Homosexuality is inherited, says psychology study

Genetics plays a role in male sexual orientation but social and environmental factors are also involved, research suggests.

Scientists tested the DNA of 410 pairs of homosexual twins, making this the largest study of its kind. They found that homosexual men shared genetic markers in a region of chromosome 8, and the Xq28 region of the X chromosome.

The findings were originally presented by Professor Michael Bailey at the annual meeting of the American Society of Human Genetics two years ago. They appear to have been resurrected for an event at the periphery of another major conference this year.

'When people say there's a gay gene, it's an oversimplification', said Dr Alan Sanders, who co-led the study. 'It seems like there's a number of genes involved so there's more work to do to narrow things down'.

The results confirm those of a similar study conducted by Dr Dean Hamer, which caused controversy at the time of its publication in 1993. Media attention centred on the prospect of a prenatal test for sexual orientation, with the Daily Mail running the headline: 'Abortion hope after "gay genes" finding'. Last year, Dr Hamer responded that any such test would be 'wrong, unethical and a terrible abuse of research'.

Professor Bailey conceded the possibility that his research could 'one day lead to a pre-natal test for male sexual orientation', though noted that such a test would not be very accurate. 'Clearly parents should not be allowed to torture or kill babies. But they can currently choose to terminate a pregnancy early on, so they should be allowed to have as much information on the future child as possible'.

Dr Qazi Rahman, a psychologist at King's College London, who was not involved with the study, said that the results were important for our understanding of male sexual orientation.

'This is not controversial or surprising and is nothing people should worry about', he said, speaking to The Guardian. 'All human psychological traits are heritable, that is, they have a genetic component. So we need to do "gene finding" studies like this [...] to have a better idea where potential genes for sexual orientation may lie'.

He added that, in his opinion, genetics explained '30 to 40 percent of the variation between people's sexual orientation'.

The findings have not been published in a peer-reviewed journal.