In this blog post, we will examine why altruistic behavior occurs in humans and animals from an evolutionary perspective, focusing on the repetition-reciprocity hypothesis.
There are many altruistic people in the world. Such behavior clearly benefits others, but in many cases, the person who performs the act receives no reward or even suffers a loss. A typical example of altruistic behavior commonly seen in human society is blood donation. While it is a precious act that can save the life of the recipient, it requires time and effort on the part of the donor and can sometimes be a troublesome and uncomfortable experience.
Altruistic behavior can also be observed in nature. For example, when an animal discovers a predator, it makes a loud noise to warn other animals in the vicinity of the danger. This behavior serves as a warning to other individuals for their survival, but the individual that issued the warning is more likely to be in danger as it attracts the attention of the predator. In this way, altruistic behavior is beneficial to others but can be detrimental to the survival of the individual.
From an evolutionary perspective, altruistic individuals are likely to suffer material and biological losses. For example, suppose that altruistic and selfish individuals coexist within a group. Altruistic individuals inevitably become poorer because they share resources with others, while selfish individuals become relatively wealthier because they receive help from others while protecting their own resources.
This imbalance ultimately puts altruistic individuals at a disadvantage in terms of survival, raising the question of whether they will eventually disappear over time. Despite this, why do humans and many other organisms continue to engage in altruistic behavior? One explanation for this question is the reciprocal altruism hypothesis.
This hypothesis is a theory about altruism that is formed through repeated interactions rather than one-time interactions, and its basic structure is as follows. First, one shows kindness to the other, and if the other repeats the same cooperative behavior, one continues to maintain cooperative behavior. On the other hand, if the other shows selfish behavior or betrayal, one retaliates in a corresponding manner.
The behavior of vampire bats is often cited as a good example of this theory. Vampire bats feed on the blood of mammals, and if an individual fails to hunt for several days, its survival may be threatened. At this time, other bats are observed vomiting the blood remaining in their stomachs and sharing it with the starving bat. On the surface, this appears to be a very altruistic behavior, but in reality, it is cooperation that stems from repeated interactions.
Individuals that have received blood in the past share their blood in return. This behavior is not a simple act of kindness, but rather a form of “strategic altruism” based on the expectation of future rewards, which clearly illustrates the core of the repetition-reciprocity hypothesis. However, this hypothesis also has its limitations. The biggest problem is that this theory only holds true in a structure where “retaliation” can function effectively. The first condition is that interactions must occur repeatedly. If a situation is a one-time relationship, even if the other party betrays you, you will not have the opportunity to retaliate, so cooperation is difficult to establish. The second condition is that the number of participants must be small. This is because retaliation is difficult to carry out effectively within a large group. Let’s look at an example.
Suppose that all members of a group contribute a certain amount of money to a fund and agree to divide the profits equally among themselves at a later date. However, the names of the contributors are not disclosed. In this case, even if someone does not contribute, they will still receive a share of the profits, so it is possible to “free ride.” Even if some members decide not to contribute in the next round as a form of retaliation, it will not have a significant impact on the total profits, and as a result, those who contributed faithfully from the beginning will suffer the greatest loss. In such cases, the repetition-reciprocity hypothesis is difficult to apply because the retaliation mechanism that suppresses selfish behavior does not function properly.
Nevertheless, the repetition-reciprocity hypothesis is a useful theory for explaining altruistic behavior observed in many real-world cases. It is like a prototype in the testing stage, which is not yet perfect but provides a structural framework that can be put to practical use. Of course, there are various other hypotheses that attempt to explain altruism, but none of them can fully explain all altruistic behavior that occurs in human society or the natural world.
The important thing is that even if we do not know the evolutionary origins or biological mechanisms of altruistic behavior, it plays an essential role in maintaining our society. Altruistic behavior, such as blood donation, small acts of kindness in everyday life, and cooperation within communities, can be described as the invisible energy that sustains communities. In this sense, exploring the motives and structure of altruistic behavior goes beyond mere academic curiosity and serves as the foundation for building a better society.
