Chimpanzee Population Conflicts Reveal Evolutionary Origins of War

Once a cohesive group, the Ngogo chimpanzees have divided, leading to escalation in violence and conflict. Researchers suggest this division might indicate that warfare is an innate aspect of our nature, rather than a recent development linked to our evolving culture.

According to Aaron Sandel and his team from the University of Texas at Austin, a comprehensive analysis of 24 years of social networks, 10 years of GPS tracking, and 30 years of demographic data on the chimpanzees (Pan troglodytes) in Kibale National Park, Uganda, was conducted.

Sandel emphasizes caution with terminology: “These are chimpanzees. Terms like war and civil war carry specific meanings for humans. While the conflict is not a civil war, there exist notable parallels, particularly regarding the shifts in group identity that precipitate lethal conflict.”

Chimpanzees are notorious for violence, predominantly targeting infants of rivals or outsider males.

The Ngogo population, comprising 150 to 200 individuals, is closely related to bonobos (Pongo niger), recognized as humans’ nearest relatives.

Between 1995 and 2015, the Ngogo chimpanzees were known for their cooperative behavior, showcasing fission-fusion dynamics, where individuals form temporary associations throughout the day and regroup each evening.

During puberty, female chimpanzees typically leave the group, while males remain for life. Prior to 2015, adult males formed alliances with females, facilitating hunting and territory patrols.

However, on June 24, 2015, a pivotal confrontation occurred when one faction, known as the central group, violently expelled the western group from their shared territory.

Following this event, the unity among the chimpanzees deteriorated. By 2018, the groups had permanently separated. During the ensuing years, the western group undertook 24 attacks, resulting in the deaths of seven adults and 17 infants from the other faction.

Sandel noted that the central chimpanzees were the first to pursue the western group; yet, the initial aggressors remain unclear. “As new factions emerged and divisions solidified, both groups engaged in territorial disputes,” he explained. “However, the western group has become the dominant aggressor, responsible for all fatal attacks.”

Various factors are believed to have contributed to the conflict’s escalation. Initial disagreements over food resources may have sparked tensions. In 2014, the deaths of five males and one female likely weakened the social structure. Changes in alpha male dynamics further exacerbated the situation, culminating in an outbreak of respiratory disease.

This outbreak, which claimed 25 Ngogo chimpanzees in January 2017, including the last surviving males of both factions, extinguished hopes for reconciliation.

Sandel and his team propose that the patterns observed in chimpanzee conflicts could provide insights into the evolutionary foundations of human warfare. While contemporary human conflicts are often attributed to ethnic, religious, and political divisions, this perspective may overlook the fundamental social dynamics shared with our primate relatives.

“In specific scenarios, the path toward peace may stem from simple, everyday acts of reconciliation,” the researchers articulated in their findings.

Maud Muzino from Boston University emphasizes that there are two predominant theories regarding the origins of human conflict. The first posits that war is a recent cultural innovation stemming from agrarian society and the establishment of nation-states. The alternative viewpoint asserts that the roots of warfare trace back through human evolution. “Ngogo’s findings significantly contribute to understanding the deep-seated origins of human conflict,” Muzino notes.

This study reveals that social fragmentation and subsequent conflicts can arise independently of the cultural differences often presumed to trigger human wars, be it in beliefs, language, or religious practices, states Luke Glowacki, also from Boston University.