In this blog post, we will look at the reasons why altruistic behavior has evolved and been maintained despite the selfishness inherent in human nature through the theory of group selection.
In our society, altruistic behavior such as donating blood or cleaning up an alley is common. However, from the perspective of natural selection, this is a kind of mystery. Altruistic people help others at a loss, while selfish people can receive help without any effort, so altruistic people are likely to be eliminated in the survival competition between the two types. According to natural selection, members of society will adopt an egoistic strategy that is advantageous in the competition for survival, and as a result, egoism will eventually become prevalent in our society. However, contrary to this prediction, there is still a lot of altruistic behavior in our society. Even though people can get greater benefits by free riding, they suppress their egoistic mind and act altruistically. Where does this altruism come from?
One of the keys to solving this mystery is the “group selection hypothesis.” Group selection is the hypothesis that the characteristics of a group also affect the survival of the group, just as the characteristics of an individual affect the survival of the individual. In other words, natural selection acts on “groups” rather than “individuals.” In individual selection, altruistic behavior, which can be a weakness, can be a strength for the group in group selection, which can give it an advantage in the competition for survival. For example, consider the situation in the game StarCraft, where the Defiler unit recovers energy at the expense of other Zerglings. If there are many selfish Zerglings, no one will be willing to sacrifice themselves, and it will be difficult to win the battle between the races. On the other hand, if there are many altruistic jugglers, they will be willing to sacrifice themselves and work for the victory of the entire race.
Looking at the history of mankind, there are times when group selection was likely to have been at work. In primitive tribal societies, wars between tribes were very frequent and the fatality rate was high. A group with many altruistic people would have been more likely to win these tribal conflicts. Even in pre-agricultural hunter-gatherer societies, the success of hunting and gathering depended largely on how altruistically members cooperated. In the harsh environment of tens of thousands of years ago, altruistic cooperation was essential, such as finding a safe place to live and protecting each other from external threats. The more altruistic a group was, the more likely it was to survive in the harsh environment.
However, there are still problems to be solved in this hypothesis. In individual selection, altruistic individuals are less likely to succeed than selfish individuals, and they are at risk of extinction. However, in group selection, groups with many altruistic individuals are more successful and have an advantage in the competition for survival than groups without them. As individual and group choices work in opposite directions, the group choice theory must be able to overwhelm the speed of individual choice in order to be convincing.
Humans have slowed down individual choice and amplified the effects of group choice through “institutions” such as rules, customs, and laws that affect interactions between members of society. One such institution is equal income distribution. The food-sharing customs of ancient hunter-gatherer tribes acted as an equal income distribution mechanism, reducing the differences between altruistic and selfish people and increasing the likelihood of group selection.
The transmission of conformist culture was also a factor that made group selection work strongly. The transmission of conformist culture means that if more than half of a group are altruistic, more people will learn altruistic strategies, making the group more altruistic; and if more than half are selfish, more people will learn selfish strategies, making the group more selfish. The reason why the transmission of conformist culture is important is that it can create a large difference between groups, even if the differences within the group are small. For example, let’s say there are two groups, one with 55% altruistic people and the other with 45%. Although the difference between the two groups is only 10%, if a conformist culture is passed on within the group, the number of altruistic people will gradually increase in the first group, while the number of altruistic people will gradually decrease in the second group. As such, the effect of group selection is increased by the conformist culture passing on, which greatly widens the gap between the groups.
So far, we have tried to solve the riddle of how altruistic humans could survive through the theory of group selection. Group selection is a hypothesis that natural selection occurs on a group basis and that the characteristics of the group affect the group’s survival. Humans have created an environment in which altruistic humans can survive by maximizing the effects of group selection through institutions and the transmission of conformist culture. Although group selection is not evolutionarily stable, it is a compelling hypothesis that explains how altruistic behavior has evolved in human society.
