John Waters was on NPR to talk about his new book, Role Models.  In the course of talking to Terry, he mentioned dealing with people with Alzheimer’s.  He asked a friend of his, a nurse who works with Alzheimer’s patients – “People forget who their family is, what they did that day or even five minutes ago.  Do they ever forget if they are gay or straight?”  And the answer was “no”.  He surmised this meant it was built in versus a choice.  Because you could forget a choice you made.  While not perfectly conclusive proof, I think it certainly adds to the idea that it is inborn rather than simply a choice.