The Emergence of Homo Sapiens 'Those Who Obeyed the Rules Were Favored by Evolution'
DER SPIEGEL: Professor Wrangham, you're interested in aggression. Why did you go to the Ugandan jungle to research it for it?
Wrangham: The jungle is full of aggression. One of my favorite things is to go for a walk in the forest, close my eyes and just listen. I hear the trills of birds, the chirping of insects, the calls of monkeys, sometimes even the sound of an elephant. And what is it that is so soothing and pleasant for us? Most of it is produced by males shouting out their maleness, their dominance. In other words, it is the language of aggression.
DER SPIEGEL: In your studies of chimpanzees, did you always focus on aggression?
Wrangham: No. First, I studied how these animals feed - -- which is a completely different subject. But when you follow a chimpanzee from dawn till dusk, the importance of aggression just hits you in your face. Compared to us humans, the rate of their aggression is enormously higher.
DER SPIEGEL: Can you give an example?
Wrangham: Take the behavior of males on the threshold of adulthood: They almost ritually attack one female after the other until each one shows signs of submission. Only when a male has achieved physical dominance over every single female is he able to enter the male hierarchy and compete there for the highest possible rank.
DER SPIEGEL: And does this brutality enable them to succeed?
Wrangham: Absolutely. Once a male is fully adult, he continues to attack females even when they give submissive signals to him. The male who beats a particular female the most is the most likely to be the father of her next offspring.
DER SPIEGEL: How do you feel when you watch something like this?
Wrangham: It upsets me. I do love chimpanzees, and I am fascinated by them. I appreciate the wonderful moments I experience with them. But they also have nasty sides. Watching a male beating up a female is horrendous - -- just as it is horrendous watching these animals tearing the guts out of a monkey that is still alive. The essential violence of chimpanzees' carnivory is thoroughly off-putting. It is why I haven't eaten meat for 40 years.
DER SPIEGEL: Is it fair for a scientist to describe this behavior as "nasty"?? Is aggression evil?
Wrangham: It would seem inhuman not to recognize that some of the chimpanzees' behaviors are deeply unpleasant. And is aggression evil? Yes, I think so, at least when it involves physical violence that is inflicting pain. Violence is the opposite of virtue. I think that a major object of human endeavor and societal ambition should be to reduce violence.
DER SPIEGEL: In this sense, at least, we humans seem to have taken a step away from chimpanzees.
Wrangham: Yes. If you trapped 300 chimpanzees who did not know each other in a plane for eight hours, many of them probably wouldn't leave it alive. People, on the other hand, barely touch each other on a long-haul flight. The level of violence has been monitored in a group of hunters and gatherers in Australia. These Aborigines suffer from strong social upheavals, alcohol abuse is high. Still, even under these conditions, the frequency of violence among these people is 500 to 1,000 times lower than among chimpanzees.
DER SPIEGEL: Though people are also capable of torturing each other, and our history is replete with war and genocide. Given this, how can you speak of the placidity of human nature?
Wrangham: You're right, it seems paradoxical. But it is important to understand that there are two different types of aggressiveness. Violence in war is mostly planned, deliberate and cold-blooded. The everyday aggression of chimpanzees, on the other hand, is spontaneous, short-tempered and born directly from the moment. Here we have one of the great mysteries of human nature: Why do we treat each other so peacefully in everyday life when we are capable of such a degree of deliberate cruelty?
DER SPIEGEL: Is this deliberate, planneding form of aggression a peculiarity of humans?
Wrangham: Not at all. You find it among chimpanzees as well. Konrad Lorenz believed that animals do not kill each other. But he was proven wrong. I was part of Jane Goodall's team, who first observed how chimpanzees attacked members of neighboring groups to kill them deliberately. The discovery of warlike patterns of aggression among chimpanzees was one of the big surprises of our research.
DER SPIEGEL: In other words, we have inherited the brutal part of our nature from our ancestors, whereas the peaceful part distinguishes us from them?
Wrangham: Yes, that's one way of putting it.
DER SPIEGEL: You write that humans owe their placidity to their own domestication. What do you mean by that?
Wrangham: We humans exhibit a number of biological characteristics that are more typical of pets than of wild animals, including a very low rate of face-to-face aggression. The reason that I attribute our peaceableness to our having been domesticated is because we share with our pets and farm animals some of these other characteristics, which we now call a domestication syndrome. Charles Darwin was already fascinated by this phenomenon. He studied domestic animals, and he noticed that they share a multitude of peculiarities not found in wild animals.
DER SPIEGEL: Like what?
Wrangham: Many pets have white spots in their fur. They often have floppy ears, a short face or a curved tail. All these traits are rare among wild animals, but common among pets. And the interesting thing is that humans didn't select their pets specifically for these traits.
DER SPIEGEL: How do you know? Maybe Stone Age farmers were fond of pigs with floppy ears or cows with spots.
Wrangham: We know it thanks to the ingenious experiments of the Russian geneticist Dmitri Belyaev. He bred silver foxes with only one trait in mind: He selected the most tame and peaceful individuals from each generation. And behold, many of the other typical characteristics of pets emerged on their own.
DER SPIEGEL: Cuddly foxes sound cute. Have you seen them yourself?
The article you are reading originally appeared in German in issue 12/2019 (March 16th, 2019) of DER SPIEGEL.
Wrangham: No, unfortunately I haven't. But my student Brian Hare went to Novosibirsk, where Belyaev's team continues to work. He wondered why dogs understand human signals better than wolves. He assumed that it might be a result of targeted selection by humans. But then he examined Belyaev's foxes and found that they also know how to interpret human signals. So the ability to understand human signals seems to be another trait, like white patches of fur, that emerges as a side effect of selection for less aggression.
DER SPIEGEL: You claim humans are also domesticated. What makes you think that? We don't have white spots, or floppy ears, or a curly tail.
Wrangham: You're right. We have no tail, so it can't bend. But if you look at our skeleton, you will find a lot of peculiarities that are characteristic of pets. Four of them stand out compared to our ancestors: a shorter face; smaller teeth; reduced sex differences, with males becoming more female-like; and, finally, a smaller brain. This latest development is particularly fascinating. In fact, the evolution of humans is naturally characterized by a continuous increase in brain size. But it turns out this trend has reversed in the last 30,000 years.
DER SPIEGEL: How could a package of traits like that develop when it was not under any selection pressure?
Wrangham: We are still not sure what biological mechanisms produce the domestication syndrome. But we have circumstantial evidence. It is noticeable, for example, that many of the domestication traits are typical for young animals ...
DER SPIEGEL: ... in other words, dogs resemble wolf pups, just as we resemble Neanderthals who never reached adulthood?
Wrangham: Yes. Young animals are usually characterized by a lower level of reactive aggression. One way nature might evolve reduced aggressiveness is by allowing creatures to reach adulthood while still being emotionally juvenile. All the other juvenile traits are then nothing but side effects of the reduction of aggression.
DER SPIEGEL: You said earlier that our brain began shrinking 30,000 years ago. Is this when humans started getting tamed?
Wrangham: No. We can follow the process of domestication pretty thoroughly in the fossil record. According to that, the development started about 300,000 years ago. Brain size only began to decrease at the very end.
DER SPIEGEL: Obviously, we domesticated dogs, horses and cats, but who domesticated us?
Wrangham: The word "domestication" is somewhat misleading. It implies a relationship with humans. But Belyaev's fox experiments show us that only the selection of non-aggressive behavior is important. Whether this selection happens in captivity or the wild doesn't matter. While some species have been domesticated by humans, others have been domesticated, in the sense of reducing their aggressiveness, on their own. We are one of the species that domesticated ourselves.
DER SPIEGEL: What kind of domesticated animals are there in the wild?
Wrangham: The best example can be found among our closest relatives: the bonobos. They look very similar to chimpanzees, but their skulls show the characteristics of domestication: a shorter face, smaller teeth, a smaller brain, and reduced differences between the sexes.
DER SPIEGEL: And their behavior is more peaceful?
Wrangham: Dramatically so. When a bonobo male attacks a female, she will call for help, and within minutes the male will face an alliance of females who put him in his place.
DER SPIEGEL: Females bonobos domesticated the males?
Wrangham: Yes, probably. The bonobos live in a habitat that allows females to travel together all the time, unlike chimpanzees. This has favored social alliances among the females.
DER SPIEGEL: Are bonobos the better chimpanzees?
Wrangham: They're much nicer to each other, that's true. But of course bonobos also have some dark sides. There was this guy in France who started a commune based on the principle of living the bonobo way. He ended up in prison for pedophilia.
DER SPIEGEL: What about humans? Did women civilize us men as well?
Wrangham: That seems unlikely. There are many mythological memories of an era in which power was in the hands of women, but today there is no such thing as matriarchy anywhere in the world, and we have no evidence that there ever was.
DER SPIEGEL: If it wasn't women, who tamed men?
Wrangham: Here we enter the terrain of speculation, because fossils don't tell us exactly what happened. What we have to do instead is to see how today's hunters and gatherers treat individuals that behave aggressively. There are, in fact, even in these generally peaceable peoples, some individuals who, like alpha chimpanzees, try to dominate the others by violence. How do the members of such a community react - -- without prisons, without military, without police? There is only one way for them to defend themselves against the determined perpetrator: He is executed. The killing is done by agreement among the other men in the society.
DER SPIEGEL: You argue that this is how aggressiveness was systematically eradicated from the gene pool of mankind?
Wrangham: Well yes, aggressiveness was reduced, even if it was not eradicated. Virtue seems to have evolved from something as violent as killing. But don't misunderstand. I am not advocating executions in today's world. Justice is fallible, so the death penalty inevitably leads to the killing of innocent people; furthermore, there is no evidence that it really effectively deters people from committing crimes.
DER SPIEGEL: It is quite a daring hypothesis to argue that the death penalty has made us what we are. How did you come up with it?
Wrangham: It was when I read a book by Christopher Boehm entitled "Hierarchy in the Forest". In this book, he describes how aggression in communities of hunters and gatherers is controlled by executions. My goodness, I thought when I read this, maybe this mechanism has even shaped our evolution?
DER SPIEGEL: If anyone who strives for power is killed, does that mean there are no chiefs in communities of hunters and gatherers?
Wrangham: Yes, hunter-gatherers are very egalitarian in their relationships among men.
DER SPIEGEL: So when the fathers of the American constitution famously proclaimed, "All men are made created equal,", they were really just reanimating a principle that has shaped our species over many millennia?
Wrangham: Yeah. Isn't that fascinating? And even the fact that the Declaration of Independence only mentions men, but not women, corresponds to the situation in communities of hunters and gatherers. Egalitarianism among them only applies to men. Women, on the other hand, are dominated by men.
DER SPIEGEL: And how do you think it all began? Why did the men of lower rank eventually join together to kill the tyrant?
Wrangham: Well, it's quite dangerous to rebel against the alpha male. The one who throws the first stone will risk his life. No lion or chimpanzee would dare to do that. Only humans were able to squat together and whisper: "Let's meet at the big stone, then attack and kill him."
DER SPIEGEL: In other words, language facilitated the rebellion of the underdogs?
Wrangham: Yes, because only by discussing and planning how to kill the tyrant could they be sure that they wouldn't be harmed themselves.
DER SPIEGEL: Unlike all animals, man is capable of moral action. In your book, you claim that this is another consequence of the beta male's uprising against the alpha?
Wrangham: Yes. At some point the community of beta men united against the powerful. Then they realized that from now on they themselves had the power to kill everyone in the group. They established rules for living together, and anyone who violated them had to fear death. In this way, those who obeyed the rules were favored by evolution.
DER SPIEGEL: Submission made us moral beings?
Wrangham: You put it in a handy phrase. It may be disillusioning. But I'm afraid it was like this: Morality was born in an effort not to be targeted by the justice of the community.
DER SPIEGEL: And little by little, cowardice wrote itself into our genes.
Wrangham: Yes. And the fossil record suggests that the domestication process even accelerated.
DER SPIEGEL: Is it now complete? Or is man still taming himself?
Wrangham: There is, at least, no indication that the process has come to a halt.
DER SPIEGEL: What will we humans look like after another 10,000 generations?
Wrangham: That's speculative, of course. But if the domestication process continues as it has, we will probably look even more childlike than we do nowadays. The juvenile features will be even more exaggerated: the high forehead, the big eyes, the narrow chin.
DER SPIEGEL: The ultimate in anti-aging.
Wrangham: That's one way of looking at it.
DER SPIEGEL: Professor Wrangham, thank you for this interview.