That's a pretty silly question, I think. Of course it exists. Just like bigfoot exists.
See, just like cultural gender assignments, bigfoot can be found worldwide. From sasquatch, to yetis, to the apen-men of Africa - all over. Sure, some might argue that bigfoot is mythical, but why does nearly every culture have this strong belief in his existence? At least on a legendary, traditional level?
Kind of like gender. Sure, girls can be soldiers. They can be carpenters and engineers and other traidtionally male roles, just like men can nurture and take care of young and be sensitive. But as an active bisexual, I can definitely say that one gender is generally predisposed to one thing, in general. So there you go. It's not exclusive, it's just a generalization. Let's not forget, hormones do stuff to your brain. I mean, even TS people are the result of a mismatched hormone saturation during fetal development (or so it is suspected.)
In closing, I believe bigfoot exists!
~ BB