Značajka oko 10% bilo koje populacije. Zadnja istraživanja ukazuju na genetske utjecaje. Those who argue that homosexuality is "unnatural" are apparently unaware of the behavior in birds, sheep, beetles, bats, penguins, dolphins, orcas, macaques, bonobos (some 75% of whom are thought to be bisexual), black swans, orangutans, and roughly 1,500 species.