Indeed, human friendship does not have a monopoly over trust.
A new study led by researchers from the Max Planck Institute for Evolutionary Anthropology in Germany suggests that chimpanzee pals also consider trust as an integral element of their friendship. The findings show that trust-based friendship among these animals have deep roots.
Study author Jan Engelmann says that humans’ trust of their friends when it comes to secrets or important resources is not a far cry from those of chimpanzees and others they maintain a close bond with.
“Our findings suggest that they do indeed, and thus that current characteristics of human friendships have a long evolutionary history and extend to primate social bonds,” Engelmann says.
Venturing to know which chimp interactions are anchored on trust, the researchers observed 15 chimpanzees in Kenya for five months. They identified each “friend” or “non-friend” based on friendly relations among pairs, such as grooming and eating together.
The chimps were made to participate in their version of the human “trust rope” game, where they were offered two types of food: something they didn’t really like or something they preferred, which also came with the option to send back a treat to the other chimp. The second option is likely a win-win situation, but only if the first chimp trusted the other chimp well enough to give the treat. The chimpanzees played the game 12 times with their friends and 12 times more with their non-friends.
The results exhibit a much stronger trust level between chimp friends than non-friends, with the chimps substantially tending to voluntarily provide resources for their partner and to opt for “a risky but potentially high-payoff option” when they played with their friend, according to the researchers.
Engelmann says the findings are rather surprising in light of previous depictions of these creatures.
"Some researchers depict chimpanzee social life as dominated by conflict, competition, and dominance," he says in an interview. "Our research suggests that chimpanzees are able to form friendships that are based on trust; so chimpanzees, like humans, show trust-based co-operation."
The human bond based on trust is therefore not unique after all, with these animal friendships demonstrating close, lasting emotional bonds seen and well-understood in humans. In rather costly situations, both humans and chimpanzees tend to selectively trust their friends.
The findings were published in the journal Current Biology on Jan. 14.
Photo: Day Donaldson | Flickr