Good point. And even if we take it for granted that prehistoric man was not "obese" (not sure where this information comes from), how could they tell if his diet was nutritious enough? Possibly through bone samples, but I imagine that prehistoric man's body was adapted to a different environment and diet to begin with. I'm actually kind of interested in what kind of raw mean the modern diet entails. I believe it's alright to eat raw red meat which is very fresh....but how many people living in New York or London will get their hands on that kind of stuff?
As a Christian I know this just isn't totally true. It is true in certain cultures and certain climatological conditions during specific time periods, but not universally true. I really have no idea how researchers can pinpoint average lifespans based on the few samples we have to go on.
Hobbes said it best and his characterization has largely been corroborated through modern research.
the life of man, solitary, poor, nasty, brutish, and short.
A short average lifespan was common until relatively recently and is still common in some parts of the world such as sub-Saharan Africa and parst of Asia.