Insights into the evolution of homosexuality

26 August 2021

Associate Professor Brendan Zietsch from UQ's School of Psychology features in COSMOS discussing his study on how genes associated with homosexuality may have more than one function.

“A long-standing mystery is why same-sex sexual behaviour, which is known to be influenced by genes, has survived evolution,” says Brendan Zietsch, who led the study.

“This is mysterious because same-sex sex doesn’t lead to reproduction, which is the currency of natural selection.

In the study, published in Nature Human Behaviour, researchers conducted a genome-wide association study – a technique that scans for genes that are common in people who exhibit a specific trait – to establish whether a set of genes was prominent in people who had same-sex partners.

Interestingly, once the common genes were found, the team also discovered that they may have been advantageous to heterosexuals by helping them have more offspring.

“We found that the genetic variants associated with having had same-sex partners are also associated with having more opposite-sex partners in people who’ve never had a same-sex partner.

“Our findings provide a possible solution to this mystery – the genes for same-sex sexual behaviour may have survived because they provide a mating advantage in heterosexuals, which during evolution would have increased reproduction.”

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