Last updated November 10, 2017 at 4:54 pm
Evolutionary geneticists bring their own perspective to the investigation, seeking to explain the prevalence of the trait of homosexuality across cultures and history.
This is often used by those who would argue against the biological nature of same sex attraction, by treating biological factors as immutable, a fixed point in human development. The science suggests that this is not the case.
Jenny Graves, professor of genetics at LaTrobe University in Melbourne, has no problem with the concept of gay genes.
“The idea that a person’s genetic makeup affects their mating preference is unsurprising,” she writes in The Conversation. “We see it in the animal world all the time. There are probably many genes that affect human sexual orientation.
But rather than thinking of them as “gay genes”, perhaps, she says, we should consider them “male-loving genes”.
“They may be common because these variant genes, in a female, predispose her to mate earlier and more often, and to have more children.”
She also notes that it would be surprising if there were not “female-loving genes” in lesbian women that, in a male, predispose him to mate earlier and have more children. It’s important to acknowledge that these possibilities are limited to binary genders and it doesn’t include those who see themselves as non-binary or otherwise.
Regardless, it leads to one of the more remarkable findings across the investigations into the origins of sexual orientation – the “fertile female” hypothesis, one possible explanation as to why, if gay men have fewer children on average, the “gay gene” variants don’t disappear.
Graves cites an Italian study that shows female relatives of gay men having 1.3 times as many children as the female relatives of straight men. One possible explanation is that “male-loving” alleles – our gene variants – in a female they predispose her to mate earlier and have more children, so making up for the fewer children of gay males.
That way, there could be thousands of male-loving and female-loving alleles in the population, with everyone inheriting a mixture of different variants.
“Combined with environmental influences, it will be hard to detect individual genes,” Graves writes.
She compares it to height, which is influenced by variants in thousands of genes, as well as the environment, and produces a distribution of people of different heights between the two extremes of very tall and the very short.
“In the same way, at each end of a continuous distribution of human mating preference, we would expect the ‘very male-loving’ and the ‘very female-loving’ in both sexes.”