Just read this article - http://www.bbc.co.uk/news/magazine-26089486
, its not really saying anything that hasn't been discussed here before but does give a condensed version of ideas spread over several threads here.
I did find this part particularly interesting though
Qazi Rahman says that alleles coding for same sex attraction only explain some of the variety in human sexuality. Other, naturally varying biological factors come into play, with about one in seven gay men, he says, owing their sexuality to the "big brother effect".
This has nothing to do with George Orwell, but describes the observation that boys with older brothers are significantly more likely to become gay - with every older brother the chance of homosexuality increases by about a third. No-one knows why this is, but one theory is that with each male pregnancy, a woman's body forms an immune reaction to proteins that have a role in the development of the male brain. Since this only comes into play after several siblings have been born - most of whom are heterosexual and go on to have children - this pre-natal quirk hasn't been selected away by evolution.
This idea is new to me.
A pretty good biological rebuttal of the old "well, how can they pass on the gay gene" chestnut.