The authors of an international research project into the genetics of same-sex behaviour recently reported their findings, and created a minor media stir. The international team of researchers looked at DNA markers and data from surveys of sexual behaviour completed by over 400,000 UK Biobank participants, as well as 69,000 users of 23andMe, and found five genetic markers associated with same-sex behaviour. The authors concluded that genetics can explain between 8 percent and 25 percent of the variation in same-sex sexual behaviour. A debate over the extent to which human sexuality is linked to genetics, if at all, has been going on since at least 1993, when a controversial study appeared to find that some people have a genetic predisposition to homosexuality, and gave rise to the concept of the “gay gene.” The idea that a single gene might be responsible for sexual behaviour—or, indeed, any other psychological trait—has since been discredited and we now know that human behaviour is influenced by many genes, each having a small effect. The media coverage of the recent …