Well the defenders of homosexuality say they are 'born' with it and its simply not a perversion of the mind or unnatural. Perhaps psychological studies could give a definite answer.
Personally, though I don't know how I would take a homosexual in my family, section 377 seems to be curbing individual freedom. If the role of the govt is to prevent the deterioration of society, then the fact that the govt. can allow physically harmful things like cigarettes and alcohol to exist (and earn revenue) but cannot allow a person to follow their sexual orientation seems a bit odd to me.