Anthropologists study the genesis of reciprocity in food sharing

Aug 20, 2013

When you share your lunch with someone less fortunate or give your friend half of your dessert, does that act of generosity flow from the milk of human kindness, or is it a subconscious strategy to assure reciprocity should you one day find yourself on the other side of the empty plate?

And how do those actions among humans compare to those of our chimpanzee cousins and other ?

Through two separate studies, UC Santa Barbara Adrian Jaeggi and Michael Gurven found that reciprocity is similar among monkeys, apes, and humans, even when considering other factors that might otherwise predict helping behavior. However, they also found that only humans showed evidence of reciprocity in food sharing. Their research appears in the current issues of the Proceedings of the Royal Society B and of the journal Evolutionary Anthropology.

"Reciprocity Explains Food Sharing in Humans and Other Primates Independent of Kin Selection and Tolerated Scrounging: A Phylogenetic Meta-Analysis," the Proceedings of the Royal Society B article, compiles quantitative date on from all existing studies in a number of . "Natural Cooperators: Food Sharing in Humans and Other Primates," the article in Evolutionary Anthropology, goes into greater detail about the origins and maintenance of cooperation among a wide range of primate species, with particular attention to the case.

"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 , dominance relationships, and spatial proximity," said Jaeggi, a postdoctoral student in anthropology at UCSB. "Based on our meta-analysis of existing studies, we were able to find no significant differences between humans, monkeys, and apes."

However, Jaeggi noted, humans tend to exchange food for food, while primates tend to barter food for other services, such as grooming or coalition support (e.g. assistance in dominance fights). The relative effects of reciprocity, kinship, and tolerated scrounging were similar, highlighting that all are important factors in explaining the act of sharing.

"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," Jaeggi said. "Of course, the giver doesn't have to be consciously aware of the return benefits."

Through natural selection, humans have evolved to form emotional attachments to others and engage in long-term relationships within which reciprocity benefits everyone involved. "This is supported by research showing that reciprocity in many species develops over long periods of time –– much more so than on an immediate tit-for-tat basis," said Jaeggi.

While the research conducted by Jaeggi and Gurven, a professor of anthropology at UCSB, identified reciprocity as an important factor in food sharing, kin selection –– sharing food with genetic relatives –– and tolerated scrounging are also important. In fact, the researchers' meta-analysis shows them to be roughly equal. "But of these three factors, reciprocity has always been the most disputed," Jaeggi said.

"But the meta-analysis now establishes that makes a significant contribution. This makes sense given that humans and other primates form long-term relationships for mutual gains, within which benefits given to others tend to be returned," he continued. "Again, this doesn't mean that food is shared with the conscious expectation of receiving shares in return. Reciprocity need not require detailed scorekeeping, but could arise from simpler mechanisms such as preferentially associating with friends, or only allowing friends to take shares of your food."

While humans exchange food on a more in-kind basis, primates tend to share their grub in exchange for services. One reason for this is that human foragers –– people who rely on a hunting-and-gathering lifestyle –– always run the risk of food shortfalls because hunting and foraging returns are unpredictable. When a hunt is successful, however, it provides an abundance that can be shared with others. Gathered fruits can be brought back to a central home base for subsequent sharing. Reciprocal sharing creates a buffer against the risk of shortfalls, ensuring that no one goes hungry.

"Sharing doesn't just enhance the welfare of humans," explained Gurven. "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."

Among primates, however, food for sharing tends to be something of a luxury that is often monopolized by the high-ranking, dominant individuals, and they share with those who provide other services to them (e.g. grooming, coalitions). In those species where coalitions are more important for achieving a high dominance rank –– among , for example –– sharing tends to be more common because the dominants rely on others.

While sharing helps primates cement social relationships, the level and diversity of helping behavior is limited compared to what is observed in human societies. "Through sharing, trust, and reputation management, humans found social means of handling different types of risk –– not just day-to-day variation in foraging success –– but also disruptions due to injury, sickness, divorce, and death," Gurven said. "Sharing, therefore, is central to human life history evolution –– from the dependency of children and intergenerational support networks, to the division of labor and cooperative production, to the expansion of human life spans."

Explore further: Sex? It all started 385 million years ago (w/ Video)

add to favorites email to friend print save as pdf

Related Stories

Women are 'socially' networked, study shows

Jan 11, 2012

(PhysOrg.com) -- Bloggers and other social network users are more likely to share knowledge online where the qualities of trust, strong social ties and reciprocity are present, according to a study forthcoming in the Journal of ...

Monkey generosity: No strings attached

Jul 14, 2010

(PhysOrg.com) -- Among monkeys that split child care responsibilities, sharing extends to dinnertime, but grudges do not, according to research published July 14 in Proceedings of the Royal Society B.

Recommended for you

'Red effect' sparks interest in female monkeys

Oct 17, 2014

Recent studies showed that the color red tends increase our attraction toward others, feelings of jealousy, and even reaction times. Now, new research shows that female monkeys also respond to the color red, ...

Roads negatively affect frogs and toads, study finds

Oct 17, 2014

The development of roads has a significant negative and pervasive effect on frog and toad populations, according to a new study conducted by a team of researchers that included undergraduate students and ...

All in a flap: Seychelles fears foreign bird invader

Oct 17, 2014

It was just a feather: but in the tropical paradise of the Seychelles, the discovery of parakeet plumage has put environmentalists in a flutter, with a foreign invading bird threatening the national parrot.

Amphibians being wiped out by emerging viruses

Oct 16, 2014

Scientists tracing the real-time impact of viruses in the wild have found that entire amphibian communities are being killed off by closely related viruses introduced to mountainous areas of northern Spain.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

OdinsAcolyte
1 / 5 (1) Aug 20, 2013
I have a wolf hybrid (mostly wolf) that will share his food with other dogs. He is a generous and loving soul. He has a sweet temperament but his appearance will make folks stand still. I call him my little bad wolf. The canine has many traits in common with humans I notice. I like them better than most people...