According to a genome-wide association study involving more than 470,000 people, a person's genetic variants do not meaningfully predict whether they will engage in same-sex sexual behavior. The findings suggest same-sex sexual behavior is influenced by a complex mix of genetic and environmental influences, similar to what's seen for most other human traits. There is no single "gay gene," the study's authors say, and instead there are thousands of genetic variants linked to the trait, each with small effects. Andrea Ganna et al. examined the genetics of individuals who self-reported on whether they had ever engaged in same-sex sexual behavior. The authors analyzed survey responses and performed genome-wide association studies (GWAS) on data from over 470,000 people in the UK Biobank and 23andMe, Inc. The researchers could not find any patterns among genetic variants that could be used to meaningfully predict or identify a person's sexual behavior, they say. "[M]any loci with individually small effects...additively contribute to individual differences in predisposition to same-sex sexual behavior," they write, describing genetic patterns consistent with many personality, behavioral, and physical traits. In their study, only five genetic variants were "significantly" associated with same-sex behavior, and thousands more appear to also be involved, but taken together these variants had only small effects and are far from being predictive, the authors emphasize. They note that some among these variants are linked to the biological pathways for sex hormones and olfaction, providing clues into mechanisms influencing same-sex behavior. "Our findings provide insights into the biological underpinnings of same-sex sexual behavior," say Ganna et al., "but [they] also underscore the importance of resisting simplistic conclusions because the behavioral phenotypes are complex, because our genetic insights are rudimentary, and because there is a long history of misusing genetic results for social purposes." In a Perspective, Melinda Mills emphasizes the limitations of the study results: "...although they did find particular genetic loci associated with same-sex behavior, when they combine the effects of these loci together into one comprehensive score, the effects are so small (under 1%) that this genetic score could not be reliably used to predict same-sex sexual behavior of an individual." She adds that "using these results for prediction, intervention or a supposed 'cure' is wholly and unreservedly impossible."