Writing at The Thinking Housewife, Laura Wood examines an article, by one Alice Dreger, about the sexuality of two African tribes, the Aka and the Ngandu, in which both masturbation and homosexuality are absent. Mrs. Wood writes:
Dreger says that the absence of homosexuality does not conflict with the prevailing belief in the West that homosexuality is genetic. (That homosexuality can be genetic given that homosexuals do not reproduce is a mystery we never find adequately answered by most who make the claim that it is.)
I have often wondered about this myself. Living in New York and working in the record business (and having a wife who is a senior VP at a major NYC real-estate firm) I’ve known lots of gay people — almost all of whom have said, when I’ve asked, that they couldn’t remember a time that they weren’t certain about their sexual identification. I’ve also known children who were clearly homosexual from very early childhood, and never wavered. All of this has inclined me to think that these folks really are, mostly, “born that way” — but I could never make much sense of it as a hereditary factor, for the obvious reason that one would expect a gene that causes homosexuality to disappear from the population. (Of course, the idea of ‘a’ gene that causes homosexuality is itself rather simplistic, I’m sure.) Also, studies with rats have shown that homosexuality increases in succeeding generations when population density gets too high, which seems incompatible with a purely hereditary explanation.
The other way that a trait can exist in the phenotype without being transmitted genetically is if the modification is epigenetic — that is to say, the appearance of the trait in the phenotype is not caused by a gene, but rather by causes, external to the genome itself, that affect how certain genes are expressed. For the reasons given above, I’ve long suspected that innate homosexuality is due to some sort of epigenetic factor.