gay_genes_rectInternational: An American study has found new evidence that male homosexuality is influenced by genes although environmental and social factors also play a role, says a The Independent report published in

In the study, which was presented at the annual meeting of the American Association for the Advancement of Science on February 13, scientists tested the DNA of 400 sets of brothers to find out if some men are predisposed to being gay.

They found that a region of the X chromosome Xq28 had an impact on male sexuality, as did a stretch of DNA on chromosome 8.

Dr Michael Bailey, of Northwestern University, Illinois, said: “Sexual orientation has nothing to do with choice. Our findings suggest there may be genes at play – we found evidence for two sets that affect whether a man is gay or straight. But it is not completely determinative; there are certainly other environmental factors involved.”

The work has not yet been published, but it builds on a previous study carried out in 1993 by Dr Dean Hamer from the US National Cancer Institute, who also found that gay men shared genetic signatures on the X chromosome. However, the findings raise the prospect of a genetic test that could be used to determine sexual orientation in the womb.

“Although this could one day lead to a pre-natal test for male sexual orientation, it would not be very accurate, as there are other factors that can influence the outcome,” Dr Bailey said in the report.

But Dr Alan Sanders, clinical associate Professor of Psychiatry at Northwestern University, who led the study, said that identifying a specifically “gay gene” was “oversimplification.”

“We also don’t think genetics is the whole story. It’s not. And whatever genes contribute to sexual orientation, you can think of it contributing to heterosexuality as much as you can think of it contributing to homosexuality. It contributes to variation of a trait,” he said.

Dr Bailey said environmental factors were likely to have the biggest impact on homosexuality. “Don’t confuse ‘environmental’ with ‘socially acquired’. Environment means anything that is not in our DNA at birth, and that includes a lot of stuff that is not social,” he said.