In this blog post, we’ll examine the situations in which human altruism and selfishness manifest, and explore how altruistic behavior has been maintained and passed down through generations.
The moment that determines whether a person acts selfishly or altruistically always occurs when something is in short supply. When two people face each other with limited resources, the decision of whether to act selfishly or altruistically is made. If two people have both finished eating at an all-you-can-eat barbecue restaurant and are faced with leftover food, a situation where they have to decide whether to fight over it or share it is unlikely to arise. However, in a situation where resources are scarce, a selfish person will try to claim the resources for themselves. In that case, the person who fails to obtain the resources will suffer as a result of the actions of the one who took them. Most situations in our lives are not like an all-you-can-eat barbecue restaurant; rather, they are more akin to facing a limited resource, such as 200 grams of pork belly on a grill. When resources are limited, it is obvious which behavior is most advantageous for oneself. Selfish behavior—prioritizing one’s own interests even at the expense of others—may be more advantageous for survival. However, if we look around us, we see that humans do not always act solely in their own self-interest. From a survival perspective, some people exhibit altruistic behavior to such an extent that it’s puzzling why they make such choices. Examples include the owner of a small business who sacrifices their own salary to ensure their employees are paid, or people who compete by adhering to fair rules even though they could gain more profit by deceiving others. Why has this altruistic behavior persisted to this day? Clearly, in the short term, such behavior is disadvantageous for survival and involves the risk of suffering a loss when encountering selfish individuals. So, could it be that people who act altruistically today are the descendants of altruistic groups? While altruistic individuals may suffer losses, might altruistic groups have actually been more resilient in terms of survival?
In everyday life, situations where outcomes differ depending on whether others act selfishly or altruistically in the context of limited resources occur dozens of times a day. Examples range widely, from advertising competition among companies to disputes over practice room usage among college clubs and the allocation of library seats. The Prisoner’s Dilemma is a representative model that generalizes and explains these situations. In the Prisoner’s Dilemma, one can gain the greatest benefit by betraying a partner who acts altruistically. Conversely, since being betrayed by one’s partner results in the greatest loss, individuals in that situation are prone to acting selfishly. When a selfish person encounters an altruistic person, only the selfish person can gain an advantage that benefits their survival. However, when two altruistic people meet, both can benefit. So, what would happen if an altruistic group existed? Because they trust one another and act altruistically, fewer members within the group suffer losses due to betrayal or face disadvantages in survival; as a result, the group can sustain itself over time. Furthermore, even if they do not achieve the maximum benefit obtainable through betrayal, they can still gain steady benefits, giving them an advantage in survival. Such groups are likely to persist across generations, and altruistic behavior can continue throughout that process. This explanation—that altruistic people come together to form groups that are advantageous for survival, and as a result, altruistic behavior has been perpetuated—is precisely the “birds of a feather flock together” hypothesis.
