Up the airy mountain

I suppose we shall learn to love DNA, the stuff that uses us to make more of itself in shape of yet more people. Or perhaps at least come to accept, in Richard Dawkins's "profound and precise answer", that the perpetuation of DNA is what we're really here for also the sole purpose of flowers, bees and elephants.

If only he weren't quite so gung-ho and uplifted by it all, like a frock coated evangelist who has crossed the floor to science. We may be the robots who carry DNA a bit further on its road to God knows where we don't have to feel ecstatic about it, though Dawkins does his considerable best to get us high on an the facts (stylishly wrapped, as always).

In his last book, DNA was the River Out of Eden here, it is piled up in a new topographical metaphor. The cruder critics of evolutionary theory have often misrepresented the degree to which it rests on chance. How, they ask, could such an exquisite piece of engineering as the eye come into existence by any permutation of mere luck?

But to invoke chance, on its own, as Dawkins says, is to try jumping up the mountain. Darwinians claim only that mutation error in the copying of DNA programmes can be random. Thereafter, it is natural selection, acting infinitely slowly and gradually through countless generations, which works to refine a piece of physical design or, sometimes, to find a new use for it. The way to climb the mountain, therefore, is gently, up the long slope at the back.

Reviewing here recently a new book of essays by Stephen Jay Gould, Richard Dawkins's sparring partner in evolutionary biology, l expressed surprise that he should still spend so such energy on confounding America's creationists. Some of the same feeling is evoked by this book, which seems to insist, almost perversely, on rehearsing old conundrums and confrontations.

Thus, it takes us through the origins of bird flight Dawkins is a jumping up after insects man, rather than a proponent of gliding down from trees. And he spends a whole chapter on the evolution of the eye, marking the value of every gradual stage from photo cells to camera style models "No animal ever made a living purely by being on the evolutionary path to something better.

That eyes have evolved at least 40 times in independent groups of animals is one of the facts that may lodge in public discourse from this book, together, perhaps, with the computer modelled estimate that evolution from flat eye to "fish" eye would take a mere 364,000 generations, or less than half a million years. "The plaint that there hasn't been enough time for the eye to evolve turns out to be not just wrong but dramatically, decisively, ignominiously wrong." Dawkins, like Gould, enjoys a good crow.

Computer modelling of evolutionary change and selection, pioneered in his earlier bestseller, Tile Blind Watchmaker, contributes much that is fascinating biomorphs and other computer animals crowd the illustrations with creatures that could and should exist, even when they don't.

The central difficulty of simulating natural selection on a computer is in constructing enough of the variables. Nor is a two dimension screen well matched to changes in the real world.

A natural arena which does lend itself to lines and dots is the weaving of webs by orb spiders. But the chapter that explores this is most gripping when it describes what real spiders do and least persuasive when stuck in the world of graphic computation. Dawkins lets this make an important point for him that natural selection is actually a very simple sorting process, while computer models of it have to pile one complication on another.

A sense of the mysterious mathematics by which nature runs her own affairs is brought out to dizzying effect in the book's final chapter, which deals with the co-evolution of figs and their "private" species of pollinating wasps. "Their relationship," as Dawkins says, "is almost ludicrously tortuous and subtle", and its game plans are so breathtakingly involved that only the Ultimate Computer, storing its data in DNA, could keep track of counterbalancing costs and benefits.

There is little comfort in Climbing Mount Improbable for either old or new religions. "We must have no truck with the pop ecologist's fallacy, the holisty (sic) grail of all individuals striving for the good of the community, the ecosystem, Gaia. It is time to get fussy and sharpen up what we mean whenever we talk of a living creature being there for the benefit of anything." In Dawkins's book, the only entity that benefits from anything living is the unending river of DNA, which carries one message in its bottle Duplicate Me.