Bees dedicate their lives to helping the queen lay eggs, which can be explained by the kin selection hypothesis. The kin selection hypothesis states that an individual’s reproductive success should not only be considered, but also the reproductive success of its relatives with whom it shares genes. However, this hypothesis does not explain altruistic behavior in all animals, and there are many exceptions.
Readers may have seen TV documentaries or read about honey bee colonies and their lives in books. Honey bees do not lay eggs themselves, but spend their lives doing chores to help the queen lay eggs. How do we explain this highly altruistic behavior, where bees spend their entire lives helping the queen lay eggs, as opposed to reproduction, where they typically leave behind their own offspring? This can be explained through the hypothesis of kin selection, formalized by William Hamilton.
The kin selection hypothesis is a theory in evolutionary biology that states that when looking at the evolution of organisms by natural selection, we should consider not only the number of offspring an individual leaves behind, but also the effect it has on the reproductive success of relatives with whom it shares genes. The hypothesis of kin selection can be described by Hamilton’s law: “Genetic relatedness X benefit ＞ cost”. In human terms, this means that if you satisfy Hamilton’s law, you will not only reproduce yourself, but also help your siblings, children, and relatives survive and reproduce, as they are more likely to have the same genes as you, and this will favor the passing on of your genes to future generations.
In this context, the reproductive behavior of bee colonies is an extreme example of altruism due to the kin selection described above. To understand the altruistic behavior of bees, we first need to understand the reproduction and genotypes of bee colonies. Unlike humans, who reproduce by fertilizing an egg with a sperm, bees reproduce through a process called virgin reproduction. Virgin reproduction can be understood by comparing it to two types of eggs you can find in the supermarket: fertilized eggs and unfertilized eggs. A fertilized egg is a viable egg that was laid after a hen and a rooster mated and the rooster’s sperm fertilized the hen’s egg, while a non-viable egg is an egg that was laid without a rooster. Unlike chickens, in honey bees, sterile eggs can also result in reproduction, and male bees are born this way. In the case of ovulated eggs, the queen or worker bee (honey bee) can be the source of the egg. In this situation, the closeness of the individuals to the queen is 0.75 and the closeness of the queen’s eggs to the worker bees is 0.5. The 0.5 inbreeding rate is the same as the worker bee would have if it were to have its own children, which means that from the worker bee’s perspective, raising the eggs laid by the queen is no different from raising its own children, and furthermore, the separation of nurturing and laying between the worker bee and queen is more efficient for the reproduction of the species.
This behavior is actually an amazing biological phenomenon that deserves further study. Recent studies have shown that bees are not just mechanical beings that follow the queen’s orders, but have a complex social structure that includes a communication system to check on her health and raise new queens when necessary. In this sense, we can see that bee society has a complex biological and social system that goes beyond a simple division of labor.
However, these hypotheses don’t explain the behavior of all animals. For example, the behavior of colonial meerkats is altruistic in that they sacrifice foraging time to watch the net for the safety of the group, which cannot be explained using the kin selection hypothesis because their group includes unrelated immigrants. Furthermore, in humans, altruistic behavior exists beyond kinship, and various hypotheses have been proposed to explain it. Therefore, the kin selection hypothesis is not a universal theory of altruism. However, the kin selection hypothesis has opened up a new way of analyzing altruistic behavior in animals using innate “genes” and has opened up a discussion that has led to other hypotheses being proposed for various exceptions that cannot be explained by this hypothesis.
