They are looking at the bones plus they already know how these folks live - they follow the animal herds
Anyway, we do have evidence of "paleo" diets by looking at certain tribes in Africa - those on the "ancestral" diets do not have modern diseases; but the same folks who follow a western diet did
That kind of rules out genetics doesn't it?
Even in China, there's growing evidence that the increased consumption of western diets have led to a huge increase in diseases previously not present like diabetes, CHD etc
If consumption of a highly processed diet is toxic over the long run, do we still want to eat that in "moderation"?
Call me KS, I rather not
Anyway, who said our diet doesn't have variety just because we don't eat cai png?