"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.