“You can’t have a large brain and big guts at the same time,” explains Leslie Aiello of our evolutionary ancestors. She’s an anthropologist and direct for he Wenner-Gren Foundation in New York City, which funds research on evolution. Before eating meat, our ancestors had to have big stomachs to digest large amounts of fruits, nuts, roots, tubers, and berries. These raw foods have few calories and require lots of chewing and digestive work for the body to extract the nutrient it needs, so our ancestors spent a lot time eating. The switch to high-fat and high-calorie meat allowed the body to devote less energy to digestion and permitted growth elsewhere, particularly in the brain. The brain uses 20 times as much energy as the same weight in muscle.
Having a bigger brain lead to building better tools. “What we think is that this dietary change around 2.3 million years ago was one of the major significant factors in the evolution of our own species,” Aiello said. Evidence of the carnivorous change can been detected from the presence of a tapeworm that jumped from wild dogs to early humans, meaning we once scavenged the same carcasses as hyenas. But the use of tools soon gave humans the upper hand.
“If you look in your dog’s mouth and cat’s mouth, and open up your own mouth, our teeth are quite different,” said Aiello. “What allows us to do what a cat or dog can do are tools.” Our teeth and jaws changed as tools made hunting and eating more efficient, because they weren’t needed to do as much grinding.
Sorry vegetarians, but it looks like meat was the original brain food.