Homosexuality may be due to chemical changes in the genome.

This, according to new research by an American team of researchers who have conducted a twin study.

The evidence that one is born homosexually is vague, while there is no evidence at all that homosexuality is a “choice” relating to the environment we live in.

Researchers at the University of California is now proposing a third explanation, that homosexuality is instead due to epigenetic changes.

Epigenetic changes of the genome are due to the methyl groups that binds to genes and alter their gene expressions without changing the genes themselves.

These epigenetic changes are usually something that happens during our lifetime, but they can also be inherited.

The research team at the University of California mapped 140,000 regions of the genome from 37 identical male twins, for which one was heterosexual and the other homosexual, and then ten twin pairs for which both twins were gay.

Using this approach, the researchers could identify five areas where the pattern of the methyl groups had a close relationship with whether the person was homosexual or heterosexual.

The researchers presented their results at a congress in Baltimore, U.S. But point out that the sample size for research was small and that the purpose of the study was in no way a genetic test, for either homosexuality or heterosexuality.

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Homosexuality as a Consequence of Epigenetically Canalized Sexual Development
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