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It seems to me that, evolutionarily speaking, the fitness of a purely homosexual animal or human is much lower than that of a heterosexual one, and therefore would be strongly selected against. Thus I am puzzled at the apparent rate of homosexuality in the human population.

I am aware that homosexual behavior has been observed in other animals, but I suspect that they many of them are actually bisexual rather than homosexual. On the other hand, there are many animals (such as beta male hyenas, or lions) who do not reproduce but play important supporting social roles. Perhaps homosexuality is similar to this? Maybe it keeps occurring as a side effect of some genetically advantageous traits?

Basically I am not sure how to reconcile the theory of evolution with the claims that homosexuality is innate. And saying that gay people for centuries were forced to marry and have children doesn't seem to resolve this, unless there's data behind it.

  • While purely homosexuals animal/humans may have a lower chance of reproducing, they probably do not in general have lower fitness to survive. Also, evolution does not always necessarily favour only those with the best fitness (e.g. peacock's tails); if a trait isn't particularly disadvantageous (i.e. it is neutral), the trait could survive along for many generations without receding. – Lie Ryan Dec 5 '13 at 12:41
  • Strictly related Does homosexuality preserve the species. – Carlo Alterego Dec 5 '13 at 19:01
  • @LieRyan and remember that homosexual behaviour does not preclude propagation, many individuals may have homosexual tendencies while also showing heterosexual tendencies, iow they are bisexual in their sexual interests. – jwenting Dec 6 '13 at 6:51

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