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Is there a gay gene?

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Why do people behave the way they do? This question has vexed human thought for thousands of years. And one of the most intriguing aspects of human behaviour is sex.

We are all the result of sexual activity between two individuals and most of us spend a considerable amount of time engaged in it (or at least thinking about it). The desire for sexual gratification is one of the most potent drives we experience, and for millennia its associated problems have been among the deepest causes of human misery.

Some people are attracted to the opposite sex, some to the same sex, some merely to themselves. Throughout human history, in all its varied social forms, sexual activity and sexual orientation have shown an ingenious variability.

Despite this ages old interest in sex—both theoretical and practical—our ideas as to why we behave the way we do have not changed very much. From primitive religious beliefs (possession by evil spirits, “original sin” etc) through to modern psychoanalytic and neurogenetic explanations, two basic factors have consistently been identified: nature and nurture.

The latest chapter in this unfolding story was made public in the middle of July, when five US scientists announced that they had identified a part of a human chromosome—the cellular structures that carry our genetic information—which was linked with male homosexuality. Immediately the world’s press was full of predictable headlines: “Gay gene identified” they claimed, suggesting that the factor causing homosexual behaviour had been discovered. The truth is different.

The study, led by Dean Hamer, had two parts. The first was relatively unadventurous; he identified 76 families of homosexual men, and traced the expression of homosexuality in a traditional pedigree study. The result was a set of family trees which showed that gay male relatives tended to be on the mothers’ side of a gay man’s family tree.

There was nothing particularly new about this first result, and in itself it does not tell us how sexual orientation might be transmitted. The cause could equally well be cultural or familial.

The excitement in the press and in the scientific, gay and lesbian communities was caused by the second part of the study. Using techniques developed over the last four years, Hamer and his colleagues took 40 pairs of homosexual brothers, their mothers, brothers and sisters and looked at their genetic make-up.

Human beings have 23 pairs of chromosomes—small wiry structures present in every cell of our bodies—which carry the genes that determine much of our anatomy and physiology. One pair of chromosomes is different in men and women. Women have two X chromosomes; men have one X and one small Y chromosome. The presence of a single gene on the Y chromosome determines if we are a man or a woman.

Hamer’s study concentrated on the X chromosome, which men receive from their mothers, and which would be a logical site for any maternally-transmitted genetic factor involved in sexual orientation. They found that 83% of the gay brothers shared a particular part of the X chromosome, much higher than would be expected by chance. This strongly suggested a relationship between the behaviour the men had in common—homosexuality—and some genetic information contained in the chromosome.

This does not mean that there is a “gay gene” with codes for homosexuality. First, 17% of the brothers did not both have this part of the X chromosome. Secondly, the part of the X chromosome they identified contains hundreds of genes, none of which have been identified. If there is a genetic component to homosexuality, it seems most likely that it will be complex, involving the action of several different genes.

And even this does not mean that if you have the “gay gene” you will be homosexual. To understand what is really going on between us and our genes, we need to transcend the old “nature-nurture” debate.

Human beings are animals; our anatomy, brain structure and our social behaviour are all the product of evolution, of natural selection which operates first and foremost on our genes. To that extent “nature” is predominant.

Yet we are not merely animals. We are conscious beings, engaged for tens of thousands of years in a struggle to master nature in all its forms. We have created societies which have enabled us to partly overcome the limitations of our genetic make-up. “Nature” never meant humans to fly and yet every day millions of people take to the air in aeroplanes.

The relationship between nature and nurture, between genes and environment, is an intensely dialectical one for all animals, not only for human beings. The environment plays a key role in determining how and whether genes are expressed.

For example, there is a human disease known as phenylketonuria, PKU. Children suffering from it are healthy at birth but quickly develop serious brain defects. This disease is genetic; there is a defect in the gene coding for a particular enzyme which leads to the accumulation of certain toxins which literally poison the brain. And yet PKU, a 100% genetic disease, is far from inevitable. By avoiding certain foods which the defective enzyme is involved in digesting, the child will grow up without the disease.

If we apply this to the “gay gene”, we can see that even if there is a single gene which codes for homosexuality (which is extremely unlikely) the expression of this gene would not be constant: in some people it would be expressed more or less strongly, in others it would not be expressed and in still others the same result—homosexuality—would be the result of other factors.

“Nature” and “nurture” on their own are not sufficient to explain homosexuality, or anything else. For example, are differences between men and women genetically determined? Yes and no. There is a genetic difference between men and women—one small gene. But the many differences between the sexes are not all due to biology. Disentangling the interactions between “nature” and “nurture” in the context of a society which is based upon the systematic oppression of women is virtually impossible.

There is a widespread distrust on the left when scientists talk about genetic factors in human behaviour. And with reason. Bad science has been put forward to justify some of the most evil ideas in human history.

The Nazis justified the extermination of the Jews in the name of “racial purity”. Racial oppression of blacks has been “explained” by pseudoscientific claims of genetic differences in IQ. This malign rubbish must be rejected out of hand.

But as materialists, Marxists should not deny either the theoretical or practical importance of our genes. “Eugenics”—the idea of using selective breeding to produce better humans—has had a particularly bad name since the Nazis adopted it.

And yet genetic screening, which tests foetuses for genetic abnormalities and gives women the choice of terminating their pregnancy, is a form of eugenics which only a religious nutcase could oppose.

The dangers, however, are obvious. Hamer’s research could give the reactionaries a new weapon in their war against gay men and lesbians. Lord Jakobovitz, retired Chief Rabbi and full-time reactionary, quickly saw the possibilities when he acclaimed the discovery and called for genetic screening to eliminate homosexual foetuses.

This kind of response shows that the problem is not the science itself, but the use that is made of the results.

There is nothing wrong or dangerous about trying to discover the biological bases of human behaviour, or in untangling the complex relationships between genes and culture which produce a given human being.

The dangers come from the society we live in, a society based on oppression and exploitation which will try to turn any discovery or talent against those who have nothing, in favour of the powerful.

Only in a truly classless society, where research priorities are decided collectively, where everyone is informed of the scope and importance of new discoveries, will humanity finally be able to master the relationship between its animal past and its truly human future.n