/watch?v=xlIj-BtYWn4)

- See the 29:50 mark, where McKay proudly points out just how often he is wrong ….

A professional 'wrong' publishing machine(??), he seems to be, (by his own word).

I mentioned a specific argument by McKay about Titan, thermodynamics, and life.

You've answered that McKay gets things wrong sometimes: he even admits it...

OK...

Now would you like to tell us specifically what you think is wrong about the particular line of reasoning which I mentioned, about Titan, thermodynamics, and life?

Selfsim
2012-Oct-22, 01:48 AM
That life is unique to Earth is not verifiable. It is however, falsifiable, but only in considering the implications of the more useful hypothesis that life is not unique to Earth.You may have read what I wrote in a different way from the way I intended it. Let's not worry about what may have been abiguity in my wording .. what you say about verification/falsification viewpoints, applied to both alternatives, is the same as what I meant. That being said however, consideration of: 'life is not unique to Earth', being merely the flip-side of 'life is unique to Earth', demands equal deliberation if one is making any attempt at maintaining objectivity. This is why both are on an equal footing, given that we have no relevant evidence to tip the balance one way or the other .. which is my overall point.


The latter hypothesis is also fruitful in the sense that it inspires us to come up with testable hypotheses about specific life on specific planets. We can design our payload instruments based on hypothesised life and what we expect to observe if such life exists or doesn't exist.What test is needed if we already think life doesn't exist?? … None in particular of course, thereby also highlighting the flaw in focussing too heavily on this equally biased perspective.

Where is there a benefit for maintaining a balanced viewpoint on both perspectives? … Take the Viking tests as a demonstration of exactly why we shouldn't assume specifics, and then over-engineer tests, all based on speculative thinking. The Viking tests yielded basically no conclusion, supposedly because of an 'hypothesis' along the lines you argue in favour of. NASA learned from this experience .. the evidence being that Curiosity is designed with way less specific experiments .. hopefully thus allowing whatever might be there, to reveal itself, free from these speculative ideas. (Ie: the 'follow the data' approach). Parts of the Viking experiments were clearly demonstrated to be specifically how not to design an experiment based on the 'life exists' premise, (supposedly because of the effects of unforeseen perchlorate release on organics, for eg ...)


The same cannot be said of the former hypothesis, because it doesn't specify what it is that we must be looking for.

Can you provide us with possible tests or experiments for the hypothesis that life is unique to Earth?The presence of any of the rovers may lead to a discovery … gee, even a simple camera could possibly do the trick …. depending on what may/may not be there, to be found. Clearly sending only a camera, may end up disappointing, if whatever might reside there, cannot be resolved by visual examination of images! (The 'apparently' invisible elf syndrome). There's a balance which evolves from a balanced initial perspective, which optimises the return.

Pursuing the 'does not exist' option, invariably leads to the same result as the 'exists' option, if both verification and falsification testing is held in mind. All that matters in the end, is that the experiment is designed to produce a specific outcome. The verification and falsification approaches are two sides of the same coin … one doesn't design an experiment to 'prove' (or disprove) an hypothesis, either.

Selfsim
2012-Oct-22, 04:46 AM
... and yet none of these other self-catalysing alternative chemistries, appears to have ever resulted in another lifeform on Earth. How did you determine that? Well, now, let's see …

"As of 15 October 2012, GenBank release 192.0 has 157,889,737 loci, 145,430,961,262 bases, from 157,889,737 reported sequences*"… and not one of them has non-nucleic acid genetic material. All make use of our standard genetic code, in spite of the vast number of other theoretical 'possibilities'. They all use the same polymers and have the same chiralities. All use the same ATP for energy transfer .. and this is just for starters …

Notice in my quoted words above, I used the word 'appears'. This was deliberate, as there always exists the 'possibility' that falsification of the LUCA theory will be found. This theory is presently widely regarded as being capable of producing 'strong' predictions. The current 'strong' prediction, is that we will never find any modern species from known phyla on Earth with non-nucleic acid genetic material, or one which does not use the standard genetic code.


All we have are fossil records and what we can determine from currently existing life. Fossilization is more the exception than the rule, so we'll likely never know about most of the life that has existed on Earth. Even when there are fossils, little can be determined directly about biochemistry, so generally fossils are compared to currently existing life. A second, or even multiple abiogenesis events can't be ruled out on Earth.Sure … and I didn't say that it was ruled out.

*See http://en.wikipedia.org/wiki/Genbank

Selfsim
2012-Oct-22, 05:55 AM
I am sure you are familiar with the creationist argument that says that life as it appears is intrinsically unlikely, so many combinations required, like the odds of a particular draw of cards from the deck etc, so it must have been designed just so. The problem with the argument is that it doesn't recognise that life as we see is the result of a large set of stacked contingent events in evolution and history.Evolution is not about pure randomness. I agree that the Creationist arguments, like the one you mention, represent a misconception about how mutation and natural selection works. Chaos is a different mode of natural systems behaviour, quite separate from the Creationist randomness argument. Proximity with criticality is what life seems to have mastered .. (all underpinned by the laws of physics and chemistry). Unpredictability means just that ... 'unpredictable'.

If the events had different results then what we would see before us would not be 'no-life', instead what we would see is 'different life'. The likelihood of permutations, peturbations, variations would not necessarily lead to life exactly as we recognise it here, but with the variety of molecules, the availability of energy, the existance of mixing environments, then something is going to develop emergent complexity comparable to our biosphere. Then where is the evidence supporting this assertion?
I'm afraid that Physics and Chemistry theory cannot give us definitive answers about a system as complex as life. For example, whilst other molecules such as CTP, TTP, UTP, ITP, (etc), might be shown to be theoretically capable of the same task as ATP, in Biology, empirical evidence must be produced in order to demonstrate relevance.
I think this is where Biology and Astrophysical speculation deviate from eachother.
I mean, the next time your doctor recommends your taking some kind of drug, wouldn't you expect there to have been a lot of rigorous, empirically blind trials to have been conducted?

Whilst bio-engineering and synthesis of things like ribosomes, (from their consituents), have been demonstrated to result in viable 'machinery', I'm not aware of where any alterntive 'fundamental' substitutions, (ie: of the basic essentials of cellular life), have been shown to actually result in viable life in the lab. (This is not to say that the added component of evolutionary processes acting over such substitutions, wouldn't make the difference .. but yet again, this is yet again 'terra incognita'.

Might anyone here be aware of any such examples?
(After all, I do acknowledge the classically-based, theoretical 'possibility' .. its the relative 'importance' of it, which is a matter of pure opinion ... ).


Does it act is such a way that we could call it life, who knows, certainly we are in the realm of speculation in trying to predict the characteristics of possible alien life analogs, I agree that trying to predict the characteristics of emergent complexity, other than our own 'life' characteristics, are in the realm of speculation.
but it is not unreasonable to expect such complexity to arise, as opposed to potentially life bearing enironments remain sterile and inert in some low energy configuration of abundant pre-biotic molecules.We shall see, eh? We shall see ... (ie: let's go where the data leads us ... as opposed to making non-evidence based speculations about what the outcomes 'might' be).

All we presently know, is that there is no evidence of other modern lifeforms having emerged from significant excursions, beyond the bounds of the standard genetic model, (and other components of LUCA theory).

Selfsim
2012-Oct-22, 06:35 AM
Even so, some characteristics of life beyond Earth may be predictable.

For instance, a number of scientists, including David Grinspoon and Chris McKay, have predicted that life on Titan, if it exists, would consume acetylene plus hydrogen (or ethane plus hydrogen) and produce methane.

Their reasoning (as I understand it) is this...

According the laws of thermodynamics, a living thing needs a energy source to keep functioning, just like a machine needs an energy source to keep functioning. Life (as often defined) is a special sort of chemical system, therefore its logical source of energy is chemical energy. We certainly know of organisms that can utilize other forms of energy, e.g. plants using sunlight, but even they do so by first converting the light energy into chemical energy (in the form of sugars).

So these scientists considered the question: Are there sources of chemical energy on Titan, and if so, what are they?
I mentioned a specific argument by McKay about Titan, thermodynamics, and life.

You've answered that McKay gets things wrong sometimes: he even admits it...

OK...

Now would you like to tell us specifically what you think is wrong about the particular line of reasoning which I mentioned, about Titan, thermodynamics, and life? Well, for starters, the 'logic' leading one towards assuming that the source of energy is purely chemical, is presently under investigation ... (http://physicsworld.com/cws/article/news/2012/oct/10/a-casimir-force-for-life)


It was known that above 25 °C membranes isolated from live mammal cells exist in a single liquid phase, whereas below that temperature they separate out into two distinct phases, composed of different kinds of lipids and proteins – a bit like oil and water refusing to mix when brought together. What Veatch's group discovered was that as they lowered the temperature of the membranes close to that at which the phases separate out, known as the critical point, small fluctuating patches of the second phase started to appear. Such fluctuations – which measured several microns across and were visible in an optical microscope – do not require large amounts of energy to form.
...
He found that, as expected, the forces are attractive for like proteins and repulsive for unlike ones, and that they yield a potential energy several times that of the proteins' thermal energy, over distances of tens of nanometres. Much stronger electrostatic interactions, he explains, are limited to ranges of about a nanometre by the screening effects of ions inside the cell. "We have found that by tuning close to criticality, cells have arranged for a long-ranged force to act between proteins," he says.

Sethna adds a broader perspective. "It is amazing how many reactions in cells all involve energies of the same size as thermal fluctuations," he says. "We think that it is the cell being economical – why pay more?"Note that his research has its skeptics at present .. but that's a good thing! :)

The idea that cells can derive energy from quantum mechanically initiated phase transitions, points to the non-linearly behaving, random end of the physics spectrum. (This is not a new idea, either).

MarianoRF
2012-Oct-22, 12:04 PM
I am sure you are familiar with the creationist argument that says that life as it appears is intrinsically unlikely, so many combinations required, like the odds of a particular draw of cards from the deck etc, so it must have been designed just so. The problem with the argument is that it doesn't recognise that life as we see is the result of a large set of stacked contingent events in evolution and history. If the events had different results then what we would see before us would not be 'no-life', instead what we would see is 'different life'. The likelihood of permutations, peturbations, variations would not necessarily lead to life exactly as we recognise it here, but with the variety of molecules, the availability of energy, the existance of mixing environments, then something is going to develop emergent complexity comparable to our biosphere. Does it act is such a way that we could call it life, who knows, certainly we are in the realm of speculation in trying to predict the characteristics of possible alien life analogs, but it is not unreasonable to expect such complexity to arise, as opposed to potentially life bearing enironments remain sterile and inert in some low energy configuration of abundant pre-biotic molecules.

Interesting analysis, I agree with you. The thing is, we are thinking in the odds that life as we know it, would have been emerged somewhere. And there are many variables to take into account, maybe more than we can imagine. But, life as we know it, has developed here, on planet Earth. So, if we take into account the vastness of the space, there are infinte alien worlds for the same process to happen. And, when we calculate -or at least, estimate- in figures the number of worlds, well, that's a huge number... just in our Milky Way. And how many galaxies are there? millons. So... that huge number continues to increase... as you can see, from a mathematical point of view, there are MANY, MANY possibilities that there's life out there. The problem is, the huge distances in order to make contact, or being detected.


You may have read what I wrote in a different way from the way I intended it. Let's not worry about what may have been abiguity in my wording .. what you say about verification/falsification viewpoints, applied to both alternatives, is the same as what I meant. That being said however, consideration of: 'life is not unique to Earth', being merely the flip-side of 'life is unique to Earth', demands equal deliberation if one is making any attempt at maintaining objectivity. This is why both are on an equal footing, given that we have no relevant evidence to tip the balance one way or the other .. which is my overall point.

In my opinion, life on Earth is unique. Life out there, has to be different. Why? because there are not two identical enviornments, so each planet, each star, each solar system, has its own parameters, where certain types of life, might have evolved in THAT particular enviornment, different than our's.

Selfsim
2012-Oct-22, 08:26 PM
Interesting analysis, I agree with you. The thing is, we are thinking in the odds that life as we know it, would have been emerged somewhere. And there are many variables to take into account, maybe more than we can imagine. But, life as we know it, has developed here, on planet Earth. So, if we take into account the vastness of the space, there are infinte alien worlds for the same process to happen. And, when we calculate -or at least, estimate- in figures the number of worlds, well, that's a huge number... just in our Milky Way. And how many galaxies are there? millons. So... that huge number continues to increase... as you can see, from a mathematical point of view, there are MANY, MANY possibilities that there's life out there. The problem is, the huge distances in order to make contact, or being detected.MarianoRF;
I have no problems with people stating their opinions on this issue. (Just sayin'). I have no desire to change those opinions .. after all, everyone's got one. I think you'd be welcome to express them as opinions, but I also think you might find conversations drawn from them become quite 'brief'. Opinions formed from evidence on the other hand, allow other folk some leeway to discuss the interpretation of that evidence.

I do have a problem with folk distorting science as a way of making their opinions 'right'. From a mathematical point of view, it matters not how many galaxies, Earth-like planets, habitable zones, exo-moons, etc there are …. it makes zero difference (from a statistical perspective) … unless another example of life is discovered elsewhere. Extrapolation from a sample size of one, is not a valid mathematical operation to draw conclusions from. Studies making use of Bayesian analysis techniques have shown that the only difference maker in statistical studies, invariably turns out to be one's own initial pet view (or opinion), which in our case, and by necessity, has to be drawn from explanations developed from observations our own past and presence/existence. (Unless of course, one is from Alien parentage. :) )

As a consequence, and by necessity, most discussions in this forum are framed in terms of 'like' 'might', 'possibility', etc.


In my opinion, life on Earth is unique. Right … got it!
Life out there, has to be different. Why? because there are not two identical enviornments, so each planet, each star, each solar system, has its own parameters, where certain types of life, might have evolved in THAT particular enviornment, different than our's.I think this is the same argument as that pertaining to the sensitivity emerging life might have to the environment from which it emerges. I'd like to re-emphasise that I, for one, have no idea whether the 'sensitivity' premise is valid or not. My point has been that until we have another sample of non-Earth (or synthesised) life to compare with, we won't have any idea as to the validity of the idea. The results flowing on from that idea, (or premise), are on an equal footing as most others, due to a lack of relevant data. That doesn't make the idea right, or gives it any special meaning. It does seem to cause some grief for those who have convinced themselves (in the absence of data) that the emergence of life elsewhere is in fact, inevitable.

Colin Robinson
2012-Oct-22, 11:23 PM
I am sure you are familiar with the creationist argument that says that life as it appears is intrinsically unlikely, so many combinations required, like the odds of a particular draw of cards from the deck etc, so it must have been designed just so.

An often-quoted argument, that abiogenesis is extremely improbable, was published back in 1947, by the French scientist Pierre Lecomte du Noüy, based on earlier work by Charles-Eugene Guye. The calculation concerned odds that a particular protein molecule containing a couple of thousand atoms would form by random combination of atoms... Odds against, of ten to the power of two hundred and something... Du Noüy went on to say that a single molecule would not have been enough anyway... He argued that science itself points to the conclusion that the origin of life was a miracle.


The problem with the argument is that it doesn't recognise that life as we see is the result of a large set of stacked contingent events in evolution and history. If the events had different results then what we would see before us would not be 'no-life', instead what we would see is 'different life'.

Yes, that is a possibility that Guye and Du Noüy seem not to have considered...

To estimate your chances of winning a game of cards, it is not enough to estimate the odds of particular draw, you also have to look at the total number of possible winning draws.

E.g. What are the chances that a randomly selected protein-like molecule (a peptide) can perform a particular catalytic function? This is discussed in Stuart Kauffman's paper Approaches to the Origin of Life on Earth (http://www.mdpi.com/2075-1729/1/1/34), which is available as a free PDF download.

According to Kauffman, the probability that a random peptide will bind to a particular ligand is about one in a million. This alone would not enable it to complete the catalytic function, but it's a good start... And one in a million is not bad odds, if you happen to have millions of molecules to play with...

MarianoRF
2012-Oct-23, 12:15 AM
I do have a problem with folk distorting science as a way of making their opinions 'right'. From a mathematical point of view, it matters not how many galaxies, Earth-like planets, habitable zones, exo-moons, etc there are …. it makes zero difference (from a statistical perspective) … unless another example of life is discovered elsewhere.

I don't agree. So, you must see it before believing, right? You should think that we may never be able to find the evidence, never. Because, as I said, distances are too vast for us to travel/observe. So? because there's zero evidence and until we find it, we say "life out there doesn't exist"? wrong. We should say: life out there MIGHT exist, and it's almost a matter of common sense.
However, I do agree with you in that: as there's zero evidence, we'll always use these words: MAY, MAYBE, MIGHT, COULD... this is a big hypothesis, and it may remain like that forever.

Paul Wally
2012-Oct-23, 12:16 AM
From a mathematical point of view, it matters not how many galaxies, Earth-like planets, habitable zones, exo-moons, etc there are …. it makes zero difference (from a statistical perspective) … unless another example of life is discovered elsewhere.

That's incorrect. If the emergence of life is a non-zero probability event then a larger number of planets, stars, galaxies etc. increases the likelihood that it also happened somewhere else.


My point has been that until we have another sample of non-Earth (or synthesised) life to compare with, we won't have any idea as to the validity of the idea. The results flowing on from that idea, (or premise), are on an equal footing as most others, due to a lack of relevant data. That doesn't make the idea right, or gives it any special meaning. It does seem to cause some grief for those who have convinced themselves (in the absence of data) that the emergence of life elsewhere is in fact, inevitable.

The issue is how we should go about in finding another sample. Do we want to find it sooner rather than later?



No, they are not on equal footing. That life is unique to Earth is not verifiable. It is however, falsifiable, but only in considering the implications of the more useful hypothesis that life is not unique to Earth. The latter hypothesis is also fruitful in the sense that it inspires us to come up with testable hypotheses about specific life on specific planets. We can design our payload instruments based on hypothesised life and what we expect to observe if such life exists or doesn't exist. The same cannot be said of the former hypothesis, because it doesn't specify what it is that we must be looking for.

Can you provide us with possible tests or experiments for the hypothesis that life is unique to Earth?

You may have read what I wrote in a different way from the way I intended it. Let's not worry about what may have been abiguity in my wording .. what you say about verification/falsification viewpoints, applied to both alternatives, is the same as what I meant. That being said however, consideration of: 'life is not unique to Earth', being merely the flip-side of 'life is unique to Earth', demands equal deliberation if one is making any attempt at maintaining objectivity. This is why both are on an equal footing, given that we have no relevant evidence to tip the balance one way or the other .. which is my overall point.

So how are we going to verify that life is unique to Earth? If it's not verifiable then it's an invisible elf.


What test is needed if we already think life doesn't exist??

We don't think that. Non-existence is simply the negative outcome of testing the hypothesis.


The Viking tests yielded basically no conclusion, supposedly because of an 'hypothesis' along the lines you argue in favour of. NASA learned from this experience .. the evidence being that Curiosity is designed with way less specific experiments .. hopefully thus allowing whatever might be there, to reveal itself, free from these speculative ideas. (Ie: the 'follow the data' approach). Parts of the Viking experiments were clearly demonstrated to be specifically how not to design an experiment based on the 'life exists' premise, (supposedly because of the effects of unforeseen perchlorate release on organics, for eg ...)

Exactly! They learned something. That's the whole point of posing hypotheses and testing it.

It's fine if you think that the "follow the data approach" (whatever that means) will lead to exolife discovery sooner rather than later. I prefer a more systematic approach, like the Curiosity mission. With Curiosity mission there is an hypothesis called past habitability on Mars. The outcome is going to be positive, negative or inconclusive, just like the Viking Mission.



The presence of any of the rovers may lead to a discovery … gee, even a simple camera could possibly do the trick …. depending on what may/may not be there, to be found. Clearly sending only a camera, may end up disappointing, if whatever might reside there, cannot be resolved by visual examination of images! (The 'apparently' invisible elf syndrome). There's a balance which evolves from a balanced initial perspective, which optimises the return.

Your lack of consideration for the science payload suggests a different kind of optimization and that is: You want to reduce the chances of making an exo-life discovery with as much as possible without making it apparent that you don't really care about such a discovery.

Colin Robinson
2012-Oct-23, 12:27 AM
Well, for starters, the 'logic' leading one towards assuming that the source of energy is purely chemical, is presently under investigation ... (http://physicsworld.com/cws/article/news/2012/oct/10/a-casimir-force-for-life)

Note that his research has its skeptics at present .. but that's a good thing! :)

The idea that cells can derive energy from quantum mechanically initiated phase transitions, points to the non-linearly behaving, random end of the physics spectrum. (This is not a new idea, either).

If Sarah Veatch is right about Casimir forces operating between lipid molecules in cellular membranes, it's a very interesting finding...

But would it argue against Gerald F. Joyce's definition of life as a "self-sustaining chemical process that can undergo Darwinian evolution"? I'm not sure it would, because I'm not convinced by your distinction between quantum mechanics and the "purely chemical". Chemistry is about the way atoms and molecules interact, and modern chemistry is very largely based on quantum mechanics.

And would it mean that living things can now live quite happily without sources of chemical energy -- exothermic reactions that are simple in terms of their overall inputs and outputs, though intricate in terms of the catalytic mechanisms -- reactions such as oxidization of sugars, or (in reducing environments) hydrogenation of carbon dioxide?

I'm not sure it would mean that either...

Selfsim
2012-Oct-23, 08:20 AM
I do have a problem with folk distorting science as a way of making their opinions 'right'. From a mathematical point of view, it matters not how many galaxies, Earth-like planets, habitable zones, exo-moons, etc there are …. it makes zero difference (from a statistical perspective) … unless another example of life is discovered elsewhere.I don't agree.Ok then go right ahead .. be my guest ... prove it here, using mathematics!

So, you must see it before believing, right?Belief is irrelevant.
You should think that we may never be able to find the evidence, never. Is that a question, or a statement?
Because, as I said, distances are too vast for us to travel/observe. So? because there's zero evidence and until we find it, we say "life out there doesn't exist"? wrong. We should say: life out there MIGHT exist, and it's almost a matter of common sense.
We know of extant life on one planet only.

The existence of life on Earth, does not infer life elsewhere.


However, I do agree with you in that: as there's zero evidence, we'll always use these words: MAY, MAYBE, MIGHT, COULD... this is a big hypothesis, and it may remain like that forever.
But wait! ... There's a third alternative! ... "Unknown !! .. (for the time being)!!

Paul Wally
2012-Oct-23, 11:21 AM
But wait! ... There's a third alternative! ... "Unknown !! .. (for the time being)!!

As far as I know, the only life-form capable of that feat is Schrodinger's cat. :D

MarianoRF
2012-Oct-23, 02:53 PM
It's fine if you think that the "follow the data approach" (whatever that means) will lead to exolife discovery sooner rather than later. I prefer a more systematic approach, like the Curiosity mission. With Curiosity mission there is an hypothesis called past habitability on Mars. The outcome is going to be positive, negative or inconclusive, just like the Viking Mission.

Speaking of Curiosity... until now, they didn't find any evidence of ancient life signs... right? They did found evidence of ancient oceans, rivers and lakes... but still, no signs of bacterias...


The existence of life on Earth, does not infer life elsewhere.

But it leaves a door open. If life happened here, it could happen in another similar or different world. Every planet is its own Universe. And in every planet, there's a unique composition of chemicals reactions. Can some form of life develop in those conditions? we simply don't know. Could be, couldn't be. For me, life always finds itw way. It adapts. It develops.

Selfsim
2012-Oct-23, 08:58 PM
That's incorrect. If the emergence of life is a non-zero probability event then a larger number of planets, stars, galaxies etc. increases the likelihood that it also happened somewhere else.If the emergence of life is dependent on outcomes of stacked sets of unique contingent events, then there is no increase in 'likelihood'.


The issue is how we should go about in finding another sample. Do we want to find it sooner rather than later?Exploration of reachable targets would seem to be the appropriate strategy.


So how are we going to verify that life is unique to Earth? If it's not verifiable then it's an invisible elf.What classic! The two 'hypotheses' are flip-sides of the same coin. One is not practically falsifiable, as the entire search space cannot be searched (if life is rare), and the other is not practically verifiable (that life is unique to Earth) - for the same reason. You are now convincingly arguing that the quest for: 'Exo-life exists' is empirically unscientific (from a practicality perspective), because both aspects cannot be practically tested.
Well done. I rest my case ….



What test is needed if we already think life doesn't exist?? … None in particular of course, thereby also highlighting the flaw in focussing too heavily on this equally biased perspective.We don't think that. Non-existence is simply the negative outcome of testing the hypothesis.So therefore we can conclude that 'exo-life does not exist' once the test is applied in, now let me see, how many habitable locations did you say??… ( … where's my dice ... so I can roll them to make today's call on that) ….


Exactly! They learned something. That's the whole point of posing hypotheses and testing it. What they learned came from the Phoenix mission wet chemistry soil tests … not Viking's L/R (etc) biological tests!


Your lack of consideration for the science payload suggests a different kind of optimization and that is: You want to reduce the chances of making an exo-life discovery with as much as possible without making it apparent that you don't really care about such a discovery.Well that's a bunch of assumptions and wild conclusions about where I was coming from with my above words, right there …. who said I haven't considered the science payload? I've written entire threads about this! (http://cosmoquest.org/forum/showthread.php/137170-Mars-Organics-and-Curiosity)

Its true that I have no particular vested interest, one way or the other, about the discovery of exo-life, should it happen. Why should I care? Apart from satisfying some curiosity about the topic, I'd much prefer to remain unbiased and 'un-obsessed' about it. At least that way, if something does come along which has merit, I can look at it with impartiality before making any premature conclusions (or new sci-fi stories, which seems to be an emerging trend …)

Paul Wally
2012-Oct-24, 04:08 AM
Speaking of Curiosity... until now, they didn't find any evidence of ancient life signs... right? They did found evidence of ancient oceans, rivers and lakes... but still, no signs of bacterias...

As of yet, no evidence of past or present life has been found on Mars. However, the possibility that such evidence may be found in the future is not yet ruled out either. Indeed, they did find abundant evidence that there was liquid water on the surface of Mars at some time in the past. I think it is still uncertain whether that water took the form of general surface features like lakes, rivers or oceans, or whether it was just episodic or periodic flooding caused by melting ice. A question that I've been pondering is that if there were large bodies of surface water on Mars for extended periods, whether there was then also some kind of water cycle, i.e. did it rain on Mars?



If the emergence of life is dependent on outcomes of stacked sets of unique contingent events, then there is no increase in 'likelihood'.

That would make the emergence of life a zero-probability event, which would not be like the rolling of dice but more like rolling a perfectly smooth sphere where the life outcome is a single mathematical point on that sphere.


Exploration of reachable targets would seem to be the appropriate strategy.

It looks more like no strategy. So we shouldn't explore other solar systems remotely because they are physically unreachable?



What classic! The two 'hypotheses' are flip-sides of the same coin. One is not practically falsifiable, as the entire search space cannot be searched (if life is rare), and the other is not practically verifiable (that life is unique to Earth) - for the same reason. You are now convincingly arguing that the quest for: 'Exo-life exists' is empirically unscientific (from a practicality perspective), because both aspects cannot be practically tested.
Well done. I rest my case ….

That's because you believe that the two are flip-sides of the same coin. It's not a symmetrical situation. Only positive verifiability defines scientific meaningfulness, according logical positivism at least. That is also what van Rijn's invisible elf refers to; something that cannot be verified in principle is not scientifically meaningful. So let me ask you this question: If life is unique to Earth how would we ever verify that fact? Is there even anything deducible from that hypothesis such that if it is ever observed will tell us that life is indeed unique to Earth?



So therefore we can conclude that 'exo-life does not exist' once the test is applied in, now let me see, how many habitable locations did you say??… ( … where's my dice ... so I can roll them to make today's call on that) ….


We would be testing for the existence of a postulated life-form at the location where-ever it is tested. A negative result would mean that the postulated life doesn't exist at that location. If we work from the hypothesis that exo-life exists then we are free to postulate any particular kind of life based on our definition of life and the laws of nature, and then test for that particular form of life. If however, we work from the hypothesis that life is unique to Earth then there is no possible test that we could perform at that location that could possibly confirm that Earth is the only planet with life on it. At least, none comes to mind, but I would expect you to provide us with some more detail as to what such a test procedure would entail.



What they learned came from the Phoenix mission wet chemistry soil tests … not Viking's L/R (etc) biological tests!


It is precisely because Viking performed those tests that we have the luxury of retrospective judgment and, by your own admission, design follow-up missions based on what we have learned. Inconclusive results can sometimes be the most interesting.




Its true that I have no particular vested interest, one way or the other, about the discovery of exo-life, should it happen. Why should I care? Apart from satisfying some curiosity about the topic, I'd much prefer to remain unbiased and 'un-obsessed' about it. At least that way, if something does come along which has merit, I can look at it with impartiality before making any premature conclusions (or new sci-fi stories, which seems to be an emerging trend …)

And if exo-life is eventually discovered to exist somewhere under very specific test conditions predicted by theoretical speculation will you then give credit to the full process that made the discovery possible?

Selfsim
2012-Oct-24, 09:15 AM
If Sarah Veatch is right about Casimir forces operating between lipid molecules in cellular membranes, it's a very interesting finding… I agree … :surprised:
(I'd also agree with the view that it might be a more interesting discussion topic …)

But would it argue against Gerald F. Joyce's definition of life as a "self-sustaining chemical process that can undergo Darwinian evolution"? I'm not sure it would, because I'm not convinced by your distinction between quantum mechanics and the "purely chemical". Chemistry is about the way atoms and molecules interact, and modern chemistry is very largely based on quantum mechanics.I don't think it changes the idea of the 'evolvability' of chemistry very much at all(??)


And would it mean that living things can now live quite happily without sources of chemical energy -- exothermic reactions that are simple in terms of their overall inputs and outputs, though intricate in terms of the catalytic mechanisms -- reactions such as oxidization of sugars, or (in reducing environments) hydrogenation of carbon dioxide?

I'm not sure it would mean that either...Interestingly, I think the idea of Casmir forces being coralled for signalling of this type, is closely related to the newly emerging physics associated with soft matter. The soft matter physics field is presently at a cross-roads of divergence between a physical chemistry approach, and a complex systems approach .. and the crux of the matter seems to revolve around biophysics. It seems that the behaviours of soft matter in biological systems are subject to: "large thermal fluctuations, a wide variety of forms, sensitivity of equilibrium structures to external conditions, macroscopic softness, and metastable states".

Whilst we might be talking about how a modern-day cell goes about its business, the way it functions in the present day, 'probably' points more to the way it emerged, rather than to a backdrop of the more formulaic, classical chemistry approach (with all its rigidity and predictability). More background here. (http://en.wikipedia.org/wiki/Soft_condensed_matter)

Fields of study like this, are advancing thinking about the complex interplay between chemistry, physics and biology, (and I think its leaving 'Astrobiologists' in a wake of its dust). It certainly seems to have done so, for those thinking that life necessarily (or inevitably) functions from a fixed set of physical conditions and linear relationships.

MarianoRF
2012-Oct-24, 11:38 AM
As of yet, no evidence of past or present life has been found on Mars. However, the possibility that such evidence may be found in the future is not yet ruled out either. Indeed, they did find abundant evidence that there was liquid water on the surface of Mars at some time in the past. I think it is still uncertain whether that water took the form of general surface features like lakes, rivers or oceans, or whether it was just episodic or periodic flooding caused by melting ice. A question that I've been pondering is that if there were large bodies of surface water on Mars for extended periods, whether there was then also some kind of water cycle, i.e. did it rain on Mars?

Interesting question. Well, I think we won't be able to find the answer... if it happened, it happened million of years ago... so we can't be sure. We can estimate or think that there was some kind of water cycle... but given the present facts, we can't be totally sure.
For me, the big big question is: we are quite sure that liquid water was once present in abundance on the surface of Mars, in its ancient past. So, what happened with those oceans, lakes and rivers? What catastrophic event evaporated that huge amount of water?


That's because you believe that the two are flip-sides of the same coin. It's not a symmetrical situation. Only positive verifiability defines scientific meaningfulness, according logical positivism at least. That is also what van Rijn's invisible elf refers to; something that cannot be verified in principle is not scientifically meaningful. So let me ask you this question: If life is unique to Earth how would we ever verify that fact? Is there even anything deducible from that hypothesis such that if it is ever observed will tell us that life is indeed unique to Earth?

We would be testing for the existence of a postulated life-form at the location where-ever it is tested. A negative result would mean that the postulated life doesn't exist at that location. If we work from the hypothesis that exo-life exists then we are free to postulate any particular kind of life based on our definition of life and the laws of nature, and then test for that particular form of life. If however, we work from the hypothesis that life is unique to Earth then there is no possible test that we could perform at that location that could possibly confirm that Earth is the only planet with life on it. At least, none comes to mind, but I would expect you to provide us with some more detail as to what such a test procedure would entail.

It is precisely because Viking performed those tests that we have the luxury of retrospective judgment and, by your own admission, design follow-up missions based on what we have learned. Inconclusive results can sometimes be the most interesting.

The "problem" in the search for ET life, is that we don't know exactly what to look for. I mean, if we think that life out there is similar to us (which I highly doubt), we design equipment to make experiments based on the life-chemistry that we know. But, what if life out there is something completely new and totally different than our's? How could we find it? We know nothing about its chemistry and biological patterns. So, maybe what's happening in the search of ET life, is that we are searching in "our biological terms", not in the "biological terms of ET life". Hope that I made myself clear.

Paul Wally
2012-Oct-24, 05:07 PM
Interestingly, I think the idea of Casmir forces being coralled for signalling of this type, is closely related to the newly emerging physics associated with soft matter. The soft matter physics field is presently at a cross-roads of divergence between a physical chemistry approach, and a complex systems approach .. and the crux of the matter seems to revolve around biophysics. It seems that the behaviours of soft matter in biological systems are subject to: "large thermal fluctuations, a wide variety of forms, sensitivity of equilibrium structures to external conditions, macroscopic softness, and metastable states".

I don't see how this is bad news for exobiology. Mathematical theories of self-organizing complexity is key to solving the problem of life-emergence and since it has mathematical underpinnings it's certainly no surprise that it also exists on the most fundamental levels of material properties.



Interesting question. Well, I think we won't be able to find the answer... if it happened, it happened million of years ago... so we can't be sure. We can estimate or think that there was some kind of water cycle... but given the present facts, we can't be totally sure.
For me, the big big question is: we are quite sure that liquid water was once present in abundance on the surface of Mars, in its ancient past. So, what happened with those oceans, lakes and rivers? What catastrophic event evaporated that huge amount of water?

There are some evidence that, if found, would indicate the existence of a water cycle. For example rivers would originate in a mountain catchment area or the existence of rounded pebbles would indicate the presence of more long-term water-flow in the past. The images taken from space do however suggest that many river features originate in so-called chaos regions. Chaos regions are believed to be ground that collapsed when sub-surface ice melted and the water drained out.



The "problem" in the search for ET life, is that we don't know exactly what to look for. I mean, if we think that life out there is similar to us (which I highly doubt), we design equipment to make experiments based on the life-chemistry that we know. But, what if life out there is something completely new and totally different than our's? How could we find it? We know nothing about its chemistry and biological patterns. So, maybe what's happening in the search of ET life, is that we are searching in "our biological terms", not in the "biological terms of ET life". Hope that I made myself clear.

I have a somewhat different view. We don't have to know what to look for, we only have to suppose it and define it clearly enough such that it is verifiable in principle. But this requires some original scientific and mathematical thought.

transreality
2012-Oct-24, 11:19 PM
Evolution is not about pure randomness...

Then where is the evidence supporting this assertion?


The history of life is not just about evolution. The extinction of the dinosaurs was not an evolution event. It was a contingent event. It didn't matter how well adapted any particular species was to its pre-impact niche.; in the conditions of the post-impact survival of the species is a (almost) purely random event. If that impact didn't occur then a mammalian megafauna would not have arisen in a world where those niches were already occupied. Perhaps the world would be full of feathery dinosaurians. That is just one recent event in the last 10% of biotic history, every other major impact event is another source of contingent variation. Not only impacts, but major tectonic events, volcanic episodes, atmospheric shifts are similar, and we know many from the last 600mya or so. Before that in the earlier pre-multi-cellular-life phase that extended another three billion years before that, and before that a pre-biotic phase of chemical evolution of another half a billion years, from which our scope for evidence is very limited, but we must expect that events of similar magnitude were occurring.

Another approach from the Miller/Urey type spark experiments shows that introducing a energy flux to a pre-biotic mixture of simple molecules, results in an outcome of more complex molecules. But the cascade of such more complex molecules varies from zap to zap. This is a crude attempt to simulate the most primitive steps in the series of events that lead to life. Yet already chemicals appear that are not present on any meterorite (for example) that has been in space for millions or billions of years.




I'm afraid that Physics and Chemistry theory cannot give us definitive answers about a system as complex as life. For example, whilst other molecules such as CTP, TTP, UTP, ITP, (etc), might be shown to be theoretically capable of the same task as ATP, in Biology, empirical evidence must be produced in order to demonstrate relevance.
I think this is where Biology and Astrophysical speculation deviate from eachother.


For the evidence that all organisms use ATP, a reasonable interpretation is that the common ancestor of all life used ATP, rather than necessarily the use of ATP is inevitable or has adapative advantages over the other combinations you list. This is an example of reasoning based on recognising contingency rather than looking only to realm of (our particular) biology for evidence about all biology. Just looking at our biology would lead you to the conclusion that life elsewhere in the universe should include ATP, which is same as expecting humanoids with bumpy heads. Yet this is a contingent event that necessarily predated the evolution of life of earth.






I agree that trying to predict the characteristics of emergent complexity, other than our own 'life' characteristics, are in the realm of speculation.We shall see, eh? We shall see ... (ie: let's go where the data leads us ... as opposed to making non-evidence based speculations about what the outcomes 'might' be).

All we presently know, is that there is no evidence of other modern lifeforms having emerged from significant excursions, beyond the bounds of the standard genetic model, (and other components of LUCA theory).

By the time life arises, a whole lot of pre-biotic processes have already competed for abundance. For example, the appearance of Adenine synthesis and ATP
have already taken place. So once a life has emerged that works with whatever equilibirum the process of 500 million years of chemical evolution has contingently produced, it is not easy for a competitive life to emerge and use what is left over. We can speculate again, but we must expect the local failure of variant life to emerge is a process governed by the limitation of resources, rather than by any intrinsic impossibility for a variant life to possible. That is by processes inherent to the emergence of complexity, rather than universal limitations on the modes of that complexity.

MarianoRF
2012-Oct-25, 10:40 AM
I have a somewhat different view. We don't have to know what to look for, we only have to suppose it and define it clearly enough such that it is verifiable in principle. But this requires some original scientific and mathematical thought.

I don't follow you. My point is, when you look for something, you have to know what you are looking for, otherwise, how are you supposed to find it? I mean, if we know nothing about other life-forms, then where must we look for? how? and when? because, knowing nothing, leave us all opened doors. In practical speaking: should we expect some kind of life in Mars? we think so, but we don't know. Should we expect some kind of life in Neptune? we don't think so, but, why not? we can't be %100 sure, because we have no evidence at all.
If we had some clue, some small evidence, knew that life-out there has some specific features, we would be able to look for an specific environment and not the whole universe, understand? at present, we believe that planets in the habitable zone of its star, might harbor conditions for life... but, for what kind of life? something similar to us? ok, maybe that's our mistake, assuming that other life forms are similar to us...


The history of life is not just about evolution. The extinction of the dinosaurs was not an evolution event. It was a contingent event.

Following this approach, we should think that maybe, an ET life form was present at a certain moment, but then was extincted by some event, like the dinosaurs here on Earth. There were several species that lived in this planet, but now they don't. So, we should take into account that some kind of primitive life (aka, dinosaurs, insects, or something else) MIGHT have taken place somewhere in the Universe.

Paul Wally
2012-Oct-25, 01:06 PM
I don't follow you. My point is, when you look for something, you have to know what you are looking for, otherwise, how are you supposed to find it? I mean, if we know nothing about other life-forms, then where must we look for? how? and when? because, knowing nothing, leave us all opened doors. In practical speaking: should we expect some kind of life in Mars? we think so, but we don't know. Should we expect some kind of life in Neptune? we don't think so, but, why not? we can't be %100 sure, because we have no evidence at all.
If we had some clue, some small evidence, knew that life-out there has some specific features, we would be able to look for an specific environment and not the whole universe, understand? at present, we believe that planets in the habitable zone of its star, might harbor conditions for life... but, for what kind of life? something similar to us? ok, maybe that's our mistake, assuming that other life forms are similar to us...

My point is that to look for something, we only need to define what we are looking for and under what conditions etc. It's like taking a guess to see whether it turns out to be true or not. We need no prior evidence of other life in order to look for it.

Colin Robinson
2012-Oct-25, 08:14 PM
My point is that to look for something, we only need to define what we are looking for and under what conditions etc. It's like taking a guess to see whether it turns out to be true or not. We need no prior evidence of other life in order to look for it.

I agree. I'm reminded of Karl Popper's metaphors of the bucket and the searchlight. Is science like dipping a bucket in a well and just letting it fill with water (data), or is it more like aiming a searchlight in a direction where you suspect (but don't yet know) that there might be something of particular interest?

Not only conjectures about life can be tested by the searchlight method, but also conjectures about complex non-living systems. For instance, non-living "attractors" within an organic soup where there are flows of energy... I'm not sure how likely/unlikely it is that non-living attractors would persist long-term without having or developing characteristics of life, like growth, reproduction, mutation... But if someone can suggest a theoretical model for a persistent non-living attractor, Titan and Enceladus might be good places to look for an example.

Selfsim
2012-Oct-25, 08:49 PM
I have a somewhat different view. We don't have to know what to look for, we only have to suppose it and define it clearly enough such that it is verifiable in principle. But this requires some original scientific and mathematical thought.Nonsense!

An experiment is designed to test a theory .. not to verify it!

This is precisely why one needs to consider the equally likely possibility that the results might show the opposite (thus leading to falsification) during the construction phase of the theory/hypothesis. If one turns a blind eye to such a possibility from the outset, (by invoking a particular philosophical belief in 'logical positivism', for example), then falsification would not be possible .. and in this case, … it isn't …. made especially so, by setting out with the firmly held belief that 'Earth-like exo-life exists' in the first place.

The above thinking is sadly lacking in a balanced view, and is merely a disguised hunt for a holy grail .. and a quite likely highly specific one at that.

Paul Wally
2012-Oct-25, 11:49 PM
An experiment is designed to test a theory .. not to verify it!


But I'm referring to particular life postulated to exist on particular planets like Mars or Neptune, in the context of my discussion with Mariano. In this case whatever particular life is postulated must be verifiable. If there is a general theory behind the prediction of such particular life instances then that theory is still falsifiable because the particular predictions could be wrong.

MarianoRF
2012-Oct-26, 12:08 AM
I agree. I'm reminded of Karl Popper's metaphors of the bucket and the searchlight. Is science like dipping a bucket in a well and just letting it fill with water (data), or is it more like aiming a searchlight in a direction where you suspect (but don't yet know) that there might be something of particular interest?

Not only conjectures about life can be tested by the searchlight method, but also conjectures about complex non-living systems. For instance, non-living "attractors" within an organic soup where there are flows of energy... I'm not sure how likely/unlikely it is that non-living attractors would persist long-term without having or developing characteristics of life, like growth, reproduction, mutation... But if someone can suggest a theoretical model for a persistent non-living attractor, Titan and Enceladus might be good places to look for an example.

I agree, Titan and Enceladus are good places to look for an example. The problem is the distance and the harsh environments in those worlds. I definitely believe that we might find something in both worlds.