Let a bunch of chimpanzees into a yard filled with watermelons and while a few of them may horde the fruit at first, eventually they will share. If not, their whole social system will be disrupted.
"If things get totally out of whack, you keep everything and I get nothing, yes, there is going to be some protest," eminent biologist Frans De Waal said.
De Waal has spent over 30 years studying primates. He said that the primates' protest against those who don't share is the equivalent of the righteous indignation we humans sometimes display.
Take Americans' frustration with Wall Street executives getting big bonuses. De Waal said that those feelings of outrage are rooted in the same feelings that a primate feels when his fellow monkey stiffs him.
De Waal, a pioneer in the topic of animal empathy, said that this is just one example of mammals displaying something approaching a moral sense. He said that mammals frequently display empathy and reciprocity, crucial components of morality.
"I do think that human morality didn't start from scratch -- human morality started with the primate psychology which has all these tendencies of reciprocity and empathy and following social rules and so on...so we took that psychology and we turned it into a moral system," he said.
Examples of this empathy include the way chimps will hug and kiss after a fight and the way they help out elderly members.
The professor recalled a group of chimpanzees rallying around an older, arthritic female chimp.
"On certain days, she could barely walk and we noticed that on those days, other younger females would run to the water spigot and get water and they would run up to her and she would open her mouth and they would spit it in there," De Waal said.
Chimpanzees also mourn.
"If one of the members of the group dies...the rest don't eat for a day. They're very silent. They don't eat, even though normally they would always eat," he said.
De Waal also designed an experiment with Capuchin monkeys where a female gets a choice between a token that will result in just her getting a treat or one that results in both her and a friend getting treats.
"Over time if you do this often enough, the monkeys start to prefer the pro-social token as we call it," De Waal said.
The pro-social token means the monkey chooses the option that will help her friend too.
It's not just primates who show a moral sense. Dogs console their owners. If a mouse sees another mouse it knows is in pain, it will become more sensitive to pain. Dolphins and beluga whales have been known to help humans in distress.
All of these examples make De Waal pose a provocative question. Is morality inherited from our primate ancestors or did belief systems and religions create a moral code?
He argues that the building blocks of morality come from our animal ancestors, not religion.
"I'm not sure that religion is at the root of morality because I personally think that morality probably existed long before we had religions," De Waal said. "We are very much group animals, we want to fit in the group, we are interested in the community life that we are part of and so we will contribute to it ... all these tendencies that are important for morality."
He argues that we evolved to be moral, that humans, like primates, are group animals and groups that work well together tend to survive.
There is, however, a twist. De Waal still thinks religion may be useful for encouraging morality.
"For me, the question is all human societies have some form of religion, so what does it contribute to human society?" he said. "I think religion probably contributes to the desire to be a moral being."
De Waal is one biologist with a theory that angers both atheists and the faithful.