This blog post takes an interesting look at why worker bees risk their lives to protect the queen bee and how altruistic behavior evolved.
If a worker bee could speak, it would not be difficult to hear it say, “Protect the queen!” Worker bees do not have the ability to reproduce, but they devote their entire lives to protecting the queen bee and her eggs. They take care of the eggs laid by the queen bee and defend the hive with their lives when there is an invasion. They sacrifice their entire lives for others, not themselves. As such, the role of worker bees in a bee colony is not limited to physical labor. They perform their duties as if they were a single organism, and work to ensure the survival of the entire colony. In particular, the role of the worker bee is crucial in maintaining the order of the bee society and ensuring the future generations by safely protecting the queen bee, who is responsible for reproduction. However, such altruistic sacrifice poses a fatal threat to the survival of each individual. Nevertheless, why has altruistic behavior not disappeared and evolved not only in bees but also in human and other animal societies? To solve this mystery, we need a convincing hypothesis, one of which is the kin selection hypothesis. This hypothesis explains how altruistic behavior evolved based on the fact that individuals in a kinship share the same genes. Considering the fact that relatives share genes with each other, we can discover something we have not thought about the behavior of each individual.
Genes are information that makes an individual’s characteristics appear, and they are passed down from parents to children. Individuals with genes that are advantageous for survival will survive competition, reproduce, and leave many offspring, while individuals with genes that are disadvantageous for survival will slowly disappear. This is natural selection from the perspective of an individual, which many people commonly think of. What would happen if genes were shared between these individuals? Generally, when a living being reproduces, its offspring inherit genes from the sperm and egg of their parents, so they share some genes with their parents, and siblings who inherit genes from the same parents also share genes. In particular, in the case of bees, since the sperm from the father all have the same chromosomes, the degree of sharing of genes among relatives is higher than in other species. The queen bee and worker bee share 75% of their genes, and the queen bee’s eggs and worker bees share 50% of their genes. This is a fairly high level of genetic sharing even when compared to human society, and it is thanks to this genetic structure that bees feel an instinctive sense of responsibility for the survival of other individuals. Therefore, the worker bee’s devotion to the queen bee and her eggs may be a disadvantage for the individual itself, but it may be beneficial for the spread of the genes they share. The kin selection hypothesis explains that altruistic acts evolved between individuals in a kin group because they share the same genes.
What does this mean from the perspective of genes when it comes to altruistic behavior between blood relations? Biologist Richard Dawkins argued that altruistic sacrifice between individuals is selfish from the perspective of genes. He believed that it is genes, not individuals, that compete to survive and increase their numbers, and that individuals are nothing more than survival machines controlled by these genes. In other words, genes are selfish because they work to increase their own number rather than the survival of the individual. If there is a gene a, individuals with the gene a will work not only for their own survival but also for the survival of other individuals with the same gene a. Looking at the world from the perspective of selfish genes can help us better understand the acts of devotion between blood relations. Let’s consider a situation where an enemy invades a bee colony, putting the queen bee and her eggs in danger, and where a worker bee sacrifices her life to save the queen and her eggs. As mentioned above, due to the bee’s special breeding process, worker bees share 75% of their genes with the queen bee and 50% of their genes with her eggs. If a worker bee sacrifices itself to save the queen bee and one egg, it is as if it sacrifices 100% to save 125% (75% + 50%) of its genes. In other words, from the perspective of selfish genes, such behavior is completely rational.
So far, we have seen how altruistic acts that could be a disadvantage from an individual’s perspective could evolve without being eliminated based on the blood-choice hypothesis. However, the origin of altruistic behavior is not only found in bee or insect societies. In human societies, there are many cases of self-sacrifice for family or close acquaintances. The kin selection hypothesis explains that altruistic behavior between blood relations is detrimental to the individual, but beneficial to the genes, and therefore, altruistic behavior has evolved. This is one of the most logical, compelling, and influential hypotheses that can explain how altruistic behavior evolved by introducing the concept of genes. The kin selection hypothesis effectively explains even those aspects that other hypotheses, such as the group selection hypothesis, cannot explain. Of course, it has the limitation of not explaining altruistic behavior between individuals who are not related. However, these limitations can be supplemented by the explanation that individuals only show kindness to those who have shown kindness to them, or that altruistic individuals gather together to gain benefits. Therefore, if we continue to develop the key to solving the mystery of altruistic sacrifice, we will be able to uncover the mysterious secrets of the behavior of humans and other living things.
