Did Assassinating Bullies Make Humans More Domesticated?

In the closing chapter of his thought-provoking book The Goodness Paradox, Richard Wrangham observes that he is patently opposed to capital punishment in modern society. But the preceding chapters develop the case that capital punishment may have played an important role in our evolution – indeed making human beings less prone to violence. The gist of the argument is that when bullying alpha males got out of hand, our ancestors banded together to assassinate them. Wrangham argues that this ancient practice of tyrant culling is part of a process of “self-domestication” – akin to the selection procedures that changed vicious wild wolves into friendly and affable dogs.

Wrangham is a professor of human evolutionary biology at Harvard University. He studied primatology with Cambridge’s Robert Hinde and worked on the Gombe Stream Reserve with Jane Goodall (another student of Hinde).

I met Wrangham in a small seminar room at Harvard, and have later described him to my students as the prototype of a distinguished university professor. Speaking with a smooth British accent that could have qualified him to be an announcer for the BBC, he had the visage of a movie star, graying hair, and was dressed in a dapper gray suit that looked as if it had been tailored for him by Giorgio Armani. This might sound like the picture of someone who would trigger resentment, but Wrangham turned out to be a very likable fellow. He makes up for all his jealousy-inspiring traits by being warm and decidedly non-arrogant. Indeed, his default facial expression seems to be an inviting and accepting smile.

When John Tooby introduced Professor Wrangham’s plenary address at the recent meetings of the Human Behavior and Evolutionary Society (HBES), Tooby noted that Wrangham’s kind and peaceful demeanor contrasted starkly with some of the brutish research topics he has studied. For example, one of Wrangham’s earlier books is titled Demonic Males, and it describes the parallels between roving homicidal bands of male chimpanzees and roving homicidal bands of male humans.

The Two Extremes of Human Nature

In his talk to HBES, Wrangham discussed the equally eyebrow-raising central ideas in his more recent book The Goodness Paradox: The Strange Relationship Between Virtue and Violence in Human Evolution. The paradox to which Wrangham refers is that humans are, on the one hand, a lot nicer to one another than are most other mammals. We do things like share with strangers and contribute to charities, and in most neighborhoods in the world, you can walk around unmolested by the locals. Indeed, if someone in Italy or Spain hears your foreign accent, they may even invite you to share a glass of wine. Our chimpanzee cousins do not treat strangers with nearly such civility; instead, the default reaction is to kill them.

If you are wondering, what about those nasty wars that have, in recent years, ravaged human populations from Afghanistan to Nanking to Vietnam? That is, of course, the “other hand” that makes our species so paradoxical. Wrangham argues that the very selection pressures that made us nicer to the people we encounter on a one-to-one face-to-face basis – our ability to suppress angry outbursts — co-evolved with our proclivity to more effectively carry out cold-blooded premeditated acts of group-based aggression. In making his argument, Wrangham distinguishes between what he calls reactive and proactive aggression.

Reactive aggression involves those sudden angry outbursts that happen when one organism feels threatened or challenged by another. In comparing such outbursts in chimpanzees to those in human brats on the schoolyard, the chimpanzees are many times more aggressive to one another.

Proactive aggression is cold-blooded and planned, by contrast. Wrangham notes that humans are strongly inclined toward a particular kind of proactive aggression – in which a group of individuals organizes a coordinated attack on another individual who has been bullying or annoying others, or who has been failing to live up to the group's standards of cooperation and sharing. Chimps sometimes gang up on one of their fellows, but they lack an important tool that makes our species especially pre-adapted to succeed at these coordinated attacks: language. By using their words, humans are able to plot against someone behind their back and to combine their problem-solving capacities to do in the offender in a way that minimizes the danger to themselves – planning surprise attacks under the cover of darkness, for example. By organizing in advance and cooperating with one another, a group of plotters can easily take out one of those big bad alpha males that no single one of them might have beaten in a fair fight (as in the case of Julius Caesar).

Selecting Docility

Wrangam’s book is an impressive tour of data from anthropology, zoology, social psychology, history, and developmental neuroscience. He notes that domesticated species, such as dogs, cats, and barnyard animals, manifest a number of common features, including smaller faces, smaller skulls, smaller teeth, less muscular bodies, and even white patches on their heads and paws. He discusses fascinating findings supporting the idea that these are all byproducts of having been selected for docility, and may be linked at a developmental level to slower migration of neural crest cells in the embryo. In reading the section on neural crest cells, I felt something of the awe that I have experienced in reading Sean B. Carroll’s books describing the amazing ways in which genes work (see books about sex, murder, and the meaning of life).

At one level, Wrangham’s argument that our ancestors were assassins might be surprising. But a little reflection reveals it’s not that outlandish of a claim. In a study I conducted several decades back with Virgil Sheets, we asked the smiling and friendly students in my psychology classes whether they had ever considered murdering another person. Three out of four of the guys had. More surprisingly, 6 out of 10 of the women had also considered committing homicide. And the top reasons that those nice people gave for fantasizing about murder were right in line with Wrangham’s arguments – the other person had been a bully — threatening, humiliating, or physically attacking them or someone else they cared about (Kenrick & Sheets, 1993; see also “Have You Had a Homicidal Fantasy Today?”).

Even if Wrangham is not right in every aspect of his argument, it is mind-expanding to see how he weaves together so many diverse threads of evidence to develop what is certainly a case worth careful consideration. His conclusions are part of an emerging consensus that neither a simple Hobbesian view (of humans as nasty brutes contained only by social convention) or a simple Rousseauian view (of humans as intrinsically angelic organisms who are only made nasty by society) are correct (see also "Is the world becoming a nicer place to live?") The paradox is that, if Wrangham is right, the same evolutionary pressures may have simultaneously enhanced the angelic and the diabolic aspects of human nature.