There is an order to the universe, part moral, part political, part ecological. When that order is violated, eventually there is chaos.

Reciprocal altruism occurs where the roles of the donor and recipient are later reversed. This often occurs in social animals. For example, vampire bats feed only on blood. An individual cannot ...

For cooperation to be maintained reciprocal altruism, individuals must be able to assess the equitability of their own payoffs relative to their partners. In captivity, capuchin monkeys have ...