Richard Wrangham has studied the diets of wild chimpanzees.

By CLAUDIA DREIFUS

Richard Wrangham, a primatologist and anthropologist, has spent four decades observing wild chimpanzees in Africa to see what their behavior might tell us about prehistoric humans. Dr.Wrangham, 60, was born in Britain and since 1989 has been at Harvard University, where he is a professor of biological anthropology. He is about to publish another book,“Catching Fire: How Cooking Made Us Human.”


Q. In your new book, you suggest that cooking was what facilitated our evolution from ape to human. Until now scientists have theorized that tool making and meat eating set the conditions for the ascent of man. Why do you argue that cooking was the main factor?

A. All that you mention were drivers of the evolution of our species. However, our large brain and the shape of our bodies are the product of a rich diet that was only available to us after we began cooking our foods. It was cooking that provided our bodies with more energy than we’d previously obtained as foraging animals eating raw food.

Modern chimps are likely to take the same kinds of foods as our early ancestors. In the wild, they’ll be lucky to find a fruit as delicious as a raspberry. More often they locate a patch of fruits as dry and strongtasting as rose hips, which they’ll masticate for a full hour. Chimps spend most of their day finding and chewing extremely fibrous foods. Their diet is very unsatisfying to humans. But once our ancestors began eating cooked foods - approximately 1.8 million years ago - their diet became softer, safer and far more nutritious.

And that’s what fueled the development of the upright body and large brain that we associate with modern humans. Earlier ancestors had a relatively big gut and apelike proportions.


Q. To cook, you need fire. How did early humans get it?

A. The austrolopithicines, the predecessors of our prehuman ancestors, lived in savannahs with dry uplands. They would often have encountered natural fires and food improved by those fires. Moreover, we know from cut marks on old bones that our distant ancestor Homo habilis ate meat. They certainly made hammers from stones, which they may have used to tenderize it. We know that sparks fly when you hammer stone. It’s reasonable to imagine that our ancestors ate food warmed by the fires they ignited when they prepared their meat.

Now, once you had communal fires and cooking and a higher-calorie diet, the social world of our ancestors changed, too. Once individuals were drawn to a specific attractive location that had a fire, they spent a lot of time around it together.


Q. Your critics say you have a nice theory, but no proof. They say that there’s no evidence of fireplaces 1.8 million years ago.
How do you answer them?

A. Yes, there are those who say we need archaeological proof that we made fires 1.8 million years ago. And yes, thus far, none have been found. There is evidence from Israel showing the control of fire at about 800,000 years ago. I’d love to see older archaeological signals. At some point, we’ll get them.

We have strong biological evidence. Our teeth and our gut became small at 1.8 million years. This change can only be explained by the fact that our ancestors were getting more nutrition and softer foods. And this could only have happened because they were cooking.


Q. Since you believe that the raw fare of prehistory would leave a modern person starving, does that mean we are adapted to the foods that we currently eat - McDonald’s, pizza?

A. I think we’re adapted to our diet. It’s that our lifestyle is not. We’re adapted in the sense that our bodies are designed to maximize the amount of energy we get from our foods. So we are very good at selecting the foods that produce a lot of energy. However, we take in far more than we need. That’s not adaptive.