M.Gurven & H.Kaplan Longevity Among Hunter-Gatherers: A Cross-Cultural Examination has a conclusion of "The average modal age of adult death for hunter-gatherers is 72 with a range of 68–78 years."

It's not about the ancient societies but is relevant because for this discussion the point is not history, but the effects of a hunter-gatherer diet.

http://www.anth.ucsb.edu/faculty/gurven/papers/GurvenKaplan2...