Question

What were identifiable strengths of the GWAS Same-Sex Behavior research?

Answer 1

Across human societies and in both sexes, some 2 to 10% of individuals report engaging in sex with same-sex partners, either exclusively or in addition to sex with opposite-sex partners.

Twin and family studies have shown that same-sex sexual behavior is partly genetically influenced, but previous searches for the specific genes involved have been underpowered to detect effect sizes realistic for complex traits.

A genome-wide association study (GWAS) was performed on 477,522 individuals, revealing five loci significantly associated with same-sex sexual behavior. Follow-up of these loci suggested links to biological pathways that involve sex hormone regulation and olfaction. Three of the loci were significant in a meta-analysis of smaller, independent replication samples.

Figure: A genome-wide association study (GWAS) of same-sex sexual behavior reveals five loci and high polygenicity.

In aggregate, all tested genetic variants accounted for 8 to 25% of variation in same-sex sexual behavior, only partially overlapped between males and females, and do not allow meaningful prediction of an individual’s sexual behavior. Comparing these GWAS results with those for the proportion of same-sex to total number of sexual partners among nonheterosexuals suggests that there is no single continuum from opposite-sex to same-sex sexual behavior. Overall, the findings provide insights into the genetics underlying same-sex sexual behavior and underscore the complexity of sexuality.

The biological factors that contribute to sexual preference are largely unknown, but genetic influences are suggested by the observation that same-sex sexual behavior appears to run in families and is concordant more often in genetically identical (monozygotic) twin pairs than in fraternal twin pairs or siblings.

Same-sex sexual behavior is influenced by not one or a few genes but many. The findings suggest that genetic influences on same-sex sexual behavior are highly polygenic and are not specific to the discovery samples or measures. All the SNPs measured, when combined, do not capture the entirety of family-based heritability (8 to 25% from GWAS versus 32% from family-based methods).

The research also focuses partly different genetic influences on same-sex sexual behavior in females and males; this could reflect sex differences in hormonal influences on sexual behavior (for example, importance of testosterone versus estrogen) but could also relate to different sociocultural contexts of female and male same-sex behavior and different demographics of gay, lesbian, and bisexual groups.