Sexual orientation is genetic. This will be proven beyond reasonable doubt in our lifetimes.
The Christian fundamentalists will go crazy when the scientific evidence comes to light.
Then why do gay genes continue on if gays don't have children?
Mutations of the Genetic code. That's right, if genes determine sexual orientations then you come to the conclusion that gays are mutants.
Then we are all mutants to be honest. The genetic code is mutating at all times you realise, some are advantageous, some are not and thus die out. Mutations occur all the time.