In this blog post, we will examine the various interpretations of evolutionary theory and their implications, focusing on the debate between gene selection theory and multilevel selection theory.
Evolutionary theory has long been one of the topics where science and religion have clashed most sharply. The biblical verse, “Let us make humankind in our image!” (Genesis 1:26), represents the creationist worldview that humans were created by God. Until the emergence of Darwin’s theory of evolution, the belief that humans were created by God was widely accepted for a long time and, particularly in Western society, had become an important value rooted in Christian culture. Western civilization has long developed under the influence of Christianity, and at its foundation lay the belief in the existence of God and Jesus Christ, as well as faith in the theory of creation. Darwin’s theory of evolution was a major event that shook these conventional beliefs and the ideological foundation of Western civilization. Naturally, the theory of evolution faced numerous criticisms, and even today, debates surrounding creationism and evolution continue in various forms across many countries. This serves as an example of how new perspectives that challenge long-held beliefs—even when they stem from scientific and logical disciplines—are not easily accepted.
Ironically, a similar phenomenon occurs within the field of evolutionary theory itself. In evolutionary biology, gene-centered evolutionary theory has long held significant influence. In particular, the theory of gene selection gained even wider recognition following the massive popular success of Richard Dawkins’ ‘The Selfish Gene’. The theory of gene selection, epitomized by Richard Dawkins, argues that the behavior of all living organisms—including humans, animals, and plants—can be explained primarily in terms of the preservation and spread of their genes. In short, this means that “natural selection operates at the gene level.” Opposing this perspective is the camp advocating for multilevel selection, led by Stephen J. Gould. They argue that it is difficult to explain the behavior of living organisms solely through genes, and that natural selection occurs simultaneously at multiple levels—including the individual and the population—rather than just at the gene level. Just as creationism has struggled to readily accept the theory of evolution, multilevel selection—which challenges the established theory of gene selection—remains a subject of vigorous debate even within the field of evolutionary biology.
Let’s examine this book in a bit more detail. The Dawkins camp views genes as the key factor in trait expression. They regard the environment as merely a backdrop and liken genes not to members of an orchestra but to its conductor. They cite the Pax6 gene experiment as a prime example. The Pax6 gene is known to play a crucial role in eye development. When the Pax6 genes from mice and fruit flies were swapped, it was observed that normal eyes developed even when using the Pax6 genes from different species. Based on these results, the Dawkins camp interprets that “since swapping genes with the same function between species does not cause problems in phenotypic expression, genes are the key factor in phenotypic expression.”
However, is this interpretation truly valid? Upon closer examination, there are logical limitations in the process of interpreting the experimental results. In this experiment, the independent variable is the Pax6 gene, and the dependent variable is the trait of the eye. Conversely, the developmental environments of the mice and fruit flies remained unchanged. In other words, since the environment remained the same, it could also be interpreted that normal traits were expressed even when the gene was swapped. To use an analogy, genes are merely individual musicians in an orchestra alongside the environment; any musician capable of playing the same instrument can step in and perform the same role. Ultimately, this suggests that trait expression does not occur through genes alone but arises from complex interactions between the environment and various biological factors, making it difficult to view the environment as merely a backdrop.
Next, let’s examine the theory of gene selection, which is a central argument of Dawkins’s camp. As mentioned in the book, the theory of gene selection is very simple and easy to understand, and because it possesses explanatory power that can be applied to various situations, it is difficult to refute. Dawkins’ “selfish gene” can be viewed as a theory that builds upon Hamilton’s rule: “r×b-c>0” (where r is the genetic relatedness, b is the benefit gained by the other party, and c is the cost incurred by oneself). Hamilton’s rule explains that altruistic behavior in living organisms occurs when the probability of preserving one’s own genes exceeds the cost one must bear, and it identifies genetic relatedness as a key factor in determining this. In other words, even human altruistic behavior is ultimately a strategy to protect one’s own genes and pass them on to the next generation. The way this simple principle alone explains the behavior of sterile worker bees is truly impressive. Furthermore, regarding traits such as the white fur of polar bears, a gene-selection theory or a gene-centered explanation feels more persuasive than Gould’s theory of individual selection. It is also true that many other examples introduced in the book—such as interpreting the behavior of vampire bats sharing prey as a survival strategy—can be explained by gene selection theory.
However, Dawkins and his supporters tend to view individuals as mere carriers of genes or tools for the survival of genes. In reality, though, there are behaviors that are difficult to explain solely in terms of genes or kinship. A prime example is one of the book’s discussion topics: “Can Mother Teresa be explained by the selfish gene?” Did Mother Teresa calculate her genetic relatedness whenever she helped someone? Of course, this does not mean she did so consciously; rather, let us assume that Hamilton’s rule operated instinctively. However, her genetic relatedness to the people she helped can be considered very low or virtually nonexistent. In other words, while altruistic behavior aimed at preserving one’s own genes does exist, human society also contains purely altruistic behavior that is unrelated to such a goal. Unfortunately, the book does not sufficiently address how genetic selection theory can explain such cases. This raises the question of whether Dawkins would ultimately explain even Mother Teresa’s actions as selfish behavior.
Why was Galileo forced to face a religious trial when he advocated for the heliocentric theory based on scientific knowledge? It was because, at the time, the heliocentric theory conflicted with the existing worldview based on the Bible. The existence of God and the theory of creation had long been the cornerstone of the Christian worldview, and the heliocentric theory was a new perspective that shook that foundation. Therefore, even though objective scientific evidence existed, it was not readily accepted. Similarly, it is worth considering whether Dawkins, in overemphasizing the importance of genes, might be relying too heavily on a single explanatory framework. Just as living organisms constantly evolve, science also advances through new evidence and diverse perspectives. Rather than putting multilevel selection on trial against evolutionary theory, an attitude that seeks to examine phenomena not fully explained by gene selection from the perspective of multilevel selection as well will be more conducive to the advancement and evolution of science.
