Study: Gay men tied to population growth

PADOVA, Italy, June 24 (UPI) -- Italian scientists say they've found the same genetic factors leading to male homosexuality also lead to increased fertility in the homosexuals' mothers.

The researchers said male homosexuality is associated with a phenomenon called sexually antagonistic selection, in which a genetic factor confers a reproductive advantage.

University of Padova Professors Andrea Camperio Ciani and Giovanni Zanzotto, along with Paolo Cermelli of the University of Torino, said the persistence of gay men in a population isn't easily explained by Darwin's theory of evolution, because men who possess genes predisposing them to homosexual behavior are much less likely to reproduce.

Gay men's lower rate of reproduction would be expected to lead to their eventual disappearance from a population, the researchers said. Empirical studies, however, have revealed steady rates of gay men in populations.

The researchers screened a large set of explanatory models and eliminated those inconsistent with observed data. They concluded that male homosexuality benefits populations by promoting female fecundity. Gay men, therefore, give rise to an increase of the fecundity of the whole population, they said.

The study is reported in the online journal PLoS One.