Chimpanzees take revenge upon one another, but only if it doesn't cost them. Humans, however, will inflict suffering on themselves in order to punish someone else. It may be that our willingness to punish others even if it hurts us is as important to the evolution of human society as our ability to cooperate with each other.
This week's PNAS describes an experiment where a chimpanzee that has access to a rope which can collapse a table with food on it (sending the food onto the floor and out of reach of all chimpanzees) will yank the rope 30% of the time if it can see the food but not reach it, or if it cannot reach the food itself but can see another chimpanzee eating it. It will yank the rope significantly more if another chimpanzee has pulled the food out of its reach. What chimpanzees won't do is send the food to the floor to punish
another chimpanzee if they themselves are
eating. New Scientist, Science Now.
Two of the researchers behind these findings, Josep Call and Michael Tomasello, appear in The First Word. Tomasello was also behind the research on generosity in humans and chimpanzees, reported in the July 8 post.