Elegant experiments with apes and other animals are convincing researchers that humans aren't the only creatures on Earth to act in moral ways.

Speaking at the AAAS Annual Meeting, primatologist Frans de Waal argued that humans share behaviors like cooperation, consolation, and even distaste for inequity with animals from monkeys to elephants to wolves. "Humans would have never developed the moral systems that they have," he argued, "without those kinds of tendencies in place."

The studies also weaken the idea that people themselves are nasty at the core with only a polite veneer of morality covering their less sympathetic selves, he said. Instead, that trend is is giving way to an idea that Darwin proposed more than 100 years ago: Natural selection probably is responsible for making people nice.

The lessons learned from animals are not applicable perfectly to humans, de Waal told the AAAS audience, but knowing more about why empathy works may help explain why a movement like the Occupy protests take hold, or why it's difficult sometimes to sustain international aid efforts.

De Waal is a behavioral biologist most well-known for his studies of the social intelligence of primates. His books, Chimpanzee Politics--comparing the power struggle of chimp communities and American politicians--as well the more recent The Age of Empathy: Nature's Lessons for a Kinder Society, successfully blend science and social concerns. He delivered the plenary address on Monday 20 February, the closing day of the AAAS Annual Meeting in Vancouver, British Columbia.

Using frequent video clips to illustrate the latest studies--much of the research conducted by de Waal and his research team--the primatologist showed how scientists look for empathy across a variety of animals. Simple experiments--prompting a chimp's yawn by showing her an iPhone photo of another yawning friend, or making a mouse fearful after he sees his companions in pain--demonstrate that many animals can share the emotions of others, he said.

At the same time, an animal like an ape or an elephant has the capacity to distinguish itself as an individual apart from others, which gives it the cognitive ability to know when another needs help or consolation. Testing this "I/you" understanding without a questionnaire is difficult, de Waal admitted. Researchers working with elephants, for instance, build giant mirrors for elephants to find out whether the animals can recognize themselves. After peering at their reflections, the elephants scrub at harmless marks painted on their cheeks and open wide to examine their own teeth.

But the research has also revealed a "sometimes unfortunate" thing, de Waal noted. Strangers in any group of animals are much less likely to receive compassion. "Empathy is much more easily generated between individuals who know each other, or who are close to each other, than individuals who are more distant."

In remarks to reporters after the plenary talk, de Waal said this "in-group bias" has made it more difficult to "stretch empathy and solidarity. We now live in a world where all sorts of groups mingle in a society...so it's something that should be tried, but it's a challenge."

The experiments even reveal that monkeys and apes have a sense of fair play, demanding "equal pay" in the form of grapes rather than cucumber slices when they see their companions getting the sweeter treat.

De Waal compared the scenario to the human frustrations about income equality expressed in the Occupy Wall Street movement. "If you live in a cooperative society where you work together, where you bring in benefits together," he said, "you need to watch what you get."