The Moral Necessity to Give to the Distant Poor

Even monkeys will reject a reward for a task, if they see another monkey getting a better reward. Why would people and monkeys act in ways that seem contrary to their own interest? The most plausible answer is that moral intuitions developed because they enhanced the reproductive fitness of those who had them. A society in which most people act fairly will generally do better than one in which everyone seeks to take unfair advantage.