Why do humans and animals sacrifice themselves to help others? In this blog post, we’ll explore the evolutionary reasons for altruism through the kin selection hypothesis.
In the human story movie genre, we often see scenes of family devotion, such as the protagonist risking his life to earn money for his younger siblings’ school fees. This kind of behavior may seem natural at first glance, but it is a “selfless” act of giving up one’s own interests and sacrificing for the sake of others. Altruistic behavior is not limited to humans, but also occurs among animals, such as bees that live their entire lives for their queen, or chimpanzees that pick each other’s fur. However, because altruistic individuals sacrifice themselves to benefit others, they are less likely to survive and reproduce compared to selfish individuals. Simply put, if an individual dies before others, it will have fewer opportunities to reproduce. However, from an evolutionary perspective, where only the fittest individuals survive and reproduce, altruistic individuals should have been culled, so the fact that altruistic animals and humans are still thriving contradicts evolutionary theory. Among the many hypotheses that explain how altruistic behavior has survived, I’d like to introduce the kin selection hypothesis.
At its core, the kin selection hypothesis states that sacrifice between relatives with shared genes may not be a sacrifice from a genetic standpoint. To understand the kin selection hypothesis, it’s important to recognize that the survival of genes is more important than the survival of individuals. The reason individuals reproduce is to spread their genes, so if there is a way for an individual with a gene to sacrifice another individual so that the gene can spread more widely, it is not a sacrifice from the gene’s perspective. The classic example of this is family sacrifice. Put yourself in the shoes of Gene X. Gene X wants to spread as widely as possible, and to do so, Gene X will make sure that I have many children. How many children I can have is determined by my economic ability. In a simplistic way, Gene X might decide that the best strategy is to have many children because it increases my economic ability, but here’s something to think about. Half of your genes are passed on to your children. In other words, there is a high probability that my children will have gene X. So what happens if I sacrifice myself to increase my children’s economic power? My economic power will decrease, but my children will have more grandchildren. Again, my grandchildren will still have a high probability of carrying my gene X. My children will then have more grandchildren, which in turn will have the effect of spreading gene X more widely. Furthermore, my siblings share a gene with me, so there is a high probability that they have Gene X, and there is also a high probability that my nephews have Gene X. In other words, my altruistic behavior toward them will have the effect of spreading Gene X further. Overall, from Gene X’s point of view, my altruistic behavior toward my blood relatives may be helping people who are more likely to have Gene X and thus spreading Gene X more widely.
To understand this, consider an example. If you have 10 copies of yourself and 10 copies of yours, and you sacrifice yourself so that all 10 copies can survive, it stands to reason that it might be more beneficial to sacrifice yourself so that 10 copies can survive. Let’s apply this to humans. As mentioned above, my children share genes with me. Therefore, my children can be described as “50% me”. It stands to reason, then, that it would be in their survival interest if I sacrifice myself so that many of the “50% me” can thrive even more. In simple terms, if three “50% me’s” can thrive better at my expense than I can thrive alone through my selfish behavior, then this is better for survival.
This hypothesis can also explain the phenomenon of bees sacrificing themselves for the queen. First, let’s look at how bees reproduce. The queen bee produces an egg, which turns into an individual and becomes a male bee. This egg is fertilized with the sperm of another male bee, resulting in a large number of worker bees, of which one is chosen to be queen. In other words, the queen and the worker bees are all sisters. This relationship is stronger than the human sisterhood. This is because the queen’s genes are only passed on half as much as in humans, but the male bee’s genes are passed on 100% to the worker bees, so there is a much higher probability that the worker bee’s genes will be in another sibling. So, as explained above, the worker bees helping the queen is a way for the genes to increase the chances of their genes spreading more widely. Of course, here, if the cost of sacrificing oneself is greater than the benefit of sacrificing, one would not help, and if the benefit is greater, one would help. In other words, if the gene is more likely to be passed on more widely if I sacrifice, I will sacrifice, and if not, I will not sacrifice.
So far, we’ve discussed the kin selection hypothesis. The kin selection hypothesis states that altruistic behaviors that individuals perform may actually be genetically selfish, as they help those with whom they share genes so that their genes can thrive. This explains why human sacrifice among relatives and altruistic behavior in many animals is not inconsistent with evolutionary theory. It is possible that the sacrifice process of Duksu in the international market was also a selfish selection of Duksu’s genes for his own propagation. However, the kin selection hypothesis is also questionable. For example, not all bees live with a queen. Some bees don’t form colonies and live alone. Also, according to the kin selection hypothesis, there’s no reason to sacrifice yourself for someone you don’t share genes with, but we do act altruistically toward others beyond our family. Again, the kin selection hypothesis cannot explain this. These points are later explained by hypotheses such as the reciprocal reciprocity hypothesis or the group selection hypothesis. These hypotheses also explain altruistic behavior among individuals who are not related to each other. Despite its limitations, the kin selection hypothesis is significant in that it provides a complete explanation for altruistic behavior in kinship groups.
Altruism is one of the most important survival strategies found in both humans and animals. Even in our own society, many people sacrifice themselves for others, and this can be explained not just for moral reasons, but also for biological and evolutionary reasons. As more studies and hypotheses emerge, we will continue to gain a deeper understanding of altruistic behavior.
