While female sexuality appears to be more fluid, research suggests that male gayness is an inborn, unalterable, strongly genetically influenced trait

Put differently, why haven't gay man genes driven themselves extinct? This longstanding question is finally being answered by new and ongoing research. For several years, studies led by Andrea Camperio Ciani at the University of Padova in Italy and others have found that mothers and maternal aunts of gay men tend to have significantly more offspring than the maternal relatives of straight men. The results show strong support for the "balancing selection hypothesis," which is fast becoming the accepted theory of the genetic basis of male homosexuality.