Some popular books tell you that because some prehistoric humans lived on large amounts of meat and ate no grains, you should do the same. That's lousy advice.

We do know that humans' nutritional needs and system of digesting, processing and using nutrients have not changed significantly in two million years. We are omnivores and can get nutrients from plants, animals or both. The human race has managed to acquire food and survive on every body of land on earth except Antartica, and has adapted to major climate changes. No single food or group of foods is essential; humans can get the nutrients they need from any reasonably varied selection of plants and/or animals as they are found in nature.

We know what our ancestors ate by studying their fossilized feces; as you would expect, they ate whatever was most available in their place and climate, and within their skills. The books that tell you to eat meat focus on groups who had fire and domesticated dogs, hunting weapons, and sparse vegetation