SEXUAL ATTRACTION ISN’T defined by one gene alone, according to a new scientific study. Instead, it’s the result of a complex interplay between multiple regions of the genome and environmental factors.

The study was conducted on half a million DNA profiles as part of a giant study by researchers in Europe and the US published in the influential journal Science today.

The study’s authors hope to challenge the notion, popularised in the 1990s, of the existence of a “gay gene” that determines sexuality in the same way eye color is defined.

“We… found that it’s effectively impossible to predict an individual’s sexual behavior from their genome,” said Ben Neale, a member of MIT and Harvard’s Broad Institute, one of several organizations involved in the work.

Sexual orientation does have a genetic component, say the researchers, confirming previous smaller studies, notably on twins.

The scientists wrote: “When we analyse all common genetic markers together, they capture between 8% and 25% of the individual differences in same-sex sexual behavior.”

The figure is a statistical concept used by scientists when studying populations and does not apply at an individual level.

The effect is mediated by multiple genes. “There is no single gay gene but rather the contribution of many small genetic effects scattered across the genome,” said Neale. Added to this are various environmental factors. 

The new statistical analysis revealed five points in our chromosomes, called loci, which appear closely linked to sexuality, though each individually has a “very small” influence.

It’s believed that these five markers could be just the beginning, with thousands more awaiting discovery in future.

Fah Sathirapongsasuti, a scientist from the company 23andMe which contributed to the study with the profiles of customers who had volunteered to participate, added:

Genetics definitely play a part, but nonetheless, it is possibly a minority part – and there is an unexplained environmental effect that one can never put a finger on exactly.

The bulk of the data came from the UK Biobank among individuals – mainly people of European ancestry – responding to the question: have you had sexual relations with a person of the same sex?  

The authors consulted with LGBT groups on the best way to communicate their findings.

The LGBT advocacy group GLAAD praised the work, saying it “provides even more evidence that being gay or lesbian is a natural part of human life”. 

© – AFP 2019