Illustration by Daniel Pudles

The Greatest Show on Earth: The Evidence for Evolution. By Richard Dawkins. Simon and Schuster; 480 pages; $30. Bantam Press; £20. Buy from Amazon.com, Amazon.co.uk

A SCIENTIST on a flight across America falls into conversation with his neighbour, who turns out to be gratifyingly interested in his research on wild guppy populations in Trinidad. He probes deeply the scientist's methods, his findings and setbacks. Then comes the big question: what is the theory underlying the work? Darwin's theory of evolution by natural selection, replies the scientist. The rest of the journey passes in chilly silence.

This anecdote was related by the biologist in question to Richard Dawkins, one of the ablest and certainly the most high-profile of the many scientists trying to dispel the belief that man, rather than descending from other animals, was created in his current form by some divinity. In his previous books the British biologist has presented new ways of looking at evolution, demolished barriers to understanding it and traced the family tree of all life back through its branching points to a single origin. These books all started with evolution. But in the bicentennial year of Darwin's birth Mr Dawkins fills a gap in his oeuvre by setting out the evidence that the “theory” of evolution is a fact—“as incontrovertible a fact as any in science”.

And what a lot of evidence there is. The fossil record, far from the tenuous succession of gaps described by creationists, provides an admittedly incomplete but beautiful and coherent set of clues to life in the distant past. That any traces at all remain from so long ago is astounding, and anyway it is not the completeness of the fossil record but its consistency that matters. When asked what observation would disprove the theory of evolution, J.B.S. Haldane, a pioneering British geneticist, replied: “Fossil rabbits in the Precambrian era.” But such anachronisms have never been found.

Then there is the evidence written on the bodies of all living things. The mammalian skeleton is consistently recognisable in creatures as various as bats, monkeys, horses and humans. Vestiges such as the stumpy wings of flightless birds, and the hairs that prickle on human skin just like the rising hackles on furry mammals, are further testimony to our shared origins. Glitches, like the laryngeal nerves that are so neatly laid out in fish but that must detour in animals with necks—by a crazy 15 feet (4.6m) in the case of giraffes—demonstrate the incremental, undirected business of evolution in touching detail. At the microscopic scale, molecular genetics connects the various parts of the grand family tree with fantastic detail and accuracy.

The evidence that Mr Dawkins sets out so persuasively here is already widely known. Yet two-fifths of Americans still refuse to accept that human beings share a common ancestry with animals, preferring to believe that they were created in their present form in the past 10,000 years.

Perhaps some evolution-deniers will read this book and be convinced. But even to pick it up they would have to ignore a determined campaign of misinformation: polemicists demanding that schools “teach the controversy” (there is none); books about “intelligent design” written by “creationist scientists” (a ragbag of nonentities, mostly engineers or chemists rather than biologists); untruths and ad hominem attacks (few [scientists] “accept that an amoeba can evolve into a human being, even one as flawed as Richard Dawkins,” wrote one Christian essayist recently, neatly combining both genres).

Those who do read it will find that among the many puzzles that evolution explains so well are the futility and suffering that are ubiquitous in the natural world. All trees would benefit from sticking to a pact to stay small, but natural selection drives them ever upward in search of the light that their competitors also seek. Surely an intelligent designer would have put the rainforest canopy somewhat lower, and saved on tree trunks? The cheetah is perfectly honed to hunt gazelles—but the gazelle is equally well equipped to escape cheetahs. So whose side is the designer on?

The ichneumon wasp paralyses its prey without killing it and lays its larva inside this convenient source of fresh meat, to eat it slowly alive. This is just one striking instance of the immensity of pain in the animal kingdom, which defies explanation except via the unyielding calculus of competitive survival.