>There's little evolutionary need another generation beyond them, so you'd expect mortality to increase rapidly after 60
That's exactly my point. Hunter-gatherer diet didn't need to work very well against cancer, heart disease or Alzheimer's and hence we shouldn't expect it to promote what we consider longevity today.
But I think you're overestimating the value of grandparents for breast feeding toddlers. Population growth wasn't very rapid back then because most kids died at birth or very soon after. So there weren't actually that many kids around I think.
That's exactly my point. Hunter-gatherer diet didn't need to work very well against cancer, heart disease or Alzheimer's and hence we shouldn't expect it to promote what we consider longevity today.
But I think you're overestimating the value of grandparents for breast feeding toddlers. Population growth wasn't very rapid back then because most kids died at birth or very soon after. So there weren't actually that many kids around I think.