Chimp vs Chimp Violence and Insights into Human vs Human Violence

A new study, published in the journal Nature recently, has presented insights into how chimpanzees engage in violence against one another. Why is this important? How chimps engage in violence provides insight into the nature of human violence.

This new study was led by Richard Wrangham, a professor of human evolutionary biology at Harvard who has been working in Africa since the 1970’s. The study chronicled the following.

“Overall, the researchers chronicled 152 killings by chimpanzees that were directly observed, suspected, or inferred in 18 communities that had been followed for decades. The attackers were overwhelmingly male, and the majority were attacking other males from other groups. They attacked when they outnumbered their victims — by eight to one, on average.”

Building on the eight to one advantage from above, the study continues.

“The aggressors can kill at incredibly low risk to themselves, and the reason is that they chose to attack only when they have an overwhelming imbalance of power.”

Remember that this type of violence was being conducted against other groups, it was not being acted out within a group. This is predatory behaviour where one group was targeting another group with overwhelming combative power and strength.

“…lethal attacks seem to be more common in crowded communities with lots of males, suggesting that the violence may be an adaptation that helps in the competition for food and mates.”


Whereas above we are seeing high male chimp numbers leading to high levels of violence we have seen similar outcomes regarding human violence.

Violent Land (Amazon link), by David Courtwright, has determined high numbers of young males leads to high levels of violence. Courtwright explores the human factor of this interesting area along the frontier in the days of the Wild West in the U.S.


“Young men are prone to violence and disorder; America attracted unusually large numbers of young men; therefore America, or at any rate that part of it to which the surplus young men gravitated, was a more violent and disorderly place. Wherever and whenever young men have appeared in disproportionate numbers, there has been a disproportionate likelihood of trouble.”

This is a similar observation to what Wrangham observed in chimps. High numbers of males equals high levels of violence. In humans it is especially correlated with young men.

Courtwright determined that high male populations, especially young males, was a key contributing factor leading to human to human violence so it should not be surprising to see that chimp communities with high male populations sees the highest levels of violence amongst chimps.

It is important to highlight that Professor Wrangham was observing predatory combative behaviour in chimps that occurred between two different communities whereas Courtwright was observing alpha male and predatory violence occurring in humans that involved a large array of factors where alienated, drifting young men are more likley to act aggressively. Combine this with a cultural sense of honour within this highly male population, large migrations of people from a broad range of backgrounds all mix in to create an environment where violence cooks. The similarity I am drawing out between chimp violence and human violence is the high male populations. This factor appears consistent for violence types across mammals it seems.

Previous interesting research was published in Slate:

“In 1974, Jane Goodall witnessed a disturbing scene in Gombe Stream National Park, Tanzania. A gang of male chimpanzees invaded their neighbors’ territory and attacked a male chimp sitting by himself in a tree. The intruders dragged the chimpanzee to the ground, pinned him down, and bit and hit him all over his body. The attack ended when one member of the gang threw a rock at the bleeding victim. The battered chimp was never seen again and presumably died from his injuries.”

This was a shocking thing to witness at that time as this behaviour was not well known. It goes on:

“The murderous chimpanzees weren’t attacking a stranger: They had recently all belonged to the same group. When the group split in two, one community took over the northern half of the range and the other the southern half. From 1974 to 1977, during the “four-year war,” the northern males obliterated the southern community, hunting down and killing all of its adult males. The northerners took over their enemies’ territory and females.”

Although they were not strangers it must be highlighted that the groups had recently split. So the groups were two very different groups now. The fact that these chimps were originally all from the same group, had a falling out, and are now in competing groups can really increase the fierceness of inter group violence.


In the ageing though still important book On Aggression (Amazon link), Konrad Lorenz explained that it is common in the animal kingdom that the most aggressive behaviour is often reserved for those most similar to each other. This was seen in animals as varied as fish, herd animals and lions.

So whereas these chimps were from different groups which is where most lethal violence occurs, they were also previously together which would also add to the propensity of violence.

The chimps in Tanzania knew each other. They were similar, which meant there would be a high level of rivalry, competition and aggression between these two groups. Perhaps there was also some bad blood over the falling out.

Are humans so different?

The Slate article goes on:

“In 2002 to 2003, anthropologist Filippo Aureli of Liverpool John Moores University in England and his colleagues observed seven instances of male spider monkeys from one group, in the eastern part of a field site in Mexico, raiding the territory of their neighbors to the west and wreaking havoc.”

The following is a key indicator regarding the nature of these attacks:

“The raids followed a similar script. Three or four adult males of the eastern community would descend to the forest floor—which they normally avoid—and form a single-file line. The monkeys walked on all fours with their tails sticking straight up—another thing they don’t normally do. As the monkeys marched into the homeland of the western community, they were as stealthy as a group of Green Berets. They didn’t snap twigs. They didn’t rustle leaves. Sometimes they would stop, stand up on two legs, take a look around, and listen.”

Clear predatory behaviour. As Hunter B. Armstrong highlighted in the Two Faces of Combatives key differences in animal combative behaviour occur depending on whether the violence is intra group or inter group. In this case these animals were not involved in posturing or building their reputation or status within a group in an emotional display. They were coolly going about hunting. They were claiming their resource which was territory. This behaviour was cold predatory combative behaviour.


This raiding activity, of the type observed in Mexico, was similar to some of the earliest forms of predatory combative behaviour that occurred with humans as demonstrated in the fantastic book

The Most Dangerous Animal (Amazon link) written by David Livingstone Smith.

Both chimps and humans engage in raiding and raiding was indeed likely how war as we know it all began. Smith:

“The distinction between raiding and “true war” is also reflected in their chronology. “True war” is a relatively recent development; as far as we know, it began in the Middle East around ten thousand years ago. Raiding is much more ancient, so ancient, in fact, that it probably predates the hominid line.”

It is this predatory raiding that evolved into modern warfare as our intelligence evolved. It is our intelligence that enables more effective means of engaging in predatory combative behaviour that results in mass lethality and today, higher precision.

David Watts of Yale University in New Haven, Connecticut writes:

“Chimps live in groups called communities. Most reported violence occurs when chimps wander near or into the territory of a neighboring chimp community. If they come across a chimp from that community who is alone, they may attack.”

Watts continues:

“Watts declares the incidents back up a proposal that war is rooted in evolution. This view, called the imbalance of power hypothesis, holds that animals that conduct mutual group violence do so because it helps them win resources and territory.”
“Lethal coalitionary aggression is part of the natural behavioral repertoire of chimpanzees,”

Predatory behaviour.



Richard Wrangham, from the new study I opened with at the top of the article, continues with a hypothesis:

"The imbalance of power hypothesis states… that evolution favored humans and chimps who warred when and because they could get away with it. This makes grisly sense in terms of natural selection,”

Moving briefly away from predatory and inter group combative behaviour and towards intra group combative behaviour in primates we see a key determination from Psychology Today:

“Across the primates you find that within-species violence resulting in death is rare, and not wide-scale.”

Reaearch I have personally conducted through an analysis of large data sets of statistics shows the same results in humans. Violence between people who know each other (such as in assault) is far less lethal than violence that occurs between separate groups involving strangers (such as in robbery or muggings). Less lethal assault is far more common than crimes such as robbery.

Lorenz provides further insight into why intra group, alpha male, combative behaviour is so endemic, especially amongst primates and people:

“All social animals are ‘status seekers’, hence there is always particularly high tension between individuals who hold immediately adjoining positions in the ranking order; conversely, this tension diminishes the farther apart the two animals are in rank.”

And further:

“We do not know of a single animal which is capable of personal friendship and which lacks aggression.”


Armstrong distinguishes between intra and inter group violence in some detail and differently to how we have done here. Armstrong examines how animals of the same species engage in combat (posturing, fighting for status) and how animals of different species engage in combat (leopard stalking and killing prey). He draws on these examples (intra and inter species) and demonstrates the two types of combative behaviour are similar to how humans engage in violence with one another.

In intra species violence, Armstrong highlights high levels of arousal, intimidation, angry emotions and self esteem and insults are just some factors present in these encounters. In inter species violence, Armstrong highlights low or no arousal, not provoked but initiated and unattached to opponent being just some factors present in these encounters.

Intra group violence in chimps and humans is the same sort of combative behaviour as what Armstrong has highlighted with intra species violence; emotional and status seeking.

Inter group violence in chimps and humans is the same sort of combative behaviour as what Armstrong has highlighted with inter species violence. Examples such as a chimp, human or big cat hunting down and attempting to obtain some resource (food, territory, money etc.) are easy to raise.

So we see intra species and intra group violence is broadly the same whether it is exhibited between seals, horses, chimps or humans. Inter species and inter group violence is seen in the animal kingdom with predators (eagles, tigers and sharks) hunting prey and sometimes by chimps and humans against their own species (hunting territory or cash) though between different groups. Humans that hunt in this way have dehumanised their target. This is the essence of the meaning of the term pseudo-speciation.


This type of predatory combative behaviour within a species against itself is extremely rare in the animal kingdom. That is why the research being conducted into chimpanzee violence is so fascinating. We are seeing high correlations with how chimps engage in violence to how humans engage in violence. It is quite rare to see predatory combative behaviour occur within a species. To see it documented and researched occurring in chimps in such thorough detail and over time is really insightful.

Most of the violence that occurs within a group revolves around jockeying for the status of the Alpha Male (or Beta Male and so on down the line). This is the posturing that is seen frequently on wildlife documentaries where chimps, and other primates, stand up on hind legs, bang their chests, look big tall and strong and engage in fighting that is rarely lethal. The outcome is normally that one primate submits to the other and saunters off defeated with the victor gaining status within the group. This activity is seen across the animal kingdom.

We see similar posturing, pushing and fighting in humans.

When animals get involved in violence from within a group, the violence is rarely lethal. However violence that occurs between two separate groups results in violence that much more frequently results in death (thanks to dehumanisation and pseudo-speciation).

I also corroborated a lot of these outcomes regarding human violence when I conducted a detailed statistical analysis of human to human violence. These results and more are included in our Understanding Modern Violence course.

One example from the course saw that crimes such as assault (alpha male) were far less lethal than robberies (predatory). Another example saw that assaults involved people that knew each other in more than 50% of instances whereas in robbery both parties rarely knew each other. This demonstrated that assault was very much an Alpha Male type of encounter whereas robbery was very much a Predatory type of combative encounter.


So what we have seen here is that there are many instances of robust academic research adding further validity to the hypothesis that there are really two key types of human combative behaviour.

These are one, Alpha Male combative behaviour

- that is violence that occurs within a social group or community,

and two, Predatory combative behaviour

- that is violence that occurs between two separate social groups or communities.

Once we can understand this we can start to predict how violence is likely to unfold depending on where we are and at what time.

Intuitively now we can start to anticipate what sort of violence to expect when walking through a dark street to get to a train station late at night. We can anticipate the type of violence that may occur when we go to a family barbecue where there will be lots of relatives that have not gotten together for a while and lots of alcohol is likely to flow.

Once we understand these fundamentals we can explore how these forms of violence begin to unfold and develop strategies and tactics for how to neutralise these two very different threats. Preferably we can prevent an encounter even getting to the physical stage if we recognise what is going on and mitigate the risk.


For more information regarding details of how humans engage in combat and violence with one another you may want to check out our free online course Understanding Modern Violence. This course goes into a lot of analysis into human to human violence and explores the Alpha Male and Predator in some detail - and it is free! Be sure to check it out.

Image source:  Eric Kilby