“Adam liked sugar and ate an apple and reproduced, Barbara liked sugar and ate an apple and reproduced, Charlie liked sugar and ate an apple and reproduced, and 2763 generations later, the allele became fixed in the population. For convenience of thought, we sometimes compress this giant history and say: “Evolution did it.” “
“Evolution does not explain the origin of life; evolutionary biology is not supposed to explain the first replicator, because the first replicator does not come from another replicator. Evolution describes statistical trends in replication. The first replicator wasn’t a statistical trend, it was a pure accident. The notion that evolution should explain the origin of life is a pure strawman.”
“To praise evolution too highly destroys the real wonder, which is not how well evolution designs things, but that a naturally occurring process manages to design anything at all.“
—Eliezer Yudkowsky, “The Wonder of Evolution”
This post is a continuation of yesterday’s post. Select portions of this post by Eliezer are reproduced below.
The wonder of evolution is that it works at all.
I mean that literally: If you want to marvel at evolution, that’s what’s marvel-worthy.
How does optimization first arise in the universe? If an intelligent agent designed Nature, who designed the intelligent agent? Where is the first design that has no designer? The puzzle is not how the first stage of the bootstrap can be super-clever and super-efficient; the puzzle is how it can happen at all.
Evolution resolves the infinite regression, not by being super-clever and super-efficient, but by being stupid and inefficient and working anyway. This is the marvel.
For professional reasons, I often have to discuss the slowness, randomness, and blindness of evolution. Afterward someone says: “You just said that evolution can’t plan simultaneous changes, and that evolution is very inefficient because mutations are random. Isn’t that what the creationists say? That you couldn’t assemble a watch by randomly shaking the parts in a box?”
But the reply to creationists is not that you can assemble a watch by shaking the parts in a box. The reply is that this is not how evolution works. If you think that evolution does work by whirlwinds assembling 747s, then the creationists have successfully misrepresented biology to you; they’ve sold the strawman.
The real answer is that complex machinery evolves either incrementally, or by adapting previous complex machinery used for a new purpose. Squirrels jump from treetop to treetop using just their muscles, but the length they can jump depends to some extent on the aerodynamics of their bodies. So now there are flying squirrels, so aerodynamic they can glide short distances. If birds were wiped out, the descendants of flying squirrels might reoccupy that ecological niche in ten million years, gliding membranes transformed into wings. And the creationists would say, “What good is half a wing? You’d just fall down and splat. How could squirrelbirds possibly have evolved incrementally?”
That’s how one complex adaptation can jump-start a new complex adaptation. Complexity can also accrete incrementally, starting from a single mutation.
First comes some gene A which is simple, but at least a little useful on its own, so that A increases to universality in the gene pool. Now along comes gene B, which is only useful in the presence of A, but A is reliably present in the gene pool, so there’s a reliable selection pressure in favor of B. Now a modified version of A* arises, which depends on B, but doesn’t break B’s dependency on A/A*. Then along comes C, which depends on A* and B, and B*, which depends on A* and C. Soon you’ve got “irreducibly complex” machinery that breaks if you take out any single piece.
And yet you can still visualize the trail backward to that single piece: you can, without breaking the whole machine, make one piece less dependent on another piece, and do this a few times, until you can take out one whole piecewithout breaking the machine, and so on until you’ve turned a ticking watch back into a crude sundial.
Here’s an example: DNA stores information very nicely, in a durable format that allows for exact duplication. A ribosome turns that stored information into a sequence of amino acids, a protein, which folds up into a variety of chemically active shapes. The combined system, DNA and ribosome, can build all sorts of protein machinery. But what good is DNA, without a ribosome that turns DNA information into proteins? What good is a ribosome, without DNA to tell it which proteins to make?
Organisms don’t always leave fossils, and evolutionary biology can’t always figure out the incremental pathway. But in this case we do know how it happened. RNA shares with DNA the property of being able to carry information and replicate itself, although RNA is less durable and copies less accurately. And RNA also shares the ability of proteins to fold up into chemically active shapes, though it’s not as versatile as the amino acid chains of proteins. Almost certainly, RNA is the single A which predates the mutually dependent A* and B.
It’s just as important to note that RNA does the combined job of DNA and proteins poorly, as that it does the combined job at all. It’s amazing enough that a single molecule can both store information and manipulate chemistry. For it to do the job well would be a wholly unnecessary miracle.
What was the very first replicator ever to exist? It may well have been an RNA strand, because by some strange coincidence, the chemical ingredients of RNA are chemicals that would have arisen naturally on the prebiotic Earth of 4 billion years ago. Please note: evolution does not explain the origin of life; evolutionary biology is not supposed toexplain the first replicator, because the first replicator does not come from another replicator. Evolution describes statistical trends in replication. The first replicator wasn’t a statistical trend, it was a pure accident. The notion that evolution should explain the origin of life is a pure strawman—more creationist misrepresentation.
If you’d been watching the primordial soup on the day of the first replicator, the day that reshaped the Earth, you would not have been impressed by how well the first replicator replicated. The first replicator probably copied itself like a drunken monkey on LSD. It would have exhibited none of the signs of careful fine-tuning embodied in modern replicators, because the first replicator was an accident. It was not needful for that single strand of RNA, or chemical hypercycle, or pattern in clay, to replicate gracefully. It just had to happen at all. Even so, it was probably very improbable, considered in an isolated event—but it only had to happen once, and there were a lot of tide pools. A few billions of years later, the replicators are walking on the moon.
The first accidental replicator was the most important molecule in the history of time. But if you praised it too highly, attributing to it all sorts of wonderful replication-aiding capabilities, you would be missing the whole point.
Don’t think that, in the political battle between evolutionists and creationists, whoever praises evolution must be on the side of science. Science has a very exact idea of the capabilities of evolution. If you praise evolution one millimeter higher than this, you’re not “fighting on evolution’s side” against creationism. You’re being scientifically inaccurate, full stop. You’re falling into a creationist trap by insisting that, yes, a whirlwind does have the power to assemble a 747! Isn’t that amazing! How wonderfully intelligent is evolution, how praiseworthy! Look at me, I’m pledging my allegiance to science! The more nice things I say about evolution, the more I must be on evolution’s side against the creationists!
But to praise evolution too highly destroys the real wonder, which is not how well evolution designs things, but that a naturally occurring process manages to design anything at all.