Steve Jones - The Language of the Genes

One study of American male homosexuals hinted at an association between such behaviour and a group of genes near the tip of the X chromosome. First, the brothers of gay men were more likely to be gay than are males in the general population. This does not in itself say much, as brothers share an environment as well as genes. However, gay men's relatives on the mother's side were more liable to be gay than were those on the father's, suggesting that the trait is passed through females. Again, this is not proof of an innate predisposition (even if it implies a possible gene on the X chromosome). The best evidence seemed to come from the X chromosomes of pairs of homosexual brothers. Most who took part in the study shared a particular segment of DNA towards one end of that chromosome. Somewhere in its hundred or more genes may, it was suggested, be one that inclines some carriers to that form of sexual behaviour.

After an initial burst of publicity, the result proved hard to replicate (as is often the case for such characters, in which different genes might be involved in different families) and the simple idea of a 'gay gene' is now dismissed. Whatever the science, the main interest lay in the response by some — but not all — of the gay community. Many, it transpired, were happy to use biology as a justification for their way of life. The idea that sexual preference was inherited meant, they concluded, that sexuality was not contagious and that battles by bigots to dismiss homosexual teachers were not justified. More important, it gave a welcome sense of separation: of a shared difference that was present for reasons beyond individual control. All this disconcerted the many biologists who had spent years fighting the idea that sexual preference, crime or poverty are inborn and cannot be altered by social means.

This new hereditarian orthodoxy, like the old liberalism, asks too much of biology. It echoes a forgotten dispute of the 1930s. The German geneticist Theobald Lang claimed to have found that the sisters of gay men had somewhat masculine characters, and that male homosexuality might therefore be inherited. Whatever the accuracy of his claim that hint of a 'gay gene' gave rise to two quite opposed (albeit equally logical) responses. The Nazis, needless to say, took the brutal view: 'they are not poor sick people to be treated; they are enemies of the state to be eliminated!' In contrast — and faced with the same information — the socialist medical association (then in exile) wrote that 'Homosexuality is inborn and not subject to the free will of the individuals who come into the world with this inversion. The laws against it should be abolished.'

Like some members of today's gay community, both left and right felt that if that behaviour was innate it must be outside the control of those who display it. Each political group saw its response — eugenic sterilisation versus liberal legalisation — as consistent. Neither asked what is meant by a gene 'for' something, homosexuality included. The story of the German 'gay gene' points up the irrelevance of genetics to political opinion. Whatever inherited basis a character may have, preconceived views about its merits will not be changed by science.

Nowhere is the difficulty of separating science from politics, and the confusions of nature and nurture, more malign than in the study of differences among human groups. Older textbooks on race sooner or later come to the question, always treated with a certain prurience, of inherited differences in intelligence. That such dillm*uces existed and that they were inborn once seemed obvious. I.imucus himself classified humans as Homo sti^icus, thinking man. For the species as a whole, he could be no more pivusi- in his definition than Homo, nosce te ipsiwr. M.in, know thyself. His description of the different varieties ot humankind, in contrast, used behaviour as a character. Linnaeus' definition of an Asian, for example, was someone who was yellow, melancholic and flexible. Even forty years ago, racial stereotypes of the most predictable kind were still the norm.

Much of the work on inherited differences in intellect among races is contemptible and most of the rest is wrong. The wrong argument goes like this. Blacks do less well than whites on IQ tests, so that they are less intelligent. The IQ scores of parents and children are similar, so that differences in intelligence are controlled by genes. The difference between blacks and whites must therefore be set in DNA.

This argument is deceptively simple. It was once used in the USA as an excuse not to spend money on black education, and a variant of the theory, which sees poor rather than black children as victims of their genes, is employed in Britain by those who resent investment in state education (although, oddly enough, the most devoted hereditarians improve their children's environment by sending them to private schools). Simple as it may be, the argument is utterly false.

Whether IQ tests are an unbiased measure of intelligence is a matter for those who design them. The general consistency in the ability to move shapes around, or to do simple language puzzles and sums suggests a certain objectivity in the measure. The similarity of parents and children in their ability to do the test does not in itself say much, as families share the same environment as well as the same genes. It would be surprising if there were no genetic component in IQ variation. Many with low IQ suffer for genetic reasons, as several inborn illnesses manifest part of their effect by damaging the brain. Although normal variation in intelligence may not be related to such genes — after all, inborn blindness has nothing to do with variation in colour perception — a few inherited diseases do alter specific parts of the IQ mix. One, Williams syndrome {which involves the loss of a tiny section of chromosome), causes heart problems and a rather odd appearance; and a complete inability to deal with objects in space. Patients asked to draw a bicycle do a reasonable job with the wheels, the handlebars and the pedals — but they are scattered on the page. They find it impossible to arrange the parts into an image of the whole machine. However, their ability to speak or to do sums is not much affected.

This rare disease suggests that separate genes affect different parts of the IQ mix but, as always when using the abnormal to study the normal, says little about variation in the population as a whole. A mass of evidence from twins and adoption does suggest an inherited component to IQ. Indeed, a variant form of one gene involved in the growth of cells is frequent among children of very high intelligence (although it explains just a small part of the total variation). The gene involved helps move enzymes around inside cells and those of high intelligence may be more effective at burning sugar in the brain. Some claim that as much as seventy per cent of the variation in score within a population is due to diversity in its genes. This figure seems high, but can be accepted for the present. At first sight it looks like powerful evidence for the view that any racial differences in IQ must be set by biology.

In fact it has no relevance to understanding whether such differences — if they exist —;m iinborn or acquired. Why this is so can be seen in another character. In the United States, the blood pressure of middle-aged black men is about fifteen points higher than that of whites. Twin and other studies show that about half the variation in blood pressure within a group is due to genetic variation, and some genes that influence the character have been tracked down. The figures for blood pressure look similar to those for IQ although in this case blacks come out with a higher score.

Doctors and educationists have a subtle difference in world-view when faced with such figures. Doctors are optimists. They concentrate on the environment, the fact that blacks smoke more and have poorer diets than do whites, and try to change it. In the USA, optimism has paid off and high blood pressure among blacks is less of a problem than before. Many educationists are less hopeful. To them, the existence of inherited variation in intelligence removes the point of trying to improve matters with changes in the environment. Blacks, they say, have worse genes. These cannot be altered, so that it is futile to spend money on better schools. Their theory has been proved wrong. Over the past thirty years the average IQ of Japanese children has risen to ten points higher than that of Americans. Not even the most radical hereditarian claims that this is due to a sudden burst of evolution in the Far East. Instead, the schools are getting better.