The average includes a huge number of deaths of children and of mothers though - not counting those risks (childhood, especially the very early one, and giving birth) it's higher than most people think. In a lecture on microbes (http://www.gresham.ac.uk/lectures-and-events/return-of-the-m...) the professor mentions as an aside that a late Victorian British citizen after excluding those risks actually had a slightly longer life-expectancy than a modern British citizen! While that is fairly recent it still is long before modern medicine and antibiotics.
Quote:
> And what is interesting, if you take out the childhood mortality, the Victorian person between 1850 and 1880 lived slightly longer, if he was a male, than you do today.
("if he was male": giving birth was very risky)
So it seems that good food (variety plus enough of it) and hygiene did most of the job of extending life-expectancy outside the above two risks - and modern medicine very significantly lowered childhood and birth (mother) deaths. In the light of such evidence modern medicine does not seem to have had a great effect on life expectancy once you made it past childhood. We can't do anything against "aging".
There is plenty anthropological research on the social structures of these hunter-gatherer humans and children were usually collectively raised by the whole group rather than in their biological families.
Life was not as easy and it was likely much shorter on average. In a more primitive society, if a newborn's mother dies, that newborn probably has very low survival odds. Older women could definitely still have played an important role in raising children in the context of the family/tribe, but I see clear evolutionary advantages to having your children while younger, because you are simply more likely to be alive to raise them.