In this blog post, we explore how group selection maintains altruistic behavior and enables social cooperation in human society, where self-interest and altruism coexist.
“Are you selfish or altruistic?” It’s not a simple question to answer, as everyone likely possesses both selfish and altruistic traits. While the coexistence of selfishness and altruism within us may seem natural, it is difficult to explain from an evolutionary perspective. According to natural selection, only individuals with traits best suited to the environment survive, and since altruistic behavior involves sacrificing one’s own interests, it is a disadvantage for survival compared to selfish behavior. Ultimately, from an evolutionary perspective, only selfish individuals would remain. However, altruism clearly exists in reality, and scholars have proposed various hypotheses to explain it. Among these, the group selection hypothesis views the evolutionary process from a “group” perspective rather than an ‘individual’ one, and holds significant importance in explaining altruism in humans, who are social animals. Let us now examine the group selection hypothesis.
Natural selection can be divided into individual selection and group selection. The natural selection mentioned earlier refers to selection centered on the individual, which is called “individual selection.” According to individual selection, individuals with selfish traits have a survival advantage over altruistic individuals because they maximize their own interests. Therefore, over time, altruistic individuals disappear, leaving only selfish individuals. But what if natural selection were applied to groups? Which group—one composed of selfish individuals or one composed of altruistic individuals—would be better suited to the environment? Natural selection operating from this perspective is called “group selection.” Under group selection, altruistic behavior yields “social” benefits, meaning that altruistic groups are better adapted to the environment than selfish groups. For example, if a war breaks out between groups, an altruistic group is likely to have many brave and self-sacrificing warriors, giving it a greater chance of prevailing over a selfish group.
Now, let’s consider a situation where individual selection and group selection act simultaneously. From the perspective of individual selection, selfishness prevails, while from the perspective of group selection, altruism prevails. Therefore, for altruism to survive, group selection must act more rapidly than individual selection. And the fact that altruism actually exists in our society implies that group selection acts faster than individual selection, or at least at a similar pace.
To illustrate this, let’s consider a tribal society that shares food. If both selfish and altruistic individuals coexist within a tribe, individual selection within the group will eventually leave only the selfish individuals. Altruistic individuals share their food with others, while selfish individuals take others’ food without sharing; consequently, the altruistic individuals gradually become poorer, and the selfish individuals become wealthier. As a result, it becomes difficult for altruistic individuals to survive, and only the selfish ones remain. In such a tribe composed solely of selfish individuals, it is difficult to survive unless one can gather food oneself.
However, the situation changes if there exists a tribe among many that consists entirely of altruistic individuals. An altruistic tribe helps and cooperates with one another, ensuring that even the weak, the elderly, and orphans can secure food. Consequently, more people survive than in a tribe composed of selfish individuals. Therefore, viewed as a whole, even though there may be many selfish tribes, a single altruistic tribe can have a very large population, leading to an increase in the number of altruistic individuals. In this context, when individual selection and group selection occur simultaneously, altruism is likely to increase overall, and over time, altruism can coexist with selfishness.
In this way, the group selection hypothesis provides an evolutionary explanation for the altruism we observe around us. However, some scholars criticize this theory, arguing that group selection is unlikely to keep pace with the speed of individual selection in reality. Yet, unlike other animals, humans possess “institutions” that can slow down the pace of individual selection. As in the previous example, in a situation without institutions, if a selfish individual emerges within an altruistic tribe, that individual will accumulate more food, thereby accelerating individual selection. However, an altruistic tribe can prevent the progression of individual selection—which leads to an increase in selfish individuals—by introducing a system of communal ownership of resources. In other words, humans are social animals that form various types of communities, ranging from broad groups like nations to narrow groups like families, and use institutions to slow down the pace of individual selection and regulate society so that altruism is maintained. As a result, human altruism can coexist with selfishness through group selection.
