Friendship emerged in Africa 6 million years ago in the last common ancestor of chimpanzees and humans, a new study has found.
The preference to form friendships with individuals much like oneself was present in this primate, researchers said.
"We know that it must have been a group-living species with relatively developed cognitive skills," co-author Sonja Koski of the University of Zurich told 'Discovery News'.
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"The groups consisted of many males and females, and individuals formed cooperative friendships.
"Our results suggest that the preference to form these friendships with individuals much like oneself was present in the ancestor of chimpanzees and humans," Koski said.
Koski and co-author Jorg Massen of the University of Vienna found that chimpanzee buddies are remarkably similar to human friends.
Both need emotionally rewarding, positive interactions with others, and these connections result in durable and mutually beneficial bonds. Chimp friendships, like human ones, can last for a very long time.
The researchers, including co-author Jorg Massen of the University of Vienna, investigated the personality similarity of friends among 38 captive chimpanzees.
They found that chimps were more likely to be friends if they possessed similar tendencies for sociability and boldness.
Sociability refers to how gregarious the individual is. In chimps, this is evident in grooming behaviours.
"So, highly sociable individuals hang out with others and groom them more often, while less sociable individuals are more aloof and do not groom much," Koski said.
The study was published in the journal Evolution & Human Behavior.