"A second example of dogmatic ethics gone wrong for lack of knowledge is homophobia. The basal reasoning is much the same as for opposition to artificial contraception: sex not intended for reproduction must be an aberration and a sin. But an abundance of evidence points to the opposite. Committed homosexuality, with the preference appearing in childhood, is heritable. This means the trait is not always fixed, but part of the greater likelihood of a person's developing into a homosexual is prescribed by genes that differ from those that lead to heterosexuality. It has further turned out that heredity-influenced homosexuality occurs in populations worldwide too frequently to be due to mutations alone. Population geneticists use a rule of thumb to account for abundance at this level: if a trait cannot be due solely to random mutations, and yet it lowers or eliminates reproduction in those who have it, then the trait must be favored by natural selection working on a target of some other kind. For example, a low dose of homosexual-tending genes may give competitive advantages to a practicing heterosexual. Or, homosexuality may give advantages to the group by special talents, unusual qualities of personality, and the specialized roles and professions it generates. There is abundant evidence that such is the case in both preliterate and modern societies. Either way, societies are mistaken to disapprove of homosexuality because gays have different sexual preferences and reproduce less. Their presence should be valued instead for what they contribute constructively to human diversity. A society that condemns homosexuality harms itself."