School of War - Why Chimpanzees Go to War, with John Mitani

Episode Date: June 26, 2026

Dr. John Mitani, professor emeritus in the Department of Anthropology at the University of Michigan and recipient of the Charles R. Darwin Lifetime Achievement Award, joins School of War to discuss the violent chimpanzee civil war he documented among the Ngogo chimpanzees in Uganda. What caused one of the world's largest chimpanzee communities to turn on itself? What does chimpanzee warfare reveal about the origins of human conflict? And what separates humans from our closest living relatives? 02:39 - How Dr. Mitani became an ape researcher 04:02 - Why chimpanzees? 05:13 - Humans' closest living relatives 08:38 - The Ngogo chimpanzees 09:31 - The chimpanzee civil war begins 13:35 - Living among wild chimpanzees 17:09 - Territorial patrols and warfare 22:34 - Why the chimpanzee community split 26:26 - How chimpanzees fight 29:14 - The strategy behind chimp warfare 31:24 - Why full stomachs lead to war 33:10 - Land, food, and reproduction 37:27 - Infanticide and the mystery of female survival 39:26 - When civil war becomes permanent 41:13 - What chimpanzees teach us about human nature Follow along on Instagram, X @schoolofwarpod, and YouTube @SchoolofWarPodcast Find more at The Free Press. Learn more about your ad choices. Visit megaphone.fm/adchoices

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free of charge. BetMGM operates pursuant to an operating agreement with Eye Gaming, Ontario. A little bit of a departure for a lot of. us today here on School of War, but I hope you'll agree with me. It's a super fun and interesting one. We're going to talk about civil war amongst the apes, specifically chimpanzees, a group of whom in the center of Africa some years ago fell out with one another and devolved into ongoing attritional warfare amongst themselves subdividing into groups. It has aspects that are eerily human and aspects that are clearly not like anything we do at all.

What are the origins of human violence? What can we learn from the study of these creatures? Let's get into it. It is for a war. This block and a invasion of way. December 7, 1941, a date which will live in history. A bloody experience of Vietnam is to end in a state. We continue to face a great situation.

People are not being. You'll bite down the media. a fight on the landing ground. We shall fight in the fields and in the streets. We shall never have no rest. Hey, y'all. It's Kelly Clarkson with Wayfair. Ever order furniture online

and wonder, what if? Like, what if it doesn't hold up? That sofa was four days old. You should have ordered from Wayfair. With Wayfair, there's no what if. Just style you love and quality you can trust. Visit Wayfair.com. Wayfair, every style, every home. Hi, I'm Aaron McLean. Thanks for joining School of War. I am delighted to welcome to the show today.

Dr. John Mitani. He is Professor Emeritus in the Department of Anthropology at the University of Michigan. He taught there for over three decades. And he is an expert in a primate behavioral ecology, 45 years studying all five kinds of apes, gibbons, orangutans, gorillas. Dr. Matani, the author of many books and papers. And we're going to talk today about Civil War amongst the chimps. Thank you so much for coming on School of War. Well, thanks for having me.

I find myself sort of weirdly excited by our subject today, which is a departure for us here on School of War, you know, violence amongst the primates. But I think listeners will get pretty quickly why I'm interested in it because it potentially has important things to tell us about the nature of human violence. And really, we're going to be talking about a kind of war amongst a particular group of chimps. And I find it totally fascinating. I actually had the opportunity to talk recently. I met for the first time Richard Rangham and talked to him about his whole notion of

was a targeted conspiratorial killing and sort of the foundation of politics which I'm hoping to get him on School of War here soon to discuss that. So maybe we'll do more with apes in the days to come. You must know and have worked with Dr. Rangham. Of course. Richard is a good friend and old colleague of mine.

How does one get into this crazy line of work of stalking chimps and apes and all sorts of near but not quite human things through the jungles of Africa. Well, I think those of us who do this all have our own stories. Mine is just been serendipitous one accident after another, how I got involved in this. As I was growing up, I had no particular interest in the natural world or history or animals in their behavior. but when I went off to college at Berkeley,

I started to take classes with one of the founding fathers of the study of primatology in America. Sort of one thing led to another. I got hooked. It took me a while to convince myself that I can actually make a living doing this, but I did. And went off to graduate school,

started to study orangutans and Gibbons in Asia for over a decade, and to be quite honest, got bored with that and got nudged into the study of chimpanzees again by accident by my post-doctoral supervisor who had spent some time previously studying chimps with Jane Goodall. What was more exciting about chimps than orangutans and other creatures of the east? I got bored studying orangutans because for the most part they live alone. They live by themselves as a result. They don't do a lot. I often tell people you and many others have not sat underneath an orangutan for six hours at a time while it's slapped 40 meters above you. That gets pretty boring pretty quickly.

Yet I did that for 12 years, off and on for 12 years of my life. and decided, well, there were questions I wanted to answer and pursue with them. I thought that it would take decades more than my lifetime to answer those questions. So, again, there were studies of chimps. Chimps are social. They're together all the time. They're doing a lot of things. A lot more activity and excitement.

And as soon as I arrived in Africa, I immediately got hooked. Maybe you could do us the favor of explaining the family tree here of how these different species relate to one another and then critically to us, to humans, because that, of course, is one of the main sources of the enduring interest in apes, right, is that we feel like we can learn something foundational about our own way of being in the world, because if I'm not mistaken, the idea is we share a common ancestor with these species. It's not that we're descended directly from them, but we're somehow cousins or something. like that. Could you walk us through that? Oh, absolutely. And in your correct, part of our interests in these specific animals that I've studied

lies in the fact that they are humankind's closest living relatives. The two Asian apes that I studied before Gibbons and orangutans are slightly more distantly related to us. There are three

African apes, the Bedambo, chimpanzee, and gorilla, they share a closer relationship to us than orangutans and gibbons. Gorillas are a bit more distantly related, and chimps and bonobos are our closest living relatives. We split off from them, there's a debate about this a long ago, but anywhere from six to eight million years ago. They themselves, split off from each other after having split off from us, six to eight million years ago,

somewhere on the order of about two million years ago. So collectively, those two individuals, those two species, chimps and bonobos are our closest living relatives, and it's for that reason that there's so much interest in them. Before we get into the subject of the day, which is violence amongst chimps, if we couldn't just sort of stay very broad for a moment.

What happened that led humans on the path to where we are and chimps and bonobos on the path to where they are? Is it geographic separation? You know, why are they, them and we us? A very 30,000 foot question I grant, but what's the sort of conventional wisdom or the range of debate? The honest answer is we really don't know because although since we as humans separated from chimps and gorillas those million years ago, there have been many spectacular finds of our human ancestors that dot the landscape over those six or so million years ago. But the problem in answering your question is that there are no fossil chimps or the nebos.

And that's probably due to the fact that they were living in forest environments, forest environments, where fossilization just doesn't occur. So if I'm really honest with you here, we don't really know the specifics of how things happened during that split. And that's probably going to be an issue. that's going to be shrouded in mystery for years to come. So at some point in your career, and maybe you'll give us the backstory here,

you found yourself tracking a pretty large, you know, a couple hundred chimps, collected together in something referred to as the Ngogo. I don't know if this is, the Ngogo has clusters. I'm not sure we could we call it the Ngogo group? Or what's the name for the hole? The name of the original group we started to study is the Ngogo-Chimmoniz.

It takes its name after a hill in the area. It's the highest spot in our study area. And when we began the study over 30 years ago in 1995, all these individuals in this group were a single unit, members of the same group, same community. They split subsequently, and that's part of the story here. Well, let's skip to the very dramatic incident. that sort of sets this, or at least visibly sets it in motion,

and then again, you can give us some backstory. But there you are. My understanding is you're an eyewitness to this. On June the 24th, 2015, you're following a group of these chimps, and what do you see happen? Well, up until that time, they've been living together in a very large group. They've been living together,

and they've been quite successful. There's actually part of the story is what's happened 20 years, before these events involved. Part of our interest in this particular group of chimpanzees lies in the fact that it was large. It was well over 100 individuals, about twice as large as any other group of chimps that have been your typical average group of chimps

that have studied elsewhere in Africa. Those groups average in around 40, 50, 60. Now here we have a group that's much, much larger. And over time, during those first, 20 years, they thrived. Because they were living together with so many others, they were able to dominate their neighbors.

They actually started to kill a lot of their neighbors. And as they killed those neighbors, they were able to reduce the collective strength of those neighbors. They expanded their territory into areas

previously occupied by their neighbors. they acquired more land, more food. Food happens to be the fuel that promotes female primate reproduction. So after this land grab, this territorial expansion, females in the group start to reproduce much more successfully than they had before. Those females are better fed, mothers are better fed, in better condition. Infant survivorship increases as well. So this group continues to grow.

So before I get finally to your question and what you want answered, what one really has to understand is that for many years, this group was the most successful group that had ever been studied in Africa. It was thriving. And that's why this event in June of 2015 was so surprising. And what happened there was instead of coming together, peacefully as they had for so many years before they engaged in an aggressive interaction. I was following one of the members of one group. We crusted a hill. They started to go down the hill.

And as soon as they started to go down the hill, they started to run. I caught up with them after a few hundred meters. and I was surprised to see members of this other subgroup there. And as soon as I saw this, all owl broke loose. They're running around, chasing each other, shouting, screaming. Interestingly and uniquely, members of both sides started to give calls that are only given during inner group encounters when they're engaging members from other groups. but they're members of the same group, but here they're acting as if they're strangers. Before you know it, I'm just, it's chaotic.

The scene's chaotic. I'm just trying to follow whatever is going on. Before I know it, I'm over 500 meters away. Huffing and puffing with the individuals that I originally started with. Members of the other group were nowhere to be seen. That started a period of two and a half years of increasing conflict avoidance

between members of these two sides. Okay, so I have so many questions. We'll spend some time on this. First of all, just you personally, you must get questions like this all the time, so forgive me for asking it for the thousandth time, but just on a personal level, how do you relate to these pretty sophisticated animals,

that is to say they must know you're there if you're out there chasing after them through the jungle, Do they acknowledge you somehow as some strange thing and just sort of put you out of their minds? Like, how did they account for you and how do you stay safe in midst all this? Well, initially, when we first enter their world, you know, back in 1995, when we first entered their world, they're quite naturally scared of us. As if an alien, you know, would drop into your studio right now. You're not going to go up and pet it or try to engage it. you're naturally going to be scared, perhaps run away.

And that's what chimps in the real world do when we first enter the world. And it takes months, if not years, to gain their trust, to reach a point where they become accustomed to our presence. And it's only after those years of really hard work that we're able to start to observe and record aspects of their behavior in detail. But the surprising thing is that once you arrive at that situation, it's as if we just become part of the background. And they really do seem to ignore us. You know, some chimps are so accustomed to us and so tame, if you will, that I think they'll pass through my legs if given an opportunity.

There's a lot of inter-individual variation, just like in humans. Some are still wary and keep their distance, but yet others will brush right beside you and sit right next to you. But the really strange thing is that they ignore us. And thankfully, they've never figured out that they're much stronger than us. And they still are a lot more scared of us. than we are them. I'm thankful for that and the fact that they haven't figured out

that they can get rid of us at a moment's notice. They did realize how much stronger they are than that. Forgive me for the sort of ignorant question, but how much does an adult male chimpanzee weigh? That's not an ignorant question. They're actually, the ones that I study in East Africa are on the smaller side. There are some chimps in West Africa that are slightly bigger.

But, you know, I always thought of the largest chimp. We can't weigh them. These are all guesstimates. I've always looked at the largest male chimp that we have in our group miles. Seems to be more or less my size, 60 kilos, 130 pounds or so. Most are much smaller. When they stand up, they're not as tall as me, and I'm not a tall individual. I'm only about five, six or so.

So I think that's maybe one of the reasons why they retain this fear, because we're bipedal, we're standing on two legs, and we might seem bigger to them for that reason, and physically we are. So then back to the war. You say one of the striking moments is as this civil strife breaks out before your eyes, they're making these sounds that typically are reserved for intergroup conflict. And you alluded to how there had been territorial expansion

sort of perpetrated by the Angogo leading up to this. These neighbors that they are taking territory from, these are other chimps? So that's question one. These are other chimps? Or what are they fighting with in terms of the intergroup stuff? And then question two is how do they think about territory? Like what does territory mean to a chimp?

They are. The answer to the first question is that, they're interacting with neighbors who surround them all around from all sides. The second question is a bit harder to answer because I'm not sure I can get into the head of a chimpanzee, but they do operate over restricted territories over a bounded area. It just seems like they know what that territory is. there's a considerable amount of overlap between the territories of neighboring chimps, yet it's clear that they know what's theirs and what's not theirs.

And to give you an example of how they know this, let me tell you about another interesting aspect of chimpanzee behavior, and that regards what we call. territorial patrols. So like many other animals, chimpanzees are territorial. Interactions between members of different groups. Or typically aggressive, you know, the unusual thing about chimpanzee territoriality that we've already touched upon is that sometimes those aggressive episodes escalate to a point

where somebody falls victim. There's a killing. But these patrols are another integral aspect of chimpanzee territoriality. And to best describe what goes on there, let me take you on this little thought experiment and have you come to Ngogo with me. Let's say we're out there, we're following a group of chimps. There could be 20, 30, 40 or so. Some could be feeding.

Others can be socializing. Some others feeding off in the distance. Now, if we're to continue to watch those chimps, you might see a few of them, typically male, rise, and move off in single file fashion into the forest. They can go 100 meters, 200 meters a kilometer or more until they reach the boundary of what they recognize as their territory. when they arrive at that boundary, their demeanor and behavior changes and it changes quite dramatically. You know, they're chips.

And more often than not, they're yelling, there's screaming, they're shouting at each other. There's aggression. But on these patrols, when they arrive at the boundary of the territory, everything changes. Everybody falls completely silent.

They start sniffing the ground, They start scanning the environment. They become attentive to any and all motion in the tree canopy. Sometimes the chelps will continue on and they'll make a deep incursion into the territory of their neighbor. Neighbors, areas that, you know, are just out of bounds and they won't go. And they're all doing this surreptitiously and silently. The aim clearly seems to be that they're looking for their neighbors. neighbors. They're neighbors who they can isolate and attack and kill. Sometimes that happens,

more often than not, a dozen. These killings are fairly rare events. But that might give you an indication that they are obviously recognizing that this land is theirs, this is their territory, in this land where we rarely, if ever go, only on these territorial patrols, belongs to members of other groups. What's theirs is where they feel safe and what's not theirs is where they anticipate danger in the form of other antagonistic chimps.

And I guess other chimps not in the group are definitionally antagonistic. That's the natural situation that you see. There's not like grand, And there's not in like situations where you have different groups, but the groups are friendly or are there? No, chimps are incredibly xenophobic. Individuals within their group are individuals with whom they associate, they associate, they'll cooperate with each other. They get along.

Everybody else who comes from the outside in those neighboring groups are treated as the enemy. They will be attacked and killed if given the opportunity. If you want a $3,000 a month payday for life, what would you feel free to do? Maybe take a long weekend, every weekend, or try a bunch of new hobbies. Would you feel free to upgrade and listen ad-free? Don't worry, we get it. Every $20 ticket could win you $3,000 a month for life and supports life-saving cancer research at the Princess Margaret. Feel free to buy your payday for life ticket today.

155-2194. Please play responsibly. Okay, so back to June of 2015, you're in the midst of this melee. I'm picturing this like it's filmed by Alejandro and Yeradu or, you know, Terence Malik or something. Like it's a very cinematic kind of chaotic scene that you've painted for us with your word picture so far, and you're struck by the fact that they are acting in ways that you're accustomed to seeing them act only with out-group members. Do you have any sense, you must have thought about this for years and years. What on earth started this? Whether in the context of this battle, this altercation, or more broadly, I guess it's two different

questions. Well, for one, the group just got too large. And when groups of primates become too large, and this happens over and over and over and many other different primate species. What happens is that levels of feeding competition within the group intensify. They increase. Simple way to solve that is to split up. And that's what eventually is going to happen in this situation. As those groups increase in size, not only does feeding competition increase, but reproductive competition among the males increases as well. And this becomes a particular problem in chimpanzees because female chimpanzees give birth once every five to six years. So at any one time, there's not many females to reproduce with, mate and reproduce with.

So as the group gets larger and larger, as this group did, undoubtedly levels of reproductive competition in this group increase, perhaps creating this level of antagonism between or among members of the group, which eventually leads to a split which occurs two and a half years later. And talk about these subgroups within the Angogo that are both proceeding, but then sort of, you know, forming subsequent to the battle. You had already talked about these or identified these sort of regional clusters, a western, a central, and an eastern, and that appears to be at the root. The divisions there appear to be at the root of some of the violence, but then new subdivisions

break out as a consequence of the violence. Talk us through all that. Well, again, initially at the start of the study, the group was very large, and we always, right from the very start, recognize that there were sort of two clusters, one cluster, group of males and females that generally associated in the center and east of Lingogo Chimpanzee territory,

another group in the West. And when this fighting initiated, it was members from the West that started to fight with members from the center and east who remained as a collective. So that's, how things started and naturally continue to this day.

If I can back up, you know, you mentioned about creating this film scene of these battles. As things turn out, some of this has been filmed. My good friend James Reed is an incredibly talented filmmaker. He filmed a four-part Netflix series, release three years ago, 2023, and he was able to film some of these battles. So a lot of this is on film

and can be seen. So let's take the fighting then at different stages. The fighting itself, the interpersonal violence. How do they fight? For the most part, during these intergroup encounters, it's a lot of shouting, screaming,

they're chasing each other, two and fro. There's very little in the way of physical contact. At least, in situations where the numbers of individuals who are fighting are the same. It's only in situations where one group has a numerical advantage over often only a single individual and the other group that these killings are made. Jim's take advantage of numerical superiority to demonstrate. make relatively low-cost killings.

You know, when they, if it's a situation where there's 10, 12, 15, 20 against one, that's really not a fair fight. And those are the situations under which they will attack and kill an individual. If it's 10 to 10 versus 10, 20 versus 15, if there isn't a numerical asymmetry like that. It's for the most part during these inner grip encounters. It's just a lot of screaming, shouting, chasing back and forth

and before you know it, the encounter is over. And when they kill, are they just using their bodies to beat the other chimp to death or hit them in the head? Are there weapons of any kind, rocks, things like that?

No, chimps don't use weapons or tools to kill each other. These are actually quite gruesome affairs and they're difficult to watch. But again, it's usually a numbers game. 10 against a single individual that has been caught and is now being attacked. Ten or more individuals are just, it's a pile of chimpanzees

on top of the victim. They pummel the victim with their hands, their feet. They do so continuously and relentlessly over a period. It sometimes only takes a few minutes. Within 10, 12, 15 minutes, that individual is dead. If you were to examine the body, more often than not, they're only superficial cuts and wounds. So nothing that looks like it would actually lead to death.

And because of that, I've always thought that death results from internal injuries suffered during this relentless pounding and beating. So if the casualties tend to happen in these moments of numerical overmatch, stepping up from sort of the tactics of the fighting up to how they might operate or campaign, if you'll forgive the expression, do you see some or any level of organization to intentionally generate those moments? You mentioned patrolling or their raids, you know, how do they think about creating the moments where they might. be able to kill? Well, we did some analysis several years ago to figure out what triggered these patrols and the single factor that best predicted when male chimpanzees would go on patrol is simply how many were together. Chimpanzees are social creatures, but the usual thing about a group of chimpanzees is that you won't find all 100 or 200 individuals to

together at a single spot at a single time. They come and go, like us as humans. You could be following a group of chimps. There might be 10. A minute later, two leave. 10 minutes later, four more come. So they're constantly splitting apart, fissioning, and then coming together, fusing,

forming these temporary subgroups or parties that are constantly varying in size and composition throughout the day, and what actually affects that variation in party size is food. Chimms make a living by feeding on sugar-rich fruits and like the cases here, you know, sometimes the forest is full of fruit, other times there isn't a lot of fruit.

And they come together during fruit-rich times. When there isn't a lot of fruit in the forest, they reduce levels of feeding competition by just scattering to the winds and going off by themselves. So it's during periods one, during periods of high fruit availability, typically, when they're gathered together in large parties, actually when they have full valleys in time on their hands, that's when they go off on these territorial patrols.

That's totally fascinating because it cuts against what I imagine some would assume, which is that violence is generated by terrible scarcity and competition for resources. And you're actually suggesting the opposite. It's almost a luxury activity. It almost does seem as if it's a leisure activity that when times are good, that you don't have to work very hard to make a living

when there's tons of fruit around. You tank up, you eat for an hour or two, just stuffing yourself with fruit hand over fist, You spend an hour or two relaxing with your friends, and then you have energy to burn. And you use that energy to burn to go off on one of these patrols. I read somewhere that there's no concept of revenge killing, which I guess must mean in a very specific way that, you know, you killed specific chimp X and I am going to now find your group that did the killing and kill one of you in a kind of, you know, classic base. I mean, obviously there's ongoing exchanges of intergroup violence, but it's not, it's not like that because that would require greater capacity for, you know, language in particular than the chimp's

have. I read that in one of the articles written about your work. So when they, when they got their full bellies and they got numbers and they think the numbers are in their favor and they go off looking for trouble, is that kind of it? They're just looking for trouble or do they have any more sophisticated objectives in mind. The purpose of these patrols and ultimately killings is all about land, food, and at the end of the day, reproduction. So in this sense, it's an adaptive behavior as we think about adaptation in the biological world and as a result of the evolutionary process, individuals who are able to behave in ways

that increase their survival and reproduction do better than others. So in that sense, you know, the story isn't all that complicated in the grand scheme of our understanding of the rest of the biological world. When it comes to revenge, I'm not sure we do have any indication that chimps engage in revenge or are revengeable. revengeful in their behavior. And that might be suggested by what's transpired in all of this. So again, going back after two and a half years of conflict,

where these individuals are fighting with each other, increasingly avoiding each other, the group finally splits. And the next split. part of the story is that after they split, they start to turn on each other. And unusually, it's members of one of the splinter groups that starts to kill members of the other group. And it's all unidirectional and asymmetric in these killings. And now after eight years after the split, the death toll is up to 28 individuals, 28 killings. at least that we know of.

Now, you would think if there was revenge in the hearts of chimpanzees, that the members, the victims group, would maybe try to retaliate an attack, but they haven't. And that's all the more interesting, if not curious, because the victims group was much larger than the kids. killers group when these co-ings started.

To what do you attribute this odd, lopsided nature of the casualties? Is it just that, I guess, it's the Western chimpanzees who are the Spartan effective killers and the central chimpanzees who are the, you know, the ineffective, peace-loving, you know, you're shaking your head. I'm obviously exaggerating for comic purposes. But what way the other? They're not doing as much killer. No, no, you're not exaggerating.

just shaking my head because I have no answer to your question. I see. I see. Yeah, it's, what a mystery. I mean, you would think eventually, you know, this, the central group would get some points on the board, and yet the Western group just seems to year after year dominate them with with extraordinarily overwhelming results. It's just striking. At the time of the split, the central group, members of the victims group, was much larger. than the killers in the Western group. If I recall, the Central Group was 111, and the victims group was somewhere in the 70s, 76 or so.

And so they had, and there were over 20 adult males in the Central Group, and only seven adult males in the Western or Killers Group. Now, after eight years in all these killings, the tables have been completely flipped. There are many more Western chimps. They number over 100. And there are far fewer central chimps. They're now in the 70s.

So totally inexplicable. And that's one of the reasons I keep on going back year by year. Another lopsided aspect of the casualties is the, at least what to me seems like, the extraordinary amount of infanticide, at least compared to what the population. must be, I guess not the population of vulnerable people who are individuals or in small groups, because that presumably is why they keep getting targeted. But infanticide is something of a preferred tactic here.

Well, that might be due to the fact that infants are just easier to kill than a mature Jim and Z. That's an unfortunate but fact of life. It's easier to snatch a small infant from its mother and kill it, then isolate and attack a mature male chimpanzee. Interestingly, here's another interesting facet of chimp behavior. While they will kill mature males, they will attack females from other groups.

They'll chase them. Sometimes there will be physical contact. It's clear that they have opportunities kill those females from neighboring groups, but things don't escalate to the point where killings are made. They'll kill infants clearly. They'll kill mature, adolescent, and adult males, but they let the neighboring females go. Don't know why that happens either. If you think that it's all about land, reducing the strength of their neighbors, gaining more land, more food, that females in those neighboring groups are just going to produce more kids who

will be future competitors. Is there kidnapping or sexual violence? Like, are there Helens of Troy, as it were, in all of this? Yeah, it would make sense if those females are recruited into the killer's territory and group, but that doesn't happen. They just stay. So this thing then just grinds on and on. And at what point is it no longer a civil war, and we just have two new outgroups, essentially,

and it's almost like a cell dividing as an organism grows? Well, it has, they have divided. So again, back in 2015, there was this two-and-a-half-year period of conflict where they gradually drifted apart. They started to avoid each other. They began to avoid each other. They fought from time to time. and then two and a half years later, everything stopped.

They stopped associating. They started to use separate territories, and they stopped reproducing with each other. We actually mark the day of the split by a particular event. And that event was when members of the Western group killed a young adult male from the Central Group. After that event,

There is no further mixing between individuals from both sides. It's fascinating to speculate that in our own human origins, some incident like this might have been at the beginning of our split off from whatever common ancestor we share with these different groups of apes today. Possibly, but again, you know, the past is I'm an empirical scientist, and I like to watch observe. Maybe a little romantic with me, John. We're on a podcast area. It's okay. Well, I'm sorry.

Yeah, I just like to stick the facts or the facts as I can observe and record them. And if that's a little boring, sorry. Oh, no, no, no, no, don't get me wrong. This is the opposite. This is as far from boring as can be. I'm hanging on your every word. I'm totally fascinated by all this. And I guess one of the upshots, and that you addressed this in the paper you published

in science is, you know, if there's anything to take away from this war, it's, I'm going to put this in my own words. These are not your words. But my words, is that whatever Rousseau is right about, he doesn't seem to have been right about, you know, the state of nature being a sort of pristine place of noble savages and violence and all the terrible stuff that humans have to suffer through somehow being introduced later as a consequence of culture and property and all the trappings of being human. If anything, it probably goes too far to say we have to draw the opposite conclusions. But if anything, the world you just described is an incredibly violent place, but largely shorn of anything resembling culture or are sort of recognizably human stuff, even if the creatures themselves are obviously pretty close to us biologically. Yes, when we think of war in humans, we think this being due to ethnic conflict, religious differences, political differences between people. But that obviously doesn't apply here because

chimps don't possess any of this. The simple, and the simple lesson is that when relations break down, bad things and lethal conflict can. ensue, but I actually have a more hopeful message and the take-home a lesson I take from all this is, maybe we'll be surprising to you. And that's, human warfare isn't inevitable. And I say this because if there's one thing I've learned from studying chimpanzees for over 35, nearly 40 years now, is that we aren't chimps. That may not come as a surprise to you or any of your listeners, but, you know, we do share this common ancestry with them,

and because of that, we're similar to them. In many ways, we share quite close to them genetically. We share a common anatomy. We even share aspects of our behavior. But that shouldn't have been. obscure the fact that we've gone our separate way now for six to eight million years. And since we separated from chimps, we've changed in many and important ways. And one of the most important and critical for this story is that since our separation, we become this incredibly

pro-social and ultra-cooperative species. The thing we've learned from our paper and our observations from this study is that, one thing we've known for quite some time is that chimps will attack and kill their neighbors. The surprising thing in our study is that they will do this even when those neighbors are individuals with whom you've shared a long history. Some individuals who have been friends and allies for many years, something just seems to snap in the mind of a chip when an individual becomes a neighbor. That's no longer us. That's somebody to attack and kill. And that, to me, is not human behavior. You know, we don't act this way typically. We go out of our way to help our neighbors. Sometimes those neighbors can be complete strangers. And this ability to get along with

others is really a hallmark of humankind. It's something that sets us apart. And so, you know, wars break out among ourselves from time to time, as they are now. For the most part, and I think throughout human history, we've been able to get along and look peaceably side by side. We're doing that

now in a world where there's over 8 billion people. I find that incredibly remarkable. And it's actually something that gives me hope, if not optimism, especially during this time when there's

increasing polarization. So I think there's a hopeful message here. Dr. John Matani, Professor Emeritus, the Department of Anthropology at the University of Michigan. This is a totally fascinating conversation. I'm left with more questions than I started with, I think, but different questions. So perhaps we can keep talking here as your research continues. And I'm really grateful to you for stepping out of the world of primatology and coming on a military history and strategy podcast.

This has been super fun. Happy to do so. It's been very nice talking to you. And thank you for giving me this opportunity to reach out and maybe reach a different audience.