Adapting to cooking (Image: Rick Friedman/Corbis)

What was the central mystery of human evolution that you were trying to solve?

I was sitting next to the fire in my living room and I started asking the question, when did our ancestors last live without fire? Out of this came a paradox: it seemed to me that no human with our body form could have lived without it.

Why can’t a human exist on the same diet as a chimpanzee?

A chimpanzee’s diet is like eating crab apples and rose hips. Just go into the woods and find some fruits, and see if you can come back …