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Thread: What do you think is the most likely explanation for the Fermi paradox?

  1. #841
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    The (non-) "Vegas odds" on life arriving early and often, but intelligence arriving later, if at all.

    https://arxiv.org/abs/2005.09008
    An Objective Bayesian Analysis of Life's Early Start and Our Late Arrival
    David Kipping
    [Submitted on 18 May 2020]
    Life emerged on the Earth within the first quintile of its habitable window, but a technological civilization did not blossom until its last. Efforts to infer the rate of abiogenesis, based on its early emergence, are frustrated by the selection effect that if the evolution of intelligence is a slow process, then life's early start may simply be a prerequisite to our existence, rather than useful evidence for optimism. In this work, we interpret the chronology of these two events in a Bayesian framework, extending upon previous work by considering that the evolutionary timescale is itself an unknown that needs to be jointly inferred, rather than fiducially set. We further adopt an objective Bayesian approach, such that our results would be agreed upon even by those using wildly different priors for the rates of abiogenesis and evolution - common points of contention for this problem. It is then shown that the earliest microfossil evidence for life indicates that the rate of abiogenesis is at least 2.8 times more likely to be a typically rapid process, rather than a slow one. This modest limiting Bayes factor rises to 8.7 if we accept the more disputed evidence of C13 depleted zircon deposits (Bell et al. 2015). For intelligence evolution, it is found that a rare-intelligence scenario is slightly favored at 3:2 betting odds. Thus, if we re-ran Earth's clock, one should statistically favor life to frequently re-emerge, but intelligence may not be as inevitable.
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  2. #842
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    Quote Originally Posted by Roger E. Moore View Post
    Thus, if we re-ran Earth's clock, one should statistically favor life to frequently re-emerge, but intelligence may not be as inevitable.
    No result of biological evolution is inevitable except for reproduction, and surviving long enough for reproduction. The methods which enable these results are as varied as physically possible.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  3. #843
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    Another look at the probabilities of "Life common, Intelligence rare".

    https://www.forbes.com/sites/startsw.../#1bf1e0554ee6
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    Quote Originally Posted by Roger E. Moore View Post
    Another look at the probabilities of "Life common, Intelligence rare".

    https://www.forbes.com/sites/startsw.../#1bf1e0554ee6
    Source paper: https://www.pnas.org/content/early/2.../12/1921655117
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  5. #845
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    Quote Originally Posted by Roger E. Moore View Post
    Another look at the probabilities of "Life common, Intelligence rare".

    https://www.forbes.com/sites/startsw.../#1bf1e0554ee6
    Source for the above article is by David Kipping, same paper as the Arxiv.org cite.

    Quote Originally Posted by Roger E. Moore View Post
    https://arxiv.org/abs/2005.09008
    An Objective Bayesian Analysis of Life's Early Start and Our Late Arrival
    David Kipping
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  6. #846
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    Quote Originally Posted by Noclevername View Post
    Source for the above article is by David Kipping, same paper as the Arxiv.org cite.
    Agree, but the article explained things better in normalspeak.
    Do good work. —Virgil Ivan "Gus" Grissom

  7. #847
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    Quote Originally Posted by Roger E. Moore View Post
    Agree, but the article explained things better in normalspeak.
    OK.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  8. #848
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    Quote Originally Posted by Roger E. Moore View Post
    I suspect that life might be common, and intelligence life possible, even technological intelligence, BUT space travel and space communication, very very rare. Underground ocean life never gets above ground, high-gravity super-Earths restrict space travel, etc. We did get lucky here.
    This is my view also, but its a gut instinct based on the few observational facts we have to hand. Until we get more data from the exo planets we have discovered so far then everything we think about E.T and its possible existence is just assumption based on one example.
    I've heard good arguments for a "crowded" universe and good ones for a "rare" Earth universe. Both arguments are very plausible and both, based on the one example so far, stand up to scrutiny (accepting assumptions of course). As I said, because of these my feelings tend towards - life is common but technological life is rare hypothesis.

    No doubt, at some point, new discovery's will surprise us one way or another.

  9. #849
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    Quote Originally Posted by Roger E. Moore View Post
    I suspect that life might be common, and intelligence life possible, even technological intelligence, BUT space travel and space communication, very very rare. Underground ocean life never gets above ground, high-gravity super-Earths restrict space travel, etc. We did get lucky here.
    I tend to think that while life might be fairly common in the Universe overall, the flavor of intelligence that the Fermi Paradox addresses (aggressively colonizing potential starship builders) would be quite rare. The kind of life form that invents technology and industry as we would define it, seems like it has to be the product of some very specific evolutionary pathways.

    Life took a complex and elaborate Rube Goldberg-esque combination of factors to get from simple microbes to human minds, if a Pre-Cambrian worm had zigged instead of zagged we might never have been here at all.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    Life took a complex and elaborate Rube Goldberg-esque combination of factors to get from simple microbes to human minds, if a Pre-Cambrian worm had zigged instead of zagged we might never have been here at all.
    My suspicions are that intelligence is inevitable but long delayed, as it seems to move in small jumps. Fish are smarter than trilobites, lizards smarter than fish, mammals smarter than etc. Technology is faster, but still look at the millions of years humans used stone tools before moving on to steam power.

    The real bump is space travel. Space communications is easy comparted to space travel. The limitations that habitable planets place on space flight are considerable.
    Do good work. —Virgil Ivan "Gus" Grissom

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    Quote Originally Posted by Roger E. Moore View Post
    My suspicions are that intelligence is inevitable but long delayed, as it seems to move in small jumps. Fish are smarter than trilobites, lizards smarter than fish, mammals smarter than etc.
    Which tree is getting more intelligent? Which bacterium? Which slime mold?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    Which tree is getting more intelligent? Which bacterium? Which slime mold?
    Those three have poorly developed nervous systems, if any, but they have become more complex in other ways over time. Complex multicellular mobile life with nervous systems and a brain (or equivalent) are the key. It takes billyuns and billyuns of years, channeling Carl Sagan, to get to that point. Not every species will be equally intelligent. Within a group like dinosaurs, troodons and raptors may have been smarter than other dinosaurs. Crows seems to be smarter than other birds. Apes and monkeys, elephants, dogs, pigs, and so forth are smarter than rodents. It does seem that intelligence evolves in a general way, spreading out among highly developed species, and then one day a species crosses the intelligent tool-using line in force with at least one manipulative organ that is not its mouth. One might argue dolphins and whales are smarter than humans, but whales are not going to the stars.
    Do good work. —Virgil Ivan "Gus" Grissom

  13. #853
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    Quote Originally Posted by Roger E. Moore View Post
    Those three have poorly developed nervous systems, if any, but they have become more complex in other ways over time. Complex multicellular mobile life with nervous systems and a brain (or equivalent) are the key. It takes billyuns and billyuns of years, channeling Carl Sagan, to get to that point. Not every species will be equally intelligent. Within a group like dinosaurs, troodons and raptors may have been smarter than other dinosaurs. Crows seems to be smarter than other birds. Apes and monkeys, elephants, dogs, pigs, and so forth are smarter than rodents. It does seem that intelligence evolves in a general way, spreading out among highly developed species, and then one day a species crosses the intelligent tool-using line in force with at least one manipulative organ that is not its mouth. One might argue dolphins and whales are smarter than humans, but whales are not going to the stars.
    But all your given examples are from the same relatively narrow and recent line of development, that of tetrapods. What are the odds of a cognitively similar evolutionary branch coming about in a totally alien biosphere with no common ancestry to the vertebrates of Earth? Unknown and currently, unknowable.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  14. #854
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    It was once argued that exoplanets would be very rare. It was proposed that an extremely unusual event; the perilously close passage of one star past another was required to make one.We see how that turned out.

    There has been a long tendency in human thought, to think ourselves uniquely situated, first in one way, then in another. First, various groups thought their own territory the center of the (flat) world. Then it was that the Earth was the center of the cosmos, and then that our galaxy was unique in all of space. In every case, these assumptions have eventually been refuted by further knowledge.A human sense of self-importance affected our thinking.

    It doesn't seem such an unreasonable thing to learn from these, and other examples, and apply the principle of mediocrity to the question of other intelligent, technological life in the universe. The emergence of technical civilizations may be a longshot, but given the immense number of opportunities, the staggering numbers of stars, and, now we think, planets, too, in our galaxy, there could, quite reasonably, be many such civilizations.

    As for the tendency for such civilizations to expand their territory, we have huge numbers of examples of life on this planet doing that very thing. The example of our own species' expansion from a corner of Africa to cover an entire planet is there for our consideration, too.

    Dr. Fermi realized, seventy years ago, that even at quite reasonable (sub-light) rates of expansion, the galaxy could have been filled by elder, intelligent species, many times over, in the available time.
    Last edited by Ross 54; 2020-May-27 at 02:27 PM.

  15. #855
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    I've already expressed my views on the "principle" (assumption) of mediocrity and its applicability to science. Observation trumps philosophical viewpoints any day, and all the observations we've seen so far suggest that the Universe at life scales consists of "infinite diversity in infinite combinations".
    Last edited by Noclevername; 2020-May-27 at 04:29 PM. Reason: clarified scale
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  16. #856
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    From the Arxiv thread:
    Quote Originally Posted by Roger E. Moore View Post
    How to classify extraterrestrial civilizations?

    https://arxiv.org/abs/2005.13221
    Qualitative classification of extraterrestrial civilizations
    Valentin D. Ivanov, Juan Carlos Beamin, Claudio Caceres, Dante Minniti
    [Submitted on 27 May 2020]
    Abridged: The interest towards searches for extraterrestrial civilizations (ETCs) was boosted by the discovery of thousands of exoplanets. We turn to the classification of ETCs for new considerations that may help to design better strategies for ETCs searches. We take a basic taxonomic approach to ETCs and investigate the implications of the new classification on ETCs observational patterns. We use as a counter-example to our qualitative classification the quantitative scheme of Kardashev. We propose a classification based on the abilities of ETCs to modify their environment and to integrate with it: Class 0 uses the environment as it is, Class 1 modifies the it to fit its needs, Class 2 modifies itself to fit the environment and Class 3 ETC is fully integrated with the environment. Combined with the classical Kardashev's scale our scheme forms a 2d scheme for interpreting ETC properties. The new framework makes it obvious that the available energy is not an unique measure of ETCs, it may not even correlate with how well that energy is used. The possibility for progress without increased energy consumption implies lower detectability, so the existence of a Kardashev Type III ETC in the Milky Way cannot be ruled out. This reasoning weakens the Fermi paradox, allowing the existence of advanced, yet not energy hungry, low detectability ETCs. The integration of ETCs with environment makes it impossible to tell apart technosignatures from natural phenomena. Thus, the most likely opportunity for SETI searches is to look for beacons, specifically set up by them for young civilizations like us (if they want to do that is a matter of speculation). The other SETI window is to search for ETCs at technological level close to ours. To rephrase the saying of A. Clarke, sufficiently advanced civilizations are indistinguishable from nature.
    (bold mine)

    The idea that more efficient advances make a civilization harder to find rather than more expansive and obvious, is not a new one, so it's good that researchers are noting it.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  17. #857
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    I keep seeing the word "rare" used here to describe the possibility of other intelligent civilizations, but how does one define "rare" in what is essentially an infinite universe? On a smaller scale, taking just the Milky Way into account (est avg of ~300 Billion stars) would "rare" be 1, 10, 10,000?

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    Quote Originally Posted by Spacedude View Post
    I keep seeing the word "rare" used here to describe the possibility of other intelligent civilizations, but how does one define "rare" in what is essentially an infinite universe? On a smaller scale, taking just the Milky Way into account (est avg of ~300 Billion stars) would "rare" be 1, 10, 10,000?
    Well, that's the problem, isn't it?

    Is it "common" or "rare" relative to the number of stars, relative to the number of worlds with liquid water, to the number of life bearing worlds?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  19. #859
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    Quote Originally Posted by Noclevername View Post
    Which tree is getting more intelligent? Which bacterium? Which slime mold?
    It's not surprising that trees don't have brains. What evolutionary advantage would they get from having one, that would justify the energy costs?

    An organism that stays in one place doesn't have to make decisions about which direction to move in.

    Quote Originally Posted by Noclevername View Post
    But all your given examples are from the same relatively narrow and recent line of development, that of tetrapods.
    But organisms other than tetrapods have also developed brains: cephalopods such octopus, arthropods such as ants.

  20. #860
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    Quote Originally Posted by Colin Robinson View Post
    It's not surprising that trees don't have brains. What evolutionary advantage would they get from having one, that would justify the energy costs?

    An organism that stays in one place doesn't have to make decisions about which direction to move in.
    Missing the point. Evolution does not involve specific direction, it is an accumulation of filtered random mutations, whatever works. The developments that led to cephalization need not have happened, but life would still go on.

    But organisms other than tetrapods have also developed brains: cephalopods such octopus, arthropods such as ants.
    But not all of them experience the same sort of cephalic advancement timeline you were referring to. Ants for instance use communal instinct rather than calculative intelligence. Ants are not getting smarter.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

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    Quote Originally Posted by Noclevername View Post
    Evolution does not involve specific direction, it is an accumulation of filtered random mutations, whatever works.
    The mutations are random, but what of the filtering for whatever works? Is that a random process? What makes increasing intelligence a whatever that works?

    The developments that led to cephalization need not have happened...
    Why did cephalization happen in at least three lineages, vertebrates, cephalopods and arthropods?

    Ants for instance use communal instinct rather than calculative intelligence. Ants are not getting smarter.
    Presumably they're smarter than their pre-cephalized ancestors?
    Last edited by Colin Robinson; 2020-Jun-21 at 12:00 AM.

  22. #862
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    Quote Originally Posted by Colin Robinson View Post
    The mutations are random, but what of the filtering for whatever works? Is that a random process? What makes increasing intelligence a whatever that works?



    Why did cephalization happen in at least three lineages, vertebrates, cephalopods and arthropods?



    Presumably they're smarter than their pre-cephalized ancestors?
    Why do branches of the same tree all have the same kind of leaves? Because they have common roots.

    Would a completely alien lineage follow the same path?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  23. #863
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    Quote Originally Posted by Noclevername View Post
    Which tree is getting more intelligent? Which bacterium? Which slime mold?
    I think that with trees it's actually an interesting question. Plants actually do have a kind of intelligence, and can even communicate through chemical signaling. Now I really don't know how to measure it, but I think it's possible that plants do have a range of capacity in that area, so you might be able to rate them, and in that case to determine whether they are getting more intelligent (for example, communicating a wider range of things).
    As above, so below

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    QUOTE: "Considering stars with metal content similar to the Sun’s and a roughly 5-billion-year timescale similar to the time needed by humanity to reach its current level of technology, the researchers conclude there should be about 36 “active civilisations” across the Milky Way. As for Fermi’s famous question, the researchers say the average distance between those civilisations would be about 17,000 light years, making detection and communication extraordinarily difficult using current technology."

    https://astronomynow.com/2020/06/16/...y-far-between/
    Do good work. —Virgil Ivan "Gus" Grissom

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    Quote Originally Posted by Noclevername View Post
    Would a completely alien lineage follow the same path?
    In an organism which occupied a comparable ecological niche, wouldn't you expect comparable adaptions?

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    Quote Originally Posted by Colin Robinson View Post
    In an organism which occupied a comparable ecological niche, wouldn't you expect comparable adaptions?
    If there were the existing genetic potentials to support that adaptation. No jellyfish is going to climb a tree.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  27. #867
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    Quote Originally Posted by Noclevername View Post
    No jellyfish is going to climb a tree.
    Have you heard of the planula hypothesis? It's the theory that all animals with bilateral symmetry, including tree-climbers, are descended from a cnidarian (jellyfish family) larva that failed to grow up.

  28. #868
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    Quote Originally Posted by Colin Robinson View Post
    Have you heard of the planula hypothesis? It's the theory that all animals with bilateral symmetry, including tree-climbers, are descended from a cnidarian (jellyfish family) larva that failed to grow up.
    So you're saying we all share a common origin. Exactly my point. Alien life won't. It'll be a different line of development.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  29. #869
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    Quote Originally Posted by Noclevername View Post
    So you're saying we all share a common origin. Exactly my point. Alien life won't. It'll be a different line of development.
    So, when you said

    No jellyfish is going to climb a tree.
    You actually meant: "Nothing that isn't related to a jellyfish is going to climb a tree." ?

  30. #870
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    Quote Originally Posted by Colin Robinson View Post
    In an organism which occupied a comparable ecological niche, wouldn't you expect comparable adaptions?
    I haven't been involved much in this conversation, but I do think that it's reasonable to think you would. Or at least, that you might. I think it's likely that in an aquatic environment, you will find creatures that swim with things like fins and have streamlined bodies, because it is going to be a good adaptation. Of course, you might find things that are not streamlined but have a hard shell, for example. In the same way, just as insects and birds both have wings, I think it's likely that in an atmosphere environment you will see things that have wings. But of course, I can't state with absolute certainty that you would, as there could be other solutions that we haven't imagined.
    As above, so below

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