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March 3, 2006 [NY Times]
Chimps Display a Hallmark of Human Behavior: Cooperation
By CARL ZIMMER
One of the hallmarks of being human is cooperation. No other primate exhibits the same kind of helpfulness to others. Humans have made even violence a highly cooperative effort, and scientists have wondered how far back in evolution this trait goes.
New studies on chimpanzees suggest that this part of human nature may have already existed millions of years ago, perhaps before the human and ape lineages divided.
Scientists had observed chimpanzees in the wild apparently cooperating in the past. "They work together to chase monkeys, and they're quite effective when they chase them together," said Brian Hare of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
But skeptics argued that these observations might be illusions. "Maybe they just run at the monkey because they all want it," Dr. Hare said. "It just happens that because they're all doing it at the same time, it helps them catch the monkey. You really need an experiment to get at what they are doing."
Dr. Hare and his colleagues in Leipzig set up a series of experiments to do just that. They published their results in the current issue of Science.
In one series of experiments, Dr. Hare, Alicia P. Melis and Michael Tomasello placed an adult chimpanzee in a cage, outside of which was a plank with food on it. It was possible to get the food by pulling on two ropes. In some trials, the ropes were too far apart for one chimpanzee to get the food on its own. The chimpanzee could get help by opening the door of an adjoining cage where another chimpanzee was waiting.
The scientists found that the chimpanzees were much more likely to open the door if the ropes were too far apart for them to get the food themselves. "They know when they need help," Dr. Hare said.
The chimpanzees even kept track of who did a good job. When the scientists gave the chimpanzees a choice between two partners, they almost always chose the better rope-puller.
"So what we see in the wild may be really sophisticated," Dr. Hare said.
Chimpanzees not only cooperate, but are also willing to help even when they are not getting a direct reward.
In another series of experiments, Dr. Tomasello and Felix Warneken compared the altruism of 18-month-old children with that of juvenile chimpanzees. Chimpanzees were not as helpful as the children in complicated tasks. But in simple tasks
-- picking up a dropped sponge, for example -- they readily came to the aid of humans.
"All in all, this bolsters the view of chimpanzees as highly cooperative creatures," said Dr. Frans de Waal, a primatologist at Emory University who was not involved in the research.
Chimpanzees are the closest living relatives to humans, sharing a common ancestor that lived roughly six million years ago. If their nature is as cooperative as these studies suggest, then scientists say they may have inherited this ability from that common ancestor.
As for how human ancestors evolved more sophisticated cooperation, Dr. Hare suggests that one major adaptation must have been the ability to avoid being exploited. Psychological tests have shown that humans tend to cooperate with people who have cooperated with them in the past. They also avoid offering help to those who have not helped them.
"You can't be helpful if you don't have a way to avoid being cheated," Dr. Hare said.
PLEASE NOTE RE NEXT-TO-LAST PARAGRAPH: Similar abilities have also been shown in monkeys. See the below
MONKEYS SHOW SENSE OF JUSTICE
September 21, 2003
Researchers taught brown capuchin monkeys to swap tokens for food. Usually they were happy to exchange this "money" for cucumber. But if they saw another monkey getting a grape--a favored food--they took offence. Some refused to work, others took the food and refused to eat it.
Scientists say this work suggests that human's sense of justice is inherited and not a social construct.
The research was carried out at Emory University in the US, by Sarah Brosnan and Frans de Waal, and is reported in the journal Nature.
"I'm extremely interested in the evolution of cooperation," Sarah Brosnan said. One of the most interesting areas is the recent suggestion that human cooperation is made more effective by a sense of fairness." She wanted to find out if the human sense of fairness is an evolved behavior or a cultural construct--the result of society's rules.
So she and her colleagues devised an experiment using capuchin monkeys. "I chose the capuchin because they are very cooperative, and because they come from a very tolerant society. "We designed a very simple experiment to see whether or not they react to differential rewards and efforts."
Capuchins like cucumber, but they like grapes even more. So a system was devised whereby pairs of capuchins were treated differently after completing the same task. "They had never before been in any sort of situation where they were differentially rewarded," she said. "We put pairs of capuchins side by side and one of them would get the cucumber as a reward for a task."
The partner sometimes got the same food reward but on other occasions got a grape, sometimes without even having to work for it." The response was dramatic, the researchers said. "We were looking for a very objective reaction and we got one. They typically refused the task they were set. The other half of the time they would complete the task but wouldn't take the reward. That is a highly unusual behavior. Sometimes they ignored the reward, sometimes they took it and threw it down," Brosnan added.
The researchers were not surprised that the monkeys showed a sense of fairness, but they were taken aback that they would turn down an otherwise acceptable reward. "They never showed a reaction against their partner, they never blamed them," the researchers noted.
So does our instinctive feeling of fairness predate our species? "It may well," Sarah Brosnan said, and further experiments are planned to see how extensive a sense of justice in the animal world is.
"We are currently repeating the study on chimpanzees, a great ape species, to learn something more about the evolutionary development of the sense of fairness. I suspect that there are other non-primate species with tolerant societies that will show the same behavior."
Read more in
CHIMPS LIKE TO PLAY FAIR
February 7, 2005
We share about 99% of our DNA with chimps but we have struggled for a long time to pretend that we were "different." Yet almost every month a new piece of research comes out to prove just how similar we are. Now it seems chimpanzees display a similar sense of fairness to humans, one which is shaped by social relationships.
The researchers behind the latest study, which appears in the journal Proceedings of the Royal Society B: Biological Sciences, found that, like humans, chimps react to unfairness in various ways depending on their social situation.
What's probably even more galling to the "we are a unique species" proponents is that a similar finding has been reported in capuchin monkeys, suggesting that a sense of fairness may have a long evolutionary history in primates.
In the study, by researchers at the Yerkes National Primate Research Center in Atlanta, chimps were paired to see how they would respond if one received a better reward than the other for doing the same amount of work. When the pair came from a group that had known each other only a short time, the unfairly treated chimp responded negatively.
An animal rewarded with cucumbers -- instead of highly prized grapes -- downed tools and refused to do any more work. But when the pair were from a close-knit social group that had bonded over a long period of time, unfairness was more likely to be tolerated.
The same reaction is seen in humans, who tend to react negatively to unfair situations with strangers, but not so much when they involve family members or friends. "Human decisions tend to be emotional and vary depending on the other people involved," said Dr Sarah Brosnan, of Yerkes. "Our finding in chimpanzees implies this variability in response is adaptive and emphasizes there is not one best response for any given situation but rather it depends on the social environment at the time."
In a previous study, the same team identified a sense of fairness in capuchin monkeys. "Identifying a sense of fairness in two, closely-related nonhuman primate species implies it could have a long evolutionary history," Dr Brosnan explained. "The capuchin responses as well as those of the chimpanzees -- the most closely related species to humans -- could represent stages in the evolution of the complex responses to inequity exhibited by humans and may help explain why we make certain decisions."
The scientists found chimps demonstrated "inequity aversion" when they were treated unfairly, but not when they received the better reward. They seemed willing to take advantage of good luck while their partner lost out (how human!). The same response was seen in capuchins.
"Most people tend to respond by psychological rather than material compensation -- that is, justifying why they deserved a superior reward -- and most people will choose to ignore information that could lead to a more fair outcome at a cost to the self." How typically chimp!
Read more in the
Proceedings of the Royal Society B: Biological Sciences