Been around for a long time. I don't think there are any clear genetic markers for any sexuality and the mechanisms that determine what causes someone to be straight or gay are not well understood.

Asexuality makes the most sense as something but the way I see it used it's actually shorthand for "low libido" so it's not a sexuality so much as it's a lack of sexual drive.

Pansexual and polysexual I'm still not sure what they mean and how they differ from bisexual. My best guess from people I've met is it's a largely female phenomenon from the "I'm not like other women" personality type. Though I do think the concept of like generally vibing with the other persons personality rather than desiring sex and stuff, explanation I've heard trends as normal for women.

Frankly I think all of these are simply coping mechanisms for people who feel isolated due to perceived feelings of abnormality due to not lining up with the Hollywood ideal of sexual proclivity. Except for homosexuality cause that's actually easily defined.