Don’t wait for a chimp to offer that piece of fruit or open a door for you.
A new study by a team of anthropologists shows chimpanzees don’t share the altruistic qualities that have come to define their human relatives. Given an opportunity to share, they don’t. They are indifferent to the needs of strangers and friends alike. They are out for themselves.
“It was surprising,” said Joan Silk, a professor of anthropology at the University of California, Los Angeles. Altruism and empathy drive humans to aid in the face of trauma. Many people give blood, donate time and reach out to those in need.
Like humans, chimpanzees are social animals that form groups and show signs of cooperation. But the new research found that chimps apparently are not motivated to be generous to an unrelated chimp, even if it comes at no cost to themselves.
Silk and colleagues designed a clever apparatus that dispensed bananas with the press of either of two bars. One bar delivered a banana to the bar-pressing chimp and another banana to a chimp nearby. The second bar delivered only one banana to the chimp that pressed the bar. The bar-pressing chimps, all 18 in separate chimp colonies in Louisiana and Texas, were indifferent to providing other chimps in the room with fruit, even though they would also receive one.
“Humans in situations like this, and at a greater personal cost to themselves, are willing to behave in generous ways with complete strangers,” Silk said. “These chimps were not motivated to provide rewards to others, even those that they knew socially.”
The study was published last week in the journal Nature.
Silk and colleagues say the results tell a story about human nature and empathy. “This altruism is not in other closely related primates,” she said. “This suggests that our capacity for altruism and empathy is tied up with other features of humanity, culture, language and complex human relationships.”
Study co-author Sarah Brosnan of Emory University in Atlanta found in her earlier work that in rewarding chimps with a pleasing grape or a not-so-preferred cucumber, chimps reacted badly when they saw lab mates get the better reward. Now, Brosnan reflects on this exchange: “We didn’t see that the partner who received the grape ever tried to help the one who got the cucumber.”
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