Chimps may be one of our closest relatives, but they've shown a remarkably different approach altruism: They'll lend each other a hand, but need to be asked.
A study published this week in PLoS One showed that chimps would share tools with each other, but usually only if requested. Which raises interesting questions about why humans are so easygoing, and free with our assistance.
The experiments focused on two chimps in adjoining cages. Either both apes had a tool the other needed, or just one had the object their neighbour required: a stick to get at a juice box, or a straw to drink from a container of juice. Even when there was no reciprocal trade, the chimpanzees gave the tool, but usually required a request. How does an ape signal that it wants what you have? Vocalizing, clapping, beating against the wall, and reaching through the barrier between walls.
Professor Shinya Yamamoto, of Kyoto University, and head of the experimental unit said:
Communicative interactions play an important role in altruism in chimpanzees. While humans may help others without being solicited, the chimpanzees rarely voluntarily offered an effective tool to a struggling partner. Indeed, simple observation of another's failed attempts did not elicit voluntary helping in chimpanzees.
Why do humans, and some other animals (like capuchin monkeys), offer help spontaneously, yet an animal we're so closely related to does not? As always, no one really knows, but there are a lot of theories.
Even though half the experimental couples were non-related chimps, they were just as likely to hand over the tool, so it's not a straight out family link. If food was at stake, then the chance one chimp would share with the other plummeted from 80-90% likelihood to down around 30%.
One significant factor may be the chimps' difficulty in understanding another being's point-of-view. But from a social perspective, requested altruism makes a huge amount sense. In a situation of limited resources, be they food, tools, or anything else, unnecessary assistance can lead to wasted goods. Evolving an "altruism on request" system is a way to ensure that the "help" offered is actually helpful, and minimizes unnecessary behaviour.
So why do humans behave differently? Chimpanzees function at a level very similar to a hunter-gatherer tribe. They make and modify tools to aid in their endeavours, getting most of their calories from gathering, but with the occasional hunting boost.
Humans, on the other hand, evolved into agricultural societies several thousand year ago. There's a huge body of literature based on the premise that, among humans, the food surpluses brought about by the shift to agriculture allowed for the creation of cities and complex hierarchical societies as we understand them. Could agriculture have made humans more altruistic than their hand-to-mouth chimp brethren?
If that were the cause of the change, then we would have developed our current style of offering help whenever we thought it appropriate in the last 10,000 years or so. Maybe the change happened when we shifted from the trees into the grasslands, a situation of higher predation which would require greater teamwork within a group. While this is purely speculation, further studies of altruism in apes will perhaps provide a better idea of why this discrepancy exists.