Slippery Negotiations in a Banana Republic

If apes could negotiate, some well-known movies might have had different endings: King Kong would have lasted longer than a New York minute; the warring tribes in 2001 might have tried UN arbitration before braining each other with gazelle femurs; and Bonzo could have argued for a later bedtime. This insight comes courtesy of a recent study that shines a light on the hidden origins of human cooperative behavior.

Group decision making in humans is a complex balancing act of selfishness and altruism. In the economic ultimatum game, for instance, often used in behavioral economics experiments, one subject gets a wad of cash that he can split with a partner in any way he wants. The catch? If the partner tells him what he can—ahem—do with the offer, they’ll both get nothing. Humans use social cues and our ever-sophisticated communication skills to solve these dilemmas. In many cases, face-to-face subjects cooperate more than anonymous partners in similar experiments.

To tease out the evolutionary origins of human cooperation or the frequent lack thereof, scientists often turn to our cousins. No, not the ones you see once a year and avoid talking about politics with—chimpanzees. “Since chimpanzees are our closest relatives, they are the obvious starting point to investigate differences in cooperative behavior between humans and animals,” says ecologist Larissa Conradt of the University of Sussex, United Kingdom, a scientist who studies group decision-making. 

One such investigation has come from researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. They showed that chimpanzees could set aside conflicting interests and cooperate to win rewards: also known as bananas. In many cases, Machiavellian chimps with low social status even subtly coaxed their higher-ranking rivals to split the takings evenly, according to the study published in the November 2009 issue of the journal Evolution and Human Behavior. What’s most surprising is that they did all this without communicating vocally, suggesting that basic negotiation skills may have evolved long before humans gained the gift for gab. 

Past studies have shown that chimpanzees vocally communicate to form alliances in fights against rivals, but resource haggling—as in the ultimatum game—may require a different set of communication skills, says Alicia Melis, the study lead. 

To study primate negotiation behavior, Melis and her team paired six dominant chimpanzees with six subordinates on a sanctuary in Uganda. They gave the chimps two options, a food tray with two plates topped with equal portions of bananas, or another tray in which the portions favored one ape at the other’s expense. They kept the trays in alcoves too deep for grubby ape paws to reach. Both chimps had to pull on ropes together to fetch one of the trays. Dominants had first access to the room and “offered” a tray by sitting next to a rope. Subordinates then either accepted that offer and helped to pull the tray in or held out for more by sitting stubbornly next to the second. 

The negotiations didn’t break down into fist-fights or tears the way squabbles over toys, borders or the rules of Risk do in the human world, and the apes eventually worked together in most trials. The dominant chimps preferred the unequal tray, but the subordinates accepted these initial offers less than half of the time. Like an 80s movies about nerds in college, the subordinate chimps even cleverly convinced their jock rivals to help them pull in the equal tray on several occasions. 

“A lot of times, individuals with less power had more leverage and were able to convince dominant partners to go with the better deal,” Melis said. 

What surprised Melis most is that the chimps largely resolved their disagreements in silence. They kept a watchful eye on each other during the trials, perhaps trying to judge how long a rival could hold out before giving in to a banana craving. But they almost never called or gestured to each other, Melis explains. 

“They never really tried to do anything to directly influence the behavior of their partner,” she says. 

The lack of overt communication during the trials suggests that basic negotiation patterns evolved in a common ancestor of humans and chimps, long before complex language arose in primates, according to Melis. “You can already do a lot without any of these sophisticated human skills,” she said. 

Unlike humans, subordinate apes don’t punish dominant bullies for their greed by refusing to cooperate, Melis says. But to what extent the chimps actually understood that the shoddy deal was their partner’s fault remains unclear. 

“This paper demonstrates that chimpanzees can cooperate in a fairly sophisticated manner,” muses Conradt. “This opens many questions, and suggests that we have not yet started to even nearly understand the cooperative behavior of our closest relatives.”

The moral is, if King Kong has Fay Wray and/or Naomi Watts, save everybody a big mess and try to talk him down. You could even offer bananas. A lot of bananas.