#1304 Michael Wilson: Chimpanzee Behavior, Ecology, Violence, and Human Warfare

00:00 Ricardo Lopes: Hello everyone. Welcome to a new episode of The Dissenter. I'm your host, as always, Ricardo Lobst, and today I'm joined by Dr. Michael Wilson. He's a professor in the Department of Ecology, Evolution and Behavior at the University of Minnesota. And today we're going to talk about his work on the chimpanzees at Gombe National Park in Tanzania, animal personality, how apes are impacted by human activity. And some other related topics. So, Doctor Wilson, welcome to the show. It's a huge pleasure to everyone.

00:35 Michael Wilson: Thank you very much, Ricardo. It's a huge pleasure to be here.

00:39 Ricardo Lopes: So let's start, I mean, to introduce the audience to your work. Tell us about the chimpanzees at Gombe National Park in Tanzania. I mean, what led you to study chimpanzees there specifically, and what have you studied among them in terms of their behavior, ecology, and so on?

01:06 Michael Wilson: So the chimpanzees of Gombe National Park are the chimpanzees that Jane Goodall began studying in 1960. So they are the subjects of the first long-term study of chimpanzees in the wild and the longest running study of chimpanzees. And so I've been hearing about these chimpanzees since a child, you know, I, you know, they've been studied longer than I've been alive, and, uh, so we know. An incredible amount about their lives in, in great detail. I came to the study of chimpanzees uh through A broad interest in evolution and human origins and how we came to be the sorts of animal that we are. And my first work doing Uh, studies in the wild of primates, uh, focused on baboons. I worked for Gene Altman, uh, as a data manager for the Ambaceli Baboon Project, which is based in Ambaseli, Kenya. And I spent about 10 months in, uh, Impala Research camp in Laikipia, Kenya, studying olive baboons, and which was terrific. I, the baboons are super interesting and Being on the ground with baboons, you're following them around on foot in An area that still had elephants and lions and leopards and hyenas and all of these animals was really powerful in terms of understanding what life must have been like for our early ancestors, but it, it also made me really wonder, well, what about species that are more closely related to us? Baboons are interesting, they have fascinating social lives, but would we not learn more? Uh, BY studying our closest living relatives, and so that led me to, uh, looking into chimpanzees as, as a research, uh, focus. And so that's what I ended up doing for as a graduate student at Harvard University. I, uh, worked in Kibali National Park in western Uganda studying chimpanzees there. And then when I went on to do postdoctoral work, uh, with Ampezzi at the University of Minnesota, I. That's when I began working at Gombe, and the thing that really led me to, to work at, uh, at Gombe with Ann was that. I had become interested in this question of intergroup relations and the Kanawara chimpanzee community that uh I had been studying for my doctoral research that uh in a project that Richard Wrangham leads, they didn't have any neighbors that were habituated, meaning that you could uh follow them as well as the, the main research community. So when Interactions occurred between groups. We, we only had information from one side of the interaction. And so I, uh, I knew that at Gombe, the, there were two study groups that were habituated and so there was information from both sides of the interaction there and, uh, and Pewy had funds to support someone studying those interactions. So that's, that's what led me to Gombe. Mhm.

04:40 Ricardo Lopes: Uh, AND I mean, what aspects of, uh, chimpanzee behavior and how ecology specifically impacts their behavior, influences their behavior are you most interested in?

04:54 Michael Wilson: So I'm interested in many different aspects of their behavior, but what I've focused on, uh, in my research at Gombe has been. Aggression and the things that cause chimpanzees to behave violently um towards each other, both within groups and between groups and the relationship to ecology is that the. The environment in which an animal lives, the foods that they eat, the resources that they need to survive, have a profound impact on social behavior. Are they able to afford to live in groups given the foods that they eat? Uh, CAN they live in big groups or small groups? Chimpanzees have an unusual society, uh. Instead of traveling always in a coherent group like gorillas do or olive baboons, they have a fission fusion social structure in which individuals come together sometimes in big parties and disperse into small parties, and this. It is also similar to our own social structure. We, we're always, you know, coming and going, joining into larger parties and breaking up into smaller parties. So there's, there's an intriguing similarity with what humans do there. And this also seems to be, well, it's very much related to food. So when food is abundant. They can afford to travel in larger parties and keep themselves fed because chimpanzees, like most primates, spend most of the day looking for food. They need to feed themselves to grow and produce offspring and survive, and so they need food and they also compete over access to food, both with other members of their group and between groups, and The competition to control a particular patch of land, a territory, uh, seems to be, well, for one, it's a big driver of intergroup aggression in chimpanzees, because they need to defend their particular patch of land in order to ensure a food supply for themselves and their, their mates and their offspring. And, uh, Also the food. Uh, THE variation in the food supply means that they're not always able to travel in a big party, and this means that individuals during some seasons are scattered and alone, and that seems to play a big role in their vulnerability to intergroup violence. Mhm.

07:47 Ricardo Lopes: Yeah, because, uh, I mean, it's interesting, of course, I don't know exactly the details. I mean, I couldn't tell. I, I don't have memorized in what ways, for example, the kind of environment, if it's more mountainous, if it's more of a forest environment or something like that, and the kinds of, uh, let's say food resources. That different chimpanzee groups have access to in what ways that specific, those factors specifically influence their environment and make different groups behave in different ways, but certainly ecological factors play a big role there, right, because I would imagine that chimpanzee groups across Africa. For example, would have, uh, because they are part of the same species, some commonalities, but because they live in different ecological contexts, there's also lots of variability in terms of their sociality. I mean, am I correct here or not?

08:57 Michael Wilson: Yes, that's right. There's a tremendous amount of variation among chimpanzee populations in lots of different. Aspects they, they differ in terms of their tool use. For example, uh, at Gombe, they use, um, sticks to fish for termites and ants, and, uh, they, but they don't use stone tools, whereas in West Africa, there are chimpanzees that use stone tools to break open nuts, and chimpanzees have. Have nuts at Gombe and they have stones, but they have never figured out stone tools, so they're. There's an interesting combination of both ecological factors that can influence behavior, but also these cultural factors like the ability to use stone tools versus the ability to termite fish that seem to Very true in a way that's not directly related in an obvious way to us, at least to ecology. And It seems likely that these ecological uh variables affect social behavior, but to be honest, we don't have a very good understanding of it. We, you know, I think we're still in early stages of how do we even characterize what is in the habitat that is causing variation. So we can see that chimpanzees at You know, some sites have very high rates of intergroup killing, uh, chimpanzees at other sites have very high rates of within-group violence. Some chimpanzee communities have high rates of, of violence against infants versus others have high rates of violence against adults. And the factors that. Cause that variation, I, I think we're still in pretty early stages of, of trying to figure them out.

11:05 Ricardo Lopes: Right? Uh, SO I know that you've studied, uh, particularly animal personality at Gombe. So, uh, what do we know about personality in chimpanzees, and I mean, uh, do you, When you study animal personality, do you approach it in a similar way that we approach personality in humans, or are there differences?

11:32 Michael Wilson: So personality is one of the things that Has distinguished research at at Gombe, I think from the very beginning and that Jane Goodall was immediately struck by how different individual chimpanzees were. And at that time, The The kind of um reigning view in animal behavior was to focus on things that we could quantify scientifically, and there was a great concern with Anthropomorphizing or projecting our own traits onto animals and So, animal behavior researchers at the time were generally extremely wary of, of using terms like personality because that just seems too, too fuzzy and non-scientific and uh. So that was something that uh Jane felt she, she faced resistance to in, in among her scientific colleagues, but to her it was obvious that the chimpanzees just differed uh from one another. They had. Different tendencies to do things, and she, you know, she learned the individuals very quickly, and she kept character files where she kept track of the individual life history and the things that they did, and, and she maintained this interest in Individual distinctiveness throughout her study, uh, both, you know, from the very beginning. And In recent decades, researchers have worked to develop ways to Try to assess personality in a more, you know, in a kind of rigorous scientific way, which is not easy. It's, it's really hard to, uh, to capture this. It's something that, you know, intuitively, it's obvious. If you're watching chimpanzees, they're not all the same, they do things differently, but how do you How do you capture that? And there, there are two different approaches to doing that, and one is to take the data that we're already collecting. Quantitatively and You know Put those numbers together. You know, to look at Different individuals, how often are they aggressive, how often, uh, you know, what, what is their mating success like? What are they, uh, uh, how often do they engage in violence? And, um, so these are things that we collect data on and, and look at. And There, there is also another approach that focuses on trying to capture people's intuitions about the animals, and Alex Weiss, who's a colleague of ours who is a psychologist and has focused on studying chimpanzee personality in captivity. He came to Gombe and uh we worked uh with our Tanzanian colleagues to develop a, a questionnaire translated from English into Swahili that's based on the questionnaires that people have been using to characterize personality and in captivity and translated that to Swahili and interviewed. Many of the long-term Tanzanian researchers who've been working with the project for decades and, and have got to know each individual chimpanzee very well. And so, They answered those kind of detailed questionnaires, and then uh Alex performed some fancy statistics to try to capture different personality dimensions and uh Overall, that, that project led to uh You know, finding that some of the personality traits that have been documented in captive chimpanzees are also present in wild chimpanzees, and they, they vary a lot. And uh we've worked with um our, our colleague Joseph Feldblum at Duke University to, to see if those personality traits relate to anything else that we can quantify, you know, to see if these, uh, are, are these really accurate reflections of chimpanzee. Behavior and, and do they matter in real life and, and what, uh, what we found was that there is a, a positive correlation between the personality trait of dominant. With reproductive success. So, and, and this is a personality trait that's scored independently of knowing their dominance ranks. So it's uh it's a separate thing even though it has almost the same name. And uh so that, that finding and also I think chimpanzees that were low on the trait conscientiousness also had high reproductive success. So, so that suggests that this, this personality. Our, our, our measures of personality are capturing something that's real about chimpanzees and that matters in terms of, uh, reproductive success and hence natural selection in the long term.

17:04 Ricardo Lopes: Yeah, I would imagine that it's a bit bothersome that we cannot ask chimpanzees to just answer personality questionnaires like we do with humans, but on the other hand, since questionnaires are basically self a form of self-reporting, I mean, it's Actually, perhaps in a way more reliable to just look at their behavior and identify their personality traits through that because I mean, humans can, uh, lie.

17:39 Michael Wilson: Absolutely, and, and I personally really hate filling out personality questionnaires myself because I, I, I always feel like I'm lying on them because I have an idea of what I, I know would be. An answer that people would like to hear and so I'm tempted to give. An answer that, you know, I, I, you know, that would be admirable, I guess. I don't know, you know, it's, it's, I, I find those very difficult to, uh, to fill out. So, so I'm skeptical of them.

18:13 Ricardo Lopes: Uh, SO, uh, I have now a question, and, and this also, I guess, can relate at least to some extent to what we've already talked about when it comes to how ecological circumstances or conditions impact, uh, behavior. Uh, IN what ways have apes been impacted, uh, apes more generally, not just chimpanzees in this case, been impacted by human activity?

18:40 Michael Wilson: So Broadly speaking, apes have been enormously impacted by human activity in much the same ways that every other. Living thing on the planet has been impacted by human activity. Uh, HUMANS, uh, have taken over the world and, and undertaken this enormous effort to convert the planet into, uh, you know, human-friendly feeding habitat, and So, what that has meant has been an enormous conversion of habitat from forest to farmlands and towns and villages and cities, and also the direct extraction of wild animals for for food and uh for the pet trade, for entertainment, uh, for biomedical experimentation. So, There are a lot fewer non-human apes on the planet now than there were even a couple of decades ago, and Many places that used to have apes no longer do. Uh, SOME of the smaller apes like gibbons, uh, used to be widespread in, uh, China, for example, and now, uh, very few gibbons remain at all, uh, in that country. Orangutans also used to be found on mainland Southeast Asia, uh, and now they only exist on, uh, two islands in Indonesia where they are in extreme peril, and, uh, pretty much everywhere. Uh, THE story is the same, is that, uh, apes are being, uh, Hunted and uh deprived of their homes.

20:30 Ricardo Lopes: Right, but do they exhibit flexibility or are they able to be flexible in terms of the way they respond to human activity? And in a related question, I would also like to ask you, I mean, we have to be careful when studying. In this case, primate behavior or ape behavior in certain ecological circumstances and the kinds of conclusions we derived from that because we have to take into account that sometimes they Are change their behavior in response to human activity, right? And so maybe, I don't know, in certain, uh, circumstances, they might be, uh, more violent than usual, but that's because of, uh, uh, because of them responding to, uh, human activity and how it impacts their ecology.

21:33 Michael Wilson: Right, so apes are extremely flexible and adaptable, and they They can change their behavior in various ways to respond to, for example, the threat that humans pose. Um, ONE thing that I studied in, in my own research as a graduate student involved, uh, well, I was interested in this question of are apes, are chimpanzees. Quiet when they conduct boundary patrols of their territories, and this was something that everyone asserted that they go on a boundary patrol and they're quiet and I wanted to quantify that, and so I collected data on their vocal behavior throughout their range. And one thing that I found that I hadn't really been planning to look for initially, but this came up. As an opportunity based on what I observed was that. On one side of the park where. The chimpanzee community bordered directly with with villages where people planted crops. The chimpanzees would sometimes leave the forest and go into people's villages, or not into their villages per se, but their croplands and raid crops. And they would push over banana plants and open up the, uh, the stems to get the pith that they really like, uh, and they ate various other foods from people's crops. And very often when chimpanzees arrive at a rich food source, they give loud calls. They give pant hoots and rough grunts and Other causes that are associated with finding a lot of food. But when they would go into these croplands that had lots of food, they generally stayed very quiet. And what I think was happening is that they, they knew that there was a threat of being exposed if they made a lot of noise in these fields, and so they stayed quiet while they were. Ripping up people's gardens and so that's an example of flexibility and and how human behavior impacts ape behavior, uh, non-human ape behavior. And there are Other ways in which things that we do can impact their behavior, for example, when When Jane Goodall was first working at Gombe, she learned in the first years of her study that chimpanzees were very attracted to the food that she had in her camp, and they came to steal bananas from her, from her camp. And so she started using bananas to attract chimpanzees to a central area where she could observe them and film them and photograph them more easily. And so for the first years of the study, Well, the very first years of the study, she had focused on following chimps in the wild, but once she saw how difficult that was and how easy it was to observe them when they came to eat the bananas. She shifted the emphasis of her work and for much of the mid to later 1960s, focused her, her work on observing chimpanzees in that banana feeding area, which was A way for her to See in rich detail these things like individual differences and personalities, and she was able to document all of that sort of behavior, but it also had an impact on the chimp behavior in lots of ways because it attracted chimps to a central resource. It also attracted baboons to a central resource, and it changed behaviors in a number of ways that Richard Rangha I documented in a 1974 paper where he found that. The rates of aggression around the banana feeding station or in the banana feeding area were much higher than in the forest, and Richard was, was part of the You know, the kind of early pioneers of researchers at Gombe who were focused on, well, let's follow the chimpanzees away from the banana feeding station and into the forest and collect data. Uh, HE was one of several people who really focused on that and shifted the research back towards focusing on, on the wild behavior. And when it became clear that banana feeding was having that impact, that was one of the things that, uh, Convinced, uh, Jane Goodall to reduce the intensity of banana feeding. Eventually, we stopped it entirely, although that took some time. Um. So it's, it's clear that banana feeding had an impact on, on their behavior and then in the In the mid 1970s. Researchers at Gombe started seeing inter-community killings, and the, the main study community. Split into two, which Jane called the Casaquila community to the north and the Kahama community to the south, and Males from the Casaquila community attacked and killed a number of individuals, uh, mainly males, but also one female from the Cahama community, eventually leading to the extinction of the Cahama community. And these observations surprised. Pretty much everyone in the chimp research community. And Led to both lots of interest in what chimpanzees might tell us about the origin of this warlike behavior and how it relates to warfare in humans and also led some critics to say, well, look, it's because Jane was feeding them bananas, um, that that this caused their behavior to change and It is the case that the banana feeding increased rates of aggression, and it's also possible that the banana feeding had other impacts because as it concentrated the casaquila community into the center of their range. They were able to um Get lots of food without doing the hard work of traveling across more of their range and defending that and. So other chimpanzees, probably what we, what we speculate, and this is um And um Something that we've, we've published on, but, uh, we don't have much data on this. It's speculative that the, the other chimp communities kind of moved in to the the vacuum that Casaquila had left by not patrolling those areas. And then when the banana feeding decreased, now you have increased competition for uh land within the park. And at the same time, talking about human influences. This coincided with an increase in rates of deforestation outside the park, so chimpanzees that had been living in forests outside the park now had less forest to live in, and so they may have contracted their ranges to within the boundaries of the park today. It's, it's impossible to know. Now, what exactly went into all of these things, but, um, you know, because we, we don't have data on these unhabituated chimpanzees and we don't really know what their movements were, were like. But the The idea, uh. Has You know Persisted that somehow Gombe is unnatural because of the banana feeding, because of these, these other impacts, and therefore, well, if, if there's violence at Gombe, it's because of something that, that humans have, have done. And, and some critics of chimpanzee violent research have really run with us. Brian Ferguson recently published a whole book on this topic in which he argues that pretty much all chimpanzee violence somehow relates to human impacts, and I think that's overstating the case quite a bit because If, well, it, it raises multiple questions. For one, We see chimpanzee violence at lots of study sites, not just at Gombe, and it's not just at the sites that are most impacted by human activities, uh, the, uh, The chimpanzee community with probably more documented killings than any other is the Ngogo community at the heart of Kibali National Park, which is very far from the forest edge and, and probably is, is one of the less impacted communities uh in terms of human impacts. Although Brian Ferguson comes up with a story to explain somehow how Ngogo chimpanzees are really heavily impacted by humans, uh, But I, I think I it's You know, when, when you can Like even within Kibale National Park, the Kanuwara chimpanzees that I studied for my dissertation research are much more heavily impacted by humans than the Ngogo chimpanzees at the center of the park, and yet their, their rate of killing is, is much lower. So I don't think that's a convincing argument. And then there's also The fact that many other primate species have been observed under a broad range of human impacts, and they don't kill each other, uh, or at least not nearly at the, the high rate that chimpanzees do. Uh, BONOBOS, very few killings have been observed for bonobos, and they're, uh, very similar to chimpanzees and just as closely related to us as chimpanzees are, uh, and they live in places that are impacted to varying degrees by humans. So why? Or the human impacts make chimpanzees kill but not bonobos.

32:23 Ricardo Lopes: Right, and I, I mean, I actually want to ask you more about that and it's interesting that you also touched on the point regarding warfare because of course we know that one of the sources, it's not the only source of course, but one of the sources. OF evidence that people who argue, uh, scientists, anthropologists, so and so on, who argue that uh warfare is uh an evolved adaptation in humans, uh, uh, resort to is actually chimpanzee violence. So, uh, I mean, what, what, what can we tell, uh, from studying chimpanzee violence actually about Warfare in humans, I mean, can we tell anything about whether it is really, uh, um, more of a, let's say, a sociocultural invention or an evolved adaptation? I mean, uh, to what extent is, or, or to what extent can, can we derive conclusions or information about human warfare from studying chimp violence?

33:38 Michael Wilson: Yeah, so, this is a question that has really been at, at the heart of, of my research for a long time now. And I think there are Several different ways of thinking about or of approaching the question and For some people, The, or one way of looking at it is that if Chimpanzees and humans both share some trait. That suggests that that trait was present in our last common ancestor, and maybe that trait has been around for a long time. And so it's very intriguing from that perspective that chimpanzees and humans make and use tools, cooperate to hunt prey, large mammalian prey. Uh, DEFEND group territories, live in fusion fusion societies, that it's in both species, it's the males that do most of the hunting and the killing and the territory defense, and So this Suggests the possibility that these are all part of some set of traits that we share from our last common ancestor and that have been present since. That last common ancestor lived, maybe some 7 to 9 million years ago. The Uh, the existence of bonobos and the ways that they differ from both chimpanzees and humans. Challenges that that idea because bonobos don't have, you know, they, they don't do much with making and using tools. They, they hunt monkeys, but not really cooperatively in, in groups like chimpanzees do. Uh, THEY don't really defend territory boundaries. Uh, THEY don't engage in. Cooperative killing of other bonobos, uh, to a large degree. There, there have been some interesting, uh, cases that suggest that they, they can do that, but they, uh They don't seem to engage in those activities anywhere near the frequency that chimpanzees and humans do. Uh, SO that suggests that if these traits were present in the last common ancestor, uh. Then Bonobos must have lost those traits for some reason, or These traits evolved independently in humans and chimpanzees separately for, for similar, but perhaps for similar reasons. So people argue a lot about the. You know, the, the evolutionary history of these traits and, and what the relevance is. And I think implicit in that for for many people is this idea that The Underlying psychology of, of warfare, uh, must be something inflexible, hard to change over evolutionary time, and that if chimpanzees and humans both engage in this, it's, you know, kind of part of our, this deep nature that we can't easily change and we're, we're kind of stuck with it. And, uh, People who are very critical of the, the chimp violence hypothesis like Brian Ferguson and Doug Fry and others. I think what they're reacting, one of the things that they are concerned about is that this view of Warfare and violence coming from some Ancient deep part of our psychology means that it's an intractable problem and we uh We can't do anything to stop war and that people will use this argument to justify ongoing warfare and preparation for war.

37:47 Ricardo Lopes: Yes, that would be a form of biological determinism or something like that,

37:52 Michael Wilson: right? Yeah, and, and it's also, you know, Kind of an argument from phylogenetic inertia that these things with an old evolutionary history and old phylogeny are just going to go forward regardless of whether they're adaptive in current circumstances or not. I think the real value of studying ape violence is is really more subtle than that, and the arguments that Richard Wrangham and others have made about the relevance of chimpanzees to understanding the origins of human warfare don't depend on. PHYLOGENETIC continuity. They don't depend on these traits being um present. In some unbroken history over time, uh, that's something that, that Wrangham has often made the argument that there, there is that deep shared history, but the You know, the, the papers that he's published don't insist on that point as being the reason why these are relevant. Uh, FOR, for example, going back to, uh, a paper with Joe Manson, Manson and Ringham in 1991, uh, that paper argues that the reason that chimpanzees and humans. Kill members of rival communities. It really derives, it's, if, if you think about why animals kill in general, why does violence occur. From a behavioral ecology point of view. The, the assumption is that animals in general. Perform actions based on some kind of cost-benefit analysis. Whether they do that in their head or whether that's something that natural selection has figured out over evolutionary time and Designed their bodies in such a way that they, they respond in adaptive ways to the circumstances that they find themselves in. Some sort of assessment occurs, and the behavior should evolve if, on average, it produces net benefits. And so that suggests that for killing to occur, either the, the benefits should be very high or the costs should be low, relative to the, the benefits that you gain. And the benefits that chimpanzees gain from, from killing members of rival communities don't seem to be unusually high compared to the benefits that other primates gain from intergroup aggression. Uh, THEY compete over territory, but lots of primates compete over territory and, and don't kill each other. But What does seem to be different is that the costs of killing. Can be very low in the conditions, the circumstances in which chimpanzees usually kill members of rival communities, which is in these gang attacks on lone, isolated individuals, and this is something that happens because of the ecology of chimpanzees where the food supplies. Vary a lot during the course of the year. Sometimes food is abundant and they can travel together in cohesive groups. Other times, food is scarce, so they scatter. And the scarcity of food is not uniform across a habitat like a, a forest. In some places, there might be enough food for chimps to stay together in larger parties. In other places, they're forced to scatter. So the scattered chimps are then vulnerable to Encountering a large group of males from the neighbors who are able to stay together for whatever reason. If they find an isolated individual, they can gang up on and attack and kill that individual with impunity. And uh And by, by killing their opponent, they reduce the coalition strength of their neighbors, and that weakens them and so that in future territorial encounters, they, they won't be able to push back and, and so the, the killers can expand their range. And This is also what we see in in humans is that In subsistence level human societies like hunter-gatherers. People don't like to engage in costly fights. They much prefer killing in ambushes, sneak attacks, raids, uh, situations where they have overwhelming numerical superiority and very little risk of being injured in return. And So what this suggests is that the propensity towards killing members of of rival groups that humans and chimpanzees share. IS something that it, it may have a common evolutionary history or it may have evolved convergently in humans and chimpanzees. We, we don't know the answer to that, but the underlying Ecology Appears to be similar and Uh, and I think that's really where, where the power is more than in looking at this as some kind of phylogenetic inertia argument. Instead, it's, it's looking at this is an adaptive trait that. CAN change. And respond to local conditions. And it is not. Determined in a simple way by an inflexible biology, but instead responds. Adaptively to local ecological conditions and and social environments. And, and I think. It it's, it's useful to think about what What would be the case if if human societies Uh, You know, if, if humans Chad Only cultural. Control over propensity to engage in warfare, you know, for example, what, what if warfare is completely a cultural invention like Margaret Mead argues, and, and this is what people like Douglas Fry have argued that that warfare is something that emerged. As a cultural trait. Relatively recently in human prehistory, with the advent of complex hunter-gatherer societies that are more sedentary and then uh intensified with the origin of the domestication of crops and livestock. And What, uh, Douglas Fry and and A number of archaeologists have argued is that, you know, war really only appears. Around that time, in the last 10,000 years or so, um, and is, is a response to these changing cultural conditions. And So Let's, let's suppose that that's the case. Let's suppose that that warfare is entirely cultural and, and for the sake of the argument that that warfare didn't occur in humans before the origin of complex hunter-gatherers. Well, What does, would that change our understanding of Of warfare, would that change our understanding of of what Makes people behave in warlike ways. And I'm not really sure that it would because the We are, we know from observing human societies that We, we don't engage in warfare in a simple reflexive way that You know, there's a lot of variation in rates of war and peace around the world, and you know, the experience of You know, Parts of the world like Europe that, uh, you know, went through enormous Cataclysms of world wars in the 20th century, Europeans after the war developed institutions and frameworks that succeeded in preventing such wars for, you know, here we are 80 years after the end of World War II, and, and Apart from You know, Eastern Europe, in Central Europe, Western Europe. There's been international peace. So we know this, we, we don't have to, you know, Imagine things about our biology, you know, we know that there are conditions that can lead to more peaceful international relations. So then what are the conditions that promote that? What are the conditions that lead to, to warfare? Um, I think those are interesting questions and they don't depend on. Having an assumption about warfare being either biological or, or cultural.

47:33 Ricardo Lopes: Mhm. No, yeah, I, I would definitely, uh, like to, perhaps we would have to schedule a second interview to talk just about this topic because, uh, I've been following the discussion for a few years. I've had Doctor Rangam on the show, Dr. Glowacki on the show who fall a little bit more on the side of it being, uh, more, or adding some biological underpinnings to. And I've also had Doctor Douglas Fry and uh Brian Ferguson who fall more on the side of the cultural invention sort of approach to warfare. So I would definitely like to talk with you more about that, but we have just 12 more minutes. So if you don't mind, I would like to move on to another topic here. So, you mentioned bonobos and chimpanzees. I would like to ask you. Of course we are equally closely related to phylogenetically speaking to chimpanzees and bonobos. In terms of the rates of violence, I mean how much do they differ because for a long time I remember hearing that bonobos were much less violent than chimpanzees. There were even Sort of like a hippie ape or something like that. It was just about the sex and peace and so on, but in more recent years, I've been hearing people saying that perhaps some of that was overblown or overhyped, and actually the rates of violence are a little bit higher than people thought. So I mean, what do we know about that actually?

49:16 Michael Wilson: Yeah, so, you know, bonobos are super interesting, and there's a lot that I, I think as As a field, we still don't know or understand about bonobos. There's a lot that I don't understand about bonobos and am uh eager to, to learn, uh. And I think we're very lucky to have them because they, if, if we only had chimpanzees, we, we could tell a simple story about human evolution that, that might be wrong, but having, having bonobos and taking them seriously forces us to think a little harder about these things. Uh, BUT I think it's, it's really important to To, to do comparative studies in a way that's careful and quantitative, where we can really be confident in our results. And There have been a lot of claims, you know, for example, the claim that bonobos are such a sexy ape. Well, OK. Um, What do you mean by sexy? If, if you focus on the rate of copulation between males and females, Che Hashimoto did careful comparative work of, uh, bonobos and chimpanzees using the same methods and found that the rate of copulation between males and females is higher in chimpanzees than in bonobos. Oh,

50:46 Ricardo Lopes: OK, so that's interesting,

50:49 Michael Wilson: yeah, um. And, you know, bonobos have more same-sex interactions uh than chimpanzees do. Probably. I'm not, I'm not sure that that has been really looked at in a systematic way. Um, MAYBE it hasn't. I'm, I'm just ignorant of those studies. Uh, BUT to make claims about that, ideally, what you would have is, is a careful systematic study. And In, in our big collaborative paper from 2014 where we looked at rates of violence across Chimpanzee and bonobo study sites, we found lots of cases of killings by chimpanzees across Africa, uh, regardless of our measures of human disturbance. That didn't seem to explain rates of killing, but we didn't have any definite cases of killing by bonobos, uh, even though there were many hours of observation of bonobos, uh, already by that time. So if, if by violence, You mean Uh, Well, if you, if you define that. Or focus just on lethal violence, on killing. Bonobos Do seem to kill much less often than chimpanzees. There are some, some cases now of, of, of lethal aggression in, in bonobos, but it's, it's rare. And So that, but there's a difference between violence and aggression. So aggression. You know, more, more broadly includes things like threats and chases and, and displays, um, but also, uh, You know, physical, you know, coming to blows in ways that are not necessarily fatal. And

52:45 Ricardo Lopes: so, so, uh uh let me ask you then, in terms of uh aggression and more specifically male aggression, er, do we know if there are differences in expression of male aggression between wild bonobos and wild chimpanzees?

53:04 Michael Wilson: So this is the question that my graduate student Mode Muino sought to answer, and she worked with uh Martin Serbeck, uh, using data from Kokollopori, the field site, the Bonobo field site that, that Serbeck runs, and doing a direct, careful comparison of using the same methods, uh. Aggression from focal follows of individual males, uh, bonobos and chimpanzees at Gombe. And we thought this was just going to confirm in a simple way what we already knew that bonobos are so peaceful and What Mode found was For one, rates of aggression from females towards males were much higher in bonobos than chimpanzees. Which isn't necessarily surprising given that female bonobos are often higher ranking than males, but it, you know, it's, it, it kind of goes against this idea that they're just peaceful all the time. You know, the females are aggressive towards males at a fairly high rate, OK? And then there's male aggression towards females. This was higher in chimpanzees than in bonobos, but there was a lot of overlap, much more overlap than we expected. There were some male bonobos that were more aggressive towards females than some male chimpanzees were, and males that were more aggressive towards females had higher mating success. So, so that's, that was interesting, but the thing that really surprised us was that the rates of aggression by males towards other males were much higher in bonobos than chimpanzees. Mm, OK. So, You know, that, uh, that was very surprising. Mhm. And uh there, there's just recently been a study, and I, I haven't uh looked at it yet. It just came out looking at comparing rates of aggression in captive bonobos and chimpanzees, and I, I think they found that there was, there was no measurable difference between them. Um, AND, you know, of course, these things. They vary. There are different reasons for being aggressive in captivity versus the wild, but, you know, there, there's something, there's some interesting things going on with, with bonobos that I don't think we, we really understand.

55:33 Ricardo Lopes: OK. So, uh, I mean, since we have just 5 more minutes, let me just ask you then. I mean, at this point in time, uh, I mean, what can we say really about uh Rates of violence, I mean, and if there are differences, I, I mean, of course, you've already mentioned some differences there when it comes to female to male violence, male to female, male to male violence, but, uh, I mean, when, when it comes to rates of violence between bonobos and chimpanzees, what can we really say at this point?

56:07 Michael Wilson: Well, it relates to something else that I, uh, I was really struck by, uh, a study that, that Martin Serbeck published, uh, a number of years ago reporting that bonobos had higher rates of reproductive inequality among males than chimpanzees, meaning that the, the males that were successful at Fathering babies, uh. We, you know, the, the, the alpha male had a higher share of, of those paternities than was the case in chimpanzees. And when that paper came out, I thought, oh, this doesn't make any sense. I, you know, this has got to be wrong, because bonobos are egalitarian and they're peaceful and the males don't have high rates of aggression towards each other and, and so this is, uh, this can't be right, and I, um. Ended up, uh, In contact with, uh, with Martin over email, and we, we agreed to, to work together to try to find out, uh, to, you know, to do some comparative studies of bonobos and, and chimps, and this is what led to, to, to Mode's research looking at aggression. Mode also, uh, Worked with, uh, with Martin's team, uh, to look at the reproductive inequality data and, and generally, uh, found that the initial study that Martin published was right. It confirmed that, that the, um, there, there's quite a bit of overlap in it, you know, there's variation depending on the community size and so on. But the, um, the overall pattern seemed to be in favor of bonobos having more inequality. Of reproduction among males than than chimps, and I think this is related to the, the rates of aggression, and I think it's also related to rates of violence between groups because in bonobos, for one. Their, their grouping patterns are more cohesive. They, they tend to be in larger parties. More of the community is, is together during the day, and uh males compete in a very individualistic way with one another for access to females that are willing to mate. And uh so when females are fertile males compete to have access to those and mate with them. And in bonobos, it's very much individualistic, so males don't have much incentive to cooperate, whereas in chimpanzees, Male Reproductive success is Um More evenly distributed and it also depends on on defending a group territory, so males have an incentive to cooperate with other males to defend that group territory and The payoff for low ranking males seems to be that they, they have a greater chance of siring offspring, that they, they're not just shut out of reproductive opportunities, and it's hard to know, you know, the chicken and the egg question of, you know, what's, what's the driving factor here? Uh, BUT I, I think these things are, are intimately related to each other. Mhm

59:34 Ricardo Lopes: Great, so, um, just before we go, would you like to tell people where they can find your work on the internet?

59:42 Michael Wilson: Yes, so I have a, a website, um, a, a blog that's, uh, I, I probably haven't been super active with in, in recent years, but it does exist and, and a lot of my papers are, are up there. It's called Monkey Business. Um, AND I also, um, have, uh, you know, a Google Scholar page and, uh, a, a website at the, um, at the University of Minnesota. Uh. And um Yeah.

1:00:14 Ricardo Lopes: OK, great. So I will be leaving links to that in the description of the interview, and Dr. Wilson, thank you so much for taking the time to come on the show. It's been a fascinating conversation.

1:00:26 Michael Wilson: Great. Well, thank you so much, Ricardo. It's, it's been a pleasure, and I, if you want to talk more about warfare, I'd be happy to. Yeah.

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