[HN Gopher] Emergence of Life in an Inflationary Universe (2020)
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Emergence of Life in an Inflationary Universe (2020)
Author : yamrzou
Score : 59 points
Date : 2022-01-23 16:47 UTC (6 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| kingcharles wrote:
| All our calculations are fucked by having a sample size of one.
| nynx wrote:
| I'm curious what the actual estimates of the likelihood of a
| self-replicating RNA stand coming together randomly are. There's
| a lot of volume and time on earth where these random reactions
| could've happened.
| bmitc wrote:
| > There's a lot of volume and time on earth where these random
| reactions could've happened.
|
| Life began basically as soon as the Earth did. So, in terms of
| biological or geological time, it took almost no time.
| marcosdumay wrote:
| Well, the article is literally doing that math.
| bediger4000 wrote:
| "Random" isn't really a relevant concept when it comes to
| chemicals. Get out some vinegar and some baking soda. Mix them.
| Wow! A chemical reaction that shouldn't have happened according
| to the laws of probability!
| memling wrote:
| Can you elaborate on this further? Why don't the laws of
| probability apply to chemistry?
| bediger4000 wrote:
| They definitely do apply, but it's like laws of probability
| apply to gas dynamics: sure there's a very small, but not
| non-existent chance that all the air in your room will end
| up confined to the half you're not in. There's a very tiny
| probability that acetic acid in vinegar and sodium
| bicarbonate in baking soda won't combine. I suppose some
| extremely tiny fraction of the acid and baking soda I've
| mixed together in my life didn't react. But the probability
| is so tiny, it just doesn't matter: all my cookies and soda
| bread rose.
|
| Same with self replicating organic molecules - if you mix
| amino acids together, you're going to get some long strands
| virtually every time you try it because the probability of
| amino acids not reacting is very tiny. The probability of
| getting self-replicating strands approaches 1 after only a
| few trials. That is, your solution of amino acids would end
| up with some goop in it, some polymerized amino acid
| strands that had replicated themselves.
|
| This "what's the probability!?!?" category of anti-
| evolutionary arguments is just false. "If you put all the
| pieces of a car in a box and shook it, the probability of
| getting a car is zero!" True, but an inapplicable analogy
| to organic chemistry reactions. Intuition about probability
| leads you astray. Nuts have an extremely low probability of
| getting agitated into screwing themselves on a bolt. The
| chemicals relevant to life have an extremely high
| probability of reacting to form larger molecules.
| memling wrote:
| That's an interesting point, thanks. Please pardon some
| ignorant questioning.
|
| How far down does this apply? E.g., do amino acids come
| basically for free in the same way? If not, what's the
| bootstrapping process like, and how random is it? How
| many steps do you have to take from self replication to
| functional cells? That chemical reactions are quite
| deterministic makes sense to me, but I don't quite
| understand how one gets from chemistry to biology.
| carbonguy wrote:
| I'm not the parent commenter, but I studied biochemistry
| and find abiogenesis to be a particularly fascinating
| topic, so I'll take a crack at answering your questions:
|
| > How far down does this apply? E.g., do amino acids come
| basically for free in the same way?
|
| Broadly, I think it is fair to say that many molecules
| that we associate with biological processes (e.g. amino
| acids, nucleotides, simple alcohols, etc.) do come "for
| free" in the sense that there are known pathways for
| these molecules to be produced in the absence of living
| organisms. The Miller-Urey experiment is probably the
| most well-known proof of concept of this idea, though
| it's debated how well the experimental conditions
| correspond with "the real world."
|
| > ... [W]hat's the bootstrapping process like, and how
| random is it?
|
| If I understand you correctly, here you're asking "what
| does it take to get from prebiotic organic molecules to
| living organisms?" And that is a fascinating question
| that has, to my mind, several possible answers, though
| ultimately I think the answer is "we don't know."
|
| One very suggestive paper I read describes the
| bootstrapping process as a "surface metabolism" [1] that
| succeeds through several epochs before eventually
| producing free-floating lipid-membrane-enclosed micelles
| containing complex organic molecules and a rudimentary
| metabolism - i.e. protocells.
|
| However, the IIRC paper falls short of explaining how
| these protocells can then start to independently
| reproduce. One hypothesis I recall from David Deamer is
| that hydration/dehydration cycles in shallow pools
| promote complex organization of simpler protomolecules
| into structures we typically associate with living
| organisms [2]; in other words, given the
| protobiomolecules mentioned above, certain environmental
| conditions encourage [proto]cell formation.
|
| So, to answer your question (I think), there are many
| good candidates for the "bootstrapping process" and while
| there is randomness involved, it turns out that certain
| environmental conditions that were present on the early
| Earth (as well as currently!) tended to promote complex
| molecular formation.
|
| > How many steps do you have to take from self
| replication to functional cells?
|
| Not many; I would say that if you have something that
| looks like a cell and reproduces itself, it's a
| "functional cell." Personally, I think from that point we
| are at an, if not the, "origin of life," and understand
| in broad strokes "what happens next" - ever-more-refined
| single-celled organisms, multi-cell aggregates becoming
| "true" multi-celled organisms, and so on.
|
| Let me know if you're curious about any other aspect of
| this topic and I'll try to provide more info!
|
| [1]
| https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC373159/
|
| [2] https://www.liebertpub.com/doi/10.1089/ast.2019.2045
| yamrzou wrote:
| Good question, I wonder the same.
|
| If I may add, how far does this apply when getting from
| biology to consciousness, i.e from functional cells to
| general intelligence, as seen in living organisms and
| humans?
| titzer wrote:
| None of this probabilistic reasoning matters in the face of the
| anthropic principle. If there are infinite universes, we could
| easily be in the mostly stupidly improbable one possible, since
| we are not observing (and cannot observe) all possible universes,
| let alone an average one. This why a whole ton of speculation is
| completely meaningless, because we clearly live in a stupidly
| improbable universe that is already "fine tuned"--and that's not
| a problem. It doesn't mean there has to be God or anything. In
| fact, the settings of our universe imply _nothing_.
| sandgiant wrote:
| Indeed we might never be able to measure the global
| normalization of the likelihood function of life, but that
| doesn't mean we can't investigate it's local properties. In
| fact, I think we can learn a lot from doing just that.
| mjrpes wrote:
| This article's probabilistic reasoning seems interesting,
| because it suggests it is very unlikely we will find other
| random intelligent life within our observable universe. As
| opposed to another sense of the anthropic principle, where our
| universe is fine tuned to an extraordinary degree but the
| chances of finding other intelligent life nearby is higher.
| LegitShady wrote:
| There is no evidence that there are infinite universes and
| indeed the belief in such a concept absent any evidence beside
| "nothing says there can't be" by scientific people is a
| religious belief on the order of there being a god except with
| less elf honesty.
|
| We have never detected an alternate universe and we don't even
| have math that makes it probable. It's just a concept. The same
| way "there's no reason entropy can't run backwards according to
| the physics" doesn't stop us not having any evidence for
| backwards running entropy or negative mass or a million other
| things that might conceivably exist but have no real evidence
| but sound cool.
| titzer wrote:
| We have no evidence that we are randomly distributed over
| some population of universes, but that doesn't stop misguided
| philosophers from assuming that. I didn't assert infinite
| universes; rather the opposite. It's reasoning like this that
| is asserting other universes. One thing is certain; ours is
| super weird and has definitely produced self-aware apes in a
| long series of evolutionary accidents on a single planet.
|
| What's more interesting is whether our universe can be
| described by finite information (closed formulae or not, even
| a stupidly huge but finite trace of all quantum events would
| suffice). If it's finite information then its description is
| encoded in every transcendental number in mathematics--which
| is an infinite number, including the number pi.
|
| Don't trifle with infinity. I wasn't.
| jcims wrote:
| Having any belief at all, none, one, many, infinite, all
| falls into the same category. We don't know.
|
| To me it seems like the additional universes in this context
| serve a purpose similar to (my understanding of) additional
| dimensions in math/physics. It allows you to navigate around
| singularities.
| LegitShady wrote:
| > Having any belief at all, none, one, many, infinite, all
| falls into the same category. We don't know.
|
| If you have no evidence for it, your belief in a multiverse
| is religious not agnostic.
|
| >To me it seems like the additional universes in this
| context serve a purpose similar to (my understanding of)
| additional dimensions in math/physics. It allows you to
| navigate around singularities.
|
| This is additional dimensions in physics, and we just don't
| have any actual evidence that a multiverse exists. We have
| a some suppositions that say 'well there's nothing to say
| it couldn't exist' but no evidence that it could.
|
| You could view that as 'useful' but you can't judge its
| truthfulness or whether reality reflects such a 'purpose'.
| Either something exists or it doesn't, and a multiverse is
| a strictly religious belief at this point.
| GeorgeKangas wrote:
| I can see two ways around the low probability problem, for RNA
| abiogenesis:
|
| 1) The crystal gene hypothesis of A. G. Cairns-Smith. As a clay
| crystal grows and splits, the info in the crystal's defect
| structure is replicating with impressive fidelity, and those
| defects also interact with the surroundings. So you get the
| Darwinian game bootstrapped pretty much for free. Later on, the
| crystals start using organic polymers; later still, the polymer
| technology is developed well enough to take over from the clay.
| So this might make abiogenesis reasonably probable on one planet.
|
| 2) An observable universe is just any epsilon size patch, on an
| inflationary universe. The space-time curvature of our whole
| observable universe is too small to measure, hence the radius of
| our inflationary universe is a large multiple of the 13
| G-lightyear radius we can observe. So abiogenesis could be highly
| improbable in any observable universe, answering Fermi's paradox,
| yet be probable within the much greater volume of an inflationary
| universe (maybe this is what TFA said? TLDR [Edit: yeah, it says
| that right in the abstract]). And there could even be a large
| number of inflationary universes, for all we know.
| benlivengood wrote:
| Your second point is probably the most critical for this
| article; all we can conclude (eventually) is an upper bound on
| the probability of abiogenesis for a certain volume, total
| mass, age, or number of stars. There is literally no lower
| bound; there may be uncountably many other inflationary
| universes without life.
| scarmig wrote:
| One nice thing about 1) is that it is more falsifiable than 2).
| 2) basically gives us the ability to explain any almost
| arbitrarily unlikely event (at least unless we figured out a
| lower bound on the space time curvature of the observable
| universe). You might as well say that life is vanishingly
| unlikely but a series of vanishingly unlikely many-worlds
| quantum coincidences happened to result in the particular
| universe we see.
| sandgiant wrote:
| There is a sort of philosophical upper bound on the total
| size of the Universe in an eternal-inflation scenario. This
| is the Boltzmann brain paradox. The argument goes that if
| there are infinitely many universes it is infinitely more
| likely for you to be a brain randomly fluctuating into
| existence in the vacuum, rather than being an actual human
| being evolved through evolution.
|
| This conclusion is obviously absurd, so the argument goes
| that there can't be infinitely many places in which random
| things can happen in the Universe. Note that the size of the
| Universe required to produce a Boltzman brain is much larger
| than that discussed in the article. It's still nice to think
| that there might be an upper bound for us to avoid some of
| the more daunting implications of the anthropic principle.
| Enginerrrd wrote:
| Yeah I think the idea that the first self-replication was RNA-
| based to be really really dubious.
| nobrains wrote:
| To my simple mind, unless we find another case of life in this
| universe, there is no way to determine/estimate/calculate the
| frequency/probability of origin of life. Unless someone can
| convince me, in a simple way, that it is possible to determine.
| sandgiant wrote:
| We might never know with complete certainty, but then what can
| we know? Exploring the limits of the theories we pose is the
| only way to gain knowledge. The physical world is after all
| fairly predictable. Even if we will never know anything with
| certainty.
| betwixthewires wrote:
| Well this article/study talks about the likelihood by looking
| at the likelihood that an RNA sequence randomly forms long
| enough enough number of times until a self replicating sequence
| exists. Such a probabilistic approach indicates that life,
| while not necessarily rare in the universe, might be rare
| enough that it is unlikely for it to occur twice in a volume
| that is observable from one occurrence, or that there is some
| unknown mechanism that makes it more likely.
| ShamelessC wrote:
| > Unless someone can convince me, in a simple way
|
| Seems like you're happy with your own theories.
| bmitc wrote:
| I took a course from the Complexity Explorer on the origins of
| life. It made the point that although understanding life is
| hard, life is actually seemingly easy when considered in terms
| of it showing up or starting. It pointed to evidence that life
| began basically as soon as Earth formed, basically as soon as
| the oceans arrived.
|
| The Solar System itself has plenty of examples of water. For
| example, Enceladus is surmised to be completely covered in an
| ocean below its icy crust. As far as I know, there's not much
| evidence that points to life as being special. Earth is
| certainly special in the time window that we are experiencing
| it in given its balances of energy, heat, water, etc.
|
| Utilizing models to predict what's out there doesn't seem all
| that controversial when evidence points to life not being all
| that hard cosmically. We just don't have strong enough
| binoculars yet.
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