By Faye Flam
A NEW, massive study suggests five genes are weakly associated with self-reported same sex encounters. But the results, released last week by a group that included the Broad Institute and 23andMe, are underwhelming. The genes predicted less than 1% of people’s behavior. The researchers struggled at a press conference to tell reporters what the take home message was. We can assume that 23andMe won’t be offering a “gay gene” test any time soon.
But the result still has meaning, seen in the context of history. It’s the latest chapter in a scientific quest that got woven into a massive cultural shift. Science sometimes led, and sometimes followed.
Through most of the 20th century, mainstream psychiatry considered homosexuality a disease, and scientists studying sexual orientation did so to find a “cure.” That slowly changed, but by the 1990s, religious leaders had their own ideas, which held sway over much of the public. That’s where the roots of today’s findings started, when a National Institutes of Health geneticist named Dean Hamer set out to find the genetic basis of homosexuality.
When I interviewed him for a newspaper column in the early 2000s, he told me that he hoped finding a genetic bases for homosexuality could counter a pervasive argument coming from the then-powerful religious right that being gay was a choice — and a sin.
It was under this backdrop that Hamer, who is gay, set about to use science to get at the answer. He said he got warned that if he found any distinct genetic signatures, someone would abuse them for the purposes of discrimination, or worse.
He also got pushback from his fellow scientists who thought that what he was setting out to prove was already obvious. Of course being gay was at least partly genetic. The “gay is a choice” idea was a religious trope, not a scientific paradigm. But at the time, a well-organized group of right-wing evangelicals had pitted religion against science. Those on the side of science felt they had to fight back.
His study was tiny and limited compared to what’s possible today. He found a potential link on the X-chromosome, which got dubbed the “gay gene,” although Hamer considered it a misleading oversimplification. Hamer’s gene didn’t turn up in this new study — it is likely not a “gay gene” after all — but he deserves credit for setting the groundwork that made the new study possible. The project helped people recognize that sexual orientation was rooted in biology, and that same-sex love was part of the natural variation of human behavior — as well as in the behavioral repertoire of many animals, from manatees to mountain rams.
Most of the early studies on genes and homosexuality were done by gay men. The problem wasn’t so much that others didn’t care, but that they worried that their work would do more harm than good and didn’t want to be associated with genetic tests that might be put to bad use. And studying sexual orientation is tricky. There’s a difference between what people say they do, what they really do, and what they desire to do.
But eventually those early studies opened the way for mainstream, big science. The new study released last week was huge, using DNA samples and sexual behavior information from nearly half a million volunteers in the United States and UK and the best tools money can buy. Unlike many earlier studies, it also included subjects of both sexes.
The main findings came in two parts. In the first, the researchers were able to estimate that genes account for 8% to 25% in the variations in same-sex behavior among the subjects using a complicated technique that involved the relatedness of the volunteers.
The second part pinpointed specific genes. The five genes that were identified only make up 1% of genetic influence on same-sex behavior because they are only the tip of the iceberg. The rest of that genetic component may come from rare genes that were not detected, or by networked interactions between genes. And biology can include non-genetic influences as well — exposures to prenatal hormones and antibodies, for example, and so-called epigenetic effects.
Geneticist Michael White of Washington University, St. Louis, who has written about the genetics of sexual orientation, told me that the results are fairly similar to those linking genes to other behavioral traits — from intelligence to years of education to political affiliation. The genetic influences themselves are complex, and these are mixed up with other biological influences as well as environmental and cultural ones. But DNA tests that identify behavioral tendencies are coming. If, someday, someone tries to sell a test of probable sexual orientation, which people may want to test themselves or, possibly, their unborn children, we can only hope that the world is ready.
Seventy countries still criminalize homosexuality. That’s not likely to change because scientists find more genes influencing sexual orientation. Whether this new study had turned up five genes or 500, no result would justify persecuting people on the basis of their sexual orientation.