A group of scientists has said there is no single ‘gay gene’ after a genetic study into nearly half a million people.
Researchers based at a number of universities including Harvard and the University of Amsterdam found q mix of both genetic and non-genetic factors that influence sexual behaviour.
They said that although previous research into twins and families showed there was some biological basis to sexuality, this study confirmed there was no single gene that determined it.
The authors examined the genetics of nearly half a million people who self-reported on whether they had ever experienced same-sex sexual behaviour.
This included anyone who had ever had sex with someone of the same sex, regardless of whether they identified as gay or bisexual.
The authors analysed survey responses and performed genome-wide association studies (GWAS) on data from more than 477,522 people in databases UK Biobank and 23andMe.
In the study published last week Friday in the American Association for the Advancement of Science (AAAS) journal Science, the researchers found five genetic variants were significantly associated with same-sex sexual behaviour
However, the tested genes only accounted for 8% to 25% of the variation in same-sex sexual behaviour.
These also only partially overlapped between men and women, and the authors concluded that their findings show that sexual orientation is influenced by a combination of genetic and environmental factors.
Researchers did not find any patterns among these genetic variants that could be used to meaningfully predict or identify a person’s sexual orientation or behaviour.
Andrea Ganna, European Molecular Biology Laboratory group leader at the Institute of Molecular Medicine, Finland, and the other authors wrote:
‘We established that the underlying genetic architecture is highly complex.’
‘There is certainly no single genetic determinant – sometimes referred to as the ‘gay gene’ in the media.
‘Many loci with individually small effects, spread across the whole genome and partly overlapping in females and males, contribute to individual differences in predisposition to same-sex sexual behaviour.
‘All measured common variants together explain only part of the genetic heritability at the population level and do not allow meaningful prediction of an individual’s sexual preference.’
The researchers stressed that genetics were only one part of a person’s identity.
They added: ‘Our findings provide insights into the biological underpinnings of same-sex sexual behaviour.
‘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.’