I'm not bisexual and I don't think people can choose their sexual orientation. But there are documented societies where same sex sexuality is universal, and yes, in Sparta, homosexuality was pretty much universal. It was institutionalized. Same with Sambia. What this means is that sexuality is unconsciously learned so early that people don't realize they are learning it. This is why I compare it to one's native language. You don't get to choose that either, but you learned it, and it isn't biological. I think all societies are tilted homosexual by virtue of childhood sex segregation and gendering. I think heterosexuals sublimate their same sex attraction and as adolescents cultivate an opposite sex attraction that is so problematic you find things like widespread misogyny. All men actually seem to prefer men. Wilhelm Reich touches on this, but people just dismiss him as homophobic. What he actually said is that in indigenous societies where adolescents are allowed to explore each other sexually as they sexually mature, there is no homosexuality AND there is no homosexual taboo (in other words, it is incidental and unremarkable if it happens). The two go together. Homosexual oppression is a necessary consequence of gendering (achieved via childhood sex segregation and delayed sexual experimentation) and necessary to achieve a heterosexual orientation. It is so problematic that it creates populations that end up exclusively homosexual as a side effect, along with unconscious resentments like misogyny and sexual sadism and rape.