Emerging insights into the genetics and evolution of human same-sex sexual behavior.

Thanks to twin studies, it has been known for decades that human same-sex sexual behavior (SSB) has a substantial heritable component. However, only recently have large genome-wide association studies (GWAS) begun to illuminate the complex genetics involved. These studies have established that SSB is influenced by many common genetic variants, each with tiny but cumulative effects.

The Desirable Dad Hypothesis: Male Same-Sex Attraction as the Product of Selection for Paternal Care via Antagonistic Pleiotropy.

Same-sex attraction, a heritable trait with a reproductive cost, lacks a comprehensive evolutionary explanation. Here we build on a hypothesis invoking antagonistic pleiotropy, which suggests that genes linked to male same-sex attraction remain in the gene pool because they have conferred some fitness advantage to heterosexual men possessing them. We posit the "desirable dad hypothesis," which proposes that alleles linked to male non-heterosexual orientations increase traits conducive to childcare; heterosexual men possessing same-sex attracted alleles are more desirable mating partners as a function of possessing superior paternal qualities.