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View Full Version : Extremophiles ~ Evolved in-niche or evolved elsewhere? (Extremists are bad examples?)



Hlafordlaes
2012-Dec-02, 10:41 PM
When the presence of extremophiles is detected in an Earth environ such as the one announced today under an Antarctic lake, should we take this as evidence that life could not only exist, but have evolved in similar environs elsewhere in the Solar System?

I think we may get ahead of ourselves in this regard. For example, the extremophiles detected in many Earth environs may well have evolved elsewhere and then slowly evolved to tolerate the tough new surroundings. Thus their presence is not an indication that abiogenesis could occur under those harsh conditions.

No expert, my bet is on those organisms living near hot vents at the ocean floor, which constitute a plausible environ for abiogenesis itself. If there were such vents under the ocean of Europa, or a sort of cold analogy on Titan ("hot" being relative and energy sources still being possible), then I'd go for the notion there may be life. Similar for past life on Mars, plausible for early Earth conditions.

But unless we can posit a plausible abiogenesis on the planet or moon in an environ that makes sense (from what we have to go on), perhaps less enthusiasm for extrapolating from Earth's evolutionary niche specialists is the way to go.

[Since it's the tendency to extrapolate from extremophiles to extraterrestrial abiogenesis specifically I wished to address, did not add this to an on-going thread, but happy if a mod feels it should be and sticks it there.]

Paul Wally
2012-Dec-02, 11:26 PM
Interesting questions. It appears to be the case that the current earth environments are not suitable for abiogenesis to occur, even in those places where life is flourishing. Perhaps, it is because of current life that a second abiogenesis can never get started. On the other hand, it may also be that the conditions where abiogenesis is possible is vastly different from the conditions where life can flourish (once it finds a way to get there or to adapt).

One could also argue that what is considered "extreme" is relative. For instance, shouldn't the first oxygen breathing organisms be called extremophiles relative to that time period? Or what about the first land animals; they must have been extreme relative to their oceanic counterparts. Or what about humans in space? We've adapted technologically to live in space? Are we in that sense also extremophiles? So the question is whether there is a difference between a pioneer organism and an extremophile.

eburacum45
2012-Dec-02, 11:39 PM
We don't know for sure what sort of environment supported the first event of abiogenesis that gave rise to life on Earth. Sure there are lots of theories, but we may never know. One thing seems fairly certain, though; it wasn't anything like the environment we live in today. We exist an a high-oxygen atmosphere which did not exist back then -
Paul Wally is right, we are the extremophiles compared to the earlest life on our world.

Hlafordlaes
2012-Dec-03, 12:02 AM
Yet the press is full of such seeming assertions, that finding extremophiles here is an indication for the possibilities for life in other similar environs. This is my "rant," if you will.

I'd agree with Paul Wally's thought that it is life itself that prevents abiogenesis from reoccurring on Earth. Otherwise I should think that somewhere on the planet something akin to early conditions might be found (volcano rim, deep ocean, some such), and we'd get a redux.

Saw a video sometime back that attempted to show a plausible way for abiogenesis to occur surrounding a hot vent. Filled quite a few gaps, tho not all. Wish I could find it.

Hornblower
2012-Dec-03, 02:07 AM
Interesting questions. It appears to be the case that the current earth environments are not suitable for abiogenesis to occur, even in those places where life is flourishing. Perhaps, it is because of current life that a second abiogenesis can never get started. On the other hand, it may also be that the conditions where abiogenesis is possible is vastly different from the conditions where life can flourish (once it finds a way to get there or to adapt).

One could also argue that what is considered "extreme" is relative. For instance, shouldn't the first oxygen breathing organisms be called extremophiles relative to that time period? Or what about the first land animals; they must have been extreme relative to their oceanic counterparts. Or what about humans in space? We've adapted technologically to live in space? Are we in that sense also extremophiles? So the question is whether there is a difference between a pioneer organism and an extremophile.

My bold. I would say no. We cannot survive out there without artificial vessels (space suits or spacecraft) in which we can simulate the conditions on the surface of the Earth. Extremophiles thrive in environments that would kill us with nothing but what they were born with.

Selfsim
2012-Dec-03, 07:47 AM
But unless we can posit a plausible abiogenesis on the planet or moon in an environ that makes sense (from what we have to go on), perhaps less enthusiasm for extrapolating from Earth's evolutionary niche specialists is the way to go.I would say that both approaches are different sides of the same coin. Ie: posits made which make assumptions based on one inferred relationship with the speculated emergence of life process, (ie: the past macro-environment), or another inferred relationship with the speculated emergence of life process, (which somehow results in the extrapolation from the extremophile case), both end up being dependent on their respective initial assumptions, (which invariably turn out to be introduced, anthropocentric, terrestrial biases).

At the moment, the only ways I know for us to distance ourselves from this bias is to: (i) make a (fluke) exo-life discovery locally, which has a sufficiently dissimilar bio-chemistry so as to enable the conclusion to be drawn that its theorised environmental origin, was mutually exclusive of Earth's known, past, macro environmental conditions (underwritten by Earth's evidence-based, past macro geo-atmospheric environmental records), (ii) to synthesise in the lab, from scratch, something completely artificial which exhibits life functionalities, recording in detail the influences/sensitivities to the environment in which it emerged ('twould be even better if the outcome could be repeated, too), (iii) query ET, (via interstellar comms), in order to see what he/she/it has to say on their own abiogenetic emergence environments, (iv) make a discovery which falsifies our own standard genetic model, whilst correlating this with the discovery's localised geo-atmospheric environmental evidence based conditions. I'd guess there'd be other ways too, but the above is my 2 cents worth, (if its worth that much, that is).

With the exception of, maybe, (ii) above, even if any of these scenarios happened, the possibility that a second run of the same environmental conditions/emergence process not resulting in the same outcome, is still a theoretical possibility, as it has a valid basis in principle.

Oh, and I should also say that should any of the above turn out to be useful in forming a theory, it probably would become fairly moot, pretty quickly (for obvious reasons).

Still, at least, I've now cited my criteria for how 'Unknown' could be falsified in principle, I suppose.

jmknapp
2012-Dec-04, 09:06 PM
Cases like Mars are an intriguing possibility for extremophiles since, according to theory anyway, the environment in the past was much more benign than currently. So if life requires cushy circumstances to form (warm, wet, abundant nutrients, low radiation), maybe it had such a window on Mars. When the core froze, plate tectonics stopped, the magnetic field collapsed and the atmosphere was stripped away, extant life might have been able to adapt to extreme niches given its head start.

TooMany
2012-Dec-04, 09:51 PM
the possibility that a second run of the same environmental conditions/emergence process not resulting in the same outcome, is still a theoretical possibility, as it has a valid basis in principle.


Doesn't that require yet another extreme rarity argument? Are you positing that even with identical conditions to earth, with an unimaginable number of organic molecules doing their natural dance, that life still requires some extremely rare accident?

The interesting thing about extremophiles is that they demonstrate the robustness of life, once it's started. Perhaps it is a mistake to think that abiogenesis is not also robust. There is some evidence that life emerged "soon" after the surface of the earth became cool enough for the complex organic molecules we find in life to survive. That in itself argues against extreme rarity of abiogenesis. This is something we are striving to learn more about. There is an interesting possibility about the existence of living nanobes (tiny life forms about 1/10 the linear dimensions of bacteria), that could provide more clues to how life can start, if they actually exist.

Selfsim
2012-Dec-05, 12:04 AM
Doesn't that require yet another extreme rarity argument? Are you positing that even with identical conditions to earth, with an unimaginable number of organic molecules doing their natural dance, that life still requires some extremely rare accident?Some exposure to other facts, (and subsequent thinking), might alleviate your misperceptions of rarity and predictability.

Take the Belousov-Zhabotinsky (B-Z) reaction. In these reactions, patterns develop under stimuli, in what would otherwise be a perfectly quiescent medium. The patterns then randomly change over time.

The B-Z reaction serves as a classical example of how non-equilibrium thermodynamics can result in unpredictable results at molecular scales. They also serve as a chemical model of non-equilibrium biological phenomena and are thus, not 'rare' phenomena (at least, in our biosphere).
The growth pattern of 'Dictyostelium dicoideum', (a soil-dwelling amoeba), is another example. It also displays oscillatory spiral patterns, at very different (and unpredictable) spatial and temporal scales.

Perturbations of the systems, in both of these cases, can result in the disappearance of the observed phenomenon. They may or may not also reappear again, over certain timescales.

The point is that these phenomena are by no means rare within our biosphere, at 'familiar' spatial scale levels. Their outcomes are also not predictable over 'familiar' timescales.

There is no need to invoke 'extremely rare accidents', in order for the appearance of exo-life to be unpredictable.

Or, in other words, what happened here, may be happening everywhere, but, over certain time and spatial scales, the outcomes may very easily not have the same results, in spite of similar macro-environmental (or chemical) conditions, if non-linearty is involved. Non-linear systems in nature, far outnumber linear systems, too.


The interesting thing about extremophiles is that they demonstrate the robustness of life, once it's started. Perhaps it is a mistake to think that abiogenesis is not also robust. There is some evidence that life emerged "soon" after the surface of the earth became cool enough for the complex organic molecules we find in life to survive. That in itself argues against extreme rarity of abiogenesis.Forget the 'rarity' thing (see above). Perturbations of some (large) classes of non-linear systems, results in unpredictability at certain scales.

That there's evidence it may have happened in a particular way here on Earth, (ie: the inferences you cite), doesn't mean that it necessarily will happen that way again elsewhere, and doesn't mean that what may have happened here, was 'rare' at Cosmological scale levels.