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Complex Numbers #965240 added August 30, 2019 at 12:33am
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Life As We Know It
http://nautil.us/issue/17/big-bangs/the-unique-merger-that-made-you-and-ewe-and-...
The Unique Merger That Made You (and Ewe, and Yew)
All sophisticated life on the planet Earth may owe its existence to one freakish event.
Really, I debated with myself over linking this article here. It's not that it's very technical - it's not, at all; there's some biology lingo, but no math or physics. It's just, on the surface, not very relevant to much outside of biology. I, of course, find it fascinating.
But there's some speculation toward the end that's worth looking at. First, some highlights:
The transition from the classic prokaryotic model to the deluxe eukaryotic one is arguably the most important event in the history of life on Earth. And in more than 3 billion years of existence, it happened exactly once.
Well... [citation needed], I suppose. If it happened more than once, and the resulting organisms were out-competed or otherwise died off, we might never know. But I'll grant that the writer knows more about biology than I do; that's not a very high bar to clear.
If this story is true, and there are still those who doubt it, then all eukaryotes—every flower and fungus, spider and sparrow, man and woman—descended from a sudden and breathtakingly improbable merger between two microbes. They were our great-great-great-great-...-great-grandparents, and by becoming one, they laid the groundwork for the life forms that seem to make our planet so special. The world as we see it (and the fact that we see it at all; eyes are a eukaryotic invention) was irrevocably changed by that fateful union—a union so unlikely that it very well might not have happened at all, leaving our world forever dominated by microbes, never to welcome sophisticated and amazing life like trees, mushrooms, caterpillars, and us.
Now, those who like to deny evolution might ask something like "but if the eukaryotes were so successful, then why are there still prokaryotes?" I would suggest they read up on some basic biology; I'm certainly not going to waste time on that argument or its ilk.
“[Endosymbiosis] was taboo,” says Bill Martin. “You had to sneak into a closet to whisper to yourself about it before coming out again.”
That's legitimately funny.
The article goes on to lay out the case for eukaryotic origins - again, fascinating stuff, and it highlights how science gets shit done, but not really anything worth commenting on here - until we get to the end, where we find stuff that intersects with another of my favorite topics: extraterrestrial life.
This improbability has implications for the search for alien life. On other worlds with the right chemical conditions, Lane believes that life would be sure to emerge. But without a fateful merger, it would be forever microbial. Perhaps this is the answer to the Fermi paradox—the puzzling contradiction between the high apparent odds that intelligent life would exist elsewhere among the billions of planets in the Milky Way, and our inability to find any signs of such intelligence. As Lane wrote in 2010, “The unavoidable conclusion is that the universe should be full of bacteria, but more complex life will be rare.” And if intelligent aliens did exist, they would probably have something like mitochondria, too.
The "improbability" mentioned there is the unlikelihood of the formation of eukaryotes. Again, I'll point out that however improbable something is, once it happens, the probability of it having happened is unity - and since we eukaryotes wouldn't be around without it, we can't argue that something won't happen just because it's improbable. If that makes any sense.
I've also pointed out before that the "Fermi paradox" isn't a paradox. I don't accept the "high apparent odds that intelligent life would exist elsewhere." There's not a single rule, law, or requirement of evolution that those qualities that we call "intelligence" (please, can the "no intelligent life on Earth either" jokes; they're really tiresome) must occur, any more than there's a rule stating that eukaryotes must emerge.
So what this information does, really, is lower the odds of complex life existing in another biosphere. We don't know what those odds are, admittedly, because we simply don't have enough data points (we have precisely one data point - Earth).
Not that this idea is new to me; I've been sold on the Rare Earth Hypothesis for some years now. But this article goes into more depth than I've seen in the past, and does it without getting, as I said, too technical about it. |
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