The Goodness Paradox — Why humans are so good and so bad

Humanity has an enormous capacity for good — for self-sacrifice, generosity, and kindness. But we also have a shocking capacity for evil — for murderous hate, violence, and killing on a massive scale.

This is a central paradox in human nature — one that philosophers and theologians through the ages have tried to understand, but now it's time for an evolutionary biologist to have a try.

Richard Wrangham, a professor of biological anthropology at Harvard University, has spent his career trying to understand what makes us human. And in a new book The Goodness Paradox: The strange relationship between virtue and violence in human evolution, he's exploring why humanity can reach such heights of good, and such depths of evil.

"When people say that genocide is inhuman, it's really the opposite. Genocide is appallingly human, it's just [that] it's only one side of us," said Wrangham.

When people say that genocide is inhuman, it's really the opposite. Genocide is appallingly human, it's just [that] it's only one side of us.- Dr. Richard Wrangham, Harvard University

Bonobos are domesticated chimpanzees

Wrangham first started thinking of this paradox as part of the team that helped to discover that chimpanzees can be extraordinarily violent, "deliberately making efforts to find individuals to attack and brutally beat up, so that they actually kill them on the spot very often."

He said this raised questions for him about the similarities between chimpanzees and humans.

"Yet, at the same time, there's this huge contrast because chimps often fight on a sort of casual basis during the day whereas humans are so incredibly unaggressive in so many ways."

Bonobos, on the other hand, look very much like a chimpanzee, but behave extraordinarily differently.

"The really dramatic thing, I think, is that it is much less aggressive than the chimpanzee."

When Wrangham and his colleagues started researching the bonobo, they realized their bodies differ from chimpanzees in "a very strikingly similar way to the ways that bodies of domesticated animals differ from those of wild animals."

The process of domestication is essentially a loss of aggressiveness and fear, but it's generally accompanied by physical changes. Through that process, the bonobos' "faces became shorter, their teeth become smaller, and there is a reduction in the degree of difference between males and females."

Clues to humans being 'self-domesticated'

Wrangham said that a few years ago, it was observed that humans evolved to be — in some ways — anatomically like domesticated animals.

"That goes back to about 300,000 years ago, when — for the first time — what you start seeing is, in our ancestors, a reduction in the size of the teeth being accompanied by a reduction in the maleness, the loss of brow ridges above the eye, for instance, or the reduction of them, the face becoming narrower, and the face also becoming less protruding," said Wrangham.

This suggests to Wrangham that starting around 300,000 years, our ancestors lost their historical aggressiveness and started becoming calmer and kinder under ordinary circumstances.

Tipping point that led to our self-domestication

For an indication of how humans became "self-domesticated," Wrangham said we look at small-scale societies where there's no state intervention.

If a man becomes exceptionally aggressive and tries to use his physical dominance to persist with aggressive and violent behaviours, people in small scale societies will take matters into their own hands.

"In the end, the society is forced to do one thing and that is: they use capital punishment. They agree and they kill him," said Wrangham. "It's all done very clinically, as it were. It might be done with a weapon. It might be done at night, but somehow, they arrange to kill him in a way that means that they don't get hurt in any kind of fight. They just do it."

They're using one type of aggression, the cold, calculated proactive aggression, to defend against another type of aggression — the emotional, reactive-type of aggression. But the evolutionary result of this is that people who are routinely aggressive and violent are removed from the population — and don't contribute to the next generation.

"Essentially, what seems to be happening is that, in humans, over the last two or three hundred thousand years, our propensity for reactive aggression has been reduced because our ancestors used proactive aggression to kill those who were most effectively aggressive — those who had the highest propensity for reactive aggression."

Wrangham said the tipping point that led to our capacity to be brutal to each other, when it pays us to do so, is language.

"We are somewhat similar to our cousins the chimpanzees, much more so than bonobos, with regard to proactive aggression," said Wrangham. "The difference is, we're able to whisper among each other, to talk and develop a conspiracy and an agreement that somebody that we mutually disapprove really deserves to die."

By weeding out the most reactively aggressive members of societies, humans have developed an incredible propensity for being good, kind and cooperative while still retaining the ability to be proactively aggressive when the need arises.

Retaining proactive aggression, unfortunately, is also what makes it possible for groups of humans to cooly and dispassionately commit unspeakable atrocities, up to and including genocide.