Host: We used to think using tools made us human, but chimps hunt with crude spears, crows use sticks to dig for bugs, and elephant has been known to disable electric fences dropping rocks on them. So if your fancy, cordless drill doesn’t set you apart from the beast, what does? That’s this week’s question on science out of the box. Host: One theory comes from Harvard anthropologist, Richard Wrangham; he lays out a new book “Catching Fire-How Cooking Made Us Human”, and he’s with us now from Harvard. Now you found that human have evolved to depend on cooked food. Would you explain that a little bit and tell us how cooking does make us human? A: Well, I mean the odd thing is for years we've assumed that because humans are animals, and animals are designed to eat raw food; humans are designed to eat raw food, too. But as you look into it, you discover that it's extraordinary difficult to survive on a raw food diet. You can only really do it if you happen to live in a modern urban industrial society which you can get the very best of raw food that has been domesticated by humans. But in a while, you can’t do it. So what is going on? Well, it seems as though humans are biologically adapted to having a particular high quality of food and that high quality is produced by cooking. How does cooking make food more nutritious? It does two big things. One is it increases the proportion of the nutrients of the food that can be digested, and it does that basically by opening them up, to be accessible to enzymes. It denatures proteins for instance, and raveling them and exposing them to the action of snipping enzymes. And the other thing it does is it makes food easier to digest by softening it or gelatinizing the connective tissue in meat. Host: How did cooking, which you said started about 1.9 million years ago,… how did it change us socially? A: One of the huge things it did was it increases the amount of time available for us because once you cook, it softens the food and it means you can eat it very quickly. And this is really significant because if we were a great ape, we would spend about 6 hours a day just chewing our food, and as it is, we spend… all humans… less than an hour a day. So that suddenly frees up 5 or more hours a day. There’s another thing, too. What cooking does is to enforce ownership…ownership of things, namely of course the food, because once you are committed to cooking, then you have to collect food and put it in a pile. Well, while it’s sitting there, it’s vulnerable to somebody who hasn’t got any food coming along and stealing it, and that means you’re gonna have social rules and regulations to be able to make sure that the system doesn’t fall apart from people just stealing. I think this is very significant in generating what we think of us as…the household. We have this regulated ownership, and in many ways, I think cooking can therefore be seen as the beginning of a new kind of society- the fundamental sexual division of labor. It’s hard, of course, to know what happened originally, but suppose for the sake of argument that every individual cooked their own food. Well, it wouldn’t take long for the tougher males to realize that they didn’t have to do this. You know the big males would bully the females or smaller males into cooking for them,…and that dynamic, I think, can be argued to lead ultimately to marriage as a primitive protection racket, which means women cook for men, and what men provide for women is protection of the food through a social arrangement. So we’ve got the amazing social rules that completely changed the relationship between social behavior and food. Host: Richard Wrangham is the Ruth Moore professor of biological anthropology at Harvard University. Thanks so much for joining us. --

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