Every day, we encounter acts of kindness in various situations. We call out to people who are lost, help those carrying heavy luggage, or give up our seats to elderly passengers on trains. We all feel that such actions are "good things," and they are indeed encouraged in society. But why do humans act kindly? This question seems simple at first glance, but upon deeper reflection, it is actually a very mysterious phenomenon.First, is our kindness simply the result of education? Certainly, we have been repeatedly taught since childhood to "be kind to others." At school and at home, kind actions are praised while unkind attitudes are scolded. Through this accumulation, one could view kindness as having become ingrained as a habit.Alternatively, kindness may be a result of concern for others' opinions. If you remain seated in front of an elderly person on a train without offering your seat, you'll receive cold stares from those around you. Priority seating systems even exist, creating silent pressure on young people who sit there. This peer pressure undeniably drives us toward kind behavior.Even more interesting is the Japanese saying "情けは人の為ならず" (kindness is not for others' sake). This is the idea that we should be kind not for others, but because kindness will eventually return to benefit us. This phrase contains a perspective that views kindness as a calculated act. We're kind because it benefits us. Thinking this way, the purity of kindness begins to fade.As we continue thinking critically about kindness in this manner, we begin to feel like unpleasant people. Indeed, if we were to make statements denying kindness, we would likely be criticized by many. To such an extent has kindness become an accepted premise in our society. The equation that being unkind is inhumane has become deeply rooted in society.So how can kindness be explained scientifically? Brain science research has revealed interesting facts. When people act for the benefit of others, a part of the brain called the reward system is activated. Since the reward system is a neural circuit that produces pleasure, this means that altruistic behavior itself feels good.This discovery provides scientific basis for the interpretation that "kindness is for one's own sake." Even when we think we're acting for others, our brains are actually experiencing pleasure. We're kind because being kind makes us feel good. Thinking this way, kindness might also be considered a type of self-centered behavior.At the same time, this brain mechanism highlights another problem. For those who experience the pleasure that kind actions produce, the existence of people who cannot be kind is incomprehensible. The criticism and condemnation expressed as "Why aren't you kind?" may have this reward system functioning in the background. Why can't others do what seems natural to us? This question sometimes leads to harsh criticism.However, even considering all this, a fundamental question remains. If kindness is pleasurable and beneficial to the brain, why isn't it seen in other animals? Even primates close to us, such as chimpanzees and bonobos, don't display kind behavior as extensive as humans do.The characteristic of human kindness lies in the breadth of its targets. We are kind not only to family and friends but also to complete strangers. When disasters occur, we send donations to distant disaster areas, and when we see someone in trouble, we call out to them. We extend our hands even to people we will probably never meet again.This extensive altruistic behavior is almost unique to humans. In other animals, cooperative behavior is basically only seen toward kin or individuals with reciprocal relationships. From an evolutionary perspective, it's difficult to explain what benefit there is in helping strangers. If leaving behind one's genes is the fundamental principle of living organisms, helping unrelated strangers seems irrational.For a long time, the concept of "reciprocity" has been proposed as an answer to this puzzle. If I help you today, when I'm in trouble someday, you'll help me. If such mutual aid relationships spread throughout society, everyone benefits. This is the explanation that kindness evolved for this reason.However, this explanation has weaknesses. Even when being kind to strangers—people we'll never meet again—we can't expect anything in return. Yet we are still kind. This fact is difficult to explain through reciprocity alone.The Evolutionary Origin of Human KindnessNew light was shed on this difficult problem by research published in February 2024. A research team led by Dr. Efferson at the University of Lausanne used computer simulations to investigate the evolution of human cooperative behavior. And they reached a surprising conclusion.The research team ran extremely precise simulations many times. They set various conditions and verified how much cooperative behavior the principle of reciprocity could generate. The results were unexpected. Reciprocity alone did not create extensive cooperative relationships among people.In other words, the principle of "kindness is not for others' sake"—the idea of being kind to others because it will eventually return to you—alone cannot explain the kind behavior observed in humans. So what was necessary?The answer was "intergroup competition." This discovery seems contradictory at first glance. The cooperative behavior of kindness arose from the confrontational situation of competition. However, when you think about it carefully, this makes sense.Humans always live belonging to some group. Family, local community, company, nation—the scale varies, but everyone is a member of multiple groups. And when multiple groups exist, competition over resources and rights inevitably occurs.Imagine the hunter-gatherer era. Multiple groups used limited hunting grounds and gathering areas. Good water sources and rich forests were precious resources. Competition between groups over such resources was unavoidable.What was needed to win this competition? Individual ability was important, but even more crucial was cohesion as a group. Members cooperating with each other, helping each other, sharing information, and sometimes not hesitating to make self-sacrifices. Groups with such strong bonds were the ones that won the competition.Dr. Efferson and colleagues' research showed that extensive cooperative behavior evolved only when the two elements of intergroup competition and reciprocity combined. Reciprocity alone was insufficient. Only with the external pressure of intergroup competition was cooperation within groups strongly selected.From this perspective, the meaning of kind behavior changes significantly. Kindness is not simply an expression of a beautiful heart. It was part of a group survival strategy. By being kind to group members, the cohesion of the entire group strengthens. Groups with strong cohesion are more likely to win competition with other groups. Members of groups that won competitions survived and could leave descendants.In this way, the genes of people with a tendency to be kind were passed on to the next generation. Over a long time, kindness became part of human nature. The brain's reward system giving pleasure to kind actions is also thought to be a mechanism acquired during this evolutionary process.What's important here is that the targets of kindness are mainly directed toward the "ingroup"—members of groups to which one belongs. We have stronger feelings of kindness toward students at the same school, colleagues at the same company, and citizens of the same country. This is not coincidental but the result of evolutionary pressure from intergroup competition.Of course, modern humans are also kind to complete strangers. This is thought to be a cultural extension beyond the original evolutionary function. However, the basic mechanism remains unchanged. We could also say that the scope of the "group" we belong to has expanded to all of humanity.Kindness as Collective Self-DefenseThe perspective of "collective self-defense" demonstrated by Dr. Efferson and colleagues' research gives new meaning to the behavior of kindness. Heartwarming acts of kindness were actually strategies for surviving ugly struggles.How should we accept this fact? Some people may feel that the value of kindness has decreased upon learning that the origin of kindness lies in competition. They may be disappointed to learn it was not pure goodwill but a survival strategy.However, I don't think so. Regardless of its origin, kindness still helps people and improves society. How it was acquired through the evolutionary process and the value of current behavior are separate issues.Rather, by understanding the evolutionary origin of kindness, can't we practice kindness more wisely? Kindness is both a natural tendency and behavior that requires effort. Even though the brain provides pleasure, actually being kind requires decision and action.Also, the perspective of collective self-defense teaches us the limitations of kindness. We tend to be kind to ingroup members but cold toward outgroups. Prejudice and discrimination against people belonging to different groups are negative aspects of this evolutionary tendency.In modern society, people with different cultures and backgrounds coexist. As globalization advances, the framework of former small groups is losing meaning. What's needed in such times is kindness that transcends the distinction of who is ingroup and who is outgroup.Fortunately, humans have advanced cognitive abilities. We can recognize our instinctive tendencies and overcome them. Even if the origin of kindness lay in intergroup competition, it's possible to expand its targets to all humanity and even to other living beings.In fact, many people participate in support activities across national borders. Environmental protection and animal welfare movements are also spreading. These are expressions of kindness beyond the original evolutionary function. They can be said to be examples of human cultural ability overcoming biological constraints.The behavior of kindness, while having complex origins, continues to hold important value in modern society. It is the result of education, pleasure from the brain's reward system, and also a strategy for surviving intergroup competition. These elements combine to shape our kind behavior.What's important is to build a better society based on this understanding. Just because the origin of kindness lay in competition doesn't mean we need to abandon kindness. Rather, by understanding its mechanism, we can practice kindness more consciously and more broadly.We are products of evolution, but at the same time, we are beings that transcend evolution. Transforming kindness that began as collective self-defense into a tool for the coexistence of all humanity—that may be the challenge given to us living in the modern age.Kindness is not merely a virtue but a behavioral pattern deeply rooted as humanity's survival strategy. Knowing its origin doesn't diminish the value of kindness. Rather, it helps us deeply understand why we can be kind and why kindness is important. And that understanding itself becomes the first step toward building a better society.ReferencesEfferson, C., Bernhard, H., Fischbacher, U., & Fehr, E. (2024). 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