One explanation for why animals exhibit altruistic behavior is the kin selection hypothesis. Genes are more likely to spread by helping individuals with whom they have a high genetic match. This drives behavior that sacrifices one’s own interests for the sake of a sibling or cousin, and can also explain the altruistic behavior of social animals like ants and bees.
We’ve all seen the mystery of why animals behave altruistically on TV or in books, like the secrets of the pyramids. We’ve been taught that animals are not bonded, and that they are selfish beings who will act in their own self-interest, regardless of the situation of other individuals. The secret is explained by the kin selection hypothesis.
Would you lay down your life for two siblings or eight cousins? Some would say yes, others would say no, and some would say it’s ridiculous. There is no right answer to this question, but your genes are saying “Since you can’t do math, of course you should!” Why does the gene think this way?
Let me give you an example. Let’s look at it strictly from a gene’s point of view. A gene named A has been replicating itself over and over again, and has successfully placed itself inside individuals named a, b, c, and d. One day, A is walking down the street and sees B, C, and D playing with fire on the railroad tracks, and at the same time, a train is coming towards them. A has a choice: to save B, C, and D, he must die, or B, C, and D will die. Should A sacrifice himself in this case? The gene says again “Can’t you do math? Of course you should!” In the previous hypothetical, we said that each individual shares a copy of gene A. So if b, c, and d survive, there are three copies of gene A, but if only a lives, there is only one copy of gene A. As a result, gene A sacrifices itself to save its friends.
The kin selection hypothesis states that the criterion for altruistic behavior is whether it will spread your genes further. It also states that the cost of an altruistic behavior is related to the benefit of spreading your genes. This sounds pretty complicated, but let’s break it down a bit. What is the cost of altruism in this hypothesis? It’s the benefit of being the beneficiary of an altruistic act, that is, the person who receives the good behavior. On the other hand, the benefit of spreading your genes is thought of from the perspective of the genes, so it can be expressed as the product of your genetic match and the number of times you perform the act. The value of an altruistic act can be expected to be the benefit (spreading your genes) minus the cost (the benefit consumed by the altruistic act). For example, giving three of my siblings a piece of candy for themselves is worth 0.5x (the benefit of my siblings eating the candy) – (the benefit of me eating the candy), whereas giving three of my cousins a piece of candy for themselves is worth 0.125x (the benefit of my cousins eating the candy) – (the benefit of me eating the candy). So from the gene’s perspective, it’s sweeter to give the candy to your sister than to your cousins.
The problem of sacrificing oneself to save two siblings or eight cousins can then be theoretically explained as follows. You and your siblings each inherited half a gene from your parents, so you have a 50% genetic match. In the same way, you can see that your genetic match with your uncle is 25% and with your cousin 12.5%. So if you save your two brothers, you’ll leave about 75% of your genes, and if you save your eight cousins, you’ll leave about 70% of your genes. And if they all leave their genes to future generations, the two brothers can double their reproduction, so they can leave about 75%*2 of their genes, and the eight cousins can leave about 70%*8 of their genes. From the point of view of the genes, saving you, saving your two brothers, or saving your eight cousins has a similar or more beneficial outcome, i.e., the genes can continue to exist in the world unchanged.
The hypothesis of kin selection also helps explain the existence of perfectly altruistic populations of ants and bees, which has been a mystery for a long time. Ants and bees are haploid animals. This means that males have one “dog” gene and females have one “bee” gene, which is very different from humans, and this characteristic plays an important role in maintaining the existence of perfectly altruistic populations. In terms of genetic relatedness, the rate of genetic relatedness is 50% between queen ants and worker ants, 100% between queen ants and male ants (50% from the queen’s perspective), and a whopping 75% between worker ants and worker ants. So from the perspective of the worker ants’ genes, if they lay and raise their eggs alone, they can spread their genes at a rate of 50% per egg, whereas if they work with other ants, they can spread their genes at a rate of 75% per egg, as well as the queen and male ants. The result is a perfectly altruistic behavior, in line with the kin selection hypothesis.
In addition to theoretical explanations, real-life examples provide concrete examples of altruistic behavior. For example, bison herds in Africa cooperate with each other to protect their herd from predators. Younger and older individuals are placed in the center of the herd, while stronger and healthier individuals defend the perimeter. As another example, dolphins will often support an injured mate underwater to help them breathe. This behavior strengthens social bonds and promotes cooperation within the group. Examples like these, in line with the kin selection hypothesis, show how altruistic behavior in animals contributes to their survival and prosperity.
To summarize the above The kin selection hypothesis was introduced to provide a theoretical explanation for altruistic behavior in animals, and it looks at behavior from a genetic perspective. It also makes altruistic behavior in kinship relationships mathematically accessible. However, it has limitations in that it cannot explain altruistic behaviors that do not involve kinship, and it cannot explain the reasons for altruistic behaviors that are inconsistent with the kin selection hypothesis, such as laying down one’s life for a sibling. These limitations can be compensated for by other hypotheses, such as the reciprocity hypothesis and the eusociality hypothesis.
The reciprocity hypothesis explains that altruistic behavior can also occur in non-kinship relationships. According to this hypothesis, individuals can cooperate for mutual benefit in the long run. For example, if one entity helps another, the latter is more likely to reciprocate in the future. This mutual cooperation eventually contributes to the survival and prosperity of the species. The paraphyletic hypothesis also suggests the possibility of cooperation between individuals with similar behavior patterns. This hypothesis explains that individuals with similar behaviors can recognize each other and work together to pursue common interests.
These different hypotheses help us understand the complexity of altruistic behavior in animals. It is necessary to analyze animal behavior holistically, taking into account not only genetics, but also social and environmental factors. This approach will provide important insights not only for animal behavior, but also for understanding the complex interactions of human society.
