> Most were doing chores or actual work throughout history.

I have to disagree, the young of other social animals like dogs and lions all spend most of their time "playing". This, combined with the fact that a human child is comparatively underdeveloped compared to the young of every other animal makes it hard to conceive of any useful task a child could do in a neolithic society. It's not like toys are some recent invention, they're one of the oldest types of artefact we dig up. I believe "chores" are a modern invention that exists mostly to act as busywork. Washing dishes doesn't teach you anything important but many types of play exist as a sort of simulation of adult life.