Aaron Sandel (2:05)

Now my focus has gone from understanding friendship to sort of how do, how do friendships fall apart? How do communities fall apart?

Emily Kwong (2:12)

Oh, he sounds so sad.

Nate Rott (2:13)

I know.

Emily Kwong (2:14)

But it's also kind of fascinating to me, just as a scientist, sometimes you got to go where the research leads.

Nate Rott (2:19)

Totally. I mean, Aaron says he'll probably spend the rest of his career trying to understand this ongoing event because it is super rare, like scientists know that some other animals engage in coordinated attacks against each other, like what we might call war. Right. That includes ants and lions and wolves. But these kinds of permanent fissions that result in violence, like a group of animals breaking apart forever and fighting each other is super rare. With chimpanzees. They think this only happens, like once every 500 years.

Emily Kwong (2:50)

And the researchers have been watching this whole thing happen.

Nate Rott (2:53)

Yeah, from the very start, before it began, and even as it's ongoing right

Emily Kwong (2:57)

now today on the show, a civil war amongst one of humanity's close, closest

Nate Rott (3:02)

living relatives and what it can teach us about how communities fall apart.

Emily Kwong (3:06)

I'm Emily Kwong.

Nate Rott (3:07)

And I'm Nate Rott. And you're listening to Short Wave, the science podcast from npr.

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Emily Kwong (4:30)

where is this civil war happening?

Nate Rott (4:33)

Yeah, it's happening on the western border of Uganda in this densely forested national park. There are multiple communities of wild chimpanzees that are studied there, but the ones we're going to be focused on are part of what's called the Ngogo Group. Researchers have been observing this group for more than 30, 30 years.

Emily Kwong (4:48)

That is a long time to be studying the same group of chimps.

Nate Rott (4:51)

It is. And that's part of what makes this so interesting, because the primatologists who were working there had decades of observations of these chimpanzees. So they knew who was hanging out with who, who mated with who. They knew the chimp social bonds. AARON Sandel, the primatologist we heard from earlier started working there in 2012. He's now at the University of Texas at Austin.

Aaron Sandel (5:11)

They were so used to people by then that most of them just ignored me.

Emily Kwong (5:17)

A tightly knit group. How many chimpanzees are in this NGO group?

Nate Rott (5:22)

Yeah, so when researchers started tracking them in the mid-90s, there were about 100, which is a lot. Aaron says it like, the average group of chimpanzees is about 50. But by the time Aaron started working there, There were nearly 200 individuals in this group. Yeah, so a lot. Now, he does say there were, like, substructures in the community, almost like neighborhoods of chimps that spent more time together.

Aaron Sandel (5:43)

But still there was no sign that the group would split. Until 2014. We started seeing the first signs of these neighborhoods being really distinct. And then it was really in 2015 when the social network changed in a dramatic way.

Nate Rott (5:58)

Aaron says he can remember the specific day. June 24, 2015. He was with a group of chimps from the western cluster, the western neighborhood, when they heard other chimpanzees nearby, presumably from the central neighborhood. So these were all chimps that knew each other, but the western chimps did not act like it at all.

Aaron Sandel (6:17)

They got quiet. All of a sudden, they started touching each other in this reassurance, like they were really nervous. And to me, this seemed like they were acting as if they were hearing outsider chimps. And then when the chimps from the central neighborhood got closer, rather than reuniting in this typical chimpanzee fashion where they're constantly mixing and mingling, and instead of doing that, the western chimpanzees ran and the central chimpanzees chased them, and nothing really like that had ever been observed before. And then they avoided each other for six weeks.

Emily Kwong (6:49)

It's like a bad, bad rift. So do they know why this happened?

Nate Rott (6:54)

No, they don't. And it wasn't like this was it? Right. Like the groups had split. Aaron says after those six weeks, they did start interacting again. But over the next few years, it became increasingly clear that the groups were getting more polarized. They spent less time together. The friendships that existed, if we want to call them that, started fading away.

Aaron Sandel (7:13)

And by 2018, they were completely separate groups, no longer peacefully interacting. And that was when we saw the beginning of these lethal attacks.

Nate Rott (7:25)

Yeah, this is from a voice memo that Aaron took of an attack in 2021.

Aaron Sandel (7:28)

Alfred said Westerners attacked Bartley and Miles. Miles and Jackson ran.

Emily Kwong (7:38)

That's kind of horrifying.

Nate Rott (7:39)

Yeah, it is. It like, the first time he sent that to me, I was like, whoa. When I was talking to Aaron, you know, I asked him, well, let's just listen to it. As a scientist, as a primatologist, it's got to be remarkable, right, to observe this happening in real time. But is it also kind of sad?

Aaron Sandel (7:59)

Definitely. I saw the first two lethal attacks. And, like, the first lethal attack was a chimpanzee that I'd really watched grow up. I even remember the night before he was killed. I saw him and he was sort of running around and grooming with this adolescent female. And I remember even coming back at the end of the day that night to the campsite and sharing with the other researchers. Oh, Errol, this chimpanzee, he's really acting like an adult. And then the next morning, I saw them kill him.

Emily Kwong (8:29)

Oh, my gosh, that's so sad.

Nate Rott (8:30)

Yeah. I mean, Aaron says he feels, in some respects, kind of like a war correspondent. You know, he's just trying to observe and document everything that's happening as this has spread from males attacking males to even males attacking infants.

Aaron Sandel (8:43)

You know, I'm trying to understand this really rare behavior, and I'm thinking about what's causing this. Like, what is it? Why is this happening? What is the perspective from the chimpanzees themselves? Because we're seeing this sort of shift of relationships that you don't get when you just watch animals generally.

Emily Kwong (9:04)

Yeah, let's talk about the science of what's going on. I mean, the only other example of these kinds of wars, lethal attacks, it sounds like, is what Jane Goodall saw during her work in Tanzania, right?

Nate Rott (9:15)

Yeah, that is, right. And. But that case is a bit complicated because back then, the researchers were giving the chimpanzees bananas to sort of speed up the habituation between humans and chimps. So some researchers have hypothesized that that might have played a role in what happened in Tanzania.

Emily Kwong (9:32)

The banana wars.

Nate Rott (9:33)

The banana wars, Yeah. I talked to Ann Pusey, a retired primatologist who worked with Jane Goodall in Tanzania during that conflict in Gambe national park, and asked her what she thought of this new study.

Commercial Announcer (9:42)

Here we have a case where they never fed them, they never interfered in any way in this community of chimps, and yet they've seen this fission and this killing of one set of males by the other.

Emily Kwong (9:57)

When she looks at the observations happening in Uganda right now, what does she make of it?

Nate Rott (10:03)

She says she was struck by how many similarities there were. You know, for example, in Gambe, where She worked. There was some natural deaths of adult males before the conflict started. And the same thing happened in the Ngogo group. So maybe that frayed the social fabric enough to allow these two groups to, like, start seeing each other as enemies.

Emily Kwong (10:22)

Elders were gone, and it created new social relationships.

Nate Rott (10:26)

Yeah, like maybe some of the chimpanzees that had a close relationship with others passed away. And so all of a sudden, those kind of, like, connecting threads in the community were gone. But it also could have been about territory or resources. You know, in both cases, the researchers still aren't really sure what caused this, but what they do know is that the Gambi conflict didn't. Until one group essentially killed off the other. That has not happened with the Ngogo group. The fighting is still ongoing, and the researchers are just trying their best to follow along and see what happens.

Emily Kwong (11:00)

And I suppose the researchers can't intervene. That's the nature of this work, you know, because chimpanzees are one of our closest living relatives. Does this help us understand how war between humans happens? Am I anthropomorphizing too much?

Aaron Sandel (11:16)

No.

Nate Rott (11:16)

I mean, I think that's like. I think that's a really natural question, and it's something everybody I talked to brought up. I asked Ann for her thoughts on it, and to be fair, she kind of hedged.

Commercial Announcer (11:27)

I mean, it's rather uncomfortably familiar, seeing how these relationships can break down and then lead to antagonisms between groups which weren't there before.

Nate Rott (11:40)

Uncomfortably familiar feels like an appropriate way, Right?

Commercial Announcer (11:43)

Yeah.

Nate Rott (11:43)

You know, but Ann strongly suggested I talk to a primatologist named Michael Wilson at the University of Minnesota who studied conflict in primates, including us. And so I reached out to him.

Michael Wilson (11:54)

There are several different ways of viewing it, and one is thinking, well, they're our closest living relatives, so if they do something and we do something, then maybe our last common ancestor did it, and we're doing it because of our shared evolutionary history.

Nate Rott (12:10)

But here's the problem. Our other closest living relative kind of throws a wrench in that whole theory, because bonobos are just as similarly related to humans as chimpanzees are, and they do not kill each other like this.

Emily Kwong (12:22)

But I thought bonobos were kind of mean. You're saying they don't lethally attack each other, though?

Nate Rott (12:26)

Oh, so they'll show aggression towards each other. There was a study that was done a couple of years ago that show that says that male bonobos are actually more likely to push or bite or hit each other than chimpanzee males, but researchers have never seen one bonobo kill another.

Emily Kwong (12:40)

Wow.

Nate Rott (12:41)

So in that sense, Michael says it's kind of hard to argue that we have that shared genetic predisposition for violently turning on each other. But he still thinks that there's a lot that we can. Can learn from observations like this.

Michael Wilson (12:54)

I think it's clear from this study and from other studies of chimps and other animals that you can get these kinds of conflict without a lot of the things that we think about being the sources of conflict in humans. You know, lions don't have religion and political parties or ideology, and neither do wolves and. Or ants, for that matter.

Emily Kwong (13:18)

And neither do chimpanzees. And yet, as you said earlier, all of these animals engage in this type of intra group fighting.

Nate Rott (13:24)

Yeah. And this is one of the points that Aaron and his co authors really hit on in their new study of this most recent chimpanzee war that was published in the journal Science, that even without all of those things, without religion, without ethnicity, without politics, this kind of conflict can emerge. So maybe its cause is as simple as the breakdown of smaller relationships between individuals in a community.

Emily Kwong (13:47)

Yeah. The rupture of social bonds which, you know, we see all over the world. I don't know if that makes me feel better or worse about it, but it's the reality.

Nate Rott (13:56)

Yeah, that's fair. For what it's worth, Emily, Aaron says it actually makes him feel a little more optimistic because if that is the

Aaron Sandel (14:04)

case, that means that interventions for peace actually rest within our own lives and our own relationships in everyday life. Like with the chimps, it's like, you act like a stranger, you become a stranger. I want to avoid that in my own life.

Nate Rott (14:19)

Simple lesson from chimpanzees.

Emily Kwong (14:22)

Neyrot, thank you for this reporting.

Nate Rott (14:24)

Yeah, Emily, thank you. And I should say, do not be a stranger, Right? Let's take something from this.

Emily Kwong (14:28)

I never could. If you liked this episode, please share it with a friend because it helps our show grow. And while you're at it, download the NPR app. It's totally free and a personalized way to bring you the very best of the public radio cosmoverse. Your favorite podcasts, like us and your local station and the world's biggest stories all in one place. Download the NPR app in your App store today. This episode was produced by Rachel Carlson and edited by Rebecca Ramirez. It was fact checked by Tyler Jones. The audio engineer was Jimmy Keeley. I'm Emily Kwong. Thanks for listening to Short Wave from npr.

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