In this blog post, we will look at the evolutionary background behind humans choosing cooperation over competition, focusing on the “like attracts like” hypothesis.

Can “like attracts like” explain the evolution of altruistic humans?

According to Darwin’s theory of natural selection, organisms that adapt well to their environment survive, while those that do not are eliminated.
Surviving individuals pass on their genes to their offspring, and as this process repeats itself, species evolve in a direction that allows them to better adapt to their environment. Ultimately, only those individuals that survive the fierce competition for survival can leave behind their genes through reproduction.
In this way, competition is the essence of nature, and the principle of “survival of the fittest” prevails.
From this perspective, it seems perfectly natural for individuals to act selfishly for themselves and their offspring. However, humans are different from other animals. Humans are a highly social species, and there are many cases where they do not follow the simple law of survival of the fittest. Of course, selfish behavior is common in human society, but altruistic behavior has contributed greatly to the formation and maintenance of our complex society.
This raises the question: How did “altruistic behavior,” which seems to contradict the existing laws of survival, emerge in humans?
Various evolutionary theories have been proposed to explain this question, one of which is the “Assortative Interaction Hypothesis.”

What is the Assortative Interaction Hypothesis?

“Assortative interaction” literally means that people with similar tendencies and values are attracted to each other and tend to associate with each other. This hypothesis suggests that people with similar survival strategies and social attitudes recognize each other and gather together, and that altruistic behavior flourishes in the groups formed in this way.
When people with similar values and attitudes form a society, there are fewer conflicts of opinion, cooperation is easier, and conflicts can be minimized. As a result, a more efficient society can be formed. However, this raises questions. How can people with such similar tendencies gather together to form a society? And can such a group actually survive in a competitive environment?
The answer to these questions is “yes.”
This is because humans instinctively choose people who are similar to themselves and tend to form societies through relationships with such people. This process can be explained by the following reasons.

Three reasons why altruistic groups form

The human tendency to choose people with similar values

As social beings, humans naturally tend to prefer people with similar values and tendencies when forming relationships. For example, according to a survey, about 90% of married couples share similar political views and religious beliefs. This similarity goes beyond mere preferences and means that they share the same direction in life and principles of behavior. Having similar values means that it is possible to form a consensus on altruistic behaviors and the reasons behind them.

Acquisition of social information and selective relationship formation

Humans actively utilize social information when judging others. Especially in relatively small communities, information about the past behavior and social reputation of members is naturally shared among them. Based on this information, people try to form relationships with those they trust and who think similarly to them. This ultimately creates cooperative groups of people with similar tendencies.

Self-regulation of groups

Even if a group starts out with altruistic members, over time, some uncooperative or selfish members may emerge. However, most groups have rules and norms for maintaining the community, and members who violate them are excluded or penalized. In this way, groups maintain their internal order and, as a result, are able to sustain a community centered on altruistic members.

Can altruistic groups survive in a competitive environment?

Societies composed of altruistic individuals prioritize the well-being and cooperation of the group over that of the individual, and therefore have high organizational power and cohesion in the long term. This is because they can distribute resources more effectively and establish fast and efficient cooperation systems based on trust among members. Groups formed in this way have a higher chance of survival than other groups, which can be explained from the perspective of natural selection theory.
In other words, selfish behavior may be advantageous at the individual level, but altruistic cooperation can be the key to survival at the group level. Groups centered on altruistic people can achieve greater synergy based on cooperation and lead to sustainable evolution.

Limitations of the birds of a feather hypothesis: lack of diversity

However, the altruistic society proposed by the birds of a feather hypothesis is not always ideal. The biggest weakness of this theory is its lack of diversity.
Consider, for example, a soccer team consisting only of attackers. No matter how talented each individual player is, it would be difficult to win a game without defenders and goalkeepers. A team with a balance of different roles and perspectives can function much more powerfully and flexibly. Similarly, groups composed only of people with similar tendencies may be efficient in the short term, but in the long term, they may not be able to respond effectively to changes in the external environment or complex challenges.

Conclusion: From “birds of a feather flock together” to “partial birds of a feather flock together”

In summary, the birds of a feather hypothesis provides a useful framework for explaining how altruistic humans come together and how such groups can survive in the course of evolution. However, it has limitations in terms of its lack of diversity, which needs to be addressed.
What is noteworthy here is the “partial assortative mating hypothesis.” This refers to a flexible social structure that is not composed entirely of similar people, but rather of diverse elements with different backgrounds and roles that interact with each other based on certain commonalities.
If this hypothesis is refined further, it could become a powerful theoretical basis for explaining the evolution and survival of altruistic humans.
This is why we pursue cooperation and diversity. Ultimately, the evolution of human society may be a process of finding a balance between similarity and diversity.