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Bonobos became famous for showing that nature didn’t always have to be red in tooth and claw. “Bonobos are an icon for peace and love, the world’s ‘hippie chimps,’” Sally Coxe, a conservationist, said in 2006.

Because bonobos live in remote, swampy rainforests, it has been much more difficult to observe them in the wild than chimpanzees. More recent research has shown that bonobos live a more aggressive life than their reputation would suggest.

In a study based on thousands of hours of observations in the wild published on Friday, for example, researchers found that male bonobos commit acts of aggression nearly three times as often as male chimpanzees do.

“There is no ‘hippie ape,’”

As our closest living relatives, bonobos and chimpanzees can offer us clues about the roots of human behavior. We and the two species share a common ancestor that lived about 7 million years ago. About 5 million years later, bonobos split off from chimpanzees.

In 2012, a trio of Harvard researchers proposed that bonobos evolved much like dogs did. Less aggressive wolves were not as likely to be killed by humans, which over time led to the emergence of dogs. In a similar fashion, the researchers argued, female bonobos preferred to mate with less aggressive males, giving birth to less aggressive offspring.

The researchers called their idea the self-domestication hypothesis. In later years, they speculated that humans may have undergone a self-domestication of their own.

Dr. Mouginot soon became perplexed, as she saw that male bonobos acted aggressively on a regular basis. Unlike male chimpanzees, who started their days in a mellow mood, the male bonobos seemed to wake up ready for a fight.

She and her colleagues trained field assistants, who made more observations throughout the pandemic. The new analysis, based on 9,300 hours of observations on 12 male bonobos and 14 male chimpanzees, found that bonobos committed aggressive acts 2.8 times as frequently as than the chimpanzees did.

Dr. Mouginot found that the frequent bonobo aggressions almost always involved a single male attacking another male. Chimpanzees, in contrast, often ganged up to attack a victim.

the study set a new standard for comparing aggression in bonobos and chimpanzees.

Dr. Mouginot speculated that male chimpanzees engage in one-on-one aggression less often because it poses bigger dangers: A victim of aggression may not want to go on a border patrol with the perpetrator, for example. Or he may bring back some of his own allies to wreak vengeance.

It may be easier for male bonobos to get away with aggression, Dr. Mouginot said, because in their female-dominated society they don’t face the risks that come with male alliances. “I think that’s why we see more aggression in bonobos — because it’s less risky to act aggressively against other males,”

the apes that carried out the most aggressive acts were also the ones who mated most often.

parts of the self-domestication hypothesis “clearly need refinement.” It may be important to consider the effect that different kinds of aggression have on a species, rather than lumping them altogether, he said.

Still, he argued that the differences between the two species remained significant. “Chimpanzees murder, and bonobos don’t,

“Survival of fittest, which is what everyone has in mind as evolution and natural selection, has done the most harm of any folk theory that has penetrated society,”

“People think of it as strong alpha males who deserve to win. That’s not what Darwin suggested, or what has been demonstrated. The most successful strategy in life is friendliness and cooperation, and we see it again and again.”

Dogs were the population of wolves that decided to rely on humans — rather than hunting — and that population won big.

flowering plants attract animals to spread their pollen, forming a partnership that benefits both. “The plants provide food and energy, while the animals provide transportation for the pollen,” Hare says.

Chimps make war — males take charge — and can be quite violent, even killing one another. Bonobos, on the other hand, are governed by females, don’t kill one another and engage in sex to maintain a peaceful collective temperament. Bonobos also are natural sharers. They enjoy sharing food with other bonobos, and never outgrow their willingness to do so, unlike chimpanzees, who become more selfish in adulthood.

“The friendliest male bonobo is more successful than the unfriendliest chimpanzee,” Hare says, referring to reproduction. “The most successful bonobo males have more offspring than the most successful alpha male chimpanzees”

“friendliness is the winning strategy. Social problems require social solutions. The secret to our species’ success is the same as it is with dogs and bonobos.

Wrangham’s 2009 book, Catching Fire: How Cooking Made Us Human, pursued a very different hypothesis. Based on archaeological evidence, he made the case that our ancestors mastered fire much earlier than most of us had believed—perhaps closer to 2 million rather than 800,000 years ago—which changed everything for them

In his 1996 book, Demonic Males, co-authored with Dale Peterson, Wrangham recapped this and other evidence to draw a dire portrait of humanity (the male version) as inherently violent by evolutionary legacy. Here was vivid support for a Hobbesian view of human nature, rooted in genetics.

his two previous books, which explore the opposing poles of behavior. Renowned for his meticulous fieldwork, especially with chimps in Uganda’s Kibale National Park, Wrangham showed just how common chimp brutality is.

He also applies his evolutionary logic to studies of a wider array of animals. He dwells in particular on some marvelous experiments that explore the taming of wild foxes, minks, and other species by human-directed artificial selection over many generations.

fire extended the day into the night. Given how important we know conversations and stories told around the fire are to human hunter-gatherers, it’s easy to see how this process could have accelerated the evolution of language—an essential ingredient for less physically aggressive interactions

evidence has steadily accumulated that humans, from early on in their development, are the most cooperative species in the primate world

classic work on chimps has been complemented by new studies of bonobos, our other close relative. No more removed from us genetically than chimps are, they are a radical contrast to them, often called the “make love, not war” species. Some of our nonhuman kin, such fieldwork has revealed, can live and evolve almost without violence.

he pursues yet another ambitious hypothesis: “Reduced reactive aggression must feature alongside intelligence, cooperation, and social learning as a key contributor to the emergence and success of our species.”

“I walked around Auschwitz. I could feel the chimera at its best and worst.” Violence and virtue, he recognizes, are not opposites but powerful, not always reliable allies. “So much cooperation,” he notes of the smoothly operating human machinery of mass murder—“it can be for good or bad.”

cooking made possible a much more diverse diet

Enter the bonobos, to whom Wrangham turns as he considers how diminished aggression may have been selected for in the evolution of humans

they separated from chimps 1 to 2 million years ago, and were isolated south of a bend in the Congo River. Female bonobos form strong coalitions—partly based on sex with each other—that keep a lid on male violence. The “trust hormone” oxytocin is released during female sex: You could say that the partners are high, in both senses of the word, on trust. Because females run things, males don’t attack them, and even male-on-male violence is extremely limited. Bonobos also display the other traits common to the domestication syndrome, which suggests—as in the case of the foxes—a broad genetic dynamic at work.

He has learned that over many generations, ecological realities create species-specific behavior. In the case of bonobos, he suggests, a lush habitat in which they were protected from competition with either chimps or gorillas gave them the luxury of decreasing their own reactive aggression

Central to his argument is the idea that cooperative killing of incurably violent individuals played a central role in our self-domestication

our ancestors killed men who were guilty of repeated acts of violence. Certainly all-male raiding parties have operated in some groups of humans, seeking out and killing victims in neighboring villages

They serve as a form of capital punishment. Wrangham cites a number of examples of anthropologists witnessing a group of men collaborating to kill a violent man in their midst.

My own two years with the !Kung point to a more robust possible selection process for winnowing out aggression: female choice. Women in most hunter-gatherer groups, as I learned in the course of my experience in the field, are closer to equality with men than are women in many other societies. Evolutionary logic suggests that young women and their parents, in choosing less violent mates through the generations, could provide steady selection pressure toward lower reactive aggression—steadier pressure than infrequent dramas of capital punishment could. (

Wrangham has nonetheless highlighted a puzzle at the core of human evolution, and delivered a reminder of the double-edged nature of our virtues and vices.

Such breeding efforts, Wrangham notes, have produced “the domestication syndrome”: a change in a suite of traits, not just the low reactive aggression that breeders have deliberately singled out

Half a century and thousands of fossil finds later, we have a far more complete—and also more puzzling—view of the human past

As data pile up, so do surprises

In 1965 a remarkable book—Irven DeVore’s collection Primate Behavior (which led me to study with DeVore)—made what then seemed a radical claim: We will never understand our origins without intensive study of the wild world of our nonhuman relatives. A handful of scientists, including Jane Goodall, set up tents in distant jungles and savannas. Following monkeys, apes, and other creatures in their habitats, these scientists turned their notes and observations into voluminous, quantitative data.

I seriously question the penchant of observers (scientific and lay alike) to generalize from small samples of our unquestionably diverse species, especially about something as complex as war.

peacemaking is, if anything, more pronounced and widely distributed, especially among groups of nomadic foragers who are probably closest in ecological circumstance to our hominin ancestors.

The problem with envisioning Homo sapiens as inherently and irrevocably warlike isn’t simply that it is wrong, but also that it threatens to constrain our sense of whether peacemaking is possible and, accordingly, worth trying.

There is a story, believed to be of Cherokee origin, in which a girl is troubled by a recurring dream in which two wolves fight viciously. Seeking an explanation, she goes to her grandfather, highly regarded for his wisdom, who explains that there are two forces within each of us, struggling for supremacy, one embodying peace and the other, war. At this, the girl is even more distressed, and asks her grandfather who wins. His answer: “The one you feed.”

Apes are big business — a gorilla baby can cost as much as $250,000 — but who exactly is buying these animals is often as opaque as the traffickers’ identity.

Ape trafficking is a little-known corner of the illicit wildlife trade, a global criminal enterprise that hauls in billions of dollars. But unlike the thriving business in elephant ivory, rhino horns, tiger bone wine or pangolin scales, ape smuggling involves live animals — some of the most endangered, intelligent and sensitive animals on Earth.

n central African towns (as elsewhere in the world), many chimpanzees are kept as pets. Congo’s president, Joseph Kabila, who lives in a riverside mansion in Kinshasa, the capital, has a large chimp locked up in a cage.

But poaching an ape is a serious crime in Congo, and nonprofit wildlife groups have been assisting the Congolese authorities in prosecuting offenders.

According to Böhme, the findings suggest that our upright posture can be traced to a common ancestor of humans and great apes that lived in Europe rather than Africa.

The clay pit haul of fossils included teeth, pieces of jaw and spine, and a big toe that would have been handy for grasping tree branches. Arguably the most important fossils were a forearm and shin bone, which informed the scientists’ speculation about how the ape moved around.

The most complete skeleton, with 21 bones, was thought to belong to a male that stood a metre high and weighed about 30kg. He had a broad chest and the curved, S-shaped spine seen in humans.

Some researchers believe dryopithecins were the ancestors of the ancient African apes who ultimately gave rise to great apes more generally, including the gorillas, orangutans, chimpanzees, bonobos and humans.

Writing in the journal Nature, the scientists make the case for danuvius employing what they call “extended limb clambering” to get around. Rather than swinging from branches or walking cautiously on branches, extended limb clambering uses both arms and legs equally.

“Together, the mosaic features of D guggenmosi arguably provide the best model yet of what a common ancestor of humans and African apes might have looked like. It offers something for everyone: the forelimbs suited to life in the trees that all living apes, including humans, still have, and lower limbs suited to extended postures like those used by orangutans during bipedalism in the trees.”

“Danuvius is not a fossil hominin, but it does help inform how humans may have evolved.”

Some of the most compelling evidence for upright walking in human ancestors comes from Ardipithecus ramidus, a female skeleton dating back 4.4m years that was found in Ethiopia. Ardi, who stood about a metre tall, may not have been the most accomplished of walkers, but much of her skeleton shows adaptations to walking on two feet.