In this blog post, we’ll explore the core concepts and limitations of various evolutionary theories, with a focus on natural selection.
When we hear the term “evolutionary theory,” we often think of Darwin’s theory of evolution from Australopithecus to humans. As such, evolutionary theory is a topic we frequently encounter in our daily lives, yet it is also a subject that sparks significant controversy. However, few people actually have a clear understanding of what evolutionary theory precisely entails. In this post, we will systematically examine the premises of evolutionary theory, the theories that comprise it, and the limitations and contradictions inherent in those theories.
Evolutionary theory is not merely a theory newly proposed in modern times; its underlying ideas have existed since ancient times, and its concrete theoretical form was established in the modern and contemporary eras. The theory commonly cited as its representative starting point is Lamarck’s “theory of use and disuse.” This theory posits that in organisms, organs frequently used in response to the living environment develop, while those not used degenerate, and that these acquired traits are passed on to offspring. For example, it explains that giraffes developed long necks as a result of constantly stretching their necks to eat leaves from tall trees, and that this trait was passed down to their descendants, leading to the long-necked giraffes we see today. However, as it was scientifically proven that acquired traits are not inherited, the theory of use and disuse lost its standing in academia and faded into history. What emerged afterward were the theories of scholars we are familiar with, including Charles Darwin, who gradually developed the more logical and scientific “modern theory of evolution.”
Modern evolutionary theory is broadly divided into two schools of thought: gradualism and punctuated equilibrium. This distinction stems from the fact that the fossil record does not connect seamlessly in chronological order, making it impossible to fully explain the continuity between species. Gradualism, as the name implies, is the hypothesis that evolution occurs as organisms change very slowly, little by little, over a long period of time, and attributes the gaps in the fossil record to the “incompleteness of the fossil record.” In contrast, punctuated equilibrium explains that evolution occurred rapidly and explosively at specific points in time, arguing that the gaps in the fossil record reflect actual phenomena rather than a lack of evidence. In other words, the punctuated equilibrium theory posits that biological evolution remains stagnant under normal conditions but changes rapidly following a specific trigger.
If so, what drives evolution? Generally, four factors are cited as the driving forces of evolution: mutation, migration, genetic drift, and natural selection. For these factors to serve as the primary mechanisms of evolution, they must go through four stages: the replication of genetic information, the occurrence of variation, competition among individuals, and natural selection. Let us examine the validity of each theory based on these conditions.
First, the “mutation theory” explains that genetic variations occurring randomly within a population alter gene frequencies, and these variations undergo natural selection, thereby driving evolution. However, in real-world environments, individuals carrying mutations often struggle to win the competition for survival; thus, this hypothesis can serve as a basis for evolution only under very limited circumstances. Next, the “migration theory” posits that evolution occurs as the genetic composition changes due to the influx of individuals from external populations. However, this theory can only explain simple population movements and lacks mention of variation or competition, limiting its explanatory power.
The “genetic drift hypothesis” focuses particularly on the phenomenon where specific traits disappear by chance, especially in small populations. For example, if a colony of 60 ants originally included 20 large ants, and all of them were lost due to external factors, the entire colony would consist of relatively small ants, and as a result, “small size” could become a fixed genetic trait. However, this hypothesis is also difficult to apply to large populations or long-term evolutionary phenomena. From this perspective, the mechanism of natural selection is recognized by most scholars as the primary driving force of evolution, as it can explain evolution relatively comprehensively under various conditions.
Evolutionary theories based on the mechanism of natural selection can be broadly divided into Darwin’s theory of evolution and Dawkins’ theory of evolution. Both theories share the common premises that evolution requires: the birth of more offspring than the number of viable individuals; the presence of different traits among individuals within the same species; an advantage in survival and reproduction for individuals possessing traits suited to the environment; and the ability for these traits to be inherited by offspring. The mechanism of natural selection explains the process by which evolution occurs: when these four conditions are met, competition arises among individuals, and the traits of those that survive this competition are passed on to subsequent generations.
However, the two theories differ in their view of the unit at which evolution occurs. While Darwin viewed evolution as occurring at the “individual” level, Dawkins argued that it occurs at the “gene” level. According to Darwin’s argument, one could explain the evolution of beak length by comparing birds with different beaks. However, this risks falling into a logical fallacy similar to treating a “long chalk” and a “short chalk” as two entirely different individuals and claiming that a single individual gradually became shorter. In other words, Darwin’s theory faces criticism for its limitations because, to explain evolution, one must demonstrate that a single, identical individual or unit has gradually changed over time; yet, comparing different individuals alone cannot clearly identify the agent of that change. Furthermore, Darwin’s theory failed to provide convincing evidence for why individuals engage in altruistic behavior—that is, how to explain cooperation and self-sacrifice. This is because, if natural selection is a process that maximizes “self-survival,” cooperation is an irrational behavior.
In contrast, Dawkins sought to resolve these issues by identifying the “gene” as the agent of evolution. If evolution occurs at the genetic level, genes undergo gradual changes as they are passed down to offspring, which in turn can alter an individual’s traits. Since both mutated and unaltered traits are maintained, a “baseline for change” exists, ensuring logical consistency. Furthermore, Dawkins explained cooperation and altruism as survival strategies of genes. In other words, individuals cooperate to increase the survival chances of those carrying the same genes as themselves, thereby ensuring that those genes are passed on to the next generation more frequently. This explanation has been of great help in understanding the behavioral patterns of social animals.
Nevertheless, Dawkins’ “selfish gene” theory is also fraught with controversy. Although Dawkins argued that “we are merely survival machines and carriers of genes,” the interpretation that higher-order thoughts and emotions—such as human language ability or moral behavior—are also strategies of genes is difficult for many people to accept. For example, the behavior of bats sharing blood with unrelated bats cannot be fully explained solely as a survival strategy of genes.
As such, defining and explaining evolutionary theory is no simple task. Since evolutionary theory is a hypothesis, it has not yet been fully established, and even its basic premises are subject to diverse disagreements among scholars. For instance, while there is general agreement that natural selection is the core driving force of evolution, some scholars question even this. Furthermore, the debate over where to place the basic unit of natural selection continues to this day. While most scholars view genes as the basic unit of evolution, Edward Wilson and David Wilson advocate for multilevel selection, arguing that populations—rather than genes—can serve as the unit of evolution. In addition to this, theories such as kin selection add further perspectives, keeping this debate alive to this day.
Therefore, while it is difficult to clearly define evolution in a single sentence, based on what we have examined so far, it can be summarized as the phenomenon in which individuals or their internal traits gradually change through the mechanism of “natural selection.” Darwin argued that this evolution occurs at the “individual” level, while Dawkins argued that it occurs at the “gene” level.
The theory of evolution has not been confined to biology alone but has influenced various academic fields and society as a whole. For example, by misapplying the logic that humans also compete between races according to the principle of natural selection, the Nazis designated Jews and other ethnic groups as inferior and carried out mass murder. Furthermore, evolutionary theory was used as a justification when white people massacred and oppressed indigenous peoples. In education, it served as the foundation for fostering an environment that emphasizes wisdom and learning, based on the premise that humans overcome the competition for survival through knowledge. Religiously, while it initially enabled the claim that “God endowed humans with the ability to evolve,” it later raised questions that led to demands for scientific evidence of God’s existence. Evolutionary theory has also had a significant practical impact. The genetic algorithm proposed by American computer scientist John Henry Holland is used to enable computer programs to “evolve” much like living organisms, and it plays a crucial role in the development of artificial intelligence and optimization technologies today.
As such, evolutionary theory is not merely an academic hypothesis but a powerful intellectual framework that has exerted substantial influence across various fields. How evolutionary theory will develop in the future, and how we will understand and apply it, remains an intriguing and important challenge.
