You can’t have a large brain and big guts at the same time. Digestion was the energy-hog of our primate ancestor’s body. The brain was the poor stepsister who got the leftovers. 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.18 After we began to focus more of our energy on obtaining meat, a number of important changes to our guts, masticatory anatomy, brains, and even social systems started to take place.
