Researchers from The University of Texas at Austin and other institutions announced on Apr. 9 that the largest known group of wild chimpanzees has permanently divided into two separate communities, resulting in years of violent conflict. The findings, published in Science, are based on three decades of field observations of the Ngogo chimpanzees in Kibale National Park, Uganda—a population featured in the Netflix documentary series “Chimp Empire.”
The study is significant because it provides the first clearly documented case of permanent fission among wild chimpanzees without human intervention. Researchers say this may help explain causes of conflict not only among primates but also within human societies.
For over twenty years, the Ngogo community was cohesive with individuals moving between flexible subgroups and maintaining social ties across the whole community. In 2015, researchers observed increasing polarization between two clusters—the Western and Central groups—following changes in male dominance hierarchies and after several adult males who may have acted as social bridges died. By 2018, a complete split had occurred: one group contained 83 chimps while the other had 107.
After this division, a series of lethal attacks by members of the Western group against those from the Central group was recorded. Between 2018 and 2024, there were seven documented attacks on adult males and seventeen on infants. “What’s especially striking is that the chimpanzees are killing former group members,” said Aaron Sandel, associate professor at UT Austin and lead author. “The new group identities are overriding cooperative relationships that had existed for years.” Sandel added: “I would caution against anyone calling this a civil war. But the polarization and collective violence that we have observed with these chimpanzees may give us insight into our own species.”
Permanent splits are rare among wild chimpanzee populations; genetic evidence suggests such events occur about once every five centuries. Previous cases remain debated due to researcher intervention or incomplete data sets.
Sandel said these findings challenge common assumptions about human warfare being driven mainly by cultural identity markers like ethnicity or religion: “If relational dynamics alone can drive polarization and lethal conflict in chimps without language, ethnicity or ideology, then in humans those cultural markers might be secondary to something more basic.” He concluded: “If that’s true…it may be in small daily acts of reconciliation…that we find opportunities for peace.” Researchers continue to study ongoing developments within both groups.
