In other news, the Guardian newspaper has posted a series of articles about various evolution related topics.
First up is this characteristically lucid entry from Richard Dawkins. I especially like this:
But what makes natural selection so special? A powerful idea assumes little to explain much. It does lots of explanatory “heavy lifting”, while expending little in the way of assumptions or postulations. It gives you plenty of bangs for your explanatory buck. Its Explanation Ratio – what it explains, divided by what it needs to assume in order to do the explaining – is large.
If any reader knows of an idea that has a larger explanation ratio than Darwin’s, let’s hear it. Darwin’s big idea explains all of life and its consequences, and that means everything that possesses more than minimal complexity. That’s the numerator of the explanation ratio, and it is huge.
Yet the denominator in the explanatory equation is spectacularly small and simple: natural selection, the non-random survival of genes in gene pools (to put it in neo-Darwinian terms rather than Darwin’s own).
Explanation ratio. I like that!
I do get a little uncomfortable, however, when people say that evolution explains life. That’s too imprecise for my taste. Evolution explains how it is possible, via natural mechanisms alone, for a relatively simple sort of life a billion years ago to propagate and diversity into the enormous variety of complex life forms we see today. But it surely does not explain, nor is it intended to explain, where life comes from in the first place.
I’m also a little uncomfortable with this:
You can pare Darwin’s big idea down to a single sentence (again, this is a modern way of putting it, not quite Darwin’s): “Given sufficient time, the non-random survival of hereditary entities (which occasionally miscopy) will generate complexity, diversity, beauty, and an illusion of design so persuasive that it is almost impossible to distinguish from deliberate intelligent design.” I have put “which occasionally miscopy” in brackets because mistakes are inevitable in any copying process. We don’t need to add mutation to our assumptions. Mutational “bucks” are provided free. “Given sufficient time” is not a problem either – except for human minds struggling to take on board the terrifying magnitude of geological time.
I would feel better if Dawkins had said that non-random survival can lead to complexity, diversity and all the rest. I don’t think it’s assured that such things will arise as the result of the prolonged action of natural selection. On evolutionary questions I tend to think Dawkins gets things right far more often than his critics, but on this one I definitely side with Stephen Jay Gould. Complexity is not something that inevitably happens; it is merely one of many things that might happen in the course of evolution.