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updated 4/10/2012 9:16:08 PM ET 2012-04-11T01:16:08

Cooperation leads to intelligence.

In fact, researchers believe that intelligence in our species and others — correlated with the size of a brain’s neural network — may have been an adaptation for tool use, for social learning, and for the accumulation of culture. Intelligence might also be the result of sexual selection.

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The findings, published in the latest Proceedings of the Royal Society B, could help to explain why humans, dolphins, elephants and other clever animals are so brainy.

The idea that complex social interactions drive the evolution of intelligence has been around since the 1970’s. The problem with related studies has been how to disentangle what factors actually fuel intelligence and what were subsequent consequences of it.

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"Because experimental evolution of vertebrate brains is obviously impossible, we thought artificial intelligence would be the best way to evaluate the plausibility of the hypothesis," lead author Luke McNally told Discovery News.

The process might even be fueling the evolution of ever more intelligent individuals.

“It is conceivable that, with the rise of global networking, the demands of keeping track of an ever-growing number of social interactions may select for greater social intellect, but we’ll have to wait and see!” McNally said.

McNally, a member of Trinity College Dublin’s Theoretical Ecology Research Group, conducted the study with colleagues Sam Brown and Andrew Jackson. They created digital organisms that electronically evolved "brains" in order to succeed in social games where they could either cooperate or cheat on their opponent.

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Each individual’s fitness, based on the game outcomes, was calculated per round, with certain individuals selected to reproduce. Newly produced "offspring" underwent mutations, similar to what happens in real life. Generations also died. The researchers ran this genetic algorithm until 50,000 generations were reached.

The researchers found that the digital organisms typically started to evolve more complex brains when their societies began to develop cooperation. The results therefore support the idea that cooperation helped to drive the evolution of intelligence in at least certain species.

"The transitions to cooperative societies from uncooperative ones select for intelligence because of the constant risk of being exploited by uncooperative individuals," McNally explained. "This requires memory of past interactions and use of this memory to make decisions."

He added, however, that the process creates opportunities for "naïve individuals who always cooperate to invade the population. This can further create opportunities both for 'mean' individuals to invade and individuals that recognize and exploit the naïve competitors."

He is also quick to add that intelligence facilitates cooperation, but does not inevitably lead to it. Some of the most cooperative species are bacteria and certain social insects such as wasps, bees and ants. While these organisms are very successful, they are small and not exactly known for their big brains.

A Machiavellian arms race, where greater intelligence and complex strategies select for further intelligence and complexity, evolved in humans and other animals which may have also been affected by other factors, the researchers concluded.

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Sarah Brosnan, an assistant professor of psychology and neuroscience at Georgia State University, told Discovery News that the new study “is a really interesting addition to the literature” on what helps to explain the evolution of intelligence.

“This is one of the first models showing that selection for efficient cooperative decision making alone can influence the evolution of intelligence, so it provides a really nice proof of concept for the social intelligence hypothesis,” she said. “This could potentially explain the large brain sizes seen in several highly cooperative species, including humans.”

Robin Dunbar, director of the RSA’s Institute of Cognitive and Evolutionary Anthropology in the School of Anthropology, said that it appears “mutualism as opposed to simple altruism is critical to primate, including human, sociality,” suggesting “that it is this kind of social cooperation that has been critical in terms of selection for large brains.”

© 2012 Discovery Channel

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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