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Love thy neighbor

Wild bonobos also cooperate with members of foreign groups
Bonobo females vocalizing in a chorus during an inter-group encounter. Photo: Liran Samuni, Kokolopori Bonobo Research Project
Ein erwachsenes Bonobo-Weibchen aus der Kokolopori-Population bei der Fellpflege eines jungen Männchens aus einer benachbarten Gruppe. Foto: Martin Surbeck, Kokolopori Bonobo Research Project
Adult bonobo female from the Kokolopori population grooming an adolescent male from a neighboring group. Photo: Martin Surbeck, Kokolopori Bonobo Research Project
Friedliche Begegnung zwischen Bonobo-Gruppen in Kokolopori. Foto: Liran Samuni, Kokolopori Bonobo Research Project
Peaceful encounter among bonobo groups in Kokolopori. Photo: Liran Samuni, Kokolopori Bonobo Research Project
Dr. Liran Samuni ist Leiterin der Nachwuchsgruppe „Kooperative Evolution der Primaten“ am Deutschen Primatenzentrum – Leibniz-Institut für Primatenforschung in Göttingen. Foto: Karin Tilch
Dr Liran Samuni is head of the junior research group "Primate Cooperative Evolution" at the German Primate Center (DPZ) in Göttingen. Photo: Karin Tilch

Humans are capable of entering into strategic cooperations with strangers and sharing their resources outside their own social group. So far, prosocial behavior towards non-kin was considered a purely human ability. This assumption was partly based on observations of chimpanzees, as our closest relatives sometimes very violently fight members of other groups. Researchers from the German Primate Center – Leibniz Institute for Primate Research (DPZ) and Harvard University have now observed the social behavior of wild bonobos (Pan paniscus), a species closely related to both chimpanzees and humans. They found that bonobo cooperation extends beyond their own social group and includes societal collaboration with other groups (Science).

Although chimpanzees and bonobos live in similarly composed social groups with multiple adults of both genders, they differ fundamentally in how interactions between groups occur. In chimpanzees, relationships between different social groups are primarily hostile. Researchers draw conclusions about human traits such as cooperation and conflict based on studies of our closest living relatives. Since past research has focused almost exclusively on the social behavior of chimpanzees, many models of human evolution assume that group enmity and violence are inherent to human nature.

Tolerant bonobos

However, the present study on bonobos tells a different story. When different bonobo groups encounter each other, they often travel together and eat together. Unlike in chimpanzees, the researchers did not observe any fatal conflicts in bonobos. "While observing multiple bonobo groups, we noticed the remarkable level of tolerance among members of different groups. This tolerance paves the way for prosocial cooperative behaviors such as forming alliances and sharing food across groups. This is a stark contrast to what we observe in chimpanzees," says Liran Samuni, junior research group leader at the German Primate Center and lead author of the study.

Challenging field research

Bonobos are challenging to observe in their natural habitat as they exclusively inhabit remote, largely inaccessible parts of the Democratic Republic of the Congo. Harvard Professor Martin Surbeck, who Initiated the study and established the research station in the Kokolopori Bonobo Reserve, explains, "It is through strong collaborations with and the support of the local Mongandu population in Kokolopori, in whose ancestral forest the bonobos roam, that studies of this fascinating species become possible." Surbeck adds, "Research sites, like Kokolopori, substantially contribute not only to our understanding of the species’ biology and our evolutionary history, but also play a vital role in the conservation of this endangered species."

Targeted kindness

The researchers demonstrated that bonobos do not interact randomly between groups. Instead, they cooperate with specific members of other groups who are more likely to return the favor. This results in strong bonds between prosocial individuals, even across group boundaries. Similar bonds are also a key aspect of cooperation in human societies. "It is impressive to see in bonobos that constant confrontations between neighboring societies are not the only ancient human heritage," Samuni and Surbeck agree. Bonobos show that humans are not unique in their ability to build peaceful relations between societies.

Original publication

Samuni L & Surbeck M (2023): Cooperation across social borders in bonobos. Science, DOI: 10.1126/science.adg0844