you dont need very much to survive. how much is a regular women's calories suggestion today? for a moderately active woman usually 1600 to 1800. if you ate a chipotle burrito you'd only have enough calories left over to eat a salad and some fruit. or it would be oatmeal for bfast, salad and bread for lunch and a baked something with veggies for dinner. and maybe a couple fo fruit and handful of nuts for snacks. how many of us really eat our portion sizes or even the amount for the day? mind you this does not even include junk.
the idea that we have to eat to full is also a recent concept. when the explorers landed in new england they could not understand why the natives didnt stash away food for winter. why did they sometimes starve and not eat their full. and the natives couldnt understand why the pioneers ate such copious amounts of food. some natives died from starvation and some of us die from overeating.
all our cultural meaningful rituals are built around food. for the older cultures it wasnt. they did have feasts of course but it was more other things like dances and fasting that a community came together for.
now we cant compare hunter gatherers with agriculturists because agriculturists worked hard. hunter gatherers lived a v. relaxed life with not heavy labor. so their nutritional needs were different. farmers eat huge meals coz they work that hard.
so we cant think about yesterdays food with the eyes from todays food. the definition of food has changed immensely over time. a lot. even just from our parents generation to now.