How chimpanzee wars have taught us that murder and cruelty are not just human traits

War and violence often seem that way unique human action that have been present throughout most of our recent history. But do other animals wage ‘war’? In this excerpt from “The beast within: man as animal” (2024, Johns Hopkins University Press), scientific researcher Jessica Serra looks at the dark side of chimpanzees’ (Pan troglodytes) behavior to show what our closest living relatives also have a preference for warfare.

Among non-human mammals, hostility between rival groups is quite widespread, but it rarely leads to death. The frequent fights between males are usually limited to intimidation behavior. While it is certainly frightening, it is rarely fatal. However, there is one exception: our close cousins, the chimpanzees! Ethological studies have shown that animals are capable of forming complex political alliances. English primatologist Jane Goodall made an important discovery on this subject when she revealed an unsuspected dark side in chimpanzees.

In 1974, while studying the behavior of chimpanzee colonies in Gombe, Tanzania, she observed a social divide between two groups in one of the communities. The first group, called the Kasakela community because they occupied the northern part of the park that bears this name, consisted of eight adult males and twelve adult females, as well as their young. The second group, called the Kahama community, consisted of six adult males, one adolescent male, and three adult females.

The hostilities started in an extremely violent manner when a man from the Kasakela group killed Godi, a man from the Kahama group. The wrath of the Kasakelas continued to ravage the Kahamas for the next four years, during which time six more men were killed. As for the Kahama females, two disappeared and three were beaten by a gang of violent men.

Chimpanzee from Kibale National Park screams in center frame..

Chimpanzees show that murder and cruelty are not just human traits. (Image credit: Yannick Tylle via Getty Images)

The end of this “four-year war” resulted in the Kasakela community taking over the territory of the Kahama. It was a short-lived victory, however, as another community of chimpanzees living nearby managed to drive the Kasakelas away.

Goodall related her harrowing memories of this war in her memoirs “Through a window: my thirty years with the chimpanzees of Gombe.” She recalls, “For years I struggled to come to terms with this new knowledge. When I woke up at night, gruesome images often came to my mind: Satan (one of the monkeys), putting his hand under Sniff’s chin to drink the blood welling up from a large wound on his face; old Rodolf, usually so friendly, standing tall and hurling a 4-pound stone at Godi’s prostrate body; Jomeo tears a strip of skin from Dé’s thigh; Figan, who attacks and hits the stricken, shaking body of Goliath, one of his childhood heroes, again and again.

Related: Chimpanzees use military tactics that are only common in humans

Jane Goodall isn’t the only one haunted by the bloody images of killings between groups of chimpanzees. American researchers reported similar scenes of violence among chimpanzees in Uganda’s Kibale National Park. These primates’ fierce fights were initiated by coalitions of adult males for the sole purpose of expanding their territory. The areas where the fighting took place corresponded to the land that was conquered by force.

Screaming angry chimpanzee. The chimpanzee (Pan troglodytes) screams in the rainforest and signals to its family members. Uganda. Africa

Some researchers are now using the “chimpanzee model” to explain the origins of war in humans. (Image credit: USO via Getty Images)

Are these primates really at ‘war’? If we define war as lethal violence organized against members of another group, then the answer is clear. Like humans, chimpanzees have the ability to wage war. Before the fighting started in Kibale National Park, the males carried out systematic patrols. The location of the bodies confirms the importance of the area as a motivation for fighting: these chimpanzees had breathed their last in this coveted adjacent area. These wars were fraught with the terror of infanticide between rival gangs, atrocities also committed by humans.

Three such attacks were reported by anthropologists from Ohio University and the University of Michigan in the International Journal of Primatology. The researchers recounted how on several occasions, while on patrol, the adolescent and adult males of the Ngogo chimpanzee community attacked and killed the children of a rival gang and cannibalized one of them.

Although there are cultural differences between our ways of war and those of chimpanzees, certain similarities are striking. Both humans and chimpanzees allow killings to be committed by multiple individuals without great risk to the attackers, and both have motivations for these killings (acquisition of territory, hierarchical position, access to resources, etc.). Some researchers are now even using the “chimpanzee model” to explain the origins of war in humans.

But aggression in chimpanzees does not only manifest itself when confronted with a rival community. American anthropology professor Jill Pruetz and her team at Iowa State University shared it 2013 murder committed by several men of a member of their own group in Fongoli in Senegal. Although investigators did not see the massacre as it occurred, in the dark of night, they did hear the blood-curdling screams. In the morning, they discovered in horror the corpse of Foudouko, a 17-year-old former alpha male who had been stripped of his status in 2007 by a gang of young chimpanzees.

Sentenced to exile and isolation, the outcast regularly tried to rejoin the group, imposing himself as dominant, which the new alpha males did not like. The research team speculated that if his entrance had been more submissive, the outcome would likely not have been fatal. These fatal attacks in chimpanzees, rare but incredibly cruel, were not related to a human presence near their community (as some scientists had assumed), but to a hierarchical tension within the group and probably to intense competition for access to females .

But what concerned scientists most was how the gang treated Foudouko’s body the day after his death. Presumably to make sure they had nothing left to fear, the murderous gang dragged the body across the ground, sniffed it repeatedly, ripped out the genitals, bit it all to pieces, tore the flesh and… ate it!

Murder and cruelty are therefore not unique H. sapiens. And the animal world isn’t done surprising us yet either.

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