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[ED. NOTE: The following interview with Harvard biological anthropologist Richard Wrangham was originally published eight years ago on Edge, on February 28, 2001. Given the media interest attending the publication of Wrangham's related book, Catching Fire: How Cooking Made Us Human, we are bringing the piece back for an encore.]

A Talk With Richard Wrangham

One of the great thrusts of behavioral biology for the last three or four decades has been that if you change the conditions that an animal is in, then you change the kind of behavior that is elicited. What the genetic control of behavior means is not that instincts inevitably pop out regardless of circumstances; instead, it is that we are created with a series of emotions that are appropriate for a range of circumstances. The particular set of emotions that pop out will vary within species, but they will also vary with context, and once you know them better, then you can arrange the context.... It's much better to anticipate these things, recognize the problem, and design in advance to protect.


According to Harvard biological anthropologist Richard Wrangham, almost two million years ago humans emerged from a stock of pre-human apes. Remarkably, our species is still evolving today, faster than ever. "Why we evolved then, and why we are still changing, are problems that shape our souls," he says.

Wrangham believes that humanity was launched by an ape learning to cook. In a burst of evolution around two million years ago, our species developed the family relations that make us such a peculiar kind of animal. Cooking made us women, men and lovers.

"We behave like our two closest relatives," Wrangham says. "Chimpanzees and bonobos, because in spite of first appearances, we face somewhat similar kinds of problems to each of those species. Cooking makes our behavior partly chimpanzee-like because it intensifies a chimpanzee-like division of labor. Self-domestication, on the other hand, makes us bonobo-like by selecting for a youthful psyche. In both cases human behavior echoes the biology of our cousins, though never exactly copying it."

One of Wrangham's central ideas is that we should cherish the parallels between humans and other great apes, because they help us to understand our own behavior. "For all our self consciousness, we humans continue to follow biological rules. Life is easier if we understand those rules. Recognition of the deep contradictions in humanity binds us to our past, and also lights our future."

Other themes to his thinking: "We still have much to learn; We should not be afraid of biology; Dichotomous thinking (e.g. biology vs. culture; women vs. men) is almost always unhelpful "Evolutionary anthropology has excessively neglected females."


RICHARD WRANGHAM is a professor of biology and anthropology at Harvard University who studies chimpanzees, and their behavior, in Uganda. His main interest is in the question of human evolution from a behavioral perspective. He is the author, with Dale Peterson, of Demonic Males: Apes, and the Origins Of Human Violence, and Catching Fire: How Cooking Made Us Human.

Richard Wrangham's Edge Bio Page


RICHARD WRANGHAM: I make my living studying chimpanzees and their behavior in Uganda. I'm really interested in looking at the question of human evolution from a behavioral perspective, and I find that working with chimps is provocative because of the evidence that 5 million, 6 million, maybe even 7 million years ago, the ancestor that gave rise to the Australopithecus, the group of apes that came out into the savannahs, was probably very much like a chimpanzee. Being with chimpanzees in the forests of Uganda, as with the forests anywhere else in Africa, is pretty much like going into a time machine and enables us to think about the basic principles that underlie behavior.

Although humans are enormously different from the apes, the extraordinary thing that has emerged over the last two or three decades — and this is becoming increasingly clear recently — is that in maybe three big ways in particular, humans are more ape-like in their social behavior than you would expect to occur by chance. Moreover, there's something about our relationship to the apes that has carried through in terms of our behavior. To take an example, there are only two mammals that we know of in the world in which males live in groups of their male relatives and occasionally make attacks on individuals in neighboring groups so brutally that they kill them. Those two mammals are humans and chimpanzees. This is very odd and it needs explanation.

EDGE: Why was this not noticed until the last generation or so?

WRANGHAM: Chimpanzees weren't studied at all in the wild until 1960. It took 14 years after that before people were seeing them at the edges of their ranges. It's just difficult to follow them all over the place. It was 1974 when the first brutal attacks were seen, and these led to the extinction of an entire chimpanzee community in Gombe. People monitored that under Jane Goodall's research direction. And then slowly over the years it's been realized that chimps will carry on or will kill individuals in other communities. So now we've had chimp killing going on not only in Gombe and at the site I work at, in Kibale in west Uganda, but chimps have also killed other chimps in Budongo in Uganda and in Mahale in Tanzania. It just takes time for these observations to accumulate.

EDGE: Will the chimps kill others in their own community?

WRANGHAM: Yes, occasionally there's a Julius Caesar-like assassination, which is, of course, really intriguing, because we've got these tremendously important coalitions that go on within chimpanzee communities that determine a male's ability to do what a male is desperately striving to do all the time, which is to become the alpha male. And the question that arises once you see that on occasion these coalitions can lead to what are essentially assassinations is, what makes them stable normally? How is it that you don't get constant erosion of confidence, such that you get one individual isolated and the others all forming coalitions against him. These killings are rare events, but we know a fair amount about them. The most important aspect underlying the similarity is the fact that you can have extraordinary imbalances of power. You can have three or four individuals all jointly attacking another one, which means that it's essentially safe for the attackers. So if they decide that they are in a coalition against a victim, they can dispatch him relatively safely. That means that any animal can do that, and there are other animals that do, although they don't live in groups with their own relatives in the same way as chimpanzees do. Hyenas and female lions are other examples of animals that engage in this type of activity.

We've got three things that are really striking about humans and the great apes in parallel. The violence that chimps and humans show is pretty much unique to those two species. Then you have the extraordinary degree of social tolerance in humans and bonobos, another ape that is equally closely related to humans. And then you have a remarkable degree of eroticism in bonobos compared to humans. These parallels are not easily explained and raise all sorts of provocative questions, given the fact that humans have so many differences from the other apes in terms of our ecology, our language, our intelligence — our millions of years of separation.

EDGE: How long have you been doing field work? How did you get started?

WRANGHAM: I've been studying chimps on and off for over 30 years. I began working at Jane Goodall's site at Gombe, which is the archetypal site and represents to many people what the chimpanzee is. In 1984 I moved to Uganda and started work on a forest chimpanzee population, and began thinking particularly about cultural variation, about the kinds of behavioral traditions that vary between the two sites that I had come to know best. I then used this as a vehicle for trying to understand variations in social behavior among chimpanzees.

One of the lovely things that's going on now is the discovery that in East Africa we have a series of behaviors that characterize the chimps that are different from the behaviors that we see in extreme West Africa — in Christophe Boesch's site in the Tai forest in the Ivory Coast, for example, and Bossou. We're seeing chimps in the east that are relatively fragmented in their groups, that have relatively little sexual activity, that have few female-female alliances, that have extreme male dominance over females — and all of these things are different in the west. In the most stable groups in the west, the females form alliances, the males are much more respectful of females, and there is much less violence in the community in general. There's very much less infanticide, and there are much less severe forms of territoriality. This is exciting, because it means that we can dissect the chimpanzee species and ask, where are the ecological influences and what effects are they having? And what does this mean in terms of trying to reconstruct the kind of chimpanzee that gave rise to us seven million years ago?

The answers are becoming clearer. In my field work I am trying to understand what it is about the ecology that leads to differences in behavior. A real key that has been given extraordinarily little attention is the fact that in some populations, the apes are able to walk and feed at the same time. In others they're not, because there's no food for them as they're walking. This sounds like an extraordinarily trivial difference, but it seems to be enormously important, because if you can walk and feed at the same time, then you can stay in a group with your friends and relations without additional members causing an increased intensity of feeding competition. On the other hand, if you are walking without feeding between the key food patches, then every time an additional chimp comes along and joins your party, the effect is that feeding competition is intensified in these food patches. And there is no melioration when you're moving between food patches. The long-term effect of this is that it fragments the parties, and it's the fragmented nature of these parties of chimps that don't have ability to walk and feed at the same time that underlie all of these social differences.

EDGE: What questions are you asking yourself today?

WRANGHAM: There are two really fascinating things about human evolution that we have yet to really fully come to grips with. One is the evolution of cooking. Whenever cooking happened, it must have had absolutely monstrous effects on us, because cooking enormously increases the quality of the food we eat, and it enormously increases the range of food items that we can eat. We all know that food quality and food abundance are key variables in understanding animal ecology. But the amazing thing is that although at the moment there is no conventional wisdom that says when cooking evolved, social anthropology and all sorts of conventional wisdom say that humans are the animals that cook. We distinguish ourselves from the rest of the world because they eat raw stuff and we eat cooked stuff. The best anthropology can do at the moment is to say that maybe sometime around 250 or 300 thousand years ago cooking really got going, because there's archeological evidence of earth ovens.

This is fine, but long before earth ovens came along we must have learned to cook. And you would think that cooking would be associated with things like evidence in your body of the food being easier to digest, such as smaller teeth, or maybe a reduction in the size of the rib cage as the size of the stomach gets smaller, or maybe the jaw getting smaller. And there's only one time in human evolution that all that happens; that is, 1.9 million years ago with the evolution of the genus Homo. It's there we must look for evidence that cooking was adopted.

Once cooking happens, it completely changes the way the animal exploits its environment, because instead of moving from food patch to food patch, and eating as it goes, or eating in the food patches it finds, now for the first time it has to accumulate food, put it somewhere, and sit with it until it's cooked. It might take 20 minutes, it might take half an hour, it might take several hours. The effect is that all of a sudden there's a stealable food patch. Once you have a stealable food patch, that means that — life being what it is — somebody's going to come along and try to steal it. What this means is that you have to think about a producer/scrounger dynamic in which you've got individuals producing and individuals scrounging — and, horribly, females were the producers and males were the scroungers. Once you've got males bigger than females — fifty percent bigger by the time we're talking about, around two million years ago — then the effects on the social system would be large.

What we've got to think about is the idea that once you have females ready to make a meal by collecting food and cooking it, then they're vulnerable to having their food taken away by the scroungers — the big males — who find it easier not to go and collect food themselves or cook it, but just take it once it's ready. Therefore the females need protective bonds in order to protect themselves from thieving males, and this is the origin of human male-female relationships. The evolution of cooking is a huge topic that is virtually completely neglected. And whatever view you take about cooking, you have to say it's a problem that needs to be addressed.

The second problem is this: There is in a number of ways in the evolution of humans evidence of our behaving and looking as if we had the characteristics of a juvenile animal. For a hundred years or more people have talked about the idea that humans might be a pedomorphic species, a species that has juvenile characteristics in general, but this is too global a way to think about it. Still, it remains the case that much in our behavior, when compared with the behavior of our closest relatives, looks more playful and less aggressive when you're thinking about interactions at a social level within a group. We are also more sexual and more ready to learn, and these sorts of characteristics are characteristics generally associated with juvenility.

In a fascinating parallel, the bonobos — the second in the great pair of our two closest relatives — show all sorts of traits that are pedomorphic. We can see this throughout the head, where the morphology of the skull itself looks like the skull of an early adolescent or late-juvenile chimpanzee and much of its behavior looks juvenile-like. They are more playful, they're less sex-differentiated in all sorts of aspects of their behavior, they're more sexual, and so on. And we've yet to really come to grips with where this pedomorphic change has come from and what it means.

We've already got some wonderful examples of similar things occuring in other animals in the context of domestication. When we look at the differences between wolves and dogs, for example, we see amazing parallels to the differences between chimpanzees and bonobos. In each case for a given size of animal, you have the skull being reduced in size, and the components of the skull being reduced in size, including the jaws and teeth, and the skull looking more like the skull of a juvenile in the other form. The dog's skull looks like that of a juvenile wolf, and the bonobo's skull looks like that of a juvenile chimpanzee. And the behavior of each of them looks like it has strong components of the juvenile of the other species.

This leads to the thought that species can self-domesticate. There is good reason to think that over the course of evolution the bonobos evolved from a chimpanzee-like ancestor as a consequence of being in an environment where aggression was less beneficial to the aggressors, where there was a natural selection against aggression, and where selection favored individuals that were less aggressive. Over time, selection built on those slight variations in the timing of the arrival of the aggressive characteristics in the adult males. So it was constantly pushing back, favoring individuals that retained more juvenile-like behavior — and even juvenile-like heads — because that's what controls the behavior. Later, what you had was a species that had effectively been tamed, had been self-domesticated.

There is experimental evidence of this process. We have the Russian geneticist Belyaev, for example, who actually took wild foxes, selected for purely tame traits over 20 or 30 generations, and at the end of that time observed not only that the descendant foxes are as tame as dogs are nowadays — spontaneously — but also that they have a series of characteristics that have come along for the ride, incidental consequences that were not selected for but are just there. You have dramatic morphological ones, like the star mutation — the white spot on the forehead that you see in horses and cows and goats — that are just somehow associated genetically with tameness, and probably result from some kind of change in developmental events. There are also other morphological changes, like curly hair, short tails, and lopped ears, which happened in a number of domesticated animals, apparently because they've been selected for tameness. In addition, you get these smaller brains.

There is a remarkable thing about human evolution. We always tend to think that humans have just had a continuous surge in brain size over the last two million years, but actually over the last thirty thousand years brain size has decreased by 10 to 15 percent. The standard explanation for this is that we became more gracile at the same time — that we became thinner boned — which meant that we were lighter in body weight. And because there tends to be a correlation between body weight and brain weight, then maybe this explains our smaller brains. But I don't see any reason why brain size should be correlated with the amount of meat we carry on our bodies. This gracility is exactly the same pattern we see in the evolution of dogs from wolves, or bonobos from chimpanzees, or domesticated foxes from wild foxes. In all these cases an increasing gracility of the bone is an incidental effect.

I think that we have to start thinking about the idea that humans in the last 30, 40, or 50 thousand years have been domesticating ourselves. If we’re following the bonobo or dog pattern, we're moving toward a form of ourselves with more and more juvenile behavior. And the amazing thing once you start thinking in these terms is that you realize that we're still moving fast. Tooth size, for example, is extremely strongly genetically controlled and develops with little environmental influence, and is continuing to decline fast. I think that current evidence is that we're in the middle of an evolutionary event in which tooth size is falling, jaw size is falling, brain size is falling, and it's quite reasonable to imagine that we're continuing to tame ourselves. The way it's happening is the way it's probably happened since we became permanently settled in villages, 20 or 30 thousand years ago, or before.

People who are anti-social, for example, have their breeding opportunities reduced. They may be executed, they may be imprisoned, or they may be punished so badly that they're kept out of the breeding pool. Just as there is selection for tameness in the domestication process of wild animals, or just as in bonobos there was a natural selection against aggressiveness, here there's a sort of social selection against excessively aggressive people within communities. This puts humans in a picture of now undergoing a process of becoming increasingly a peaceful form of a more aggressive ancestor.

EDGE: Why is understanding these episodes in evolutionary history so important for us today?

WRANGHAM: We tend to think of the problems that have given rise to Al Qaeda, for example, as being concerned primarily with economic and political conflict, and obviously those are hugely important. Nevertheless, in order to understand why it is that particular countries and particular people within those countries find Osama bin Laden's wild schemes attractive, we have to think in terms of rather deeper differences among groups and sexes.

Think of it this way: Why is it that Western civilization is threatening to the people who support the Al Qaeda philosophy? And not just the Al Qaeda fighters themselves, but more importantly the great masses who are buying the Al Qaeda t-shirts in the Middle East? It's true that U.S. hegemony over oil and support for Israel in the Palestine conflict are general economic inequities that are going to contribute to people's resentment, but there are reasons why those men in particular resent Westernization.

Men in the Middle East come from a society in which there is polygany — one man having many wives — and even though polygany can never be very wide-spread within a society because there aren't enough women, it has the enormous effect that women marry upwards. Polyganous marriages are always concentrated in the upper socio-economic strata. This means that in the lower socio-economic strata you have a lot of men with very few women, and they use the typical systems for getting wives that are used in polyganous societies, which include gaining control over women. In a polyganous society, women want to marry into the polyganous society because that's where all the wealth and the opportunities are to get good food and survival opportunities for your kids. Consequently, they allow themselves to be frustrated, to be veiled and put in the burkha, to be given rules that mean they can only stay inside the house and have to blacken their windows. They allow themselves to be totally controlled by men.

So in this society you've got a lot of lower-class men, who have very few reproductive opportunities, who want to control women, and then you introduce them to this westernization that says, "Women, we will educate you, we will free you from the burkha, we will give you opportunities to be mobile, to travel, to flirt, to make your own romantic alliances." That is a very strong threat to the men who are already up against it and whose reproductive future depends on making alliances with other men who are in complete control of their own daughters. So westernization undermines reproductive strategies of men who are already desperate.

This means that in order to develop long-term strategies for reducing the degree of resentment that globalization and westernization are inducing in those countries, we should think about what we can do to reduce polygany. The countries where Al Qaeda gets the most support are the most polyganous countries: the Afghanistans, the Pakistans, the Saudi Arabias, and so on. But if you take a country like Turkey, which banned polygany in the 1920s, you see very little support. Single men are dangerous when they face a difficult reproductive future, and when they are presented with a series of economic changes that further reduce their economic futures by liberating women from their own control, then those men become peculiarly open to those wild schemes that Osama bin Laden presents. And those sorts of dangers are liable simply to continue for as long as the reproductive inequities continue in the Middle East.

EDGE: What accounts for the controversy surrounding the publication of your book Demonic Males?

WRANGHAM: Once you use biology to analyze human behavior, it's a bit like going to a psychiatrist and having somebody help you understand where your behavior is coming from. It means that you're in a little bit less internal conflict, that you can understand what you're doing, and you can shape your own behavior better. But the reaction is not always like that. A lot of people find it difficult to live with the idea that we've had a natural history of violence. We've had natural selection in favor of emotions in men that predispose us to enjoy competition, to enjoy subordinating other men, to enjoy even killing other men. These are nasty things to accept, and there are people who have written subsequently to say that it's just inappropriate to write like this, and so they look for ways to undermine the evidence of sex differences or the uniqueness of the human species. I think it's because people are very nervous about the idea that once you see a biological component to our violent behavior, then it may mean that it is inevitable.

One of the great thrusts of behavioral biology for the last three or four decades has been that if you change the conditions that an animal is in, then you change the kind of behavior that is elicited. What the genetic control of behavior means is not that instincts inevitably pop out regardless of circumstances; instead, it is that we are created with a series of emotions that are appropriate for a range of circumstances. The particular set of emotions that pop out will vary within species, but they will also vary with context, and once you know them better, then you can arrange the context.

Once you understand and admit that human males in particular have got these hideous propensities to get carried away with enthusiasm, to have war, rape, or killing sprees, or to get excited about opportunities to be engaged in violent interactions, then you can start recognizing it and doing something about it. It's much better not to have to wait for experience to tell you that it's a good idea to have a standing army to protect yourself against the neighbors, or that you need to make sure that women are not exposed to potential rapists. It's much better to anticipate these things, recognize the problem, and design in advance to protect.

There's still a huge tendency to downplay or just simplify sex differences in behavior and emotions. As we start getting a more realistic sense about the way natural selection has shaped our behavior, we're going to be increasingly aware of the fact that the ways that men and women respond emotionally to different contexts can be very different.

One of the dramatic examples is the extent to which men and women get positive illusions. In general, women tend to have negative illusions about themselves, meaning that they regard themselves as slightly less skilled or competent than they really are. On the other hand, men tend to have positive illusions, meaning they exaggerate their own abilities, compared to the way either others see them or they perform in tests. These things are certainly changeable. They depend a lot on power relations. If you put a woman in a dominant power relation, she tends to get a positive illusion; if you put a man in a subordinate relationship he tends to get a negative illusion.

Nevertheless these things emerge very predictably — and they're dangerous. If you have positive illusions then it means that you think you can fight better than you really can. It looks to me as though natural selection has favored positive illusions in men, because rather like the long canines on a male baboon they enable men to fight better against other men who really believe in themselves. You have to believe in yourself to be able to fight effectively, because if you don't believe in yourself really well, then others will take advantage of your lack of confidence and your nervousness. If you understand something about positive illusions, you can look at an engagement in which everybody believes they're going to win, and be a little more cynical about it. You can be a bit more like a lawyer looking at two clients and saying, wait a minute, neither of you has got a case just quite as good as you think you have. In the future a more sensitive appreciation for these sorts of emotional predispositions can help us generate a more refined approach to violence prevention.

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WHAT'S NEXT? Dispatches on the Future of Science
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