Did sharing evolve from group hunting?

The monkeys shared for mutual gain

The idea that co-operation during hunting led to the evolution of human social and moral behaviour has received a boost.

Another species of primate, capuchin monkeys, have been observed by scientists to pay one another for the work done in getting food.

Handling the delicate dynamics of group hunting has surely been a major theme in making human primates mentally what they are

Andrew Whiten

US primatologists discovered that, after a collaborative hunting effort, the monkey left holding the spoils willingly shared out the food.

Dr Frans de Waal, one of the team at the Living Links Center in the Yerkes Primate Research Center, said: "Tit-for-tat is essential in our economies, and even our morality emphasises how one good turn deserves another. Our lives depend on our ability to co-operate with one another and to reciprocate for the help of others."

'Really surprising'

Dr Anthony Collins, at the Gombe Stream Research Centre in Tanzania, found the results of the Yerkes study "really surprising".

"It's rather extraordinary that they were apparently sharing food spontaneously."

However, primate behaviour expert Professor Andrew Whiten, at St Andrews University, UK, told BBC News Online: "Capuchin monkeys are not our ancestors, so this study does not prove anything direct about the origins of our own preparedness to co-operate.

"But what it does show, interestingly, is that even in a monkey quite distantly related to us, there is a greater tendency to tolerate sharing of one's food with individuals who are prepared to help in getting it in the first place."

Professor Whiten says this provides a clue to answering the puzzle of how co-operation might have begun to evolve in tricky situations like group hunting, where several individuals help, yet only one ends up holding the prize.

"Handling those delicate dynamics has surely been a major theme in making human primates what they are, mentally," he said.

Large brains

Capuchin monkeys are small South American primates but have large brains. In the wild, they have been observed to co-operate during hunting to allow one individual to make a kill. That individual then shares the meat, and all the hunters get a meal.

Dr de Waal and his colleagues studied this behaviour in captivity by setting up an experiment in which the strength of two monkeys was required to pull a dish of apple slices into their cage.

However, the two monkeys were separated by a mesh, meaning that only one of them received the apples. Despite the fact that the monkey with the apples could have eaten them all with impunity, they nearly always shared through the mesh.

Sharing, caring or bribing?

One possible explanation for the behaviour could be that the monkeys have evolved an instinct that sharing is beneficial.

But Dr Collins noted that there are other potential explanations. For example, the monkey giving the food could be manipulating the other in order to ensure its future co-operation - a kind of bribe.

Research in chimps - the only other primates to have shown co-operative hunting in the wild - has suggested that sharing could be explained as getting fed up with being nagged, said Dr Collins. Some researchers argue that chimps share their food with those who pester them most persistently in order to get rid of them.

The Yerkes research is published in the journal Nature.