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Would the discovery of a gay gene be good news?

This material was presented in a workshop to the annual conference of Evangelicals Concerned (Western Region) in July 2002

A. The evidence

1. psychological evidence

There seems to be general agreement now that at least three categories are required to describe the phenomenon of human sexuality.

sex : that is the external physical characteristics, particularly the genitalia.

orientation: that is the sex by which an individual is erotically aroused.

gender-identity: that is the individual’s self-awareness as male or female.

Of these sex is definitely determined by our genes. Gender-identity is almost certainly the result of psycho-social development through childhood and adolescence. The origin of sexual orientation, however, is a matter of controversy. The emerging psychological evidence strongly suggests that it is fixed from a very early age and cannot be changed by later interventions. A simple explanation for this would be that it has a deeply embedded biological basis.

2. the physiological evidence

There is evidence that both sex and sexual orientation are reflected in the structure of the brain.

In 1991, Simon LeVay of the Salk Institute reported a study on the autopsies of homosexual men and women. He found that a small part of the anterior hypothalamus (part of the inner brain believed to be associated with sexual behaviour) was substantially smaller in 19 gay men than in 16 heterosexuals.

In 1992, Laura Allen and Richard Gorski at the University of California discovered that the corpus callosum (a bundle of fibres connecting the right and left hemispheres of the brain) was larger in gay men than straight men.

Other recent studies have identified differences between the male and female brain, and there seems to be some evidence that the brains of gay men have female characteristics. LeVay has speculated that the presence of sex hormones, particularly testosterone, has an effect on the early development of the brain, determining whether it will be "male" or "female" and decisively affecting orientation.

3. the genetic evidence

In 1991 Michael Bailey of Northwestern University studied the distribution of homosexuality among fraternal and identical twins. He found a correlation indicating that genetic inheritance linked to the X-chromosome was involved (i.e. that a predisposition to homosexuality was inherited from the maternal side).

In July 1993, Dean Hamer at the National Cancer Institute in Maryland studied the rate of homosexuality among the relatives of 76 gay men. Like Bailey, he found statistically significant evidence of gay relatives on the maternal side. He then looked for similarities in the DNA of the gay relatives. He found that 33 pairs of gay brothers shared the same five genetic markers in the region of the X-chromosome designated Xq28. In 1995 he extended this work and further confirmed it.

In June 1995, Shang-Ding Zhang and Ward Odenwald observed what they termed "homosexual" rituals in male fruit flies with by a widespread expression of the "white" gene ( so-called because it affects eye-colour).

In 1999 George Rice and George Ebers at the University of Western Ontario attempted to repeat Hamer’s work on gay brothers but were unable to confirm his results on the Xq28 markers. They did not, however, look for evidence of maternal-line inheritance patterns in the gay brothers they chose to investigate.

B. Does it matter?

It is important not to overstate the evidence. It is impossible to say, for instance, whether LeVay’s "gay" brains were the cause or consequence of gay behaviour. Hamer did not find the Xq28 markers in all the gay men he studied and his results have been challenged. The correlation Bailey found in identical twins fell far short of being 100%. And many scientists would question the validity of comparisons between the social behaviour of insects and humans.

It is also important to do justice to the complexity of human sexual behaviour. Although some people seem to be exclusively gay or straight, there are many who demonstrate both traits: e.g. late-bloomers, bisexuals and heterosexuals who experience homoerotic fantasies.

However, neither the present uncertainty in the genetic evidence nor the ambiguity of some people’s sexual orientation is fatal to the gay-gene hypothesis. If there are hereditary factors in homosexuality they are unlikely to focus around a single gene. And ambiguous orientation might be anticipated if the gene or genes defining sexual orientation were incompletely dominant/recessive (like for instance the genes for curly/straight hair—which give rise to intermediate "wavy" phenotypes).

The gay-gene question is of general interest because it is one example of the nature-nurture debate. Hamer and LeVay have experienced a considerable amount of opposition from both biologists (like R.C.Lewontin of Harvard) and cultural historians (like Jonathan Katz) because of a perceived drift toward biological determinism. This, in turn, raises the spectre of moral irresponsibility being excused on genetic grounds, or of attempts to eliminate homosexuality from the population by eugenic intervention.

These fears are largely groundless. Even if a gay gene existed, it would not imply that homosexual behaviour could be placed outside the zone of human moral responsibility. Cognitive awareness enables human beings to exercise decisive control over the expression of sexual behaviour, whether in response to social pressure or ethical belief or simply personal circumstance.

What is more, it is becoming clear that both genetic and environmental influences are entangled in the causation of many human phenomena, as diverse as schizophrenia and hay-fever. If there is a gay gene it is highly unlikely be the only factor responsible for homosexual behaviour.

Some questions to consider:

Suppose that science eventually proved that there was a physiological basis for sexual orientation—a gay gene, for instance. How do you think this would affect the perception of homosexuality: (a) in the general public (b) among Christians (c) among homosexuals themselves. How would it affect your perception of your own sexual orientation?

If it became possible to reduce the incidence of homosexuality in the population either by genetic counselling or genetic engineering techniques, do you think this would be desirable?

If it became possible to predict a child’s probable future sexual orientation, should this information be made available to the child or its parents?

Should Christian opinion on these questions be distinctive in any way? If so, why and how?

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