It is apparent that homosexuality does not have one particular "cause." It is not purely genetic in origin, for instance, because the very twin studies (Bailey and Pillard) that some interpreted as "proving" a purely genetic origin of homosexuality actually "disproved" it, because only 52% of identical twins of homosexual persons were also homosexual. If homosexuality were dependent on a particular "gay gene," both twins should have possess that gene, and thus there should have been a 100% correspondence.