The largest chimpanzee community ever observed is offering scientists a rare and unsettling glimpse into how even highly cooperative animal societies can fracture into lethal violence. A study published in Science, led by Aaron Sandel of the University of Texas at Austin, documents an unprecedented internal split among individuals that had lived and cooperated together for years.
The research focuses on the Ngogo community in Kibale National Park, Uganda, the largest known group of wild chimpanzees. For more than two decades, this community appeared remarkably cohesive. Individuals moved fluidly among subgroups, maintaining a broad and stable network of social bonds, a pattern typical of the species.
This balance began to erode around 2015, when researchers detected early signs of polarization. Certain groups started systematically avoiding one another, marking the beginning of a gradual विभाजन. The shift coincided with changes in the male dominance hierarchy and followed the deaths of several adult males who, according to researchers, had acted as key “social bridges” within the group.
By 2018, the split had become complete: the community divided into two distinct groups, each occupying its own territory. Between 2018 and 2024, researchers documented a series of violent encounters between the groups, many of them fatal. In total, seven attacks targeted adult males and seventeen targeted infants. In some cases, chimpanzees killed individuals with whom they had once shared close social ties.
According to Sandel, this reflects a profound shift: newly formed group identities are replacing long-established cooperative relationships. Such events are extremely rare among chimpanzees. While many primate species regularly split into smaller units to reduce competition, permanent fissions in chimpanzees are exceptional, with genetic evidence suggesting they may occur only once every 500 years.
The only comparable case dates back to the 1970s in Gombe National Park, Tanzania, observed by Jane Goodall. That episode, however, remains debated, partly because the chimpanzees were provisioned by researchers. In contrast, the Ngogo chimpanzees have never been artificially fed, and the observations span nearly three decades.
The researchers caution against direct comparisons with human conflict, emphasizing that this is not a “civil war.” Still, the observed polarization and collective violence raise profound questions. If relational dynamics alone can produce lethal conflict in the absence of language, ideology, or cultural identity, then such markers in humans may be less fundamental than often assumed.
Understanding these processes, Sandel suggests, may offer a useful lesson. The foundations of peace may lie not in grand structures, but in everyday acts of reconciliation and the maintenance of social bonds.
