Is there anything in the Buddhist doctrine that could be drawn upon to help explain the phenomena of same-sex attraction? A popular although rather naive answer to this question is that homosexuals were of the opposite gender in their last lives and the inclinations of the opposite gender has carried over into the present life. This explanation becomes unconvincing when we realize that many gays are happy being male, indeed some are distinctly masculine in appearance, outlook and interests, while many lesbians are content being female and are as feminine as heterosexual women.
Another version of the rebirth theory is that homosexuality is a outcome of something negative done in a former life, that it is the result of bad kamma. The problem with this theory is that it is based on a misunderstanding of the Buddha’s teaching of kamma (see Buddhist Ethics). It also incorrectly assumes that all homosexuals are inevitably unhappy or disadvantaged, which was not even the case before the enlightened reforms of the last few decades and even less so now. Did kamma change its mind about homosexuality, deciding to “punish” homosexuals previously but now changing its mind?
But perhaps it is not answers to the question of what causes homosexuality that is the problem, but the question itself. Just how problematic this question is becomes apparent when we change it slightly and ask: “What causes heterosexuality?” Most people would answer that heterosexuality does not have “a cause” beyond the natural concomitants that determine sexuality. It is a naturally occurring phenomena, and perhaps homosexuality is the same.
We might add further that the Buddha was not really in the business of giving explanations to every question that can be asked. Buddhism is quite happy to leave such matters to those who specialize in whatever field a question is related to. The Buddha’s primary concern was suffering and how it can be overcome. Punitive laws, ignorance, social exclusion, discrimination, etc are causes of a great deal of misery in the present life and they are things that can be changed or rectified.