A group of chimpanzees in Uganda waged a “civil war” for almost 10 years. Scientists have figured out how it came to this

Scientists studying Ngogoʼs chimpanzees in Kibale National Park in Uganda may have discovered the first case of "civil war" among a group of primates.

This is reported by The Guardian, citing a study by scientists published in the journal Science.

Primatologist Aaron Sandel noticed an interesting phenomenon within a group of chimpanzees in June 2015: When members of one group approached through the forest, a smaller group became nervous and behaved as if strangers were approaching. This was the first sign of a possible “civil war” among these primates.

According to researchers, chimpanzees have long been known for their aggression against strangers, but such behavior within the same group is something new.

“Cases where neighbors kill neighbors are even more disturbing and, in a way, more reflective of human nature,” Sandel said.

The researchers note that the chimpanzees were socially cohesive from at least 1995 to 2015, but by 2018, two separate groups had formed — western and central chimpanzees. Over the next seven years, members of the western group attacked the central group 24 times. At least seven adults and 17 young primates died during the clashes.

Scientists believe that similar internal conflicts have occurred before, for example, in the 1970s in Tanzania. At that time, researcher Jane Goodall observed a split in a group of chimpanzees.

However, at that time, science still knew little about the behavior of these primates, so researchers could not objectively assess how rare and unusual violence between "their own" was.

Primatologists believe that in Ngogo the chimpanzee, it all started with a power struggle. When the usual hierarchy was shaken, it provoked a surge of cruelty and, eventually, a split in the group.

The key moment was a morning in 2015, when researcher Sandel noticed a symbolic event: a leader made a strange sound and submitted to another male. The split was also facilitated by the deaths of several key leaders. Then, in 2017, an outbreak of disease — it may have accelerated the process.

Human factors can also accelerate the split in the group: deforestation, climate change, and disease.

Professor Sylvain Lemoine of the University of Cambridge notes that this case is the first detailed description of a "civil war" within a single species, which proves the fragility of social structures. Even without shared cultural symbols, group unity is maintained by personal ties and interactions that "cement" the community.

However, such cohesion often depends on a few key individuals, and if these ties are broken, stability disappears and conflict arises.

• Chimpanzees share more than 90% of their DNA with humans, so observing primates is quite popular among scientists: in April 2025, scientists from the British University of Exeter showed for the first time how chimpanzees share “alcohol”. The animals ate the fruits of the African breadfruit tree, which had time to ferment. This suggests that the tradition of people sharing alcohol — for example, during feasts or holidays — may have evolutionary roots. In September of the same year, studies showed that chimpanzees that eat fermented fruits in their native habitats consume the equivalent of almost a liter of beer daily.

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