One interesting hypothesis I've heard is that there is actually a huge selection pressure for long human lifespans, to preserve cultural knowledge and skills necessary for survival, as well as to help with child care. The parenting age adults can't exactly hunt and gather if they have to watch babies all day long- yet human children are pretty helpless and need almost constant care for years.

As a dad, even in modern times I couldn't work at all without someone to help with parenting... however if I can work, I could bring in enough resources to support an entire family.

I would imagine having pepaw & memaw around to watch the kiddos while mom and dad were out gathering food would be a huge boon as far as keeping your progeny alive to reproduce again.

>The parenting age adults can't exactly hunt and gather if they have to watch babies all day long- yet human children are pretty helpless and need almost constant care for years.

Gathering food or light manual work? You just stick 'em in a papoose (we used a shoulder sling). Heavier work, hang the papoose in a tree. Once they can walk they can gather food and do light work.

I'm not saying grandparents wouldn't make it easier, but babies/toddlers are quite adaptable.

I think for hunting (with weapons) you'd want them to be at least 5.