How did pre-agricultural man eat?
Firstly, mankind was more or less forced into agriculture as the entire world became full of hunter gatherers. With increased competition for wild tubers and game, the tribes who took care of the tubers by replanting them and/or weeding them survived better...
From a food energy perspective, our crafty and often desparate ancestors would have done well to hunt or gather only the most energy dense foods, weighed against the resource costs of hunting or gathering them (and digesting them..). Large herbivorous herd animals, such as a buffalo or deer, could provide enough food for a family for weeks, with the well timed throw of an atlatl. How many grass seeds would one have to gather, carry, and grind with rudimentary tools to provide the same calories?
Grass seeds are only available seasonally, if at all...animal meat is a year round resource!
If humans were "evolved" to eat grains, we would have five fermenting stomachs like a cow.
While we can never know exactly what ancient people ate, deductive reasoning surely points out what a healthy, enduring tribe would have focused their food-procuring efforts towards. Certainly early man ate whatever he could get his hands on, and undoubtably this would include all sorts of herbs, fruits, and vegetables, depending on the season, climate, location, and foraging competition from other animals.
What is optimal for us, doesn't depend as much on what Grok ate; as it depends on results, both individual and scientific. It seems that medical and nutritional science is too biased to give the Paleo principles a fair chance at proving their results.
How much anecdotal evidence is required to prove a theory true?