Amazing stuff! Group division and territorial disputes between new subgroups?
Oddly, the research article based on its abstract does not discuss the possibility of territorial disputes between the two subgroups of Chimpanzees.
"Chimpanzee civil war sheds light on the biology of warfare
Chimpanzees, like humans, routinely fight, and sometimes even kill each other. But unlike us, their communities rarely split into two groups and launch a civil war. By observing a chimp community in Uganda for 30 years, the researchers behind a new Science study reveal how friends turned into foes without shortages of food or cultural rifts dividing them.
More than 200 chimps in a densely forested Kibale region called Ngogo lived peacefully between 1995, when researchers first started tracking their movements and behaviors, and 2015. Although they separated into so-called Central and Western groups, the chimps frequently intermingled, with many cross-group matings.
But following the rapid death of five adult males who apparently served as peacekeepers, the Western group turned against the Central one. Over 6 years, males in the Western group killed seven adult males and 17 infants in the Central group. Even though they were larger in number, the Central group males curiously never ganged up to kill any of the Western chimps.
The civil war—only the second one ever documented in wild chimps—both clarifies motivations for human warfare and spotlights how we differ from one of our closest relatives. “You do not need ideology to generate hostilities,” ... “The motivations for warfare are much more concerned with our biology than people would have believed a long time ago.” ...
“A hostile split among wild chimpanzees is a reminder of the danger that group divisions can present to human societies.” ...
that chimps aren’t as cooperative and prosocial as humans. “Instead of attacking our neighbors, we go out of [our] way to help them, even if they are complete strangers,” ..."
From the editor's summary and abstract:
"Editor’s summary
Group conflict among nonhuman animals from mongooses to monkeys is well known. However, lethal conflict among groups of animals that were once socially affiliated has not previously been observed outside of humans, in whom cultural ideologies can drive divisions among individuals within the same group. Sandel et al. now describe the gradual dissipation of a group of Ngogo chimpanzees over many years, ending with two socially isolated groups, one of which conducted multiple lethal raids upon the other, leading to the death of both adults and infants ... The unrelated deaths of key interconnected individuals may have contributed to the eventually violent split. ...
Abstract
Territorial conflicts in animals can inform aspects of human warfare, but civil war, with its shifting group identities, has not been previously observed. We report a rare, permanent fission in the largest-known group of wild chimpanzees (Pan troglodytes).
Using 30 years of behavioral observations and network analyses, we describe a transition from cohesion to polarization in 2015 and the emergence of two distinct groups by 2018.
Over the next 7 years, members of one group made 24 attacks, killing at least seven mature males and 17 infants in the other group. These findings indicate that group identities can shift and escalate into lethal hostility in one of our closest living relatives in the absence of the cultural markers often thought necessary for human warfare."
Civil war among wild chimpanzees (Perspective, open access) "A violent split in a group of chimpanzees highlights the evolutionary roots of war and peace"
Lethal conflict after group fission in wild chimpanzees (open access)
Fig. 1. Network and spatial separation precede a shift from association to violence.
Fig. 4. Territorial patrols between Western and Central chimpanzees.
In 2016, chimpanzees that would become members of the Western group (orange) began engaging in territorial patrols toward chimpanzees that would become members of the Central group (blue). In 2017, we observed the first patrols by Central chimpanzees toward Western chimpanzees. We summed the number of these within-Ngogo patrols quarterly from 2016 to 2024.
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