Despite the eye-catching headlines, you probably can’t tell someone’s sexuality by looking at their hands or facial features. However, science has known for a long time that there is some genetic component involved – and a huge new study seems to have confirmed that, identifying a link between DNA variations and same-sex sexual behavior in humans.
Specifically, a team of researchers has discovered four genetic variants across four chromosomes that seem to be linked to same-sex attraction. And unlike previous research, which has concentrated only on same-sex attraction in men, this study has also found a genetic link for female homosexual behavior – the first ever discovered.
This fascinating result was found after the team analyzed the DNA information of over 400,000 volunteers in the UK Biobank, as well as more than 69,000 people who had given their genetic material to the private biotech company 23andMe. This data was then compared to exhaustive questionnaires covering sexual history and behavior, which participants completed when submitting their DNA.
After initially seeing the link in these two huge datasets, the team then confirmed it in three smaller studies, bringing the total number of subjects to over 490,000 people. The findings were presented at this year's meeting of the American Society of Human Genetics.
Previous research has linked sexual orientation in men to genetic variations in their DNA, and it seems this study has reinforced that finding, as two of the four genetic variants the team identified were specific to male sexuality. However, the other two were connected to sexuality in both men and women – putting a dent in some of the more, uh, controversial theories about female same-sex attraction.
Of course, sexuality is complicated, and it’s important to note here that the research looked at same-sex behavior and attraction, not sexual orientation – something far more personal and nebulous than a person's objective sexual history. In fact, the researchers warn against interpreting their result as a clear genetic cause for sexual orientation, noting that sexuality is influenced by a wide range of factors.
“There is no gay gene,” lead study author Andrea Ganna told Science News Magazine. “Non-heterosexuality is influenced by many tiny-effect genetic factors.” The team estimates their four variants account for only 8 to 12 percent of the genetics behind same-sex sexual behavior.
Despite this caution, however, the study has some major advantages over previous research into the genetics of sexuality – the most obvious being its sheer magnitude. With nearly half a million participants overall, the findings are much more likely to be replicable than those of smaller studies. And they are likely to apply to a much wider range of people, too, since it includes both men and women, and doesn’t rely on twins.
Although the team has yet to pin down the exact effect these genetic variants have on behavior, in an intriguing twist, some are already known to be associated with certain characteristics. One, for example, is linked to our sense of smell, while another is linked to male pattern baldness – meaning it probably won’t be long before we see the headline “Want to tell if a man is gay? Just look at his hairline, say scientists.”
[H/T: Science News]