>>7617156Asexuals reproduce about as much as homosexuals, so broad lack of sexual desire in some individuals is certainly not precluded by natural selection.
If you mean "how well can we quantify the level of sexual attraction or the lack thereof to various individuals," we really can't aside from subjective self-reporting and measurement of physiologic response under different conditions.
We accept the existence of homosexuals as uncontroversial fact and the DSM has recognized abnormal lack of sexual desire for ages. There's really nothing to study here, and like teh homogay, whether we call it "mental illness" or "a sexual orientation" is a purely semantic issue.
