The Political Gene, By Dennis Sewell

Darwinism here stands accused of complicity in genocide, promoting the abuse of vulnerable people, and overweening presumption. The first two charges in this book about "how Darwin's ideas changed politics" are historical, centring upon Nazism and the coercive eugenic measures pursued in other countries during the first half of the 20th century. The third arises from the sense that, instead of contritely withdrawing from the public arena, Darwinism now makes no attempt to hide its naked ambition to explain everything. Dennis Sewell thinks that Darwin needs to be "put back in his box".

The philosopher Daniel Dennett would retort that the box can't be made that could contain the "universal acid" of natural selection, an idea that dissolves all traditional certainties. Like the industrial revolution, the Darwinian revolution is still in progress; and as the Chinese premier Zhou Enlai is said to have said of the French revolution, it is too early to tell what the consequences will be.

While Darwin's great idea was utterly transformative, the naturalist's role in shaping views about human nature and variety was not as grand as Sewell implies. Ideas about human races and their ranking were firmly in the intellectual saddle by the time the Origin of Species appeared. Darwin certainly agreed that some races were superior to others, and anticipated that the former would exterminate the latter; but by omitting to set the scene, Sewell omits to acknowledge that Darwin followed the crowd.

Darwin's evolutionary idea did, however, provide a robust basis for sustaining racial theories. It also inspired Francis Galton, the founder of eugenics. Yet eugenics only took off after Mendel's findings on heredity were rediscovered at the turn of the 20th century, when Darwinism was at its lowest ebb. The new Mendelians regarded Darwinism as an outdated rival school. Later, in Germany, the Nazis did indeed consider their project to be "applied biology", as one of their leading "racial hygienists" put it. It was not simply a scientific monstrosity, though, but a chimera of science and mystical fantasies about the character of the German Volk.

Sewell draws attention to the sinister resonances of the Columbine high school killers' invocation of social Darwinism, repeated by the like-minded Finnish murderer Pekka-Eric Auvinen. Homicidal young men often identify themselves with potent forces.

But these were not political murder-suicides, unlike the far more numerous killings perpetrated by homicidal young men who identify themselves with divine will. As a final exclamation, "God is great" has infinitely more power than "natural selection".

A belief that evolutionary thinking promotes moral relativism seems to be Sewell's fundamental concern. He has little time for accounts of how moral sentiments might have evolved in humans, and no confidence that they could be a basis for a decent society. Other people of faith may take a more positive view. Britain's Chief Rabbi, Jonathan Sacks, does. "The biggest refutation of moral relativism is today coming not from religion and not from philosophy but from science itself," he recently declared.

The warmth of Sacks's endorsement contrasts with the increasingly antagonistic, sometimes petulant tone that emerges as Sewell concludes his polemic. His account of current racial-scientific claims is rather better than most, and he rightly chides liberals for not daring to engage with such claims.

But he wrongly assumes that he need not bother to engage with evolutionary psychology, dismissing it as "all this guff". His scorn for arguments that human psychology was shaped by Pleistocene conditions appears to arise from a mistaken belief that this epoch ended 780,000 years ago, which is about 770,000 years too early.

Sewell's attitude towards evolutionary thinking expands into a broader reaction against the political influence of science. He hails the British public's "healthy distrust" of scientists, as illustrated by the continuing reluctance of many parents to let their children have the MMR vaccine.

Since those members of the public have stuck to a hypothesis although investigations have found it wanting, this is not a sign of good civic, intellectual or public health. Unlike the MMR-autism hypothesis, evolutionary theory has passed the tests that it has repeatedly been set. And that is why Darwin is not going to be put back in his box.

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