Is handed-ness environmental or is it genetic? It doesn't seem likely to be environmental...

21% of Monozygotic twins are left-handed when the other is right-handed. This is higher than the general population.

Aren't there plenty of genes that just lead to higher causes of something? There are identical albino and non-albino twins.

I'm really skeptical that albinism is environmental. But stranger things have happened, I suppose.