JACKI LYDEN, host:
Welcome back to ALL THINGS CONSIDERED from NPR News. I'm Jacki Lyden. We used to think using tools made us human, but chimps hunt with crude spears, crows use sticks to dig for bugs, and elephants have been known to disable electric fences by dropping rocks on them.
So, if your fancy, cordless drill doesn't set you apart from the beasts, what does? That's this week's question on Science Out of the Box.
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LYDEN: One theory comes from Harvard anthropologist Richard Wrangham. He lays it out in a new book, "Catching Fire: How Cooking Made Us Human," and he's with us now from Harvard. Hello there, Richard Wrangham.
Mr. RICHARD WRANGHAM (Author, "Catching Fire: How Cooking Made Us Human"): Hello, Jacki, how are you?
LYDEN: Good. Now, you find that humans have evolved to depend on cooked food. Would you explain that a little bit and tell us how cooking does make us human?
Mr. WRANGHAM: Well, I mean, the odd thing is that 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 extraordinarily 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 in which you can get the very best of raw foods that have been domesticated by humans. But in the wild, you can't do it. So, what is going on?
Well, it seems as though humans have biologically adapted to having a particularly high quality of food, and that high quality is produced by cooking.
LYDEN: So, how does cooking make food more nutritious?
Mr. WRANGHAM: It does two big things. One is it increases the proportion of the nutrients in the food that can be digested, and it does that basically by opening them up to be accessible to enzymes, it denatures proteins for instances, unraveling 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.
LYDEN: How did cooking, which you say started about 1.9 million years ago, how did it change us socially?
Mr. WRANGHAM: Well, one of the huge things it did was it increased the amount of time available for us because once you cook, it softens the food, and it means that you can eat it very quickly. And this is really significant because if we were a great ape, we would spend about six 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 five or more hours a day.
There's another thing, too. What cooking does is to enforce ownership, ownership of things, and namely, of course, the foods. 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've got to have social rules and regulations to be able to make sure that the system doesn't fall apart from people just stealing. And I think that this is very significant in generating what we think of as the household.
We have these - 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 the 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 got these amazing social rules that completely change the relationship between social behavior and the food.
LYDEN: Richard Wrangham is the Ruth Moore professor of Biological Anthropology at Harvard University. Thanks so much for joining us.
Mr. WRANGHAM: Oh, pleasure to talk to you.
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