Infographic: How A Raw Food Diet Kept Primates Stupid

For human ancestors, raw diet meant tough tradeoffs between brawn and brains.

Raw Diets Mean Tradeoff Between Brawn and Brains
Emily Elert

Humans differ from their primate ancestors in a few obvious ways (our conspicuous lack of body hair, our short arms), but evolutionary researchers all agree that what really sets us apart--what makes us social and creative and _human_--is our big brains. The question researchers are still trying to answer is: How did it happen? What conditions or changes or achievements made it possible for our ancestors' brains to grow to twice the relative size of monkeys, orangutans, and chimpanzees?

A study published yesterday in the journal PNAS puts weight behind the hypothesis that--more than any social or environmental factor--humans own their giant cognitive leap to the ancestral chefs and proto grill masters who invented cooked food.

Why? According to the researchers, a diet of raw foods can's support an endless growth of both brawn and brains. Larger body sizes and bigger brains both meant more energy use, which meant more time spent eating each day.

And, since no primate can sustain a daily foraging requirement of much more than eight hours (gorillas average close to eight, but sometimes spend closer to nine), our ancestors must have found some way to get more energy in less time.