Aliens Not So Strange

If the Martian life form transpires to be eerily similar, this might only show that Life … in reality has very few options. … No sentient forms weaving their existence in vast interstellar dust clouds, farewell to bizarre filamentous species greedily soaking up the intense magnetic fields of a crushingly oppressive neutron star and on even Earth-like planets no forms that we might as well call conceptualized pancakes. … Contrary to received neo-Darwinian wisdom, life on Earth at any level of organization—from molecular to societal— will provide a remarkably good guide as to what ought to be ‘out there’.

So argues Simon Conway Morris, from inside view considerations. I think he’s mostly right, but based on an outside view.

Here it is: when relevant parameters can vary by large magnitudes, the most common type of thing is often overwhemingly more common. For example, processes that create and transmute elements vary greatly in their rates. So even though there are over a hundred elements in the periodic table, over 90% of all atoms are hydrogen, so the odds that two randomly selected atoms are the same element is >80%.

Similarly, since the influences on how many eyes a human has vary greatly across eye numbers, most humans have the same number of eyes: two. Most humans do not have the same last name, however, since rates of gaining or changing names do not vary by huge factors.

The same principle applies to life. Life might have evolved in a great many kinds of environments, based on a great many sorts of elements, and using many types of organization. To the extent that some environments are far more common, or are far more supportive of high rates of biological activity, most biological activity in the universe should occur in the few most common and supportive environments. Similarly if some elements or organizations are far more supportive of biological activity and innovation, most life should use those elements and organization.

I expect cosmic environments to vary enormously in both volume and in support for biological activity. I also expect some types of elements and organizations to be far more supportive of biological activity and innovation. I thus expect most life to be based on similar elements and organizations, to originate and be active and innovative in places similar to where our life orginated and is most active and innovative.

This view is supported by the fact that the assumption that life originates via the entropy of sunlight hitting “dust” predicts many cosmological parameters. In ’08 I reported:

This causal entropic principle so far successfully predicts dark energy strength, matter fluctuation ratio, baryonic to dark matter ratio, and baryonic to photon matter ratio! … A simple reading of the principle is that since observers need entropy gains to function physically, we can estimate the probability that any small spacetime volume contains an observer to be proportional to the entropy gain in that volume. … Exclud[ing] entropy of cosmic and black holes horizons, … ignor[ing] future observers getting far more efficient and aggressive in using entropy, … they estimate that, aside from decaying dark matter, near us most entropy is made by starlight hitting dust, and most of that is in the past.

Our life probably started from sunlight hitting “dust” (including planets). More quotes from Simon Conway Morris:

Will the extra-terrestrials be utterly familiar, completely alien (whatever that is supposed to mean) or is the search a complete waste of time? What will it be? Worlds full of shoppers and celebrities, biological constructions so unfamiliar that they are only brought home by accident and then inadvertently handed over for curation in a department of mineralogy or an exercise in galactic futility as one sterile world after another rolls beneath the spaceship windows. …

Given the likely range of planetary environments, such as a 100 km deep ocean or an atmosphere substantially denser than that of Venus, what fraction of any potentially habitable biosphere is actually occupied? Is the terrestrial ‘habitation box’ only a small proportion of all of biological occupancy space or, alternatively,has life here more or less reached the limits of what is possible anywhere? …

What we find here, therefore, will be a reliable guide to what we will find anywhere. Paradoxically, confidence that this may be correct comes from the dramatic increase in our knowledge of so-called extremophiles. … It may be that the current thermal limit (ca 120 C) of microbial activity [10] may not be much exceeded. In part, this is because water at this temperature is necessarily pressurized, and the equivalent limits of microbial habitation in the Earth’s crust (e.g. [11,12]) may not exceed ca 5 km (equivalent to ca 110 MPa; see also below) and an ambient temperature (depending on the local geothermal gradient) of at least 120 C. … While the environmental extremes of these and a few other multicellular organisms are impressive [18], the overall size of the habitation box for eukaryotes is unsurprisingly substantially smaller than that of life as a whole. … For life as a whole, there may be no lower limit in as much as at increasingly lower temperatures normal growth then yields to physiological maintenance, and ultimately dormancy where ‘coincidentally’ rates of DNA and protein repair are equal to those of macromolecular deterioration. …

A more fundamental question, however, is whether because of locally contingent circumstances terrestrial life just happens to occupy some fraction, perhaps very small, of the total carbaquist habitation box. As we have already seen, however, in the case of minimum temperatures, pH range, salinities and desiccation, arguably the defined limits for all carbaquists have been reached by life on Earth, and with somewhat less certainty this applies also to hyperthermophiles. …  there is little evidence of microbial viability significantly in excess of the tolerances seen in terrestrial piezophiles. … Given that at least in terms of carbaquist life it is likely that lipid membranes are universal, this suggests that viability may not extend much beyond the deepest oceanic trenches (ca 11 km) or equivalent pressure zone within the crust of the Earth (ca 5 km). But the viability of lipids is not the only problem. Another potential constraint of the habitation box is the behaviour under different temperature and pressure regimes of hydration water essential to biomolecular function. Not only is the optimal zone remarkably narrow, with that for temperature being curiously coincidental in both micro-organisms and homeotherms (ca 36–44 C), but the phase diagram for hydration water is circumscribed and little larger than the terrestrial habitation box.

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  • Doug

    Trying to reduce down your argument I get to the following conclusion: One’s priors about the cosmic variance of life sustainability combined with human’s selection bias should influence one’s beliefs about the variance of life.

    I.e. if one believes that most different cosmic environments vary little in the ability to sustain life then seeing life on Earth only should have little influence. After all the evolution of life on Earth could be easily due to chance out of many suitable environments. In contrast if one believes that environments vary enormously by their ability to sustain life, then the fact that life evolved on Earth makes it much more likely that an Earth like environment is substantially more life-friendly than other environments.

    You seem to contend that our priors on the cosmic variance of life friendliness should be higher than what most exo-biologists assume. I don’t think I have much disagreement with you here.

    However where you’ve failed to sell is not on life’s environment but on its organization. Even if the vast majority of cosmic life is in Earth-like environments I doubt that much of it will look much like life here on Earth. Here you can apply a similar argument, again we have selection bias in only seeing life as it formed and organized here on Earth (not having the ability to reset the clock back and rerun everything). So one’s belief in the variance of life success across difference types of possible configurations of life should influence how “common” one believes Earth like configurations to be.

    No doubt the vast majority of configurations are vastly inferior or even un-survivable. But I think it comes down to whether you believe the configuration of life on Earth is the single tallest peak in what’s a relatively flat landscape of life configuration fitness? Or do you believe that there’s a rich topography with many mountain ranges, valleys, peaks and hills.

    I think anyone who has any experience with designing and implementing complex systems that have to adapt to the real world will tend to guess the latter.

    • Jess Riedel

      Even if the vast majority of cosmic life is in Earth-like environments I doubt that much of it will look much like life here on Earth.

      I think Robin Hanson and Simon Conway Morris are trying to address the possibility that most alien life out there is really different than life on earth, e.g. life made of darkmatter “greedily soaking up the intense magnetic fields of a crushingly oppressive neutron star”. The point is that if suitability for life varies tremendously among environments, then odds are good that the most suitable environment is much more suitable than all others, and is in fact our own. Yes, if we discovered that life developed on another earth-like planet, we would not expect animals with four limbs and two eyes. But we probably *would* expect it to be carbaquist with lipid membranes, etc.

  • anon

    I thought this post was going to be about illegal aliens, not space aliens.

    For the record, I support open borders for all carbaquist lifeforms.

  • Jess Riedel

    I thus expect most life to be based on similar elements and organizations, to originate and be active and innovative in places similar to where our life orginated and is most active and innovative.

    All this reasoning is anthropic right? We can argue that environmental suitability is strongly peaked and so therefore most life should originate from the same type of environment. But to argue that our environment on earth is of this type, we need to assume we’re typical of all observers in the universe. And this still only tells us that most intelligent life develops on earth-like planets. It’s possible there are environments out there are that far more suitable to developing life than earth-like planets are, but simply cannot support observers for some reason.

    • Proper Dave

      Aha, I think I detect a bias. Anthromorphic Exceptionalism? Don’t worry there won’t be “better” more enlightned aliens “out there”, trust me!

      I can accept the limited molecular path theory but the “societal” gives the game away.

      First there is enormous variation in human culture and custom, even when we are physically almost identical. Second how would an intelligent society of reptiles or birds look like, the authors is right that physical form and function does predict somethings at least (but with enormous variation). Bird and reptile societies? Going to be the same as bipedal mammals, maybe but not definite.

  • Tim Tyler

    Simon Morris says: “I suggest, however, that terrestrial life is close to the physical and chemical limits of life anywhere.”

    I expect many readers will see how that that is wrong.

    We are surely near the starting line – not near life’s ultimate limits.

  • LeBleu

    What does “carbaquist” mean? The word is so obscure that Google and Wikipedia don’t even have definitions, and this blog entry is the top Google search hit for the word.

    As for the overall topic, since I cannot read the original article (it’s behind a US$32 paywall for us non-academics), I’m not sure how to react, because I’m not sure what definition of “not strange” you are using. Some of the text appear to imply that “not strange” means probably based on the same bio-chemistry, but still possibly as strange as anything seen in the Cambrian explosion, whereas others seem to focus as precise as 2 eyes. I believe the average person would find even aliens restricted to 2 eyes and 4-6 limbs pretty darn strange. A quick Google seems to indicate Earthly life comes with 2, 4, 5, 6, 8, and 24 eyes. (Bees, spiders, and jellyfish as examples)

    My biggest concern for using Earth life as evidence of what alien life looks like beyond the broadest areas of bio-chemistry is path dependence. Even if there are biological niches that would be better served by something that is not a bacteria, insect, vertebrate or one of the other major forms of life, the odds are one of the dominant forms will get to the niche first, and be good enough to out compete more exotic possibilities that might have been able to make better use of the niche if the field was wide open to all comers.

    • Steven

      “Carbaquist”, as defined here by the same Simon Conway Morris, means using carbon chains structurally and water (aqua) as the solvent.

      Which doesn’t strike me as particularly more useful than the traditional term “carbon-based”, even if it specifically marks the claim for water.

      It also doesn’t strike me as a claim that actually needs to be based on any argument other than mere chemical abundances. Hydrogen, helium, oxygen, and carbon are in that order the four most common elements in the galaxy. Given helium’s nonreactivity, that makes “carbon and water” Hobson’s choice.

    • Hopefully Anonymous

      There’s a good chance this will change with the human propensity for systematic trials as a part of optimization.
      I’m interested in analysis of how at a local level human activity has overcome path dependence through optimization efforts.

      • Hopefully Anonymous

        Hits on this a little but not as directly as I’d like:

        Lot of interesting talk about post WWII german economic management & US military discussion, though, focused around tension between cartelisation vs. antitrust policy that would seem current and relevant to Yglesias blog readers.

  • Robin Hanson

    Doug, it isn’t clear exo-biologists do assume a low environmental variance.

    Jess, yes, the main point is to have low estimates of really different life. Yes if there were some very different places suitable for lots of bio activity but with a low chance of evolving civilization, there could be more of those places. But we don’t yet have much reason to think such places exist.

    LeBleu, yes there could be things as strange or stranger than anything seen in the Cambrian explosion. Yes what tends to colonize first may not be what would colonize best.

    Steven, yup, mere cosmic abundances suggests CHO based life dominates.

  • Joshua Zelinsky

    Note that Simon Conway Morris is a religious Christian and that his views about extra-terrestrial life are connected to his own non-standard beliefs. Most biologists who have thought about these issues don’t agree with him.

  • Evan

    I can see this argument for making perfect sense on Earth-like planets. Since the type of life we see on Earth seems to be of a common and effective type, it seems likely that life on other planets will resemble life here, at least on the cellular level.

    On non-Earthlike planets though, it seems to me fairly common sense that life, if it existed at all, would likely be somewhat different from the typical carbaquist.

  • TGGP

    He strikes me as using the term “Neo-Darwinian” in a non-standard way.

  • Jason

    Interesting paper on a thermodynamic origin of life. Aliens could even have RNA and DNA.

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  • Richard Duckworth

    If I had to place bets, it would be that life on other planets, would be dangerously similar to ours. As for ‘re-rolling the dice’ on earth, every species of birds, reptiles, primates, etc, would evolve differently, however, they would still, end up, very similar to what we have now. They would all end up with 2 eyes, one mouth, one nose, because it works best.

    Consider this, all, alien, automobiles, would also go through a similar evolution as ours have. There is no way around it. All cars need 4 wheels, a body, steering wheel, etc. The first ‘ steering wheel’ was a stick. then a round wheel. The first materials, out of necessity would be metal, wood, leather, etc. This would make the first cars on other planets, almost identical to the model A, on earth. . How could an automobile, built be aliens, on another planet, evolve any differently, than ours have, on earth?? The same is probably true with life’s chemical process’s. We could probably interbreed with aliens also.