Giant Study Helps Clarify Role of Genes in Same-Sex Sex

Emma Yasinski in The Scientist:

Genes play a role in—but cannot alone predict—same-sex sexual behaviors, according to a study published today (August 29) in ScienceUsing genetic data from nearly half a million participants who consented to be surveyed about their sexual experiences, the authors find that at most, genetics accounts for 825 percent of the variation in sexual behaviors and only some of the genes involved are shared between men and women. “The strength of the paper is that it used a very large dataset,” says Jacqueline Vink, a behavioral geneticist at Radbound University who was not part of the study but has worked with some of the researchers before. The methods allowed the researchers to “find novel genes associated with same-sex sexual behavior and learn more about possible biological pathways.”

Joel Gelernter, a psychiatrist and geneticist at the Yale School of Medicine who was not involved in the study, agrees. “This study included the largest sample to date for this kind of trait, and meticulously careful analyses,” he says. “There is a high level of support here that the genetics of same-sex sexual behavior is similar to that of other complex traits,” in that many genes are involved, each of which only has a very minor effect on its own. Previous studies of families had suggested that about one-third of the variation in sexual behaviors could be explained by genetics. Others have attempted to study the genetic underpinnings of these behaviors but have only been able to analyze data from limited numbers of participants.

The researchers gathered genetic information from people who had submitted DNA to the UK Biobank and 23andMe and asked them to answer questions about their sexual experiences and to what degree they were with partners of the same sex or other sex. “One of the top requests that we got from our customers as a topic to study is sexual orientation/sexual behavior,” says 23andMe’s Fah Sathirapongsasuti in a press conference.

The authors found two genes that were significantly associated with having engaged in same-sex sexual behaviors. Then, when the team separated the data by the individual’s sex, they found two more genes associated with same-sex sexual behaviors in men and one gene associated with the behaviors in women. These differences identified in men and women suggest that some of the variation in behavior may be related to hormonal influences, the authors say. One of the genes, for example, is tied to balding in men, which is affected by hormone levels.

More here.