Quashing the idea of a single "gay gene," scientists have found that same-sex sexual behaviour is influenced by a complex mix of genetic and environmental influences, similar to what is seen for most other human traits.
"Our findings provide insights into the biological underpinnings of same-sex sexual behaviour," said Andrea Ganna from Massachusetts General Hospital, Boston.
"But (they) also underscore the importance of resisting simplistic conclusions because the behavioural phenotypes are complex, because our genetic insights are rudimentary, and because there is a long history of misusing genetic results for social purposes," Ganna added.
For the study, published in the journal Science, the researchers examined the genetics of individuals who self-reported on whether they had ever engaged in same-sex sexual behaviour.
The authors analysed survey responses and performed genome-wide association studies on data from over 470,000 people.
The researchers could not find any patterns among genetic variants that could be used to meaningfully predict or identify a person's sexual behaviour.
According to the researchers "(m) any loci with individually small effects...additively contribute to individual differences in predisposition to same-sex sexual behaviour."
In their study, only five genetic variants were "significantly" associated with same-sex behaviour, and thousands more appear to also be involved, but taken together these variants had only small effects and are far from being predictive, the authors stressed.