Efforts to prove the superiority or inferiority of different races have a long and undistinguished history, from the justifications of slavery to the eugenic policies of Nazi Germany.
Modern studies on race and intelligence have continued to create controversy.
In 1994, a dispute erupted over the best-selling book The Bell Curve, by Charles Murray and Richard Hermstein, which argued that there were IQ differences between races that were at least partly genetic and that welfare and other polices were diluting the intelligence of the population by inadvertently encouraging the "wrong" women (with low IQs) to have babies.
The authors were attacked by, among others, the evolutionary biologist Stephen Jay Gould, who criticised the IQ test for its racial and social bias and pointed out that evidence did not indicate a genetic origin to group differences in intelligence. Intelligence could not be boiled down to a single measurable factor, he said.
Rutledge Dennis, of George Mason University, said it "paints a picture of blacks ... as collective biological illiterates" justifying those who would "disenfranchise and exclude racial minorities".
In 2002, Richard Lynn, a professor of psychology at the University of Ulster, stoked the fire with the publication of his book IQ and the Wealth of Nations, written with Tatu Vanhanen, emeritus professor of political science at the University of Tampere, Finland, and father of the Finnish Prime Minister, Matti Vanhanen. The claims were criticised on the grounds that data for many countries was flimsy and inadequate, unrepresentative of their ethnic diversity and wrongly analysed. The countries with the highest scores were those where IQ testing was part of the educational process.
Arthur Jensen, a former professor of educational psychology at the University of Berkeley, California, published The g Factor: The Science of Mental Ability in 1998 suggesting that a "genetic component" lay behind the difference between whites and blacks in intelligence. He was accused of "scientific racism", couching racial differences in IQ in a theory drawn from evolutionary biology, and of practising "social, value-laden science".
In the UK, the dispute erupted at Edinburgh University in 1996 when the psychologist Christopher Brand declared he was a "race realist". "The way in which I would try to explain higher levels of crime and out-of-wedlock births would not be by referring to blackness or race but to IQ," he said.