This article explains the kin selection hypothesis that selfish motivation at the genetic level manifests itself in altruistic behavior to defend family members, while also addressing the possibility that such altruistic behavior may also stem from social and moral factors independent of genes.
The Korean movie ‘ The Flag Flies ‘ depicts an older brother’s tearful struggle to protect his younger brother. In the movie, Lee Jin-tae (Jang Dong-gun) is not afraid to take the lead in a life-or-death battle to protect his younger brother, Lee Jin-seok (Won Bin), and when his plan to get his brother discharged from the army goes awry, he kills the battalion commander and crosses over to the North Korean army. We don’t think it’s strange that he would risk his life to save his family. But when you consider the human instinct to prioritize one’s own safety and happiness, it’s a very strange behavior. So where does the determination and motivation to protect one’s family, even at the risk of death, come from? Why do we value family so much?
The reason for this altruistic behavior can be found in our genes. That is, the existence of altruistic genes. Individuals with altruistic genes often sacrifice themselves for the good of the group. Just like the worker bees of honeybees, who die a spectacular death as they sting intruders. However, the existence of altruistic genes alone does not explain all of this altruistic behavior. Genes are passed on through reproduction, and if an individual with an altruistic gene sacrifices itself, it will not be able to reproduce. Altruistic strategies are not evolutionarily stable. Of course, even if altruistic genes are not passed on through reproduction, it is possible for them to arise through mutation. However, this is a very small probability, and not enough to explain altruistic behavior within a population.
William Hamilton’s theory of “kin selection” explains this problem. According to the kin selection hypothesis, individuals act altruistically toward individuals with the same genes as themselves, meaning that they will sacrifice themselves to help their relatives, who are more likely to have similar genes to them. From the individual’s point of view, it’s hard to see why they should help someone who has the same genes as them, but from the gene’s point of view, helping individuals with the same genes as you is helping the gene itself. For example, imagine that a gene called x exists in individuals A, B, C, and D. If sacrificing individual A would ensure the survival and thriving of individuals B, C, and D, then the gene x in individual A would be willing to sacrifice A in order to make more copies of itself. From a gene’s perspective, it is in its best interest to make as many copies of itself and similar genes as possible, so the sacrifices that occur between relatives who are likely to share the same genes are driven by this selfish motivation. And the more closely related they are, the more likely they are to share the same genes. Assuming sexual reproduction, on average, parents and children share 50% of their genes, siblings share 50%, uncles share 25%, and cousins share 12.5%. From the perspective of kin selection, Jintai’s behavior can be interpreted as protecting the individuals with whom he shares 50% of his genes.
Let’s go back to the bee example. The worker bees in a bee colony are all sisters, and the queen is the chosen one, so all the eggs she lays are her nieces and nephews. Furthermore, if we consider that a male bee is created by the queen’s egg transforming into a new individual on its own, without fertilization, we can see that there is a high gene sharing of 75% between the worker bees and 50% between the queen’s eggs and the worker bees. In other words, whether the worker bees themselves or the queen’s children, they all share 50% of their genes with the worker bees. From the worker bee’s perspective, the queen’s nieces and nephews are as good as her own children. In other words, the extreme altruistic behavior of the worker bees in the bee colony can be interpreted as the selfish behavior of the genes to spread their own genes.
While selfish motivations at the genetic level can explain altruistic behavior among individuals, altruism is not necessarily attributable to genetic relationships alone. For example, in many animal populations, individuals also exhibit altruistic behavior toward non-blood relatives. This behavior is based on mutual benefit, not genetic benefit.
Can we attribute all of this altruistic behavior among individuals to kinship, i.e., to genetically selfish reasons? The short answer is no. Consider a group of meerkats in South Africa. Meerkats dig to find insects and other food, and because their entire attention is focused on the ground, they can easily become prey to their natural enemies. So, while they bury their heads and forage for food, they often lift their heads to look around, and in a group of meerkats, one or two of them will take turns looking around. In short, they stand sentinel, which is a detriment because they can’t find food while they’re watching, and they’re also likely to be targeted by intruders because they send out loud warning signals when they see an intruder. In other words, they’re selflessly acting for the safety of the group at their own risk. This behavioral trait of meerkats has been described as an example of kin selection among close kin. But Tim Clutton-Brock of the University of Cambridge has found that this sentinel behavior also applies to meerkat populations that are mixed with so-called immigrants. In human societies, as in meerkat populations, we see a wide range of interactions and sacrifices that are not explained by the selfish self-replication of genes, meaning that altruistic behavior in groups cannot be explained solely by the kin selection hypothesis.
Examples of such non-kin altruism abound in human society. Humans have a biologically complex social structure, and altruistic behavior plays an important role in the survival and prosperity of communities. It’s not just a genetic benefit, but is also heavily influenced by cultural and social factors. Altruistic behavior in human societies is often mediated by moral norms or social discipline, which are mechanisms that are separate from selfish motivations at the genetic level.
So far, the genetics of altruistic behavior in humans and animals has been explained by the kin selection hypothesis, which states that altruistic behavior among individuals is due to the self-replication of selfish genes. Obviously, the kin selection hypothesis cannot explain all altruistic behaviors in real human societies. However, the kin selection hypothesis is significant because it attempts to explain the genetics of altruistic behavior in individuals. In addition, various hypotheses such as the reciprocal reciprocity hypothesis and the group selection hypothesis have emerged later to explain the parts that are not explained by the kin selection hypothesis, but the kin selection hypothesis is still valuable because it explains a large part of altruistic behavior and is the theoretical foundation for other hypotheses.
