 Dear students, in this topic, we shall discuss the reciprocal altruism. The animals occasionally behave altruistically toward unrelated individuals. This altruistic behavior is actually in expectation of return of favor in future, that is reciprocity. For example, a baboon may help an unrelated companion in a fight. Or a wolf, a wolf who is not related at all can offer food. This is an example of reciprocal altruism. Reciprocal altruism is limited to only those species which have stable social groups, for example chimpanzees and humans and some other mammals. In such groups, individuals are likely to meet again and get the chance to exchange it. Dear students, reciprocal altruism is also associated with negative consequences. Because if favors are not returned to the individual who had been helpful in past, such unreciprocated behavior is referred to as cheating by behavioral ecologists. It occurs because cheating may benefit the cheater substantially. It may be useful to not help anyone at all, so cheating is done. However, the reciprocal altruism dominates over cheating behavior. This is explained by the game theory which involves a behavioral strategy which is called tit for tat. In this strategy, an individual treats other in the same way it was treated in their last encounter. In other words, the way it was treated is treated in the same way it was treated in the last encounter. It is called tit for tat. Individuals adopting tit for tat behavior are always altruistic i.e. cooperative on their first encounter with the other. This remains so. Cooperative behavior can continue as long as their altruism is reciprocated. However, when the cooperation is not reciprocated, individuals employ tit for tat i.e. they retaliate immediately. However, cooperative behavior returns as soon as other individual becomes cooperative.