Few aspects of human biology are as complex—or politically fraught—as sexual orientation. Now, a new study claims to dispel the notion that a single gene or handful of genes make a person prone to same-sex behavior. The analysis, which examined the genomes of nearly half a million men and women, found that although genetics are certainly involved in who people choose to have sex with, there are no specific genetic predictors. Yet some researchers question whether the analysis, which looked at genes associated with sexual activity rather than attraction, can draw any real conclusions about sexual orientation. The handful of genetic studies conducted in the past few decades have looked at only a few hundred individuals at most—and almost exclusively men.
Biology and sexual orientation
Massive Study Finds No Single Genetic Cause of Same-Sex Sexual Behavior - Scientific American
A genetic analysis of almost half a million people has concluded there is no single "gay gene". The study, published in Science , used data from the UK Biobank and 23andMe, and found some genetic variants associated with same-sex relationships. Advocacy group GLAAD said the study confirmed "no conclusive degree to which nature or nurture influenced how a gay or lesbian person behaves. The researchers scanned the genomes - the entire genetic make-up - of , people signed up to the UK Biobank project, and 68, registered with the genetics company 23andMe. Participants were also asked whether they had same-sex partners exclusively, or as well as opposite-sex partners. Five specific genetic variants were found to be particularly associated with same-sex behaviour, including one linked to the biological pathway for smell, and others to those for sex hormones. Ben Neale, an associate professor in the Analytic and Translational Genetics Unit at Massachusetts General Hospital, who worked on the study, said: "Genetics is less than half of this story for sexual behaviour, but it's still a very important contributing factor.
Massive Study Finds No Single Genetic Cause of Same-Sex Sexual Behavior
How do genes influence our sexuality? The question has long been fraught with controversy. An ambitious new study — the largest ever to analyze the genetics of same-sex sexual behavior — found that genetics does play a role, responsible for perhaps a third of the influence on whether someone has same-sex sex. The study of nearly half a million people, funded by the National Institutes of Health and other agencies, found differences in the genetic details of same-sex behavior in men and women.
But geneticists have had only a handful of underpowered studies to address a complex, fraught, and often stigmatized area of human behavior. Now, the largest-ever study of the genetics of sexual orientation has revealed four genetic variants strongly associated with what the researchers call nonheterosexual behavior. Some geneticists are hailing the findings as a cautious but significant step in understanding the role of genes in sexuality. Others question the wisdom of asking the question in the first place. Andrea Ganna, a research fellow with the Broad Institute in Cambridge, Massachusetts, and Harvard Medical School in Boston, and colleagues examined data from hundreds of thousands of people who provided both DNA and behavioral information to two large genetic surveys, the UK Biobank study and the private genetics firm 23andMe.