Epigenetics and evolution: ‘the significant biological puzzle’ of sexual orientation

The ‘gay gene’ some touted as explaining widespread homosexuality in humans has not been found. Might epigenetics hold the answer?

Follow our Australia news live blog for latest updatesGet our morning and afternoon news emails, free app or daily news podcast

Last century, when things were a whole lot worse for gay people than they are today, there was a widely held notion that human homosexual behaviour was a choice, and that a homosexual person could change their ways and become heterosexual. For this reason, the occasional report of a “gay” gene was welcomed by many progressive people. The existence of such genes would show that homosexuality was not a choice but an inevitable consequence of development and genetics. Indeed, gay genes were perhaps the only example where many left-leaning people heartily embraced genetic determinism.

Awkwardly, like cold fusion, reports of genes that “cause” human homosexuality (and many other human behaviours) have failed to stand up to scrutiny – there is no “gay gene” in the sense that no one has identified genetic markers or genes that reliably predict sexual orientation in humans. Moreover, since homosexuality would generally be reckoned to reduce reproductive output of an individual, an allele (a gene variant) that directly causes homosexuality is unlikely to spread in a population.