EXPERT REACTION: There is no single 'gay gene'
There is no single “gay gene”, say Aussie and international researchers who analysed survey responses from people about their same-sex sexual behaviour, and analysed genetic data from over 470,000 people. The researchers could not find any way to meaningfully predict or identify a person’s sexual behaviour on the basis of their genes. While they did find five genetic variants associated with same-sex behaviour (and lots of others which may also be involved) at best these genetic differences could only account for between 8 and 25 per cent of variation in same-sex sexual behaviour and could not be used to predict it. The findings suggest same-sex sexual behaviour is influenced by a complex mix of genetic and environmental influences, similar to most other human traits.
Organisation/s: The University of Queensland, Monash University, The University of Sydney, The University of Western Australia, University of South Australia
Funder: A.R.S. received funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development specifically to investigate the genetics of sexual orientation: R01HD041563 (A.R.S., principal investigator) and R21HD080410 (A.R.S. and E.R.M., multiple principal investigators). E.R.M., G.W.B., and S.G. are also supported by R21HD080410. No other member of the group received funding specifically for this study, but members of our team received salary funding from organizations as well as our own universities. B.P.Z. received funding from The Australian Research Council (FT160100298). A.G. was supported by the Knut and Alice Wallenberg Foundation (2015.0327) and the Swedish Research Council (2016-00250). A.G., R.M., and B.M.N. were supported by National Institutes of Health (NIH) grant 1R01MH107649-03 (to B.M.N.). R.W. was supported by the National Science Foundation’s Graduate Research Fellowship Program (DGE1144083). Any opinion, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. M.G.N. is supported by ZonMw grants 849200011 and 531003014 from the Netherlands Organisation for Health Research and Development. This research used data from Add Health, a program project directed by K.M.H. (principal investigator) and designed by J. R. Udry, P. S. Bearman, and K.M.H. at the University of North Carolina at Chapel Hill, and funded by grant P01-HD031921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 23 other federal agencies and foundations. Information on how to obtain the Add Health data files is available on the Add Health website (www.cpc.unc.edu/addhealth). This research used Add Health GWAS data funded by Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) grants R01 HD073342 to K.M.H. (principal investigator) and R01 HD060726 to K.M.H., J. D. Boardman, and M. B. McQueen (multiple principal investigators). The genetic part of the CATSS study was supported by grant 2014-0834 from the Swedish Council for Working Life and Social Research.
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.”