Catching Fire is a well-written book with an interesting thesis but, after reading the book, I can’t quite completely believe the thesis.

Wrangham is a primatologist, and his years of studying monkeys surely contributed to his thesis, which is this: the control of fire, and the use of cooking, caused evolutionary changes in our ancestors that directly caused us to become human.

The evolutionary chain is this: about 3 million years ago were the australopithecines, who walked upright but mostly looked like apes. By about 2.3 million years ago some australopithecines had evolved into habilines, who had bigger brains than their ancestors and could make knives. Then, between about 1.9 and 1.8 million years ago, the habilines evolved into Homo erectus, who had smaller brains than we do but were fairly similar to us.

The traditional explanation of how our ancestors evolved into Homo erectus was that they began eating meat. Since they could not control fire, they would’ve eaten all of their meat raw. This change in diet would have led to an increase in calorie intake, which resulted in an evolutionary transformation, with bigger brains and slightly different bodies.

In the book, Wrangham argues that the meat eating hypothesis alone does not make sense since there were two transformations, when the habilines showed up and then later when Home erectus showed up. Wrangham believes that the first transformation was due to meat eating, but the second transformation was due to the control of fire, and cooking.

It’s an interesting hypothesis, and Wrangham provides lots of data to back up his idea. He looks at studies as varied as research on modern humans who are vegetarian, and archaeological evidence of knife making millions of years ago, and his own experiments in eating raw meat. Some primates that eat raw meat also mix in leaves, not to affect the taste of the meat but to get a better grip on the tough meat, as he himself learns with a mouthful of raw goat. Wrangham also does an excellent job describing the changes in our ancestors’ bodies that came from eating cooked food. Because cooked food is more processed than raw food our bodies can digest it easier, so our digestive systems became shorter than our ancestors.

Wrangham is a primatologist, not an anthropologist or archaeologist, which are the specialties that would more typically write a book like this, and the book is best when he is quoting from or responding to experts in the field. There are some sections of the book, however, where Wrangham writes about his own ideas while ignoring the experts, and in these sections it’s hard to judge Wrangham’s ideas. For example, Wrangham believes that the control of fire brought our ancestors out of the trees and permanently onto the ground. A fire that could be kept going continuously during the night, he writes, would scare away any predators, so sleeping on the ground became a safe option. It’s an interesting idea, but what have anthropologists written about this earlier? Wrangham doesn’t say.

Despite sections like this, Catching Fire is a worthwhile read, full of interesting facts and a thought-provoking thesis.