Animals of the genus Homo are defined by their little mouths, large guts, big brains -- and appetite for bratwurst. This, at least, is the provocative theory of evolution put forth by Dr. Richard Wrangham in his fascinating new book, "Catching Fire: How Cooking Made Us Human."
Wrangham, the Ruth B. Moore Professor of Biological Anthropology at Harvard University's Peabody Museum of Archaeology and Ethnology, began his career studying chimpanzees alongside Jane Goodall, and rose to academic acclaim as a primatologist specializing in the roots of male aggression. Naturally, he tends to think of most scientific questions in relation to chimps. And so it was that a few years ago, while sitting in front of his fireplace preparing a lecture on human evolution, he wondered, "What would it take to turn a chimpanzee-like animal into a human?" The answer, he decided, was in front of him: fire to cook food.
For years, accepted wisdom has held that it was a transition to meat eating that prompted human evolution -- which makes Wrangham's hypothesis a radical departure. Yet, the more he tested his theory, the more he found the science to back it up: Cooked food is universally easier to process and more nutritionally dense than raw food, which means adopting a cooked diet would have given man a biological advantage. The energy he once spent consuming and digesting raw food could be diverted to other physiological functions, leading to the development of bigger bodies and brains. And Wrangham's "cooking hypothesis" not only explains the physical changes that humans underwent but also the social ones: Cooking created a sexual division of labor that informs our ideas of gender, love, family and marriage even to this day. "Humans are adapted to eating cooked food in the same essential way as cows adapted to eating grass, or fleas to sucking blood," Wrangham concludes. "And the results pervade our lives, from our bodies to our minds. We humans are the cooking apes, the creatures of the flame."
Salon spoke with Wrangham, 60, by telephone from his research station in Uganda, about the dangers of strictly raw-food diets, why women are the ones who cook and the tricky business of calorie counting.
For years scientists have suggested that the making of tools, and then using tools for hunting and meat-eating, were factors that prompted the evolution of man as we know him. You push that theory farther to say that it was not eating meat, but cooking it and eating it, that's responsible for the transformation. How did you make that leap?
In the very beginning, I wasn't even thinking about human evolution. In fact, the basic idea came to me after long days of following chimpanzees, when -- because I was hungry, and sometimes I didn't take my food with me -- I tried to eat what they ate. I assumed that since I was a member of a species that was so closely related to chimps -- different only in terms of bodies and brains -- I would be able to eat anything that they could. But in actuality, though I could force it down, I quickly realized that I could not eat enough of what they ate to satisfy my hunger.
That started me subconsciously wondering about the question of food's role in human evolution. But it wasn't until some years later -- when I was sitting in front of my fireplace one night, thinking how nice and comforting a fire is, and how long ago back it would have been that our ancestors had been doing the same thing -- that I went further back in time in my mind, and realized it was very difficult to imagine our ancestors having fire and not cooking. And from there, I began to find it very hard to imagine any creature with the basic human shape surviving on raw food.
Still, when I started my research, I was amazed to discover how little investigation had been done into the nutritional and biological aspects of cooking. In particular, I was amazed by how many people thought that humans could live perfectly well on raw food.
Yes, you do quite a convincing job of arguing that a purely raw diet cannot sustain an active human. Do you believe that we have evolved to a point where a raw diet is fundamentally against our biology?
Yes, I suppose I do. If I hesitate, it is because I certainly recognize that raw foodists who live in an urban area of a well-to-do nation can make it work, so it's not that much against our biology. But I do feel very confident now that going off into the wild and living like a hunter-gatherer on raw food is not possible. People who switch to a raw diet report feeling constant hunger and lose large amounts of weight, even when they are careful to take in at least the nutritionally suggested number of calories a day for an adult. Basically, all the studies show that over the long term, a strictly raw diet cannot guarantee an adequate energy supply for our bodies. In other words, raw foodism is against our biology in a state of nature.
How do you respond to raw foodists who say a raw diet makes them feel healthier than they ever have before?
My response is that under modern conditions, living in places where you have money and grocery stores that make a super abundance of high-class domesticated foods accessible, I think it probably can be a healthy way of eating. Don't get me wrong: I have tremendous admiration for raw food devotees because it is a very hard life to resist the temptations of cooked food, and they must build their whole life around it. And of course, because they build their lives around it, they are very, very committed to the idea that it is a valuable diet. That makes them feel some resentment toward me, I guess. But the irony is that these days, very often, cooked food can be unhealthy, too. The most obvious way is that people eat too much of it.
But raw foodism seems like a pretty extreme response to the problem of obesity, doesn't it? And from what I can tell, most people don't eat raw food just to lose weight -- there seems to be a philosophical element to it, an idea that as though by choosing a raw diet, they can get back to a pure state.
Yes, of course, raw foodists argue quite strongly that it is our natural diet. My response to them is to say that yes it is, in a way. But it was natural 2 million years ago, not a few thousand years ago.
You write that cooked foods give our bodies more energy than raw foods. Can you explain that, because it seems somewhat counterintuitive. Even when you're not adding anything -- oils or fats -- the caloric value goes up?
It's really very simple. Cooking doesn't change the actual number of calories in food -- meaning that, if you take two portions of raw vegetable or animal product and cook one of them, when you blow it up in a bomb calorimeter and compare the two, you'd get the same number of calories. But there are two big things that cooking does. One is that it increases the proportion of the nutrients that our bodies digest, and from the data I reviewed -- for instance, in the case of egg protein it goes from 50 percent to 90 percent -- it looks as though that effect can make an enormous difference. And the second thing it does is that cooking reduces the costs we pay to digest our food.
So, eating cooked food conserves our energy?
That's right. We all fall asleep after a heavy meal, but if you eat a large meal of raw food, you'll fall asleep faster, because your body is working harder. More oxygen will be leaving your peripheral tissues and going to your intestinal organs.
Basically, cooking makes the food we eat more nutritionally efficient?
Yes. And that's why in my last chapter, I take on the issue of our food labeling system. When you treat food through processing or grinding, you're not actually creating more calories -- so technically, the food labeling system we have now is correct. But, if we want to be realistic about the caloric value we actually get from a food, we need to modify our labels to reflect more subtle measurements -- something like: "This item has been given a level 2 processing, which has increased its nutritional value by 50 percent."
You argue that cooking not only shaped our bodies, but it also shaped our households and our most basic ideas of gender. How so?
Well, without language, we can't be absolutely sure about what happened right in the beginning. But with what knowledge we have, I do think that cooking has this huge impact on households and our system of gender as we see it today -- and I've been trying to figure out where my thinking on this began. I've been fascinated for a long time by the idea that cooking basically produces a lump of food -- yet unlike any other primate, we humans have an extraordinary degree of respect for women who make it. Other men -- bachelors, children -- almost never take food from them. And the more I thought about this, I concluded that it looked to me like a system in which women cook for their husbands to earn the social protections that only men can give them through their membership in the male community.
So the concept of marriage began fundamentally not as about power or sex, but food?
Yes, though that would mean that women always do the cooking, and when I first started down this path, I wasn't at all sure that was the case. So, I went to the anthropological literature, and sure enough, I found reports of societies where men did the cooking. But then I dug into it more carefully -- and I discovered that, in the cases where the anthropologists claimed the men had done the cooking, the scientists had been wrong. In every single society women cook for men. And, what's more fascinating, in many societies you can really say that food or domestic promiscuity is far more serious than sexual promiscuity. In other words, it's more of a breach of social convention for a woman to feed the wrong man than it is for her to have sex with him.
Why do you think societies have evolved that way?
Because it is, and has always been, so critical for a man to be able to know that someone is going to give him a meal in the evening – because this enables him to spend the whole day doing what he wants -- doing, as it were, manly things. It's very clear from the literature on small-scale societies – and probably true even in our society today – that bachelors have a very hard time of it. They are thin, they are looked down upon by married men, they deeply desire to have a wife in order to be able to join the ranks of the elders. The problem that bachelors face is that they have to spend time during the day not simply doing things that will bring them glory -- like hunting -- but making sure they have a way of feeding themselves in the evening. And it uses up a lot of energy and time to take care of yourself.
A lot of my book has been challenging to people, but because the male-female relationship is so central to the way we think about humans, and because for so long people have tended to think about pair bonding as being about mating competition and choice of a sexual partner, this in particular has been quite a difficult theory for people to chew over.
Does that mean that, evolutionarily, men should focus on finding a wife who can cook instead of a beauty?
Yes, essentially. I know that from our perspective in the West, where we tend to focus even more than other societies on questions of sexual morality, it's rather an immoral suggestion that I'm making -- basically that men set themselves up with wives in order to have the freedom to be men, as it were -- and then go ahead and design their sexual strategy from that point on.
Now, in modern Western societies, that strategy is usually to stay with one's wife -- but not always, as we know! From the woman's point of view, the wife wants the security of knowing that she has her husband to protect her from the scrounging "others." It's not a notion of a love relationship. That's less common and more nakedly economic in many societies than in our own.
Haven't we evolved an emotional attachment to cooked food as well as a physical one? It didn't occur to me until I was reading your book, but raw foods have little scent -- yet the sense of smell is one of our most powerful senses. And elemental smells like warm vanilla or baked apples or grilled meat -- all cooked foods -- are ones that humans seem to respond to positively and universally across age and culture and place.
Absolutely, and as Proust says, smells definitely have an immense effect on our memory and our biology. But it's a complex question. When I was working on the book, I tested apes on a diet of cooked food, and they liked it spontaneously. You can understand why: The physical characteristics of cooked food have commonalities with other foods that are good for them in the wild. But the smells of cooked food are not like anything you'd find in the wild. They're really totally different -- though I admit I have no chemical data to support that. So, you might think that we have adapted to appreciating and enjoying cooked food as a result of our evolutionary history of exposure to it. But, in that case, other animals should not be adapted to like the smell of cooked food. And we simply have no data to reflect that at the moment.
Did your your studies change the way you thought about the way we should be eating?
Not really. I'd like people to be aware of how easy it is to overeat in today's world. But personally I've always been on a quasi-Mediterranean diet: lots of vegetables, some oil, not too much of anything and not much red meat. I don't think this experience changed the way I choose to eat, though frankly, if I had the courage, I might try a raw diet for a bit -- just to see how it is.
You haven't ever gone on a completely raw diet?
No, I haven't. It just seems such a social inconvenience. But maybe that's just an excuse.