There was a (brief) article in New Scientist a couple of years ago ('96, maybe
'97) about some suggestion that homosexuality would be beneficial in that the
male without offspring would donate his resources to his sister's offspring (as
there is a higher certainty of them being related than brother's offspring).
They were backing this up with some data showing a higher than random
correlation between homosexual males and maternal uncles who were homosexual
males. My memory is sketchy but i remember there wasn't that much detail given
in the article either (one of those in the 'This week' section at the front).
Alejandro Dubrovsky