The Greatest Show on Earth, By Richard Dawkins

Creationists believe evolution is true. They just don't believe it's evolution. In the most back-handed of testaments to the power of the idea of natural selection, many of them profess themselves to be comfortable with the idea that groups of organisms can become different from their ancestors – longer beaks, darker markings, stronger jaws – because these traits enabled their ancestors to leave more descendants than others that lacked them. Yet the Creation Museum in Kentucky still insists that "natural selection is not evolution" in the same breath as it acknowledges that selection shapes living forms.

This species of creationist has abandoned attempts to deny that natural selection pervades nature, and they have started helping themselves to scientific phrases like "adaptive radiation" so as to imply that their version of events should be accorded parity with science. Instead, they draw a line: natural selection can make adjustments, but it cannot create new kinds of organisms; for to claim that it could would be to challenge the authority of God as laid down in Scripture.

Their strategy is itself an adaptation to the environmental pressures upon them. It suggests that reason and empirical observation exert sufficient influence in today's world that dogma cannot survive by Genesis alone. Just because they are dogmatists doesn't mean that creationists aren't adaptable. They are evolving quicker than a family of spiders set loose on a tropical island. To coin one of Richard Dawkins's many phrases, they have evolved evolvability. And Dawkins himself has adapted. One of the pleasant surprises in his new book is his willingness to welcome expressions of belief in evolution even if they are combined with expressions of belief in God.

Public opinion weighs heavy on his mind, with opinion polls affirming that over 40 per cent of Americans believe humans were created by God within the past few thousand years, and that a sizeable minority of Britons agree.

The zero-tolerance stance he took towards religion in The God Delusion set atheists up as an exclusive sect, proudly isolated. Now he seems to have embraced the power of coalition and common cause, complaining that an opinion survey does not offer an option for people to agree that humans evolved over millions of years but that God had a hand in the process, and putting in a good word for the "churchmen and women who accept the evidence for evolution".

The good word is "rational". It implies that he can work with these people – as he did before Delusion, in the 2002 letter to Tony Blair, pointedly reproduced in the opening pages of Greatest Show, that he organised with Bishop Harries of Oxford to protest against the infiltration of creationism into a school curriculum. It's pleasant to see him revert to his earlier strategy as alliances often get somewhere, but sects usually go nowhere.

A side-effect of his new readiness to compromise is that he seems older, having shed some of the stringent impatience with the shortcomings of others that is more typically seen in much younger men. It suits him, though. He is in good humour, revelling in the marvels of evolved life and the pleasure of expounding them.

Dawkins has never been one to refrain from an aside, and there's fun to be had in his footnotes. It's rather endearing to be told in one of them that he finds the TV show Grumpy Old Men "rather charming". He is growing more and more like that great grumpy old man of British popular science, the biologist JBS Haldane. Some of his best passages of prose here are not the literary flourishes – though he deserves an ovation for his opening sally, in which he compares the frustrations for a scientist challenged by creationists to the plight of a teacher of Latin and its associated history, from "the strategic niceties of the Punic Wars" to the "voluptuous excesses of the later emperors", beset by fanatics who deny the Romans ever existed. They are the many expositions of how things like protons and proteins behave, set out in the kind of robust, shirt-sleeved prose of which Haldane would have approved.

Dawkins unbuttoned is not Dawkins at his best, though. The Greatest Show on Earth is not the only show in town. It's hardly the first popular case for evolution, and it's not the only new one.

Dawkins is the first and most fulsome to praise the American biologist Jerry Coyne's book Why Evolution is True, which appeared earlier this year. Coyne's account is a sharper guide to the issues; Dawkins's suffers from deferential editing that makes it harder to see the wood for the trees. It loses definition under the sheer weight of the evidence it presents – though if it were comprehensive it would include all of biology. Much of the case is familiar, from explanations for the umpteenth time that humans aren't descended from monkeys to the roundabout anatomical routes for nerves and tubes that no self-respecting Designer would design. Dawkins has generally worked with material that is well known at least to his peers, but his genius in the past has been to arrange it so that his readers' understanding of the world is transformed. That doesn't happen here.

Nevertheless, there are classic qualities in these pages; those of the old-fashioned science teacher rattling with well-polished quirks, his legend trailing in his wake, still fired with the passion to explain and inspire. If I found myself needing to rebut creationists, Coyne's book is the one I would reach for. But if I were a teacher, I would treasure Greatest Show as a compendium of enlightening passages for my students. If Dawkins carries on this way, he'll be hailed as a national treasure yet.

Marek Kohn's 'A Reason for Everything' is published by Faber & Faber