Genetics may explain up to 25% of same-sex behavior, giant analysis reveals

People who have had same-sex partners are more likely to have one or more of certain DNA markers, according to the largest ever search for genes linked to sexual orientation. Even all the markers taken together, however, cannot predict whether a person is gay, bisexual, or straight. Instead, hundreds or thousands of genes, each with small effects, apparently influence sexual behavior.

The paper, published today in Science, builds on results presented by the same team at a 2018 meeting. The published study emphasizes that the genetic markers cannot be used to predict sexual behavior.

Still, the work is being hailed as the most solid evidence to date linking specific genetic markers to same-sex sexual behavior. “For the first time we can say without a reasonable doubt that some genes do influence the propensity to have same-sex partners,” says psychologist Michael Bailey of Northwestern University in Evanston, Illinois, who was not involved in the study. The results come with caveats, however, he and others say.