Andrew Sullivan poses a purposefully stupid question: If gayness is genetic, why doesn't it die out?
While the premise of the query is silly (if cancer is genetic, why doesn't that die out too?) - the reasons behind the success of a homosexual gene are less clear. Neuro Scientist Simon LeVay provides a hypothesis:
The usual idea is that a gene predisposing some individuals tohomosexuality might promote the reproductive success of others, and thetwo effects might balance out. It might be that a gene predisposing aman to be gay might make a woman even more attracted to men than sheotherwise would be, so that she would engage in more heterosexual sexand thus become pregnant more often. There are a couple of studiesreporting that women who have gay male relatives (and who may thereforecarry the same "gay gene") do indeed have more children than womenwithout any gay male relatives. The answer will remain speculative,however, until the actual genes have been identified and their mode ofaction worked out.