Walking on two feet wasn't an advance, having to two free hands to wield weapons was. That combined with envy led to murder then tribal warfare, which is essentially the modulated evolutionary pressure that drives human brain development while leaving all other animals untouched. If it wasn't for envious leftists always trying to take our stuff we would still be eating grubs from a stick.
mmmmmmmmm grubs on a stick.
Wow! They might have been good for something after all!
Once. A long time ago.