Marcel Schauer / Dreamstime.com
Though often considered selfish, chimpanzees have shown altruistic tendences in a recent study by primatologists at Emory University in Atlanta and in other studies.
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updated 8/8/2011 4:16:55 PM ET 2011-08-08T20:16:55

Chimpanzees, long considered reluctant to share, apparently can display selfless tendencies, revealing one more key way our closest living relatives are like humans, scientists find.

These findings could shed light on the evolution of altruism in humans, showing that selflessness is less of an anomaly among our relatives than before suggested, researchers added.

In recent years, research has revealed just how much chimpanzees have in common with us. They can hunt with spears, play with improvised dolls and mourn their dead.

However, past experiments had suggested that chimps were loath to share, being what scientists had classified as antisocially selfish instead of pro-socially altruistic. This led to a widely held belief that human altruism evolved only after humans split from their ape cousins about 6 million years ago.

"For the past decade we have lived through the curious situation — frustrating for many chimpanzee fieldworkers and observers — that chimps are well known for spontaneous acts of altruism, yet have not shown the same tendencies in well-controlled experiments," said researcher Frans de Waal, a primatologist at Emory University in Atlanta.

It turns out this past failure to find such altruistic behavior might have been due to the experiments on the chimpanzees themselves.

"Most earlier studies had presented the apes with a complex apparatus that helped them deliver food to themselves or others, often so complicated that the experiments tested tool skills rather than social tendencies," de Waal told LiveScience. "Ours is the first study that uses no such apparatus at all."

In addition to using complex food-delivery systems, past experiments often placed the chimpanzees so far apart that they might not have realized how their actions benefited others.

Simple tests of altruism
In these new, simplified experiments, two apes were housed next to each other with a screen through which they could see each other. Then, one chimpanzee had to choose between two differently colored tokens from a bin, one of which represented a pro-social option, the other a selfish option. The pro-social option would cause both chimpanzees to receive a piece of banana wrapped in paper. (The paper made a loud noise upon removal, helping chimps to know that another was benefiting from his actions.) The selfish option only rewarded the ape who made the choice.

In a study with seven adult female chimps placed into various pairs, the scientists found all the apes showed a definite preference for the pro-social option.

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"For me, the most important finding is that like us, chimpanzees take into account the needs and wishes of others," researcher Victoria Horner, a comparative psychologist at Emory University, told LiveScience.

"The idea that chimps are indifferent to the welfare of others can now hopefully be put to rest," de Waal said.

The chimpanzees behaved especially altruistically toward partners who either patiently waited or gently reminded them that they were there by drawing attention to themselves. They were less likely to reward partners who exerted pressure by making a fuss, begging persistently or spitting water at them.

"This is interesting because there has been a long-standing view that the chimpanzees only share food under pressure," Horner said. "Our results suggest the opposite — chimpanzees share when there is no to little pressure, but direct pressure or threats reduce sharing, possibly due to negative emotions."

Evolution of altruism
The researchers say these findings, along with studies showing other primate species with similar tendencies, suggest pro-sociality may have deeper evolutionary origins than previously thought.

Past research had shown that chimpanzees were capable of altruistically providing assistance. "Our results are subtly different," Horner said. "When you provide assistance, it's really a test between doing something or nothing. In our study, the chimps really have three choices — they can do nothing, they can be pro-social or they can be selfish."

The current studies were conducted with chimpanzees of all one sex to simplify its design, as including both sexes would have added complex questions of why the chimps might or might not have shared.

"Many anecdotal reports of altruism in both the wild and captivity involve females, but that's not to say that males aren't also altruistic," Horner said. Also, "researchers may be unintentionally focusing more on female altruism because they expect to see it more in females than males."

In addition, "males may show their pro-social side in different contexts," she added. "For example, reports from the wild indicate that female chimpanzees use tools more frequently than males, but our previous research with captive chimpanzees has shown that males are just as good as females at tool use. It's just that males in the wild have other priorities, such as border patrols and hunting, so that we don't see their tool-using abilities as frequently as we do with females. The same may be true of male pro-sociality."

"Gender differences would be an interesting study for future research," Horner concluded.

Horner and de Waal detailed their findings online Aug. 8 in the Proceedings of the National Academy of Sciences.

Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Explainer: The world’s 10 smartest animals

  • EBU

    We humans have the ability to learn, to reason and solve problems. We're self-aware, and we're also conscious of the presence, thoughts and feelings of others. We make tools and practice the art of deception. We're creative. We think abstractly. We have language and use it to express complex ideas. All of these are arguably signs of intelligence. Scientists may not agree on the best and fullest definition of intelligence — but they generally agree that humans are highly intelligent.

    Other members of the animal kingdom exhibit signs of intelligence as well, and some scientists might say the definition of animal vs. human intelligence is merely a matter of degree - a point that was brought home in 2005 when the London Zoo put "Homo sapiens" on display in the exhibit pictured here. Click ahead to learn about nine other species that stand out for their smarts.

  • Chimps are almost like us

    Tetsuro Matsuzawa  /  AP

    If we humans possess intelligence, chimpanzees must have some as well: Our genomes are at least 98 percent identical. Chimps make and use tools, hunt in organized groups and engage in acts of violence. Wild troops have distinct behaviors and customs. Field observations and lab experiments show chimps are capable of empathy, altruism and self-awareness. In the experiment pictured here, chimps performed better than humans on a number memory test.

  • Dolphins get creative

    Janet Mann  /  Georgetown University

    This dolphin in Australia uses a sponge to protect her snout when foraging on the seafloor, a tool use behavior that is passed on from mother to daughter. Scientists say that's just one sign of dolphin smarts. Other signs include distinct whistles and clicks that may serve as dolphin names, perhaps used in a type of language. A famous 1960s experiment found that a pair of dolphins entered a tizzy of creativity once they figured out their novel behaviors were rewarded with fish. Frustrated human test subjects just let out a sigh of relief when they caught on to the idea.

  • Elephants exhibit self-awareness

    AP

    The sheer size of their brains suggests that elephants must know a thing or two about the ways of the world. They have been seen consoling family members, helping other species in times of need, playing in water and communicating with one another via vibrations sensed in their feet. A crowning achievement, some researchers say, was when this female Asian elephant named Happy recognized herself in the mirror. The complex behavior is shared only with humans, great apes and dolphins.

  • Cephalopods have big brains

    Binyamin Hochner

    Are octopi, squids and cuttlefish smart? That's a matter of scientific intrigue, but such cephalopods are certainly among the brainiest invertebrates in the sea. The cephalopod brain surrounds the esophagus, but shares with the human brain features of complexity such as folded lobes and distinct regions for processing visual and tactile information. The how-smart debate swirls around deciphering observations that the creatures have a seemingly irrepressible curiosity, a disdain for boredom, an ability to learn and the capacity to use tools. The octopus pictured here exerts precise muscle control to eat.

  • Crows get crafty

    Alex Kacelnik et al.  /  University of Oxford

    Crows are crafty critters: They fashion tools from twigs, feathers and other bits of debris to snare food from hard-to-reach places. A crow named Betty, pictured here, uses a straight wire she bent into a hook to retrieve food from a tube. The birds are born with a tool-making ethic, but they hone their craft by watching their elders, a sign of higher intelligence. Ravens, a type of crow, have even been shown to manipulate the outcomes of their social interactions for added protection and more food.

  • Squirrels can be deceptive

    Gabriel Bouys  /  AFP - Getty Images file

    Is the squirrel pictured here plotting deception? Perhaps. Researchers recently reported that the rodents put on elaborate shows of deceptive caching to thwart would-be thieves. The behavior increased in a lab experiment after squirrels observed humans stealing their peanuts. The researchers called the finding a sign that squirrels can interpret intentions of others, though it could just be a case of learned behavior. Other studies have shown the critters make three-dimensional maps to recall where they cache their nuts. And squirrels in California will cover their fur in the scent of rattlesnakes to mask their own scent from predators.

  • Man's best friend

    University of Vienna

    Are dogs intelligent or just really good at basic obedience? They can learn to sit, lie down and fetch, for example, but can they read their owner's intentions? Research suggests they can at least find food in response to non-verbal cues, a type of understanding that scientists think may be akin to the human ability to understand someone else's point of view. The dog in the experiment pictured here accurately discriminated between photos of dogs and photos of landscapes — an indication the dog was able to form the concept of "dog."

  • Cats are adaptable

    Bob Pennell  /  AP

    Like dog owners, some cat owners have trained their pets to sit down, roll over and jump through hoops. Cats learn the tricks by observation and imitation, egged on with positive reinforcement. But training cats is harder than dogs. Does that mean they are less intelligent? Not necessarily. Cat experts say felines are just different. They are solitary animals, motivated by the need to survive. This has allowed them to adapt to a variety of domestic environments for at least 9,500 years - even the hoods of cars.

  • Pigs are wise ... and clean

    Paulo Whitaker  /  Reuters

    Here's the dirt on pigs: They are perhaps the smartest, cleanest domestic animals known - more so than cats and dogs, according to some experts. But pigs don't have sweat glands, so they roll around in the mud to stay cool. A sign of their cleverness came from experiments in the 1990s. Pigs were trained to move a cursor on a video screen with their snouts and used the cursor to distinguish between scribbles they knew and those they were seeing for the first time. They learned the task as quickly as chimpanzees.

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