The world's largest known group of wild chimpanzees has split and been locked in a vicious civil war for the last eight years, according to researchers.
It is not clear exactly why the once close-knit community of Ngogo chimpanzees at Uganda's Kibale National Park are at loggerheads, but since 2018 the scientists have recorded 24 killings, including 17 infants.
These were chimps that would hold hands, lead author Aaron Sandel said. Now they're trying to kill each other. The study, published in the journal Science, says the intensity and duration of the violence may inform how early human conflict developed.
Sandel, an anthropologist from the University of Texas in the US, and co-director of the Ngogo Chimpanzee Project, says chimpanzees are very territorial, and have hostile interactions with those from other groups. [It's] like a fear of strangers, he told the Science podcast.
But over several decades, Sandel said the nearly 200 Ngogo chimpanzees had lived in harmony. They were divided into two sets - known to researchers as Western and Central - but they had existed overall as a cohesive group. Sandel noted that he first noticed them polarising in June 2015, when the Western chimpanzees ran away and were chased by the Central group.
Following the emergence of the two distinct groups in 2018, members of the Western group started attacking the Central chimpanzees. In 24 targeted attacks since the split, at least seven adult males and 17 infants from the Central chimps have been killed, though the researchers believe the actual number of deaths is higher.
The researchers highlight several factors contributing to the violence, with three likely catalysts identified:
- The deaths of five adult males and one adult female in 2014, possibly disrupting social networks.
- A change in the alpha male coinciding with the first period of separation between the groups in 2015.
- A respiratory epidemic in 2017 that killed 25 chimps, leading to a loss of critical social connections.
Sandel and his colleagues emphasized that their findings encourage a reevaluation of the understanding of human conflict. If chimpanzees - one of the species closest to humans genetically - could do so without human constructs of religion, ethnicity and political beliefs, then relational dynamics may play a larger causal role in human conflict than often assumed, they concluded.
James Brooks, a researcher at the German Primate Center, remarked that this research serves as a reminder of the dangers of group divisions in human societies, urging a reflection on group-based behavior in both war and peace.
