For over thirty years they were considered a model of social balance. Then, in the heart of Kibale National Park, Uganda, something cracked. The largest known community of chimpanzees, that of Ngogo, has split into two rival groups, giving rise to an internal conflict that is as rare as it is disturbing.
According to the study published in the journal Science and led by anthropologist Aaron Sandel, it is the first comprehensive documentation of a permanent split followed by violence between individuals who once shared everything: territory, relationships and hierarchies.
From cohabitation to breakup: what happened
Until 2015, the community functioned according to the classic “fission-fusion” model: mobile subgroups but linked by a strong social cohesion. Then increasingly evident signs of tension emerged. The groups began to avoid each other, interactions were reduced, until the definitive breakup in 2018. Among the hypothesized causes, researchers indicate the death of key individuals, capable of maintaining balance, and changes in the male hierarchy. Factors such as disease and competition for resources may also have accelerated the rift.
As the study explains and as the graph also shows, the social network of the 219 chimpanzees evolved from an initial phase of strong territorial overlap and cohesion to a progressive separation into two distinct groups (Central and Western). The clustering analyzes highlight the formation of two components no longer connected over time, while the spatial overlap between individuals decreases to almost zero. The graph also illustrates the differences in land use patterns and interactions between individuals, which move from frequent and neutral meetings to a clear social separation, culminating in episodes of conflict between members of the two groups previously belonging to the same community:
Violence between former allies
After the separation, the conflict escalated. Between 2018 and 2024, at least seven attacks were recorded against adult males and seventeen against cubs, torn from their mothers. Brutal episodes, in which the attackers were former members of the same group. A fact that strikes scholars: new group identities have supplanted bonds built over years of coexistence. In other words, the chimpanzees began to treat their “old companions” as enemies.
A very rare event in natural history
Genetic analyzes suggest that similar phenomena may occur once every 500 years. A precedent exists, observed in the 1970s by primatologist Jane Goodall in Gombe National Park, but that case has long been discussed due to possible human interference. Kibale’s, however, is considered more solid and complete, because it is based on continuous observations and without external interventions.
What does this conflict teach us
Scholars urge caution when speaking of “civil war” given that chimpanzees do not have ethnicity, religion and political ideology, all those cultural traits that we often identify as one of the main causes of conflicts between human beings, especially internal conflicts such as civil wars.
Yet the parallel is unavoidable, as research suggests that polarization and collective violence can emerge spontaneously, even without culture, ideology or language. A discovery that opens profound questions: if similar dynamics exist in our closest relatives, then the roots of conflicts could be more biological and less cultural than we think.
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