Just like humans, apparently.

Altruism has sometimes being labelled as a human-only trait. In some cases, humans do things that directly benefit other people without any clear benefit to themselves; that is, there is not clear reciprocation, or reciprocation is unlikely. Even more convincing, sometimes the altruistic behavior is costly to the giver, which makes it even more marked.

While looking for such behavior in other primates, even the closely-related chimpanzees, no convincing evidence has been found. The current view is that in chimps, it is possible to observe altruism in limited cases, such as helping only a familiar human caregiver with whom the chimps share a close relationship.

With this backdrop, new research published in PLoS Biology provides clear-cut evidence that chimps and 18 month old human infants show altruistic behavior. There were three experiements:

• In the first experiment, the researchers looked at whether chimps and human infants are willing to help the experimenter reach for an object (a wooden stick). The object was shown to be valuable by having two experimenters fight for it. The setup was such that one of the experimenters moved the object out of reach of the other experimenter, even if he stretched to reach it. The only way for him to get hold of it is if the chimp or the infant handed it to him. There were four tests:
  • Experimenter reached for the object and the chimps were rewarded for helping
  • Experimenter reached for the object and the chimps were not rewarded for helping
  • Experimenter did not reach for the object and the chimps were rewarded for helping
  • Experimenter did not reach for the object and the chimps were not rewarded for helping
  In all four cases, both humans and chimps did hand over the object to the experimenter; all in all, 12 of the 18 chimps and 16 of the 18 infants tested helped at least once.
• The second experiment was like the first, but now the chimps and the infants had to move a greater distance to reach the stick to be able to hand it to the experimenter - i.e., there is a higher cost to helping. Again, just like the first experiment, both chimps and infants were happy to help.
• The third experiment is even more clever: food was placed in a target room such that a chimp cannot get to it unless another chimp releases the chain holding the door. What they found was that the helping chimp released the chain if the other chimp was near the door. The helpers released the chain even more frequently if the other chimp was trying (unsuccessfully) to open the door. At no time did the helper chimps beg or harass the other chimps once they got hold of the food, suggesting their motivation was not the food itself, but actually, genuine help.

So this paper really has two clear conclusions:

• Evolution of altruism is not limited to humans, and now we have to look deeper to see where it started.
• Human altruism starts at a very early age, well before society has had a chance to influence behavior.

All in all, a very good paper, and if anything, it shows that chimps are nice!

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