Pink is for girls and blue is for boys, and that’s just the way it is, right? Girls like nurturing toys and boys like toys that involve motion or action, and don’t even bother trying to change those habits—they’re ingrained at birth, yeah? Doubtless you’ve heard these and other stereotypes and claims about the biological origins of sex differences. In some cases, such as the pink/blue divide, you might already be aware of the history…