[Johnny555]

Why would I eat 1000 calories of any food? I wouldn't eat 14 slices of bread or 1.5 lbs of chicken breasts either. But I do eat normal quantities of boiled grains pretty regularly in stews or on a salad.

[sidpatil]

It's likely that the ancient people you mentioned were physical laborers. They would need the calories.

[Johnny555]

But you don't think they had more than one food source? And if they really did subsist mostly on boiled grains, wouldn't their body get used to it?