Homosexuality is influenced by genes, new study shows

MALE sexual orientation may be influenced by genes, a new study in the US has found.

Tests conducted on 400 gay men found that at least two chromosomes have an effect on whether a man was gay or straight, The Guardian reports.

Michael Bailey, a psychologist at Northwestern University in Illinois, presented the findings at the American Association for the Advancement of Science in Chicago yesterday.

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"The study shows that there are genes involved in male sexual orientation," he said.

The results of the project, which are yet to be published, confirm the findings of a previous study of the family history of 100 gay men. In 1993, Dean Hammer, a scientist at the US National Cancer Institute found that homosexuality seemed to be inherited: more than ten per cent of gay men had gay brothers compared with three per cent of the average population, Hammer found. Similar results were found in uncles and cousins on the mother's side.

However, most scientists believe that genetics is only one contributing factor in human sexuality. So what else is involved?

Environmental and biological factors

Bailey said that in his view environmental factors play a large part in determining sexuality, but they encompass a broad range of influences, not just social ones. "Don't confuse 'environmental' with 'socially acquired'," he said. "Environment means anything that is not in our DNA at birth, and that includes a lot of stuff that is not social."

A previous study published in the scientific journal Archives of Sexual Behaviour, supports this view, arguing that no one single factor is responsible for human sexuality, Science Daily reports.

"This study puts cold water on any concerns that we are looking for a single 'gay gene' or a single environmental variable which could be used to 'select out' homosexuality - the factors which influence sexual orientation are complex," explained Dr Qazi Rahman, study co-author and a leading scientist on human sexual orientation. "We are not simply talking about homosexuality here - heterosexual behaviour is also influenced by a mixture of genetic and environmental factors."

Richard Lane, of campaign group Stonewall, said that while the evidence was still inconclusive, the causes of homosexuality did seem to point to a biological root, The Times reported.

He said: "The thing that's consistent is that they all point to sexual orientation being something fundamental to a person rather than the lifestyle choice some opponents of equality repeatedly suggest."

Do the results of the study matter?

"Isn't it time we all grew up and stopped obsessing about the sexual behaviour of consenting adults," asks Alex Andreou in The Guardian. "Unless one considers homosexuality as a problematic occurrence to be studied – and eventually fixed – the continual focus on what makes some men fancy other men is nothing but morbid fascination."