A study more than 20 years in the making has confirmed what many people have long suspected: That sexual orientation may have a biological basis. But contrary to some popular theories, the study didn't reveal one definitive "gay gene." Instead, it found a new correlation between sexuality and a combination of factors — one of which may be a particular protein that can only be passed on from father to son, research leader and Brock University health sciences professor Tony Bogaert tells Bustle.
The study, published on Dec. 11, is closely related to a study he and fellow researcher Ray Blanchard conducted two decades ago, which demonstrated that on average, gay men have more older brothers than heterosexual men. Bogaert's new research, "Male Homosexuality and Maternal Immune Responsivity to the Y-Linked Protein NLGN4Y,” published in Proceedings of the National Academy of Sciences, posits that that protein, which can usually only be translated from father to son (hence, Y-chromosome linked), can sometimes end up in the mother through an "exchange of blood or body tissue" with the male fetus, and then she can develop an immune reaction to it, which may affect the "connections the brain cells have that ultimately underlie sexual attraction," Bogaert tells Bustle.
Basically speaking, when someone has already been pregnant with one male fetus, their body can be primed with an antibody response that might affect subsequent male fetuses, which is hypothesized to affect how those fetuses might process sexual attraction. Of course, oldest children, only children, and female children can also be gay, suggesting biology is only one potential factor. But the researchers' identification of this protein and its antibody response could have huge implications for how we understand the "biological basis" of being queer, Bogaert says in a press release. While Bogaert acknowledged that the findings would need to be replicated by an independent team, he also noted that the consequences could be "profound."
Though the NLGN4Y protein is the major subject of this study, it is not the only thing that can affect male sexual orientation in utero. "[T]he effect we're finding is that it's, in addition to [NLGN4Y], about a maternal immune response. So antibodies are what ends up ultimately probably changing how this protein works in the brain in male fetuses," Bogaert says.
He and Blanchard began looking into this effect over 20 years ago, and have continued to probe the nature versus nurture aspects of birth order. He found that even when subjects had never lived with their biological older brothers, those older brothers could still, from a statistical standpoint, help predict whether or not their younger sibling may or may not be straight. And nonbiological older siblings who did live with the subjects did not statistically end up increasing the likelihood of their being gay, which indicated to Bogaert that the effects may be prenatal, not social.
The research, though the NLGN4Y protein doesn't apply to female fetuses, is part of a larger body of evidence suggesting that there are biological mechanisms behind queer orientations.
This latest study is not the end of Bogaert's work. He plans to investigate how NLGN4Y works. "It's interesting to examine just the possible kinds of complex associations and functions that this particular kind of protein might have in terms of influencing gender and sexual orientation," he tells Bustle.
Bogaert's latest study could be a huge step for queer rights activists, and a gigantic rebuttal against people who insist that being anything other than straight is a "choice" or a "lifestyle" — it may well begin in utero, and we are only just beginning to understand how.