In this blog post, we will look at whether the theory of evolution merely explains changes in living organisms, or whether it can also encompass the evolution of culture and language.
People often come across the word “evolution” in broadcast media, cartoons, and movies, but many do not know exactly what evolution is. Biological evolution refers to the phenomenon of a living organism changing over time, and the theory that explains this is the theory of evolution. The theory of evolution has become a core theory of biology over a long period of time, and its importance is growing as it is now influencing not only other scientific fields but also various fields such as the humanities and philosophy. In this article, we will look at the core concepts and development process of the theory of evolution, and also examine how it is influencing other fields.
According to the biological definition, evolution means “the phenomenon of changing the frequency and proportion of genes over generations within a population of organisms.” There is a myriad of evidence that proves the existence of the phenomenon of evolution, such as observing how organisms have changed through the time of fossil formation or analyzing how species with the same ancestor have changed into different forms in different environments. However, various studies are still being conducted on the causes and mechanisms of evolution, and the most widely accepted mechanisms are natural selection and gene drift.
Natural selection refers to the phenomenon in which individuals with traits that are more suitable for a particular environment have an advantage in survival and reproduction over those without such traits, and that those traits gradually become dominant in the population. For natural selection to occur, the reproductive process, in which genes are passed on to offspring, is essential, and there must also be an opportunity for new traits to appear. This opportunity is usually caused by a mutation in a gene. Mutations are generally disadvantageous to the individual, but if a beneficial mutation occurs over several generations, individuals with that trait will have more offspring due to natural selection. In this process, individuals that have adapted well to the environment survive and influence the next generation.
The aspects of natural selection within a group can be divided into three categories. The first is directional selection, which occurs when the external environment exerts evolutionary pressure in one direction. The second is divisive selection, which is an evolutionary process in which opposing traits gradually become polarized. The third is stability selection, which refers to an evolutionary pattern in which intermediate traits of a biological population become dominant and extreme traits decrease. African cichlid fish are a prime example of directional selection, and studies analyzing their diverse oral structures and feeding methods have confirmed the effects of directional selection.
Darwin and other early evolutionists believed that sexual selection mainly occurred during the mating process. In general, females devote more energy to reproduction and rearing than males, which is why the phenomenon of “sexual selection” occurs, in which females choose males. At first, the concept of sexual selection, which was introduced to explain the advantages of sexual reproduction over asexual reproduction, was long ignored because it was associated with women’s rights, but in recent years, various studies have been conducted. A representative example is the “Red Queen hypothesis,” which explains that the diversity of sexual reproduction is advantageous for adapting to changing environments and surviving from competitors such as parasites. This hypothesis explains that this is an example of mutual competition between the parasite and the host, each of which is under evolutionary pressure. The parasite becomes difficult to adapt to the genetic diversity of the host, and conversely, the host also responds to this and is under evolutionary pressure. Another theory, the “handicap hypothesis,” explains why males have traits that are unnecessary for survival. For example, he explains that while a peacock’s colorful tail or a stag’s large antlers are not helpful for survival, females see them as evidence of survival ability and health and choose them, which leads to the evolution of a handicap. However, despite this explanation, the theory has been pointed out for its theoretical limitations, such as the fact that the purpose of mating is not limited to simply breeding and it is difficult to explain homosexuality.
Another major mechanism of evolution, gene drift, refers to the phenomenon in which the frequency of alleles varies from generation to generation. In the case of sexual reproduction, the genes of the parents are randomly combined and passed on to the offspring, so even children of the same parents can have different traits. If not affected by the environment, this tends to accumulate like sample error in statistics. However, when certain traits are selected in a certain environment, the frequency of traits that are advantageous for survival increases and the frequency of unfavorable traits decreases. If this process is repeated, genetic traits may gradually become fixed or disappear. In particular, the rate of fixation is faster in small populations, which is called the “genetic bottleneck phenomenon.” Bottlenecks can reduce genetic diversity among individuals, which can pose a threat to the maintenance of the species.
The “Neutral Evolution Theory” considers gene immobility to be a major factor in evolution. According to this theory, most mutations are not selected because they do not directly affect life activities, and since about 90% of human DNA is filled with sequences that are not related to life activities, the majority of mutations are neutral. This is different from natural selection, in which certain mutations are selected, but neutral mutations create new alleles, which are then fixed through gene drift and evolution occurs. Modern evolutionary theorists believe that both gene drift and natural selection are important factors in evolution.
Although the theory of evolution has been developed in various fields for a long time and has accumulated a lot of evidence, there are still gaps in the evolutionary lineage. This is a “missing link” that occurs because not all fossils can be preserved, and just as the whole picture can be inferred even if all the pieces of a jigsaw puzzle are not there, the theory of evolution can explain the overall phenomenon despite the lack of some evidence. Early evolutionists argued for gradual evolution, which states that certain genetic traits accumulate over time and cause changes. However, the theory was criticized for its slow rate of evolution and the lack of fossils of intermediate forms.
The theory of punctuated equilibrium, which appeared in the 1970s, argues that evolution often occurs rapidly in short periods of time, and there are no major changes in the remaining periods. According to punctuated equilibrium theory, the reason why no missing links have been found is that evolution occurs in bursts and there is no evidence of a certain period. Richard Dawkins proposed the possibility of the coexistence of both theories, explaining that the speed of evolution is explained from the perspective that different theories exist, and that changes at the gene level can be gradual, but changes in the phenotype can occur in bursts.
In modern times, as life science research and analysis technology have advanced, research on evolution has also become active. Scientists have discovered “horizontal gene transfer,” a phenomenon in which genes are directly transmitted between individuals or species without going through reproduction. This phenomenon occurs not only in microorganisms but also in plants and animals. A typical example is the chloroplasts of plant cells and mitochondria of animal cells, which are organelles with individual DNA and a double-membrane structure that are said to have come to exist in cells through horizontal gene transfer. This discovery further expands the possibilities of evolution.
Epigenetics also suggests a new evolutionary mechanism. Epigenetics argues that the environment can affect gene expression, which partially accepts Lamarck’s theory of acquired traits being inherited. In the case of the nematode, there are cases where the environmental records of ancestors have been passed on to their descendants, and epigenetic phenomena have also been confirmed in higher organisms.
The theory of evolution is not limited to biology and is influencing various fields. The theory that culture and language evolve is often discussed in academia, and memes in particular are attracting attention as an element of cultural evolution. Linda Fokas studied language from an evolutionary perspective, and recently, social structures, economics, politics, and even religious phenomena have begun to be interpreted from an evolutionary perspective. There are many differences between biological and cultural evolution, but attempts to understand society through the basic concepts of evolutionary theory show the extent to which evolutionary theory has influenced society.
