The other 13% is reserved for the possibility that MAYBE, just MAYBE we are ALL wrong and instead of being just different genders, we are actually different species altogether, and we only THINK we are of the same species because we look alike and are compatible... sexually. Well let me tell you something! A horse and a donkey can have sexual intercourse! And do you know what the product of that magical experience is? The goddamn MULE. I mean sure, mules aren't able to reproduce themselves, I think, but the point still stands.