Expansive study finds no single "gay gene" behind same-sex attraction

A study which analysed data from over 470,000 people has found no single genetic factor associated with same sex attraction, suggesting that the behaviour is a mix of genetic and environmental factors, similar to most other human traits.

A participant waves a rainbow flag during the 9th gay pride event in the Czech capital Prague on August 10, 2019. [File photo: AFP]

The international study, which was published on Friday involved researchers from Australia's University of Queensland (UQ), combining two large samples totalling nearly half a million participants whose DNA and sexual behaviour were known.

"We looked across the whole genome for locations where one letter of DNA code was more or less common in participants who reported having had same-sex sexual partners than in those who reported only opposite-sex partners," study author, Dr. Brendan Zietsch, from the School of Psychology at UQ said.

"What we found was that there is no one 'gay gene' - instead, there are many, many genes that influence a person's likelihood of having had same-sex partners," Zietsch said.

The researchers used large-scale detection of DNA polymorphisms in about 26,000 people who reported having had same-sex partners and while they did discover a range of genetic variants linked to the trait, their effects were not enough to predict a person's sexual behaviour.

"Overall, our results reveal a highly complex genetic influence on same-sex sexual behaviour," Zietsch said.

"Because of this complexity, we cannot meaningfully predict a given person's sexual preference from their DNA - nor was this our aim," he said.

The studies authors stressed that "behavioral phenotypes are complex" and urged against simplistic conclusions being drawn by the results which they described as rudimentary.

Dr. Traude Beilharz, senior research fellow in the Department of Biochemistry & Molecular Biology at Monash University agreed, pointing out that there are additional levels of epigenetics associated with the human genome which can change over time, reflecting environmental exposures.

"The complexity this brings means we are very far from understanding how genomic variance influences behaviour," Beilharz said.

"For now, to understand what it means to be gay, it might just be easier to have a conversation," Beilharz added.