This study is part of a recent line of research that examines how chimpanzees and humans are different. This one highlights the ultra-sociality of humans who are willing to undergo a net cost so that they can punish someone. ... like the ultimatum game, where an individual could accept an offer of 3 out of $10, but instead refuses to accept free money for the sake of fairness. There are several ways to interpret this. Humans are so extremely social, and punishment is a way of signalling that a person is more concerned about fairness and is willing to undergo a cost to show to others that he values fairness. In this way he gains a good reputation. It is hard to interpret behavior through these games, since it was not in a game-like environment that these behaviors evolved. Alternatively, this research could be used to argue that group selection is operating, since an individual is undergoing a net cost for the good of the group... although the counter-argument is that the individual is not undergoing a net cost - he is gaining a good reputation... bottom line here - humans are ultra-social.
Chimpanzees are vengeful but not spiteful
Keith Jensen, Josep Call, and Michael Tomasello
PNAS online before print July 20, 2007
Abstract: People are willing to punish others at a personal cost, and this apparently antisocial tendency can stabilize cooperation. What motivates humans to punish noncooperators is likely a combination of aversion to both unfair outcomes and unfair intentions. Here we report a pair of studies in which captive chimpanzees (Pan troglodytes) did not inflict costs on conspecifics by knocking food away if the outcome alone was personally disadvantageous but did retaliate against conspecifics who actually stole the food from them. Like humans, chimpanzees retaliate against personally harmful actions, but unlike humans, they are indifferent to simply personally disadvantageous outcomes and are therefore not spiteful.