The Origin of Life and Life on Other Planets

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The Origin of Life and Life on Other Planets

Several parallel discussions inspire me to write this post partly in the hope that you will chime in.

The chance of life elsewhere in the universe just went to near zero. Or did it?


I was just hanging around minding my own business the other day when someone said to me, “you know, every single one of the five thousand or so exoplanet holding stars found to date have the gas giants in the inner, Goldilocks zone, and the smaller Earth-like planets are too far out to have life. So, the chance of life on other planets is way lower. Zero, basically.”

So, that was depressing.

Then, I went to the opening of the Bell Museum, and watched the planetarium show. After the show, I asked one of the people running the show, a somewhat snotty graduate student from the U, about this news. He got even snottier and told me that was ridiculous, that there are plenty of systems with Earth-like planets in the Goldilocks zone. I asked him how many. Plenty. I asked him if the number was double digit percentage or single digit percentage. He said may be single, but that was enough. I told him I had heard zero, which is not many. He said that was wrong.

Just a few minutes later, on visiting the rest of the newly opened museum, the penny dropped.

It turns out one of the major faculty members at the U in astronomy is one of the planet hunters, and a huge portion of the overall universe level exhibitry in the museum is devoted to showing this one guy’s work and talking about exoplanets and stuff. That must have been his student. Clearly, I had stepped in a pile of something.

My question is, a pile of what, exactly? Is there really recent research that suggests that the Earth’s solar system is unique among a sample of 5,000 or so? Or not? Or what?

The origin of life vs evolution

A long time ago, maybe 20 years now, some evolution-believing but sympathetic to religion people decided to say that the origin of life is not really in the purview of biology, and therefore should not be addressed in textbooks, high school courses, etc. You can think whatever you want about the origin of life, but it has nothing to do with evolution.

I’ve written about this. See:

“We can know nothing about the origin of life”
Is the origin of life different from evolution?

More recently, I find myself repeatedly being dragged into Twitter arguments between people saying that the origin of life is separate from evolution, vs. not.

The reason to say that they are separate is to allow religious people to have their god of the gaps, in this case, the ultimate gap. The pre-life gap.

The conception involves a very serious misconception about what the word “evolution” or the term “evolutionary biology” refer to. Most people misunderstand this.

I’ll give you an example. I was at a conference many years ago at the original Bell (not the one that just opened) and a well meaning but not well informed science teacher said to a room full of science teachers, “Evolution is simple. It is simple to teach. All evolution is…” then he proceeded to lay out the three Necessary and Sufficient conditions for Natural Selection.

Unfortunately, that is not what evolution is, and even more dramatically, it is not what evolutionary biology is about.

Evolution is the change over time in organisms, no matter how that happens.

Evolution is the idea of common ancestry and differentiation of lineages form common ancestors.

Evolution is increase of diversification over time, speciation, and extinction.

So that is three or four, maybe five things, depending on how you count them, that evolution is, and none of them need involve natural selection.

Oh, and natural selection is also part of evolution.

The point is this: If you think evolution is only this one thing, and define it very narrowly, then it is easy to figure that the origin of life is not part of evolution. But evolutionary biology is really the study of life in general, and all of it, in the context of evolutionary theory, and evolutionary theory involves everything from how molecules selectively interact (in primordial soup and in cells and other places) to how genes mutate, to how populations randomly drift genetically apart, or interact genetically, to how coeval lineages of organisms affect each other’s evolution (co-evolution), to how life and non life interact, to how natural selection creatively shapes life.

Evolution and evolutionary biology are two terms that refer to a thing and the study of a thing that is whopping big and complicated and wonderful and amazing and confusing and only barley understood.

To say that the origin of this thing is somehow separate is idiotic.

But to underscore the stupidity of this idea further, allow yourself to consider the following idea as possibly true.

Life evolved more than once.

Even more amazing an idea, and a very interesting hypothesis that we hope one day to test:

Under certain conditions, which are not uncommon in the universe, life almost inevitably arises, just as under certain conditions, a crystal is likely to form, rain is likely to fall, or a fire is likely to ignite. Life, in other words, happens.

If that is true, then the multiple origins of many life systems is clearly of no small interest to evolutionary biologists, and is very much part of “evolution.”

Which brings me to my third thought.

Life evolved independently on Mars, Earth’s Moon, Earth, and who knows where else. Or not.

There is a study just out published in Astrobiology, by Dirk Schulze-Makuch, that addresses part of this. I’ve asked for a copy of the paper, and if I get it, I’ll tell you about it. Without the paper, all I have is the breathless press release, and I’m not going to report on that.

But I can tell you that the basic idea seems to be that there is vague isotopic evidence of past life on the Earth’s Moon, and reconstructions of the Moon’s history suggest that at some point after its formation, and another time later when it was very volcanic, there would have been pools of water, an atmosphere, and some degree of protection from radiation, so life could have been there.

I’m of the belief that life is not that hard to get started. Why do I think that? Because it isn’t that hard to maintain it. Bacteria, especially, survive and do well under a wide range of conditions. A very simple virus can exploit cellular machinery pretty easily. Even though conditions on the early Earth were probably pretty tough, bacteria seem to have arisen early and held on — or perhaps re-started? — for a very long time. This is little more than a gut feeling, but it seems to me that life starting up isn’t that unlikely of an event, given the right conditions.

The reason we don’t see life originating again and again on our planet now may be because the startup does poorly in aerobic conditions. It may be because any molecules that start to form up in a way that leads to life are inevitably tasty food for existing life. Hell, there may be life almost starting up all the time in some places, and then being guzzled up by bacteria of some sort. And there are people looking for that sort of thing so maybe we’ll find that eventually.

Here’s my question on this. Which is harder to see happening, harder to believe, harder to accept, given what we know, and what we like to guess, about life?

1) Life started once, say, on Mars, and that’s it. Just that one time. Life found later on the Moon or on Earth came from Mars by a large rock hitting life-bearing mars, spreading rocks across the inner solar system, and some of those rocks eventually landed on the Moon and Earth, burning to a crisp in the atmosphere but somehow the bacteria on the rocks survive.

or

2) Life starts up easily and did so on Mars, the Moon, and Earth. For the first two, conditions for life were transient and have ended. For the Earth, conditions for life are a bit longer lived, and will end later.

Yes, yes, this all assumes there was life on Mars or the Moon, and we simply do not know that to be true at this time. This argument only matters if we pretend it was true, or at least possible. So this is speculation.

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16 thoughts on “The Origin of Life and Life on Other Planets

  1. I would find it harder to believe that life started on Mars and somehow survived by moving to Earth. Is life really that tough, that unstoppable? Or isn’t it more likely to have simply originated in the only place it is currently known to exist?
    As far as multiple origins are concerned, the question should be, why not? That brings up the whole idea of “Goldilocks zones”, and the fallacy that a place must be “just right”.
    Mama Bear and Papa Bear survived to reproduce, despite their preferences being “too hot” or “too cold” by Goldilocks’ standards – which is just my silly way of saying that we really have limited ideas of what life is capable of, and our educated opinion is still just opinion. At the moment.

  2. As far as life having started on Mars and spread to Earth via meteorites, I suppose a case for that hypothesis could be built. Being smaller than Earth, and plunked down between Earth and Jupiter, it might have suffered less from the “late heavy bombardment” than Earth did — and thus life got an earlier start there.

    But I would never extend that to claim (as some do) that our solar system is the only abode of life in the entire cosmos. I share your gut feeling that microbial life got started on a host of worlds. It might have lasted on only a small fraction of those, and gone on to multicellular forms on a still smaller percentage. “Nevertheless, it still started.” (What’s Italian for “started”?)

  3. Re does the scope of evolution include the origin of life.

    There are quite practical reasons for separating science into different fields, even if, like physics and chemistry, they overlap to some extent — in this case both dealing with atoms and their interactions.

    If you want to include the origin of life in evolutionary biology that’s certainly your prerogative. Getting all evolutionary scientists to agree on that may be another thing entirely. If memory serves me, the definition of evolution used by population biologists is: change in allele frequencies with time. By that definition, evolution would seemingly not apply prior to the existence of genes. Also, there are and always have been a number of evolutionary scientists who have made a leap of faith to a belief in a creation event by a creator god which they, at least, consider beyond the realm of evolutionary science. Some of them have made very important contributions to biological science and might well disagree with the extension of the term evolution to include the origin of life.

  4. Since no life = no evolution, I would have thought that the scope of evolution could not escape consideration of the origin. If you trace life back far enough, you will presumably reach a stage where the distinction between living and non-living is tiny.
    I would say that it’s important to know whether or not some creator god intervened to kick things off or whether the right bits eventually came together under the right circumstances to live and evolve. The main problem would seem to be convincing believers or non-believers that they are actually wrong…

    1. Re: Jim Sweeney “itโ€™s important to know whether or not some creator god intervened to kick things off or whether the right bits eventually came together under the right circumstances to live and evolve. ”

      Yes it certainly would be important but that doesn’t mean it is determinable or knowable in a scientific sense. A supernatural creator could do anything — even the impossible — and deep faith in such a creator is impossible for science to refute. The best that could be done is to show that the origin of life could have occurred under conditions that once existed on Earth or elsewhere (cf Sir Francis Crick’s panspermia). I’d be happy with that but it still would not eliminate the possibility of a creator of those conditions or the laws under which they developed.

      And Its importance doesn’t mean it necessarily should be considered part of evolutionary biology. The transition between non-life and life may or may not have been some sort of evolutionary process. We don’t really know. We don’t even know what the precise difference between living and non-living is. Life may or may not be an emergent property. Are viruses alive? If not, were their ancestors alive? I don’t think we don’t know. (I’m willing to be corrected.)

      Past scientists have worked on the problem of the origin of life and there are scientists still working on it. A lot of their work could just as well be considered chemistry as biology. I wonder what the scientists involved in that work think about it being called “evolutionary biology”? (Consider that physicist Ernest Rutherford was a bit pissed that his Nobel prize was given in chemistry not physics.)

  5. Reminder: That which is asserted without evidence can be dismissed without evidence. When an extraordinary and unique event is claimed without evidence, it must be dismissed vigorously.

  6. The question of the existence (or not) of a deity should not influence a search for the truth. If we postulate the existence of some entity which is omniscient, omnipotent and immortal, but whose existence cannot yet be proven, there are only a couple of ways the discussion can go.
    One – the deity created us, the world, the universe – whatever – and left no trace (possibly out of embarrassment); or
    Two – the deity did all or some of the above and left a trace.
    In either case the search for the truth, of origins and everything else, should obviously continue until we understand how things came to be. Even if that leads to the proverbial thumbprint in the clay that says “someone made this”.
    As far as I know, all the testable evidence so far says “nobody made this”, and that’s ok by me.

  7. Scientifically, if a deity set initial conditions and the physical laws, and then initiated the big bang, would we ever be able to determine this?

    If everything from the big bang on was purely natural (versus supernatural), how would we be able to tell what caused the big bang?

    So we could postulate that a deity didn’t exist or postulate that a deity did exist, and it doesn’t really matter, because there may not ever be a way to look at the physical universe and determine what caused the big bang, or the physical constants to be the way they are or why the laws of the universe are what they are.

    Fun to think about – but impossible to answer.

  8. As I understand it, the Singularity implies that everything was once in a tiny area of “infinite density and temperature”.
    This primordial lump didn’t exist anywhere, because there was no “anywhere” for it to exist, and it had no past existence because time didn’t exist. At some point in this spaceless space and timeless time it went kablooie, and the next thing you know it’s mobile phones and pizzas.
    When you think about it, the whole idea is so absurd that the possibility of a deity inventing the whole shebang just for the hell of it sounds relatively sane by comparison.
    But that’s pushing things way back before the origins of life and our search to find them.

    1. The idea of a singularity involved in the big bang was dropped long ago. You’re going to have to develop a new reason to dismiss theories you don’t like.

  9. Ah, you misunderstand. I don’t have to have a particular reason to dismiss theories I don’t like. But I do know that if I dismiss a theory I may easily be wrong, and when it comes to the origin of the Universe my opinion is worth diddley-squat anyway.
    And just because I believe something to be absurd, that doesn’t mean it isn’t real / didn’t happen. Absurd things happen all the time, and if enough evidence is gathered that some idea can be accepted as factual, that doesn’t mean it’s not absurd – in the sense of being “inconsistent with reason or common sense”…
    Also, has the idea of a singularity been dropped? Not as far as I can see.

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