Turns out you're not born that way:
http://sourcefednews.com/theres-no-g...ys-scientists/
This is more or less what I thought to begin with, so I'm not too surprised. Although, I was starting to get comfortable with the idea of being born with it. I don't think it really changes anything one way or another, even if it can be proven 100%, but it's worth a read.
Full study if you want to read it for some reason:
http://www.jstor.org/stable/pdfplus/...?acceptTC=true