Secondly, how is it that humans are the only species with a gene for hand preference? (I think that's neat myself)
Dunno, I think it goes beyond writing, which is mostly training and practice.
Does the ambidextrous person, who is mostly "right handed" exhibit the same kind of brain development also? What about the "left handed" person who is forced to use their right hand? Is their brain development the same as a right handed person?
I'm told their are university studies being done (your tax dollars at work) to determine if there is anything humans can learn from parrots in regard to this righty-lefty stuff.
My grandmother was forced to be right-handed by the nuns. There was payback: I'm left-handed; so are my two sisters and brother. My other two brothers are right-handed. Of my aunt's four kids, two are left-handed. I'm not sure about my uncle's 3 kids, but I bet at least one of them is left-handed. So out of just the 10 grandchildren between my mother and her sister's kids, 6 are left-handed. (My two daughters, to my surprise, are righties).