Human beings are capable of forming strategic alliances with other people outside the circle of their family or significant others.
According to a study published Thursday in the journal Science, they are not the only ones. Bonobos bond with strangers in a variety of ways, such as grooming, sharing food, and even forming alliances against sexual predators.
Liran Samuni, lead author of the study and a member of the German Primate Center in Goettingen, told AFP that studying primates is like opening a “window into our past”, providing clues about how humans began to cooperate on a larger scale.
Along with chimpanzees (Pan troglodytes), bonobos (Pan paniscus) are the closest living creatures to the human species. Bonobos and chimpanzees are also very close.
Relationships between chimpanzees, which are hostile and can lead to deadly violence, are widely studied, unlike interactions between bonobos, an endangered species.
These primates are difficult to observe in their natural habitat because they live in remote areas of the Democratic Republic of Congo (DRC).
Because of the findings about chimpanzees, some researchers have concluded that hostility towards strangers is inherent in human nature, even hidden beneath a layer of social norms.
Liran Samuni and Martin Surbeck, a Harvard professor and founder of the Kokolopori bonobo reserve in DR Congo, studied the monkeys for two years.
“The first thing they do (…) is try to escape,” Martin Surbeck told AFP, explaining that the bonobos needed time to forget the presence of humans and behave normally.
The researchers got up at 4 a.m. to walk through the forest with the help of their local guides to groups of bonobos and monitor their activities during the day.
They focused on two small groups of 11 and 20 adults, and were amazed to note that they spent 20% of their time together, eating, resting, moving.
“Every individual is different,” says Liran Samuni. “There are introverts, there are extroverts, there are those who are more social than others.”
The researchers also noted that cooperation between the two groups was mostly driven by a few individuals who were already inclined to cooperate within their own group.
These individuals entered into relationships with social bonobos from another group, creating a system of mutual benefit or “reciprocal altruism.”
Chimpanzee or bonobo?
The scientists also found that females, within their own group or in alliance with those from another group, formed coalitions to chase an individual from a fruit tree or prevent unwanted sexual advances from a male.
“In bonobos, we don’t see the sexual coercion that is common in chimpanzees,” Ms. Surbeck continues, explaining that this may be partly due to mutual aid between females.
For the authors, this study offers an “alternative scenario” to those who would like cooperation to go against human nature or to arise from bonds between extended families.
But “this does not mean that the reconstruction of the human past has to be based solely on bonobos,” said Joan Silk, a scientist at Arizona State University.
Chimpanzees are closer to humans in other ways: for example, they use more tools and hunt animal prey.
Male chimpanzees form close bonds with other males and support their aggression, while male bonobos form strong bonds with females.
Understanding the selection process that led to these differences “could help shed light on how and why humans became such surprising primates,” she concludes.