A study of more than half a million people has concluded that there is no single “gay gene” but that a complex mix of genetics and environment affects whether a person has same-sex sexual partners.
The large scientific study into the biological basis of sexual behaviour analyzed data on DNA and sexual experiences finding there are thousands of genetic variants linked to same-sex sexual behaviour, most with very small effects.
Five of the genetic markers were “significantly” associated with same-sex behaviour, the researchers said, but even these are far from being predictive of a person’s sexual preferences.
Andrea Ganna, a biologist at the Institute of Molecular Medicine in Finland who co-led the research said they scanned the entire human genome and found a handful – five to be precise – of locations that are clearly associated with whether a person reports in engaging in same-sex sexual behaviour.
He said these have “a very small effect” and, combined, explain “considerably less than 1% of the variance in the self-reported same-sex sexual behaviour.”
This means that non-genetic factors – such as environment, upbringing, personality, nurture – are far more significant in influencing a person’s choice of sexual partner, just as with most other personality, behavioural and physical human traits, the researchers said.
The results, published in the Journal of Science on Thursday, found no clear patterns among genetic variants that could be used to meaningfully predict or identify a person’s sexual behaviour, the researchers said.
“We’ve clarified that there’s a lot of diversity out there,” said Benjamin Neale, a member at the Broad Institute of MIT and Harvard who worked with Ganna. “This moves our understanding (of same-sex sex) to a deeper and more nuanced place.”
Researchers since the 1940s have described sexual orientation as a single trait that exists on a scale, ranging from “exclusively heterosexual” to “exclusively homosexual.”
But the new study suggests that sexuality is more diverse than that — many different things, rather than one thing in greater or lesser degrees.
Sexual rights campaigners welcomed the study, saying it “provides even more evidence that being gay or lesbian is a natural part of human life”.
“This new research also re-confirms the long-established understanding that there is no conclusive degree to which nature or nurture influence how a gay or lesbian person behaves,” said Zeke Stokes of the U.S.-based LGBTQ rights group, GLAAD.