I'm pretty sure no one way back in time skipped any available food source they could discover to stay alive. Ancient diets high or low in carbs, fat, etc. We hear about traditional, for example Asian, diets with a lot of carbs and old-time people not becoming metabolically deranged eating them. But add sugar and processed junk to those diets and boom! Epidemic of diabetes and the like. Like many I was well-meaningly raised on foods I still recognize as healthy but also a lot of sugar and other refined carbs, trans fats and all that processed stuff people had no clue at the time were so bad for all of us. Without all that exposure to sugar etc. might I have been able to consume a high starch diet today while remaining metabolically healthy? Maybe. But can I now? No. A whole foods paleo diet is far too much carbohydrate, as are many keto plans. Regardless of what ancient people were able to eat, each of us has to figure out, with our own unique bodies and past metabolic assaults, what we can each handle now.