God used to be the ineffable subject for blasphemy. The Victorians made sex the great unmentionable. Today it is race. James Watson, who shared the Nobel prize for his part in unwinding the double helix of DNA, has been banned from delivering his lecture at the Science Museum in London. He suggested that blacks are less intelligent than whites. What Dr Watson said verbatim was that he was inherently gloomy about the prospect of Africa because “all our social policies are based on the fact that their intelligence is the same as ours – whereas all the testing says not really”.

Uproar. The rest of his lecture tour is under threat. The Equality and Human Rights Commission is casting a cold eye over the whole of Dr Watson’s newspaper interview. Should we be shocked? All experience says: “Not really.” He has form for stepping outside his laboratory into controversy. His book, published next week, the reason for his lecture tour, says: “There is no firm reason to anticipate that the intellectual capacities of peoples separated in their evolution should prove to have evolved identically.”

It is unscientific to pretend that there are no generic differences between races. In the men’s 100 metres at the Olympic Games, the finalists will almost certainly all be black. In selecting a basketball squad, Tutsis have the reach over Bushmen. Japanese, who have scant body hair, find the body odour on the London Underground even more offensive than the natives. In the most cosmopolitan city in the world, it should be possible to discuss racial differences scientifically. Censorship is as repugnant as real racism.