Does Believing Homosexuality Is Innate Increase Support for Gay Rights?

Homosexual male probands with monozygotic cotwins, dizygotic cotwins, or adoptive brothers were recruited using homophile publications. Sexual orientation of relatives was assessed either by asking relatives directly, or when this was impossible, asking the probands. Of the relatives whose sexual orientation could be rated, 52% (29/56) of monozygotic cotwins, 22% (12/54) of dizygotic cotwins, and 11% (6/57) of adoptive brothers were homosexual. Heritabilities were substantial under a wide range of assumptions about the population base rate of homosexuality and ascertainment bias. However, the rate of homosexuality among nontwin biological siblings, as reported by probands, 9.2% (13/142), was significantly lower than would be predicted by a simple genetic hypothesis and other published reports. A proband's self-reported history of childhood gender non-conformity did not predict homosexuality in relatives in any of the three subsamples. Thus, childhood gender nonconformity does not appear to be an indicator of genetic loading for homosexuality. Cotwins from concordant monozygotic pairs were very similar for childhood gender nonconformity.

Controversies are commonplace among scientists who endorse different ideas about the determinants of homosexual orientation and their concomitant social and political implications. To measure the relationship between beliefs about the determinants of homosexual orientation and attitudes toward homosexuals, we asked 745 respondents in four societies about their beliefs concerning the origins of homosexual orientation. Analysis indicated that subjects who believed that homosexuals are "born that way" held significantly more positive attitudes toward homosexuals than subjects who believed that homosexuals "choose to be that way" and/or "learn to be that way."