Humans do not have a "gay gene" that determines their sexual orientation, according to the largest study (by far) ever conducted on the issue. Researchers studied the genomes of 470,000 people, hunting for a pattern to explain human sexuality, reports Live Science. They found five genetic markers deemed to be "significantly" linked to same-sex behavior, but as the New York Times explains, "even these are far from being predictive of a person's sexual preferences." All told, the five genetic variants account for less than 1% of a person's same-sex attraction, per Healthday. Thousands more genes appear to be play a lesser role; all told, genetics explained 8% to 25% of the variation between people. The upshot is that sexuality appears to be determined by an incredibly complex stew of genetic and environmental factors—similar to other human traits like height.
"It's effectively impossible to predict an individual's sexual behavior from their genome," study co-author Ben Neale of the Broad Institute of MIT and Harvard tells Live Science. That there's no single "gay gene" should not be interpreted to mean that homosexuality is a lifestyle choice, says Brendan Zietsch of the University of Queensland in Australia, another researcher on the study in Science. "We find that there are many, many genes that predispose one to same-sex sexual behavior. Each of them individually has a very small effect, but together they have a substantial effect." But he says it's also wrong "to think that if same-sex preference is genetically influenced, it must therefore be totally genetically determined. That is not true." (In some parts of the world, homosexuals still face capital punishment.)