I suspect the ultimate causes for homosexuality (or heterosexuality as well) to be a complex mix of psychological and hormonal factors that can change subtlety over time.

It’s nature’s way of preventing overpopulation and maintaining an ecologically sound population stability, simple as. This is the reason why homosexuality can be observed in nearly all mammalian sexually reproducing species, while I’m sure fluctuating hormones play a factor in the major of the population who might be somewhat more on the bisexual spectrum than strict heterosexuality - there does exist a small portion of the population for whom homosexuality is entirely hardwired and cannot be changed. Usually these tend to be men with a surplus of older brothers according to studies, unlike the heterosexual troons you can tell these homosexuals are legit and it’s not a choice for them because they exist in every race, culture, and region in the world even despite how violently homophobic said society would be. Ironically enough, these are the types who tend to be actual transsexuals as they frequently transition in the 3-world parts of the world because they are utterly incapable of living their lives as a normative member of their biological sex and cannot change their orientation. (And yes they’ve tried conversion therapy with these actual homosexuals through the use of hormonal balancing, it didn’t work.)

Gender in the modern parlance exists only in the sense that it's part of the larger human social fabric surrounding mating rituals and is not much different than the kind of dances birds do to attract a mate. The key point we are seeing here is the female of the human species is generally the one whom decides on the attraction of their mate and they've decided that traditionally masculine expressions of "gender" are no longer in vogue so the males of the species are adapting to various non-masculine expressions of dress and behavior in order to woo the females and copulate successfully.

And this is why the modern trans slogan that orientation and gender identity are completely separate and therefore “gay transmen” and “trans lesbians” can exist is complete and utter bullshit! Sexual orientation and Gender (as we understand it to be a synonym for biological sex, not the way the troons use it to mean gender roles) are inexplicably linked, otherwise we wouldn’t be a two sex, dimorphic, sexually reproducing species and would be single-sex, asexual amoebas instead. This is why the whole “heterosexual trans” phenomena is something that is only occurring in the White & privileged West whereas you’ll never once see a straight tranny out in the 3rd-World, they’re all HSTS over there. Find me an old AGP hon trans lesbian out in like Africa or the Middle East and I’ll show you a unicorn, they just don’t exist. This more than anything else is proof that sexual orientation and gender are directly linked and all the heterosexual Western troons are just cosplaying.