In this blog post, we’ll compare the key issues of the theory of gene selection and the theory of multilevel selection, and examine the explanatory power of both theories through the debate surrounding altruistic behavior and natural selection
“Let us make humankind in our image!” (Genesis 1:26)
This is a verse from the Bible. Until the emergence of Darwin’s theory of evolution, people believed that humans were created by God. Although Catholic culture developed primarily within Western civilization, the existence of God and the theory of creation were long accepted as universal beliefs across all of humanity. After the Roman Empire adopted Catholicism as its state religion, Western civilization developed around Catholicism, grounded in the belief in the existence of God and Jesus Christ, as well as in the doctrine of creation.
Darwin’s theory of evolution was a historic event that shook these common beliefs and the ideological foundation of Western civilization. Naturally, the theory faced numerous criticisms, and the debate continues to this day. In particular, the controversy surrounding the theory of evolution is often better understood as a clash between religious and scientific perspectives rather than as an issue confined to the scientific community. This is because, no matter how scientific or logical a discipline may be, uncomfortable truths that overturn long-held beliefs are difficult to accept.
Interestingly, a similar phenomenon occurs within the field of evolutionary theory itself. Currently, the theory of genetic selection is the most widely accepted explanation within evolutionary theory. The influence of gene selection theory grew even stronger following the massive popular success of Richard Dawkins’ ‘The Selfish Gene’. The gene selection camp, represented by Richard Dawkins, argues that the behavior of all living organisms—including humans, animals, and plants—is directed toward preserving and spreading their own genes. This can be summarized in a single sentence: “Natural selection acts at the gene level.”
The theory of multilevel selection, championed by Stephen J. Gould, challenges this prevailing view. Proponents of multilevel selection argue that the behavior of living organisms cannot be explained by genes alone, and that natural selection occurs simultaneously not only at the gene level but also at the individual and population levels. Just as the Catholic Church long struggled to accept the concept of creationism, the theory of multilevel selection—which challenges the established orthodoxy of gene selection—has not been readily accepted within the field of evolutionary biology.
Let us now examine the arguments of both sides in detail. The Dawkins camp views genes as the key factor in trait expression. They contend that the environment is merely a backdrop, and that genes are not the musicians in an orchestra but rather the conductor. They cite the Pax6 gene experiment as a prime example supporting this view. The Pax6 gene plays a pivotal role in eye development. In the study, researchers swapped the Pax6 genes between mice and fruit flies to determine whether eyes would form normally. The results showed that normal eyes formed in both cases, even though the Pax6 genes from different species were introduced. Based on these results, the Dawkins camp interprets that if genes perform the same function, normal traits will be expressed even across different species; therefore, the core of trait expression ultimately lies in the genes.
However, is this interpretation truly valid? Upon closer examination, there is a logical flaw in the interpretation of the experimental results. The independent variable in this experiment is the Pax6 gene, and the dependent variable is the expression of the eye phenotype. Conversely, the developmental environments of the mice and fruit flies remained unchanged. In other words, it could also be interpreted that the identical phenotype appeared simply because the gene was altered while the environment remained constant. To use an orchestra analogy, a gene is not a conductor but rather a single musician. As long as the musicians can play the same instrument, the performance itself is possible regardless of who joins the ensemble. Ultimately, the expression of traits is not determined by a single gene alone but is the result of complex interactions among various factors, including the environment; therefore, the environment cannot be viewed merely as a backdrop.
Next, let’s examine the theory of gene selection, which is a key argument of Dawkins’ camp. The theory of gene selection is difficult to criticize because its content is very simple and easy to understand, and it can be widely applied to various situations. Dawkins’ ‘The Selfish Gene’ can be viewed as a further development of Hamilton’s rule, “r × b − c > 0” (where r is genetic relatedness, b is the benefit gained by the recipient, and c is the cost incurred by the donor). Hamilton’s rule explains that altruistic behavior in organisms occurs when the probability of one’s genes being passed on to the next generation exceeds the cost one must bear, and it identifies genetic relatedness as the key variable. In other words, even altruistic behavior in humans is, ultimately, an action intended to preserve one’s own genes and pass them on to future generations.
Even using this simple principle alone, the explanation for the behavior of non-reproductive worker bees is remarkably convincing. Furthermore, genetic selection is generally considered to provide a more compelling explanation for the evolution of the polar bear’s white fur than individual selection. The behavior of vampire bats sharing prey can also be interpreted as a strategy to increase their chances of survival. In this way, a significant number of the examples introduced in the book are explained relatively consistently by genetic selection.
However, Dawkins and his supporters tend to view individuals too narrowly, as mere carriers of genes or machines for genes. In reality, there are clearly behaviors that cannot be explained solely by genes or kinship. As was the topic of the second day’s discussion, can Mother Teresa truly be explained by ‘The Selfish Gene’ alone? Did Mother Teresa calculate her genetic relatedness when she helped someone? Even if we assume she unconsciously followed Hamilton’s rule, the genetic relatedness between her and the people she helped must be considered virtually nonexistent. Ultimately, human society contains not only purposeful altruism but also pure altruism that expects no reward. However, ‘The Selfish Gene’ does not adequately address how to explain such cases. Can even Mother Teresa’s actions be explained solely by the selfishness of genes?
The reason Galileo was forced to face a religious inquisition despite advocating the heliocentric theory based on scientific evidence was that it conflicted with the contents of the Bible. The existence of God and the theory of creation were core beliefs that underpinned Catholic society at the time. Therefore, even though the heliocentric theory was an objective scientific theory, it could not be readily accepted. Might Dawkins, too, be committing a similar error by overemphasizing the importance of genes? Just as living organisms evolve, science also evolves continuously. Rather than putting multilevel selection on trial in the court of evolutionary theory, science will be able to evolve once more when attempts are made to interpret phenomena not explained by gene selection from the perspective of multilevel selection.
