Approved research

Direct test whether genetic factors predisposing to homosexuality increase mating success in heterosexuals

Lay summary

Twin studies have shown that sexual orientation is influenced by genetic makeup, but evidence for which genes are involved is limited. We have shown indirect evidence that the genes that predispose to homosexuality increase mating success of heterosexual carriers of those genes, potentially explaining why nonheterosexuality remains relatively common despite its evolutionary disadvantage (lower reproduction). We propose to directly test whether genes associated with nonheterosexuality are also associated in heterosexuals with having more opposite-sex partners. Additionally, we will investigate the association between sexual orientation and mental health by determining the genetic correlation of sexual orientation with depression and neuroticism. Establishing a genetic basis to homosexuality has affected the culture, public policy, and mental health of homosexual people. Previously it was thought that homosexuality was an immoral choice and could be reversed. Further scientific and public understanding of the evolutionary basis of homosexuality may reduce the stigma that still exists. We will investigate the evolutionary basis of homosexuality and its association with mental health. If we find a small genetic correlation between sexual orientation and mental health, this suggests that the elevated levels mental health problems in homosexuals can mainly be explained by environmental influences such as stigmatisation and discrimination. As a first step we will use individual?s genotype information and their provided information about same-sex intercourse and number of opposite sexual partners to run two genome-wide association analyses in order to find genetic variants associated with each trait. Subsequently, we will use the summary statistics from these genome-wide association analyses to determine the genetic covariation between the traits, in order to test whether genetic factors predisposing to homosexuality increase mating success in heterosexuals. We will also use the summary statistics to determine the genetic correlation between sexual orientation and mental health. For sufficient power to run genetic association analyses and obtain accurate SNP effects, we require access to the full cohort (so including the samples that are currently being genotyped).