In this blog post, we will look at how altruism evolved into cooperation in society, focusing on the “birds of a feather flock together” hypothesis.
According to Darwin’s theory of natural selection, organisms that are better adapted to their environment are more likely to survive, while those that are not are eliminated. The genes of the surviving individuals are passed on to future generations, and through this repeated process, species gradually evolve in a direction that is more suited to their environment. Ultimately, only the individuals that win the competition gain the opportunity to reproduce and procreate. According to this logic, the natural world is a place of fierce competition, and it seems only natural for individuals to live “selfishly” in order to survive and pass on their genes.
However, some higher social animals, including humans, show patterns of evolution that go beyond the simple logic of “survival of the fittest.” Of course, selfish behavior is commonly observed in human society, but “altruistic behavior” contributes greatly to the maintenance and development of society.
However, when you think about it carefully, altruistic behavior that prioritizes the survival of others over one’s own survival or interests is difficult to explain by existing evolutionary theory. Why do some people help others even at their own expense? Various hypotheses have been proposed to answer this question, one of which is the “like attracts like hypothesis.”
This theory posits that individuals with similar values and survival strategies recognize each other and gather together, and that the groups thus formed function efficiently through altruistic behavior. In other words, “birds of a feather flock together.” Living with people who have similar thoughts and attitudes to oneself leads to fewer conflicts and easier mutual understanding and cooperation, resulting in social stability.
The question then becomes how people with similar tendencies gather to form groups and how those groups survive while maintaining their altruistic characteristics. The answer is surprisingly “yes.” Human society has several structural conditions that enable people with altruistic tendencies to gather and form cooperative communities.
The first reason is that humans instinctively tend to choose people with similar values and beliefs to form relationships. For example, according to a survey, about 90% of married couples show high similarity in political orientation and religious views. These two factors are not simply a matter of agreement, but deeply influence one’s worldview and moral standards.
In other words, people with similar values tend to associate with each other, which means that people who prefer altruistic behavior are naturally drawn to each other and form connections. The second reason is that humans are social animals and acquire information about others through society, which they then use to make judgments. In small communities in particular, members can easily share and remember specific information about the past behavior of others. The ability to judge who is altruistic and who is trustworthy stems from this flow of social information, and as a result, people surround themselves with those who have similar moral standards. The third reason is the self-regulating function of groups. Even if a community centered on altruistic members is formed through the process described above, it cannot be expected that everyone in that group will always behave altruistically.
However, most groups have certain rules to maintain trust and cooperation among their members. These norms sometimes sanction or exclude uncooperative individuals, thereby maintaining the cooperative nature of the group. If altruistic behavior is respected within a group and the opposite behavior is penalized, a community centered on altruistic members can be maintained in a stable manner.
So how long can a society made up of altruistic people survive in a competitive environment? Altruistic groups operate by sharing resources and minimizing conflict through cooperation, so in the short term, they may appear to lag behind their competitors. However, as cooperation continues, the group becomes increasingly efficient and productive, which can ultimately be a decisive factor in gaining an advantage over other groups.
Therefore, groups composed of altruistic individuals will have an advantage in the long run, according to the principle of natural selection. However, there is one important limitation to the “birds of a feather flock together” hypothesis. That is the lack of diversity. For example, imagine a soccer team composed entirely of forwards. No matter how talented the individual players are, a team without defenders, midfielders, and goalkeepers cannot function properly.
Similarly, when the members of a group have overly similar tendencies, there are limitations to the roles they can perform, and ultimately, they may become less competitive than other diverse groups.
In conclusion, the “birds of a feather flock together” hypothesis is a very useful theory for explaining how altruistic humans recognize each other, form communities, and survive in the face of competition and evolution. However, it has limitations in that it cannot completely overcome the weaknesses of groups composed solely of similar individuals. The partial similar-to-similar hypothesis emerged to address this issue. It proposes a flexible structure that allows interaction not only within the group but also with various people outside the group, in an attempt to maximize the advantages of similar-to-similar groups while minimizing the disadvantage of lack of diversity.
If this hypothesis is further refined, it could become an important theory explaining the emergence and survival of altruistic humans. Understanding this altruistic nature and its evolution is also key to understanding why human society has been able to develop through cooperation and mutual understanding rather than simply through competition.
