In a lot of ways, evolution is like unto theology. “Gods are ontologically distinct from creatures,” said Damien Broderick, “or they’re not worth the paper they’re written on.” And indeed, the Shaper of Life is not itself a creature. Evolution is bodiless, like the Judeo-Christian deity. Omnipresent in Nature, immanent in the fall of every leaf. Vast as a planet’s surface. Billions of years old. Itself unmade, arising naturally from the structure of physics. Doesn’t that all sound like something that might have been said about God?
And yet the Maker has no mind, as well as no body. In some ways, its handiwork is incredibly poor design by human standards. It is internally divided. Most of all, it isn’t nice.
In a way, Darwin discovered God—a God that failed to match the preconceptions of theology, and so passed unheralded. If Darwin had discovered that life was created by an intelligent agent—a bodiless mind that loves us, and will smite us with lightning if we dare say otherwise—people would have said “My gosh! That’s God!”
But instead Darwin discovered a strange alien God—not comfortably “ineffable,” but really genuinely different from us. Evolution is not a God, but if it were, it wouldn’t be Jehovah. It would be H. P. Lovecraft’s Azathoth, the blind idiot God burbling chaotically at the center of everything, surrounded by the thin monotonous piping of flutes.
Which you might have predicted, if you had really looked at Nature.
So much for the claim some religionists make, that they believe in a vague deity with a correspondingly high probability. Anyone who really believed in a vague deity, would have recognized their strange inhuman creator when Darwin said “Aha!”
So much for the claim some religionists make, that they are waiting innocently curious for Science to discover God. Science has already discovered the sort-of-godlike maker of humans—but it wasn’t what the religionists wanted to hear. They were waiting for the discovery of their God, the highly specific God they want to be there. They shall wait forever, for the great discovery has already taken place, and the winner is Azathoth.
Well, more power to us humans. I like having a Creator I can outwit. Beats being a pet. I’m glad it was Azathoth and not Odin.
*
1. Francis Darwin, ed., The Life and Letters of Charles Darwin, vol. 2 (John Murray, 1887).
2. George C. Williams, Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought, Princeton Science Library (Princeton, NJ: Princeton University Press, 1966).
132
The Wonder of Evolution
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 piece without 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 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—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.
So let us dispose of the idea that evolution is a wonderful designer, or a wonderful conductor of species destinies, which we human beings ought to imitate. For human intelligence to imitate evolution as a designer, would be like a sophisticated modern bacterium trying to imitate the first replicator as a biochemist. As T. H. Huxley, “Darwin’s Bulldog,” put it:1
Let us understand, once and for all, that the ethical progress of society depends, not on imitating the cosmic process, still less in running away from it, but in combating it.
Huxley didn’t say that because he disbelieved in evolution, but because he understood it all too well.
*
1. Thomas Henry Huxley, Evolution and Ethics and Other Essays (Macmillan, 1894).
133
Evolutions Are Stupid (But Work Anyway)
In the previous essay, I wrote:
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.
In this essay I describe some well-known inefficiencies and limitations of evolutions. I say “evolutions,” plural, because fox evolution works at cross-purposes to rabbit evolution, and neither can talk to snake evolution to learn how to build venomous fangs.
So I am talking about limitations of evolution here, but this does not mean I am trying to sneak in creationism. This is standard Evolutionary Biology 201. (583 if you must derive the equations.) Evolutions, thus limited, can still explain observed biology; in fact the limitations are necessary to make sense of it. Remember that the wonder of evolutions is not how well they work, but that they work at all.
Human intelligence is so complicated that no one has any good way to calculate how efficient it is. Natural selection, though not simple, is simpler than a human brain; and correspondingly slower and less efficient, as befits the first optimization process ever to exist. In fact, evolutions are simple enough that we can calculate exactly how stupid they are.
Evolutions are slow. How slow? Suppose there’s a beneficial mutation that conveys a fitness advantage of 3%: on average, bearers of this gene have 1.03 times as many children as non-bearers. Assuming that the mutation spreads at all, how long will it take to spread through the whole population? That depends on the population size. A gene conveying a 3% fitness advantage, spreading through a population of 100,000, would require an average of 768 generations to reach universality in the gene pool. A population of 500,000 would require 875 generations. The general formula is
Generations to fixation = 2ln(N) / s,
where N is the population size and (1 + s) is the fitness. (If each bearer of the gene has 1.03 times as many children as a non-bearer, s = 0.03.)
Thus, if the population size were 1,000,000—the estimated population in hunter-gatherer times—then it would require 2,763 generations for a gene conveying a 1% advantage to spread through the gene pool.1
This should not be surprising; genes have to do all their own work of spreading. There’s no Evolution Fairy who can watch the gene pool and say, “Hm, that gene seems to be spreading rapidly—I should distribute it to everyone.” In a human market economy, someone who is legitimately getting 20% returns on investment—especially if there’s an obvious, clear mechanism behind it—can rapidly acquire more capital from other investors; and others will start duplicate enterprises. Genes have to spread without stock markets or banks or imitators—as if Henry Ford had to make one car, sell it, buy the parts for 1.01 more cars (on average), sell those cars, and keep doing this until he was up to a million cars.
All this assumes that the gene spreads in the first place. Here the equation is simpler and ends up not depending at all on population size:
Probability of fixation = 2s.
A mutation conveying a 3% advantage (which is pretty darned large, as mutations go) has a 6% chance of spreading, at least on that occasion.2 Mutations can happen more than once, but in a population of a million with a copying fidelity of 10-8 errors per base per generation, you may have to wait a hundred generations for another chance, and then it still has only a 6% chance of fixating.
Still, in the long run, an evolution has a good shot at getting there eventually. (This is going to be a running theme.)
Complex adaptations take a very long time to evolve. First comes allele A, which is advantageous of itself, and requires a thousand generations to fixate in the gene pool. Only then can another allele B, which depends on A, begin rising to fixation. A fur coat is not a strong advantage unless the environment has a statistically reliable tendency to throw cold weather at you. Well, genes form part of the environment of other genes, and if B depends on A, then B will not have a strong advantage unless A is reliably present in the genetic environment.
Let’s say that B confers a 5% advantage in the presence of A, no advantage otherwise. Then while A is still at 1% frequency in the population, B only confers its advantage 1 out of 100 times, so the average fitness advantage of B is 0.05%, and B’s probability of fixation is 0.1%. With a complex adaptation, first A has to evolve over a thousand generations, then B has to evolve over another thousand generations, then A* evolves over another thousand generations . . . and several million years later, you’ve got a new complex adaptation.
Then other evolutions don’t imitate it. If snake evolution develops an amazing new venom, it doesn’t help fox evolution or lion evolution.
Contrast all this to a human programmer, who can design a new complex mechanism with a hundred interdependent parts over the course of a single afternoon. How is this even possible? I don’t know all the answer, and my guess is that neither does science; human brains are much more complicated than evolutions. I could wave my hands and say something like “goal-directed backward chaining using combinatorial modular representations,” but you would not thereby be enabled to design your own human. Still: Humans can foresightfully design new parts in anticipation of later designing other new parts; produce coordinated simultaneous changes in interdependent machinery; learn by observing single test cases; zero in on problem spots and think abstractly about how to solve them; and prioritize which tweaks are worth trying, rather than waiting for a cosmic ray strike to produce a good one. By the standards of natural selection, this is simply magic.
Humans can do things that evolutions probably can’t do period over the expected lifetime of the universe. As the eminent biologist Cynthia Kenyon once put it at a dinner I had the honor of attending, “One grad student can do things in an hour that evolution could not do in a billion years.” According to biologists’ best current knowledge, evolutions have invented a fully rotating wheel on a grand total of three occasions.
And don’t forget the part where the programmer posts the code snippet to the Internet.
Yes, some evolutionary handiwork is impressive even by comparison to the best technology of Homo sapiens. But our Cambrian explosion only started, we only really began accumulating knowledge, around . . . what, four hundred years ago? In some ways, biology still excels over the best human technology: we can’t build a self-replicating system the size of a butterfly. In other ways, human technology leaves biology in the dust. We got wheels, we got steel, we got guns, we got knives, we got pointy sticks; we got rockets, we got transistors, we got nuclear power plants. With every passing decade, that balance tips further.
So, once again: for a human to look to natural selection as inspiration on the art of design is like a sophisticated modern bacterium trying to imitate the first awkward replicator’s biochemistry. The first replicator would be eaten instantly if it popped up in today’s competitive ecology. The same fate would accrue to any human planner who tried making random point mutations to their strategies and waiting 768 iterations of testing to adopt a 3% improvement.
Don’t praise evolutions one millimeter more than they deserve.
Coming up next: More exciting mathematical bounds on evolution!
*
1. Dan Graur and Wen-Hsiung Li, Fundamentals of Molecular Evolution, 2nd ed. (Sunderland, MA: Sinauer Associates, 2000).
2. John B. S. Haldane, “A Mathematical Theory of Natural and Artificial Selection,” Mathematical Proceedings of the Cambridge Philosophical Society 23 (5 1927): 607–615, doi:10.1017/S0305004100011750.
Rationality- From AI to Zombies Page 50