In this blog post, we will look at how the theory of evolution explains the diversity and origin of living organisms, focusing on natural selection and genetic variation.
In a broad sense, the theory of evolution refers to the overall theory of evolution, and evolution simply means the process of changes in heritable traits among groups of organisms. When we talk about the theory of evolution, we usually think of Darwin’s theory of evolution and its subsequent developments, but in fact, the idea of evolution has existed since ancient Greek times. For example, philosophers such as Empedocles (c. 490-430 BC) and Anaximander (c. 610-546 BC) are considered to be the first to have thought about evolution. As such, the idea of evolution itself existed before Darwin.
After the philosophers of ancient Greece, scientific approaches to the bell and its origins did not begin in earnest until the 17th century. The origin of modern evolutionary theory is the theory of Lamarck (1744-1829), who argued that all living things evolve over generations into increasingly more complete and complex forms. According to Lamarck’s theory, the simpler living things that exist today have shorter origins. Lamarck argued that acquired characteristics, such as muscles developed through life, are passed on to offspring, but he was later criticized for failing to provide evidence for this. Lamarck’s theory and various other theories emerged and underwent criticism, leading to the emergence of Darwin’s (1809-1882) theory of evolution, which is widely accepted today.
Darwin formulated his theory of evolution in his book On the Origin of Species (1859). His theory forms the basis and foundation of modern evolutionary theory, and the main contents of “Origin of Species” can be summarized as four key conditions.
First of all, all species have the ability to reproduce through self-replication. For example, although offspring can be born between genetically close lions and tigers, these offspring are not recognized as a new species because they are incapable of reproducing. Therefore, self-replication is an essential prerequisite for evolution.
Second, mutations occur during the replication process. Mutations, such as mutations, cause differences between individuals, and these differences are often inherited. If self-replication were perfect, evolution would not occur. The imperfection of the self-replication process, or the instability of the possibility of mutation, makes evolution possible. Traits such as muscles that develop later in life cannot be a factor in evolution because they are not inherited, but mutations in the genetic code, DNA, are likely to be inherited and can play an important role in evolution.
Third, because resources are limited in the environment, competition for survival occurs between individuals. If there are enough resources in the environment for all individuals to survive, both the mutant and non-mutant individuals will survive and the species will not change in a particular direction. The process of an individual adapting to the environment is achieved through competition in a resource-limited environment. When the environment becomes saturated, intra-species competition over limited resources inevitably occurs.
Finally, the fourth condition is that individuals with an advantage in survival leave more offspring. This process is called survival of the fittest through natural selection. Individuals that are suitable for the environment have more opportunities to survive and reproduce in intra-species competition, and as a result, the number of their genes and their mutated offspring increases. All of these processes are stochastic, and individuals that have a slight survival advantage through mutation will increase in number over several generations.
Darwin’s key argument is that populations will adapt to the environment over a long period of time and change overall, and that these changes will eventually accumulate to form a new species.
Darwin’s theory of evolution later combined with Mendel’s genetics to develop into a form called Neo-Darwinism, which is considered the orthodox theory. August Weismann (1834-1914) refuted Lamarck’s claim that Darwin could not completely deny, and argued that evolution occurs only through the process of natural selection. This theory has developed into a comprehensive theory related to modern evolution by explaining Darwin’s theory of evolution with Mendel’s genetics. The core of this theory is that it has increased the logical completeness of Darwin’s theory of evolution through the fact that traits are passed on to the next generation by genes.
Another notable evolutionary theory is Richard Dawkins’ (1941~) theory. His book The Selfish Gene has become the orthodoxy in academia and the general public since its publication. The core of Dawkins’ theory is that genes function as the main agents of the evolutionary process beyond the reproduction and transmission of information of individuals, and that individuals are just vessels for carrying genes. Like Darwin’s theory of evolution, natural selection is the driving force of evolution, but the main subject of evolution has changed from individuals to genes. From Dawkins’ perspective, group behavior and altruistic behavior, which were previously difficult to explain, are now easier to understand. For example, worker bees and ants that work for the queen without the ability to reproduce may seem irrational at the individual level. However, their behavior can be explained as an effort to reproduce genes, as they share the queen’s genes. As such, it has become possible to interpret these seemingly altruistic behaviors as calculated behaviors to increase the rate of reproduction of genes themselves, and Dawkins’ theory of evolution is widely accepted in academia.
One of the reasons why the theory of evolution is still considered a hypothesis, despite being widely accepted, is the controversy surrounding creationists. Evolution has been a controversial topic for creationists and religious people because it is considered to be a sensitive subject. Some scientists even argue that the theory of evolution does not provide a complete explanation for macroevolution. However, modern evolutionary theory explains that countless microevolutionary processes can lead to macroevolutionary changes over a long period of time. There are also some controversies, and there is a trend to reject evolutionary theory.
Evolutionary theory is a theory that explains the diversity of numerous species on Earth and how organisms have changed over time. The core of the theory of evolution is that species change through the four principles of self-replication, mutation, environmental restriction, and natural selection, as explained above. Although the theory of evolution is sometimes opposed or questioned by creationists, it is significant in that it explains many natural science-related phenomena and has the potential to explain more in the future.
