As far as I can tell, the pathogen hypothesis makes the most sense. I obviously don't believe there is some "gay bug," but it could very well be some kind of virus that rewires the brain, similarly to what toxo does. I guess the next step would be to figure out if it can be contagious. And that's pretty much it. I just want to know more before I can decide if gays should be allowed to adopt kids.
If there is a pathogen causing homosexuality, it must be not only present in heterosexuals but rampant in heterosexuals. Nearly every gay person on earth was born to and raised by heterosexuals. If you are worried about a pathogen causing homosexuality you'd better look for it in the heterosexual community, perhaps in yourself and your own family. And maybe you should consider this before you decide whether straight people should be allowed to adopt kids since we know for a fact that gay kids are coming from straight parents.