[vacri]

Humans also take figuratively forever to be self-sufficient. Herd animals are born with the ability to walk, for example. Humans take about 10 years before they can be taught to be even somewhat self-sufficient, which is a ridiculously long time in comparison to others.

So, given that humans are sexually mature before they're fully self-sufficient, that enhanced ability to support their offspring is not all advantage - it's actually required for the propagation of the species. If older folks weren't taking care of the younger ones, none of them would reach reproductive age.

[devoply]

A 7 or 8 year old can hunt if you were to teach them to do so. An 8 year olds has conceived. So it's possible to do it at a much younger age if you have no choice.

[vacri]

While it may sound callous, if that 8-year-old did not produce viable offspring that could mature to reproductive age themselves, she is irrelevant to evolution. Conception is not synonymous with viable offspring.

As for the 8-year-old hunter, just how self-sufficient can they be? Procuring their own weapons, transporting their own carcasses, preparing healthy meals multiple times per day on an ongoing basis... the idea that you could just loose a 7-8 year old into the woods with a weapon and they'd survive in an ongoing sense is a bit far-fetched. Teaching someone to sneak, track, and point a gun is not the same as them being self-sufficient.