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Blanchard (2011) reanalyzed previously published data to examinethebalancingselectionhypothesis, whichconcernsthepersistence of male homosexuality. This hypothesis is based on several findings suggesting that male homosexuality is to some degree heritable (LeVay, 2011). However, since homosexual men are less fecund (ie, produce fewer offspring) than heterosexual men, some compensatory mechanism must exist. The balancing selection hypothesis states that the decreased fecundity of men who inherit a genetic contribution to homosexuality is counterbalanced by an increased fecundity of their relatives carrying the same genetic variants (Hamer & Copeland, 1994).

Blanchard (2011) noted that the balancing selection hypothesis cannot simply be tested by comparing the number of siblings of heterosexual and homosexual participants because of a robust finding termed the fraternal birth order effect …