Violence, argues Professor Richard Wrangham, made us (mostly) good.
Fiction? No. Inhuman? Certainly.
“Passion” and her daughter “Pom” were unusually homicidal members of a chimpanzee community studied by primatologist Jane Goodall. Their infanticide habit caused tension in the 60-strong group, but it worked for them, providing a supply of tender meat and keeping others away from the choice fruit trees the duo kept for themselves.
Even in chimp terms, Passion and Pom were psycho-killers, and their community not only let them get away with killing infants, but allowed the pair to benefit from it.
Humans and chimps are very close relations and have much in common, including empathy and expressions such as frowning and smiling. But the story of Passion and Pom, says Professor Richard Wrangham, illustrates a profound difference in our behaviour, one with huge implications for our own evolution.
Wrangham, who has been studying chimpanzee behaviour at the Kibale Chimpanzee Project in Uganda for nearly 50 years, earned his chimp chops in a group led by Goodall. Now he’s a Harvard professor of biological anthropology, and is known for what the Sunday Telegraph called “good, big” ideas about human evolution. His two books, Demonic Males: Apes and the Origins of Human Violence (1996) and Catching Fire: How Cooking Made Us Human (2009), are both influential best-sellers.
So a new book by Wrangham is an event. The Goodness Paradox: How Evolution Made Us More and Less Violent (Allen & Unwin) offers, true to form, startling hypotheses on our relationship with violence, which he shows is freakish in the animal world.
Fans of Al Jazeera or the BBC news may find it hard to believe that humans are less violent than chimps. In fact, says Wrangham, everyday human interactions are absurdly peaceful compared to the routine beatings endured by other species.
In male red deer, for instance, “rut fighting” is responsible for 13-29% of male deaths. If more human men behaved this way, he claims, the annual death toll from so-called “character contests” among US men would rise from estimates of fewer than 10,000 to more than 100,000 a year.
Chimps are also a surprisingly violent species. Even when they are reared in human homes, says Wrangham, “or studied all their lives by people who love them deeply and thoughtfully, chimpanzees cannot be trusted not to use their strength in aggression – even when they understand the rules perfectly well”.
He offers, as grisly exhibit A, the tale of Travis, a 13-year-old American chimp and occasionally feted TV star, treated like a member of the family by his owner. In 2009, Travis flipped, attacking a friend of the family with shocking ferocity. Charla Nash survived, but lost her face, her sight, her hands and part of her brain. She had picked up Travis’ Tickle Me Elmo, a favourite toy.
An anthropologist once noted that to pack hundreds of chimpanzees into close quarters on a plane would result in ear-splitting screeches and bloody chaos, whereas human passengers usually behave themselves even when crowded.
Our close mutual relatives, the bonobos, look almost identical to chimps, but they are much less violent. However, even they do not approach our own remarkable lack of unthinking “reactive” aggression. “Overall,” writes the prof, “physical aggression in humans happens at less than 1% of the frequency among either of our closest ape relatives. Compared to them, in this respect, we really are a dramatically peaceful species.”
How did the three species end up this way? Wrangham thinks the answer lies in the domestication of bonobos and humans.
Dmitry Belyayev, a Russian scientist who bred silver foxes, showed that selecting for a single trait – lack of aggression – produced a raft of strange, seemingly unrelated physical changes. These same traits – small teeth, floppy ears, curly tails, patches of white fur, and reduced difference between males and females – is now known as the “domestication syndrome” and is seen in domesticated species from horses to dogs.
Although we don’t have floppy ears and curly tails, human skeletons show many of the same tell-tale signs of domestication as dogs. Some 300,000 years ago, our species had much bigger heads, teeth and bones – and males had fat, glowering brow ridges compared to females.
We are to our immediate ancestors, Wrangham says, as dogs are to wolves – or bonobos are to chimps. “Differences between males and females are less developed in domesticated animals, always for the same reason: males become less exaggeratedly male,” he writes. “Around 200,000 years ago, human male faces were already becoming relatively feminised. During the last 35,000 years, males have become more like females, not only with respect to stature but also to the size of the face, the length of the canine teeth, the area of the chewing teeth and the size of the jaws.”
Domesticates also have smaller brains than their wild ancestors. In Europe, explains Wrangham, modern brains are some 10-30% smaller than those of people living there 20,000 years ago.
If you are wondering how we stayed smart enough to write books about human evolution, according to Wrangham the loss of brain size in domesticated animals doesn’t seem to reduce brainpower. “Indeed, the smaller-brained species sometimes out-perform their bigger-brained wild ancestors.”
So, what caused the “self-domestication” of bonobos and humans?
Bonobos appear to be descended from a bunch of chimpanzees that crossed the Congo River hundreds of thousands of years ago. On the far bank they found the chimp version of a well-stocked supermarket, with no gorillas to compete for food, says Wrangham. This allowed them to feed in groups, instead of the solitary forays of other chimps. It also made the male chimps’ habit of extreme male-on-female rape and violence difficult to pull off, as females combined to protect each other.
“Among chimpanzees, males are dominant over females, and they are relatively violent. Among bonobos, females are often dominant over males, violence is muted, and eroticism is a frequent substitute for aggression. The behavioural distinctions between the two eerily echo competing social stances in the modern human world: the divergence of male and female interests, for example, or between hierarchy, competition and power on one hand, and egalitarianism, tolerance and negotiated settlement on the other.”
In the human world, few dispute that violence against women is a serious problem. International figures quoted by Wrangham report 41-71% of women being beaten by a man at some point in their lives. But this is low for a primate. One hundred per cent of wild adult female chimpanzees receive regular, serious beatings from males.
The proto-bonobo females’ new power gave them, in the prof’s dry words, “an enhanced ability to choose mates”. This “sexual selection” by females favoured less aggressive males – in other words, when they could choose males who didn’t beat and rape them, they did.
When aggression is selected against, as Belyayev discovered, a wider domestication syndrome emerges. Skulls start to look like juvenile versions of their ancestors. For years, bonobos weren’t even recognised as a separate species because their adult skulls were mistaken for the skulls of immature chimps.
Our skeletons show the same pattern, but, says Wrangham, for different reasons. He argues that a clue to the forces behind our “self-domestication” can be found in our atavistic revulsion at the story of Passion and Pom.
“Though the [chimpanzees] had the means to punish or kill Passion and Pom, they did not have the mindset.”
Humans, in contrast, punish those who do wrong. Our intense loathing of being outcast has made us both reactively gentle and easily shamed, says Wrangham. Humans would expect Passion to feel shame, an un-chimp-like emotion.
Unless deranged, humans won’t rip off someone’s face for picking up a toy. But there is another type of violence we have made our own. Wrangham describes this as “proactive violence” – calculated and organised. Our comparatively low level of impulsive violence is combined with an unusual talent for planned, coordinated atrocity – the “paradox” of his book title. Humans go to war, and, crucially, have a long history of executing wrong-doers.
For millennia, he says, our communities would have killed a person like Passion. She would have been unable to pass on traits like her extreme aggression and, perhaps, her lack of remorse.
Although Wrangham is fervently opposed to capital punishment, he thinks it gave us a “moral sense” by ridding our gene pool of the Passions among us. This “unnatural selection” is just another version of the technique Belyayev used to pacify and domesticate his foxes.
“Through targeted aggression, our ancestors controlled reactive aggression and, in doing so, made us virtuous.”
Find Jenny Nicholls on Twitter @jmnicholls.
This article was first published in the July 2019 issue of North & South.