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:
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.
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.