There is no single ‘gay gene’

A study of more than 470,000 people has confirmed that there is no single “gay gene”. 

There are thousands of genetic variants linked to the trait, the researchers say, but even when combined they only contribute to one per cent of the genetic variation.  

In other words, same-sex sexual behaviour is influenced, like most other human behaviour, by a mix of genetic and environmental factors. 

“We scanned the entire human genome and found a handful, five to be precise, locations in the human genome that are clearly associated with whatever a person reports in engaging in same-sex, sexual behaviour,” says Andrea Ganna, lead author of a paper published in the journal Science.

Ganna, from Finland’s Institute of Molecular Medicine and the Massachusetts General Hospital (MGH) in the US, worked with colleagues from the US, the UK, Sweden, Denmark, the Netherlands and Australia. 

They used data sourced from the UK Biobank and the personal genetics company 23andMe to examine the genetics of over 470,000 individuals who self-reported whether they had ever engaged in same-sex behaviour. {%recommended 7901%}

They say they could not find any patterns among genetic variants that could be used to meaningfully predict or identify a person’s sexual behaviour.

They do note, however, that some among these variants are linked to the biological pathways for sex hormones and olfaction, providing clues into mechanisms influencing same-sex behaviour.

“Our findings provide insights into the biological underpinnings of same-sex sexual behaviour,” the authors write, “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.”

Co-author Ben Neale from the Broad Institute, US, and MGH says the study underscores that there is an element of environmental factors in same-sex sexual behaviour – from anything in utero to who you stand next to on the train in the morning. 

“… we can’t say what those environmental factors are, it’s more that we have a sense they exist because we put bounds on the extent to which the genetics is really influencing the trait,” he says.

“Both things matter. That’s the sort of take-home message. Yes, there’s some biology and yes, there’s likely some environment, but beyond that we can’t specify,” says Neale. 

The researchers do note the limitations to their study, including that all subjects self-reported, they came only from the US and the UK, and non-binary genders were excluded.

“I wouldn’t describe this research as the final answer,” says Neale. “I think what this research does is it moves our understanding to a slightly deeper and more nuanced place where we see there is more complexity out there than we’re capturing in our very simplistic measures.”

Perhaps most importantly, it provides “further evidence that diverse sexual behaviour is a natural part of overall human variation”.