But how much longer can we rely on science to hold the line against racism? Its endorsement of anti-racism has been part of the post-war order, like the Soviet bloc and the welfare state. Like them, however, it may prove to be no more than the product of a particular period.
Racism, in the sense of hatred, prejudice, discrimination and violence against those from different racial groups, remains one of the most evil forces in the world. It is all the more important, then, that those opposing it are equal to any new intellectual challenge - from, say, scientists who may one day claim to have isolated a gene that determines cognitive ability, rather as some scientists already claim to have found a gene that creates a predisposition to homosexuality. It may not be possible, for much longer, to regard race as the great unmentionable, to treat any discussion of racial difference as tantamount to a revival of fascism. Denial may prove to be the worst kind of wet liberalism.
Over the last 20 years, the concept of race has largely vanished from scientific textbooks, except to be labelled obsolete. A century ago, equivalent books would have spoken of little else. Indeed, until the 1940s, it was taken as axiomatic that racial biology was destiny. Scientists shared the general belief not only that biological characteristics determined the fortunes of different peoples but also that some groups were mentally and morally superior to others. Scientists rejected these views after 1945 not because of some great discovery but because of their recognition of where race biology had led in Hitler's Germany. Where their predecessors tried to categorise and classify humankind into distinct groups, post- war scientists emphasised that the varieties shade into each other, making any dividing line between one "race" and another an arbitrary one. Skin colour, say, may darken as one travels from north to south, but it does not follow that other characteristics vary with it. Divisions between racial groups can vary infinitely according to which particular trait is adopted as the criterion. For example, if the ability to digest the milk-sugar lactose were used as a criterion, northern Europeans would be assigned to the same race as the cattle-keeping Fulani people of West Africa. Race, in other words, was scientifically all but meaningless.
These arguments are powerful. But, though race may be a poor method of classifying human groups, it does not follow that all human groups are identical in their innate capacities. The uncomfortable truth is that science has not actually disproved the idea that one race might be superior in some respects to another. And, over the past two decades, a new race science has been establishing itself, rooted in the psychology of intelligence. In 1969, the American psychologist Arthur Jensen first claimed that black children might be inherently less intelligent than white ones. Last year's publication of The Bell Curve by Richard Herrnstein and Charles Murray has brought race science back into the limelight.
Yet many in the scientific anti-racist camp have been reluctant to confront their opponents' claims directly. Rather, they have continued to ridicule the concept of race and to question the motives of the authors. Race science, it is argued, should be ignored because it is bad science. But if it is so poor, why not dispose of it out in the open? It is perfectly true that there are numerous political reasons for adopting the Jensenist stance: for example, if blacks indeed have lower IQs than whites, expensive programmes to tackle their under-achievement in schools may be a waste of time and money. Scientific texts, however, cannot be adequately analysed according to the supposed motives of their authors. To call somebody a racist is not the same as proving them wrong.
Rather than dismissing the Jensenists as unworthy of discussion, it is far better to undertake solid research, as James Flynn, of the University of Otago, New Zealand, has done. He showed that, in 20 countries between 1950 and 1980, average IQ scores rose spectacularly. The gap between one generation and another, he reported, was similar to that between blacks and whites. If taken at face value, his findings suggest that African- Americans in 1980 had the same intelligence level as whites 30 years before. His conclusion was that IQ tests "do not measure intelligence but rather a correlate with a weak causal link to intelligence".
BEHIND the liberal reluctance to engage with the arguments lies the suggestion that race is not a legitimate concern of science. The truth is that science cannot help but deal with race and that it will be compelled to do so more in future.
One example is the observation that, in both Britain and America, high blood pressure is more common among blacks than among whites. Critics tend to regard any suggestion that genes may play a part as politically suspect - because it draws attention away from the tension-inducing conditions under which black people live or because it seems to deny that more health spending would make a difference or because it simply implies genetic inferiority. But, in this case, there need be no incompatibility between a genetic explanation and a belief that black people have suffered grievously from oppression. The "Grim hypothesis", named after one of its authors, Clarence E Grim, is based on the idea that diets rich in salt can cause high blood pressure. Grim argues that the main causes of death for slaves, especially during the transatlantic Middle Passage, were salt-depleting conditions such as diarrhoea, fevers and vomiting. Those whose genes allowed them to retain salt were more likely to survive. Their descendants, however, on a salt-rich modern diet, find that what was once an aid to survival has become a disadvantage.
The theory has been widely criticised by both historians and scientists. But, whatever its validity, it shows that anti-racist science need not always take a negative approach to human diversity. Genes can illuminate human history in the same way that buried relics can. They can be interpreted in unfortunate ways, but then so can archaeological finds.
Challenges to anti-racist orthodoxy will become more frequent as genetics advances. Despite a trail littered with rejected claims, geneticists are enthusiastically seeking out genetic sequences which they wish to associate with moral or mental traits, such as drug dependency or criminal aggression. A Texas research team has reported that supposed genetic "markers" for cocaine dependency occur at different rates in blacks and whites.
Far more momentous will be the search for genes influencing cognitive ability. The quickest way to establish the mental inferiority of an ethnic group as an accepted truth rather than a disturbing contention is to label a stretch of DNA the genius gene. No matter how mysterious, limited or roundabout its effects, the label will stick. Any group found to be short of this sequence will be labelled inferior.
As long as we are told that race is scientifically trivial or meaningless, it is easy to put all aspects of racial disadvantage within a single framework. There is no need to prove hostile intent, since all negative characteristics are by definition the products of prejudice. But what if science came to accept that there were meaningful differences in mental capacity between human groups? Then we would either reject science, or we would all become racists in the broad sense of the term. We could still condemn racism as hatred, aggression or the denial ofrights, but the edifice of anti- racism would have been critically weakened.
As our knowledge of human genetics grows, its power will lie not so much in the findings themselves as in how they are interpreted and how they are used. A science of human difference could enrich our understanding of human evolution and history, of who we are and where we came from. Equally, it could induce a new fatalism about the inevitability of racial disadvantage and racial conflict. The decline of the 20th century's great ideological divisions has already renewed old ethnic divisions; humankind is as permeated by consciousness of race as it has ever been. The idea that this is part of human nature is already influential. It may be only a matter of time before significant connections start to form between gene consciousness and race consciousness. This is a nettle that liberals and anti-racists will have to grasp; if they do not, there are others who will.
Marek Kohn's 'The Race Gallery' is published by Jonathan Cape on 21 September.Reuse content