Bonobos shed new light on the evolution of human cooperation

by Valentina Moya (28 November 2023)

Contrary to what was believed, humans are not the only ones capable of forming strategic relationships with others outside of their social groups. A new study suggests that bonobos also mingle and cooperate with those they share no kinship with.

The study, published in Science last week, reveals that individuals of this endangered primate species groom, share food, rest, and even travel with others outside of their group, unlike chimpanzees, who are known to have hostile intra-group behaviours, sometimes even lethal.

Both chimpanzees and bonobos are two of our closest animal relatives and understanding them can help shed light on human social evolution. However, bonobos have been less studied than chimpanzees.

According to the researchers, bonobos do not mingle randomly. It is selective. “They preferentially interact with specific members of other groups who are more likely to return the favour, resulting in strong ties between pro-social individuals. Such connections are also key aspects of the cooperation seen in human societies”, explains Dr. Martin Surbeck, a behavioural ecologist at Harvard University and researcher of the study.

The research team tracked and observed two groups of wild bonobos in the Kokolopori Bonobo Reserve, located in the Democratic Republic of Congo for a period of two years. In total, the researchers observed and logged 95 encounters across groups. Some of the interactions lasted for less than an hour, while others went on for days and even weeks.

“We’re struck by the remarkable levels of tolerance between members of different groups. This tolerance paves the way for pro-social cooperative behaviours such as forming alliances and sharing food across groups, a stark contrast to what we see in chimpanzees” says Dr. Liran Samuni from the German Primate Centre and author of the study.

This study not only challenges the notion that cross-group cooperation is a unique trait of our species, but also the assumption that violence is an innate human behaviour derived from chimpanzees’ aggressive traits.

Dr. Samuni calls for more related research to be done, but this might be complicated since establishing wild bonobo observation sites is complex for multiple reasons. These primates are an endangered species living deep in the rainforests of the Democratic Republic of Congo, which are hard to access for multiple reasons, including the country’s internal conflicts.