This blog post examines whether genes are selfish strategies for survival or evolutionary products that adapted to environmental changes.
The title of Richard Dawkins’ book, “The Selfish Gene,” is quite provocative. Having been raised to learn respect and consideration for others as human virtues, the notion that genes—which supposedly hold all our information—are selfish seems to support the idea that humans are inherently evil and must learn goodness through education, akin to the doctrine of innate evil. Yet, perhaps because of this provocation, “The Selfish Gene” became one of the world’s most widely read popular science books, and many agreed with the arguments of its author, Richard Dawkins.
In fact, when the book was first published, many strongly objected to the title. The word ‘selfish’ is typically used negatively, and people instinctively perceive it negatively. Yet, as readers delved into Dawkins’ book, they gradually came to understand that the concept of selfishness is fundamentally separate from moral judgment. The term ‘selfish’ was employed to explain how the biological unit of the gene acts to ensure its own survival; it did not represent human ethical inclinations. For this reason, many readers overcame their initial aversion and came to sympathize with Dawkins’ perspective.
The reason many could agree despite the title’s initial repulsion was likely because Dawkins emphasized viewing evolution and behavior from the gene’s standpoint—that is, from the perspective of what benefits and costs each gene incurs. Furthermore, this book does not merely address the concept of the selfish gene; it offers new insights into the role genes play within the processes of biological evolution and natural selection. By describing genes as if they possess strategies to ‘preserve’ and ‘expand’ themselves, he presented readers with a fresh perspective for understanding evolutionary theory.
So, from the gene’s perspective, how did sexual reproduction come about? Before continuing this discussion, we must first clarify what a gene actually is. While “gene” is a widely recognized scientific term, its definition is fraught with controversy and confusion. Among scientists, the concept of a gene is broadly divided into a molecular concept and an evolutionary concept. The molecular concept defines a gene as a DNA strand that encodes a protein. Typically, when referring to a DNA strand encoding a protein, it means the exons (excluding introns, which are removed during editing) and the regulatory regions controlling gene expression. However, for the actual protein to be produced, various other factors, such as RNA, are involved. This makes it ambiguous to define precisely what constitutes a gene.
A gene is not merely a biological structure; it can also be viewed as an element influenced by natural selection during evolution. For this reason, Dawkins emphasizes that genes should be understood as an evolutionary concept, considering their influence and role, rather than defined solely at the molecular level. The evolutionary concept emerged as an alternative to this. In the evolutionary concept, a gene is defined as a DNA sequence that causes differences in phenotype. That is, if substituting a specific DNA sequence with another DNA sequence changes the phenotype, then that sequence is a gene. Of these two definitions, Dawkins argues that the evolutionary concept definition should be used. Therefore, he states that if genes exhibiting similar traits come to occupy close physical proximity through mutations like inversions, they can be grouped together and newly designated as a gene.
Furthermore, the lifespan of a gene refers to the time it can be fully transmitted across generations. Consequently, shorter genes have a longer lifespan because they are less likely to be broken during crossing over in meiosis. This can be understood as part of a gene’s complexity and survival strategy. Shorter genes have more opportunities to survive, allowing them to persist longer during evolution.
According to the theory of the selfish gene, a gene’s goal is to ensure its own survival, or that of its replicator, for as long as possible. If that is the case, why do organisms engage in sexual reproduction rather than asexual reproduction, which preserves the gene unchanged? Dawkins argues that sexual reproduction itself is merely a trait controlled by a single gene, and it is irrelevant whether sexual reproduction is beneficial or detrimental to the rest of the organism’s genes. He states that sexual reproduction spread throughout the gene pool simply because it was advantageous to the gene that causes sexual reproduction. Here, the gene pool refers to the total genetic information contained within a biological population, which can be thought of as the collection of all alleles possessed by the individuals in the group.
In an evolutionarily stable population, the ratio of genes within this gene pool remains constant. Therefore, a gene surviving and spreading within the gene pool means it is included in an evolutionarily stable state, enabling it to leave its replicators to future generations. However, Dawkins avoids mentioning how sexual reproduction benefits the genes for sexual reproduction. Therefore, this article aims to propose, based on Dawkins’ argument, how sexual reproduction could have survived within the gene pool.
To examine whether Dawkins’ argument holds, we need only consider whether the process commonly called ‘evolution’ could occur: when a sexual reproduction gene emerges in a gene pool containing asexual reproduction genes, can this sexual reproduction gene avoid elimination and, through a transitional phase, form a new gene pool? However, asexual reproduction eliminates the cumbersome process of finding a mate during reproduction and avoids operations like crossing over, allowing gene lifespans to be considered nearly infinite. From this perspective, sexual reproduction genes would seem destined for elimination from the gene pool.
So, despite these advantages of asexual reproduction, is there a reason sexual reproduction genes could survive? The commonly taught advantage of sexual reproduction in educational curricula is that it creates individuals with new traits through diverse genetic combinations. This, in turn, allows superior genetic traits to persist within the species, thereby increasing its survival probability. This is the advantage of sexual reproduction from the species’ perspective. Moving beyond this view and looking at it from the gene’s perspective, we can speculate on several intriguing reasons why sexual reproduction might be advantageous for genes.
First, when sexual reproduction occurs, offspring gain relatives with genetic relatedness. These relatives are more likely to exhibit altruistic behavior toward the offspring due to this genetic relatedness, thereby increasing the offspring’s survival probability. The survival of the offspring is the survival of an individual carrying one’s own genes, directly linked to the gene’s survival. In other words, it creates allies to protect one’s genes.
Furthermore, advantages from the species perspective can sometimes become advantages from the gene perspective. This occurs precisely when environmental changes threaten the species with extinction. If both sexual and asexual reproduction genes coexist within the same gene pool, and a sudden environmental change occurs, the asexual reproduction genes cannot guarantee the survival of the individuals carrying them. Consequently, these genes will not be passed on to future generations. In contrast, individuals possessing the gene for sexual reproduction will express diverse traits through genetic mixing, ensuring some survivors emerge. Consequently, the gene that remains in the gene pool is the one for sexual reproduction. Indeed, individuals capable of sexual reproduction are known to cope better with relatively abrupt environmental changes.
Of course, these explanations remain hypotheses. However, the reason Dawkins gained attention with the term ‘selfish gene’ was that he provided a new perspective, using the biological concept of genes to reinterpret natural selection and evolution. Reading this book helps one move beyond merely acquiring genetic knowledge to understand the role genes play within the larger biological context and how individual behavior or traits are shaped in that process.
