According to the results of a genetic analysis of half a million people, the concept of there being a “gay gene” that makes some of us gay or queer or however we want to identify ourselves – well, it’s a myth.

The BBC reports that the study – conducted by Harvard and MIT researchers and published in the journal Science – did find some genetic variants associated with same-sex relationships. But these genetic factors accounted for – at most – 25% of same-sex behaviour.

As well as scanning the genomes of approximately 500,000 people, study participants were also asked whether they had same-sex partners exclusively, or as well as opposite-sex partners.

The researchers concluded that genetics could account for between 8-25% of same-sex behaviour across the population, when the whole genome is considered. Five specific genetic variants were found to be particularly associated with same-sex behaviour, including one linked to the biological pathway for smell, and others to those for sex hormones. But together they only accounted for under 1% of same-sex behaviour.

According to the BBC report, Ben Neale – an associate professor in the Analytic and Translational Genetics Unit at Massachusetts General Hospital, who worked on the study – said: “Genetics is less than half of this story for sexual behaviour, but it’s still a very important contributing factor. There is no single gay gene, and a genetic test for if you’re going to have a same-sex relationship is not going to work. It’s effectively impossible to predict an individual’s sexual behaviour from their genome.”

In further reporting by the BBC, Fah Sathirapongsasuti, senior scientist at 23andMe – which was one of the sources for the genomes studied – added; “This is a natural and normal part of the variation in our species and that should also support precisely the position that we shouldn’t try and develop gay ‘curism’. That’s not in anyone’s interest.” While David Curtis, honorary professor at the UCL Genetics Institute, University College London, said: “This study clearly shows that there is no such thing as a ‘gay gene’. There is no genetic variant in the population which has any substantial effect on sexual orientation. Rather, what we see is that there are very large numbers of variants which have extremely modest associations. Even if homosexuality is not genetically determined, as this study shows, that does not mean that it is not in some way an innate and indispensable part of an individual’s personality.”

The bottom line is that our sexuality is not as simple as a question about nature or nurture. If you identity as LGBTQ, then you’re pretty complex, and that’s cool.

Cognitive Biology

It’s a question that is endlessly fascinating — what makes us queer? It’s a line of research that’s generally found within the field of cognitive biology or cognitive psychology.

Dr Qazi Rahman is a Senior Lecturer in Cognitive Neuropsychology at King’s College London.

“We’re looking at what is the function of various human behaviours — for example, why do babies cry?” Rahman explains. “We look to understand the behaviour by asking a series of questions — How does that behaviour increase reproduction? Is it learned behaviour or genetically hard-wired? How does the behaviour develop during your life-span? Is there a similar behaviour in comparable species? I’m using that same framework to try and understand homosexual behaviour — what makes us gay?”

“Fifty years of psychological research has not been able to document any psycho-social basis or learning of homosexual orientation…” continues Rahman. “Any suggestion that you could decide or learn to be gay is based on the traditional understanding of psychology that believed that everything was learned behaviour.”

“Heterosexuality was seen as the norm, and therefore any variation from that was deviant — generally it was some form of ‘failure’ in the parenting of the child that was seen to have led to homosexual behaviour…” explains Rahman. “Around the mid-80s and up to the early-90s more detailed research was completed — particularly in relation to to kids who showed early indicators of being ‘different.’ This research has shown that differences in parental rearing style, or what parents did to their kids, didn’t predict whether kids would grow up gay.”

“In the research, some kids do report fathers being distant but there is a general acceptance that this is likely to be the parent reacting to differences in the child as opposed to the other way around…” adds Rahman. “In relation to the influence of a dominant mother, or Oedipal complex, suggesting that boys were unable to get over their attraction to their mother and therefore become gay — this just doesn’t make any sense and requires leaps in logic that don’t bear any scrutiny.”

How do you define sexual orientation?

“At its most basic level, the question is — Which gender attracts your attention?” explains Rahman. “When you walk into a room does your gaze travel to guys or girls? Sexual orientation is like a rudder — generally an either/or kind of trait. About 95–98 percent of people are oriented to the opposite sex and can be classified as heterosexual.”

“We know that there is no such thing as a ‘gay gene’ but there could be a combination of genes that leads to a guy being attracted to males…” suggests Rahman. “Research has shown us that one in seven gay men owe their sexual orientation to having an older brother. Each older brother increases your chance of being gay by 33 percent, and so the more older brothers you have the more likely you are to be gay. What we don’t know is why that is the case — we think it might be that the mother’s immune system forms antibodies against male proteins in the developing fetus, potentially making the brain more feminine. It’s just a theory but there is some interesting research that suggests that it’s part of the picture.”

“We also know that gay men generally come from larger families, not just immediate but extended, primarily on the mother’s side…” continues Rahman. “One of the theories being explored is that the evolution of homosexuality provides some sort of reproductive advantage to the relatives of gay people. For example, the female relatives of gay men appear to be more reproductive than those females without gay men in their family.”

What about comparable species?

“Loads of animals exhibit same-sex behaviour, but we don’t have any other comparable species that show life-long same-sex orientation as we know it in humans…” Rahman explains. “While there are no comparable species, we do see it in some. For example 5–10 percent of male sheep will consistently only go for other male sheep — even if other options are presented. Zebra Finches also consistently demonstrate life-long same-sex orientation. But amongst primates, humans are quite unique in this sense.”

“For me, the big question is evolutionary…” concludes Rahman. “Why does a trait like homosexuality, which is non-reproductive, persist in evolution when natural selection should have got rid of it? Genes for homosexuality exist, but gay men — who rarely have biological children — are not passing these genes on, so why does it exist?”