Let me put my two cents into the "nature vs nurture" of homosexuality. As BillD knows, I have raised Fancy English Show Mice in the DC area for more than a decade. In doing so, I carefully track the ratio of male to female offspring in each litter, since too high a proportion of either leads to trouble:
- if there are only one or two females in a large litter of, say 8 or 10, the little girls get masculinized by the high levels of testosterone in utero: they will be large, bold, aggressive animals (wonderful for the show ring) who try to mount other females, are not attractive to or interested in males, have fewer/less stable estrous cycles than normal, and often make terrible mothers, ignoring or destroying their babies. In short, lesbians.
- If, on the other hand, there are only one or two males in a large litter, the resulting boys will be smaller than normal, less aggressive, won't mount females (but will be mounted by other males), engage in nest-building behavior, and are WONDERFUL (foster) parents. In short, gays.
With this kind of direct evidence before my eyes on a regular basis, I can't help but believe that homosexuality in humans also has a similar physiological cause, and is therefore something far beyond the control of the affected person. Makes no difference to me; my proudest local affiliation is as the sole female straight member of the DC Gay Men's Garden Club.