Reciprocal altruism

Reciprocal altruism is a theory which is to explain the evolution of altruistic behavior between unrelated individuals by natural selection. It was published in 1971 by Robert Trivers.

Description and Requirements

Altruism is usually defined as conduct of an individual in favor of any individual, where the behavior of the altruistic individual immediately brings more costs than benefits. One such definition shall not preclude that altruistic behavior reacts positively to long-term reproductive success (fitness ) of the altruistic individual or individuals related to him. However, is a prerequisite for the biological- evolutionary training every altruistic behavior that the overall benefit of the altruistic behavior is positive.

Characteristics of the specific reciprocal altruism between unrelated individuals are:

• The altruistic behavior is balanced between the interacting individuals.
• In the reciprocal relationships that individuals switch between the roles of the sender and the receiver.
• The overall benefits of reciprocal altruism exceeds its total cost.

An animal can procure at his own expense another animal without fitness disadvantage an advantage if the beneficiaries responded that advantage at a later date. This requires a level of intelligence that can identify fraudulent behavior. This requirement is important because altruistic behavior from an evolutionary perspective is always prone to be exploited by not erwidernden individuals. Punishments are also necessary. Also, the memory must be strong enough to recognize scammers. Because of these conditions, the reciprocal altruism works best with intelligent, social, and long-lived species. According to the biologist Robin Dunbar developed human language, since it facilitates the identification of cheaters.

Non-human primates

Most primates live in stable social groups. It is not known whether primates possess the cognitive skills in order to recall certain behaviors of other individuals towards them. Primates are at least very intelligent and able to solve complex problems. Reciprocal grooming and Covenants has been observed in several species of macaques, baboons, vervet monkeys and chimpanzees. In some cases, grooming and support in kind were changed, in other grooming to support. Some monkeys take turns grooming, so the time is balanced during each grooming phase between individuals. Other monkeys balance this time over several grooming phases.

In male chimpanzee social ties on reciprocal exchange of many different services seem to be based. Chimpanzees in Kibale National Park selectively share meat with the individuals who have themselves shared meat with them or ensure regular support. Males, who hunt together, tend to be more selective mutual grooming and support as well as common patrolling the borders. These males are not related. These correlations are consistent with the theory of reciprocal altruism, but not prove, that these altruistic behaviors are conditioned by reciprocity. Several studies have suggested this.

In one experiment, vervet monkeys were played on tape recorded calls for help from other monkeys. The auditions take place in two different situations. In the first situation monkey A monkey B had previously maintained the fur. On the playing call for help from monkey A monkey B responded relatively quickly. In the second situation, no grooming had occurred previously. Again, responded monkey B on playing call for help from monkey A - albeit more slowly.

In another experiment, by Frans de Waal different individuals were placed in a group of chimpanzees over a period of three years, multiple bundles of leaves. The individuals were able to keep these bundles for themselves; often the bundles were, however, divided. Here were the owners of the bundles always those individuals more generous, which a short time previously had maintained the fur of the owner. Also, the owner of the leaves less strongly defended against attempts by individuals to appropriate parts of the bundle, if these individuals had previously maintained the fur of the owner.

The number of well-documented cases of reciprocal altruism in non-human primates as a whole is still small. It is therefore possible that such behavior in nature is rare. Reciprocal altruism could, however, occur more frequently than observed. Altruism manifests itself potentially in various ways (eg, grooming, protection against predators ), and it is very difficult to quantify the costs and benefits of all these altruistic behaviors.