Researchers at Duke University have conducted a study that asks who bonobos share with, friends or strangers. Bonobos, which are the most closely related primates to humans, are considered social animals like people. However, unlike mankind, bonobos were found to share with strangers more often than those they were familiar with.
Brain Hare, a Duke professor of evolutionary anthropology, believes that allow it may seem strange, there’s actually a reason for this bonobo behavior. “It seems kind of crazy to us, but bonobos prefer to share with strangers,” he said. “They’re trying to extend their social network.”
For their research project, Hare and his colleague Jingzhi Tan studied bonobos from the Lola ya Bonobo sanctuary in Kinshasa, Democratic Republic of Congo. First, the scientists allowed one bonobo to enter an enclosure full of food. They were then given the choice to allow a familiar bonobo or one they have only seen from a far into the enclosure to share the food.
The researchers deliberately set up the experiments so the bonobo had a few choices: share with the familiar bonobo, share with the stranger, share with both, or share with neither. Nine out of 14 test subjects consistently shared with the stranger first. Two of the animals chose to share with the familiar bonobo and the other three had no preference.
The familiar bonobo was not always let out, however. Over the course of many trials, Hare and Tan found that the third bonobo was often allowed into the food enclosure after a short time. Interestingly, this third bonobo was often released into the enclosure by the stranger, not the animal it knew. According to Tan, this was unexpected because the stranger bonobo allowed itself to be outnumbered one to two by animals that were familiar.
Hare and Tan more experiments, this time isolating a bonobo for some time in order to determine what role the reward social interaction played in the animal’s choice. In the first set of experiments, the decision maker was not allowed to have any food though they were still allowed to grant a stranger or a familiar bonobo access to food. Nine out of ten primates shared with the unknown animal at least once.
Another set of experiments allowed the decision maker access to food, but releasing one or both of the other bonobos meant they would lose some of their food. During this experiment it was determined that most of the animals would not share with either the stranger or the familiar bonobo. In a statement, Hare said “if they’re not going to see a social benefit, they won’t share.”
This behavior is contradictory to humans who have been found to share money even when they are anonymous, a study called the Dictator Game. Bonobos on the other hand choose not to share when anonymous if it will cost them their food reward. “When it’s a no-benefit situation, they won’t share,” Hare said. “That’s different from a human playing the dictator game. You really have to care about others to give anonymously.”