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Please note!
This fact brief was originally published as an experiment to test the concepts behind fact briefs.
Readers should be aware that while there is still a lot of useful information in fact briefs like this one, not all of them reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date, don't hesitate to contact us at support@gigafact.org.
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FACT BRIEF

Is homosexuality caused by a single gene?

By Jacob Alabab-Moser
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NO

While there may be a genetic component to homosexuality, same-sex sexual behavior is not determined by a single gene.

The largest study conducted on homosexuality and genetics to date, published in Science in 2019, identified five spots on the human genome that are linked to same-sex sexual behaviour, but cautioned that none of the markers are reliable enough to predict someone’s sexuality. After comparing the genomes and sexual behaviors of nearly half a million people, authors estimated that genetics explains 8% to 25% of homosexuality, with the rest influenced by environmental and cultural factors. The study did not find that homosexuality was associated with a stretching of DNA on the X chromosome, as a small study from 1993 had.

A study published in Nature in 2021 suggested that the mating advantages of risk-taking behavior, which authors found to be genetically correlated with same-sex sexual behavior, could explain how homosexuality persisted as a trait despite contradicting the evolutionary principle of reproduction.

This fact brief is responsive to conversations such as this one.
Sources
Science Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior
Nature Human Behavior Genomic evidence consistent with antagonistic pleiotropy may help explain the evolutionary maintenance of same-sex sexual behaviour in humans
ABOUT THE CONTRIBUTOR
Gigafact
Between 2020 and 2022, under close editorial supervision, Gigafact contracted a group of freelance writers and editors to test the concepts for fact briefs and provide inputs to our software development process. We call this effort Gigafact Foundry. Over the course of these two years, Gigafact Foundry writers published over 1500 fact briefs in response to claims they found online. Their important work forms the basis of Gigafact formats and editorial guidelines, and is available to the public on Gigafact.org. Readers should be aware that while there is still a lot of relevant information to be found, not all fact briefs produced by Gigafact Foundry reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date and need to be looked at with fresh eyes, don't hesitate to contact us at support@gigafact.org.
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About fact briefs published on Gigafact
Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.