Monkeys show sense of justice

"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 more-liked 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 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," Sarah Brosnan said."

BBC.co.uk, 17 September, 2003

A few years old story, but it was recently posted at Dawkins' site and is no less important now.