Numerous studies have established that sex is not just male or female. Nonetheless, misconceptions persist that same-sex attraction is a choice that warrants condemnation or conversion , and leads to discrimination and persecution.
I am a molecular biologist and am interested in this new study as it further illuminates the genetic contribution to human behavior. The new finding is consistent with multiple earlier studies of twins that indicated same-sex attraction is a heritable trait. As the ease and affordability of genome sequencing increased, additional gene candidates have emerged with potential links to homosexual behavior. So-called genome-wide association studies identified a gene called SLITRK6 , which is active in a brain region called the diencephalon that differs in size between people who are homosexual or heterosexual.
Genetic studies in mice have uncovered additional gene candidates that could influence sexual preference. A study linked sexual preference to a gene called fucose mutarotase. When the gene was deleted in female mice, they were attracted to female odors and preferred to mount females rather than males.
Other studies have shown that disruption of a gene called TRPC2 can cause female mice to act like males. Thank you for visiting nature. You are using a browser version with limited support for CSS.
To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Same-sex attraction seems to be at least partly controlled by genetics.
To evolutionary biologists, the genetics of homosexuality seems like a paradox. In theory, humans and other animals who are exclusively attracted to others of the same sex should be unlikely to produce many biological children, so any genes that predispose people to homosexuality would rarely be passed on to future generations. Yet same-sex attraction is widespread in humans, and research suggests that it is partly genetic. In a study of data from hundreds of thousands of people, researchers have now identified genetic patterns that could be associated with homosexual behaviour, and showed how these might also help people to find different-sex mates, and reproduce.
The authors say their findings, published on 23 August in Nature Human Behaviour 1 , could help to explain why genes that predispose people to homosexuality continue to be passed down. But other scientists question whether these data can provide definitive conclusions.
Evolutionary geneticist Brendan Zietsch at the University of Queensland in Brisbane, Australia, and his colleagues used data from the UK Biobank, the US National Longitudinal Study of Adolescent to Adult Health and the company 23andMe, based in Sunnyvale, California, which sequence genomes and use questionnaires to collect information from their participants.
The study looked only at biological sex, not gender, and excluded participants whose gender and sex did not match. Next, the researchers used a computer algorithm to simulate human evolution over 60 generations. They found that the array of genetic variations associated with same-sex behaviour would have eventually disappeared, unless it somehow helped people to survive or reproduce.
They sorted the participants who had only had heterosexual sex by the number of partners they said they had had, and found that those with numerous partners tended to share some of the markers that the team had found in people who had had a same-sex partner. And there was a small overlap between heterosexual people who had genes linked to same-sex behaviour and those whom interviewers rated as physically attractive.
Sexual-minority students more likely to abandon science majors. The authors acknowledge many limitations of the study. The authors say that they did see links between sexual orientation and sexual activity, but concede that the genetic links do not predict orientation.
Nevertheless, Hamer and others praise the new contribution to a field that suffers from a dearth of good studies. Sara Reardon is a freelance journalist based in Bozeman, Mont. She is a former staff reporter at Nature , New Scientist and Science and has a master's degree in molecular biology. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue.
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