Selfish or Generous? Sharing Food Reveals Origins of Reciprocity in Humans

First Posted: Aug 21, 2013 06:58 AM EDT

Are we selfish or are we generous? It could be a bit of both, according to new research. Scientists have discovered that when we (and apes) share our food, we may subconsciously using a strategy to assure reciprocity should we one day find ourselves on the other side of the empty plate.

In order to examine food sharing a bit more closely, the researchers examined this behavior in monkeys, apes and humans. More specifically, the study compiled quantitative data on cooperative behavior from all existing studies in a number of primate species.

"The meta-analysis clearly established that there is reciprocity in sharing both among humans and among other primates that remained significant even after controlling for other factors such as kinship, dominance relationships and spatial proximity," said Adrian Jaeggi, one of the researchers, in a news release. "Based on our meta-analysis of existing studies, we were able to find no significant differences between humans, monkeys and apes."

That said, there were a few differences. While humans tended to exchange food for food, primates bartered food for services, such as grooming or coalition support. Yet in the end, giving food also benefitted the giver. This means that sharing becomes mutually beneficial.

"Our findings support the idea that actions that benefit another individual tend to, ultimately, also benefit the giver--either because the recipient is genetically related to the giver or will eventually return the favor," said Jaeggi in a news release. "Of course, the giver doesn't have to be consciously aware of the return benefits."

In fact, the findings seem to show that humans and other primates form long-term relationships for mutual gains. Benefits given to others are more likely to be returned when these relationships are formed and could help with long-term survival.

"Sharing doesn't just enhance the welfare of humans," said Michael Gurven, one of the researchers, in a news release. "The human subsistence niche would never have been possible without sharing. It's no coincidence that sharing is most pervasive and structured among humans, the one primate whose economy is defined by high levels of interdependence."

The findings are published in two studies, one in Proceedings of the Royal Society B: Biological Sciences and the other in Evolutionary Anthropology: Issues, News and Reviews.

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