This article explains how evolutionary theory explains changes in life, how it was combined with genetics to develop into modern evolutionary theory, and covers the main theories related to the mechanisms of evolution. It also emphasizes that evolutionary theory has expanded to study not only biological evolution, but also the origin of life.
All living organisms gradually change their characteristics over generations, and these changes allow them to adapt to their environment. This process and its outcome is called “evolution,” and the various theories and disciplines related to it are collectively known as “evolutionary theory. Evolutionary theory is divided into different theories based on how they explain the causes and processes of evolution, and they offer different perspectives on how living things came to be the way they are. Evolutionary theory has grown out of “evolutionary biology,” the study of the evolutionary phenomena of living things and their causes. This discipline forms an important pillar of modern biology as part of the ongoing human endeavor to understand the origin and diversity of life.
Evolutionary biology grew out of theories about species change that emerged from fossils and studies of biodiversity in the 19th century. In 1858, Charles Darwin and Alfred Russel Wallace laid the groundwork for the theory of evolution by proposing the concept of natural selection. This period was dominated by attempts to explain changes in living things by analyzing the morphological similarities between fossils and living things, which was an important foundation for understanding the mechanisms of evolution. Early evolutionary theories focused on simple morphological changes, but when combined with genetics, they evolved into modern evolutionary theory. In particular, the rediscovery of Mendel’s laws of inheritance in the early 20th century allowed evolutionary biology to explain the mechanisms of evolution in a more sophisticated way, with clear evidence of genes.
Modern evolutionary theory defines evolution as the change in gene frequencies in a population of organisms over generations, and identifies natural selection, gene drift, and mutation as the factors responsible. The theory of natural selection, which states that individuals with traits adapted to a given environment benefit from survival and reproduction, forms the core of the evolutionary mechanism. Darwin’s early theories suggested that traits that favor survival are passed on to the next generation, but the concept of natural selection was later refined when it was discovered that individual variation is inherited. A classic example is the gray moth in 19th-century England. As industrialization made it easier for gray moths to survive in darker environments, their numbers increased, while white moths had a higher survival rate in less polluted areas. This phenomenon has become an important example of empirical support for the theory of natural selection.
Gene floating is an important concept in modern evolutionary theory, alongside natural selection, and is essential to understanding evolution. It is a phenomenon characterized by changes in the frequency of allele expression during reproduction in a population, which can occur independently of fitness for survival. This concept is particularly strong in small populations and plays an important role in explaining how changes in the gene pool occur. Moto Kimura’s theory of neutral evolution, which proposed gene immobility as a major factor in evolution, argued that the vast majority of mutations are neutral, and that evolution proceeds as they are passed on by chance to the next generation. This theory provided a new perspective on understanding the complexity of evolution and is now recognized as a major mechanism of evolution, along with natural selection.
Another prominent theory in modern evolutionary theory is Richard Dawkins’ theory of the selfish gene. In his theory, Dawkins argues that genes are the agents of evolution, and that living things are merely vehicles that help them replicate. This theory builds on Darwin’s theory of natural selection and attempts to explain that all behavior, including altruistic behavior, is ultimately for the survival and replication of the genes. By reinterpreting the behavior of living things in terms of genes, this theory has contributed to the expansion of evolutionary theory into philosophical discussions.
Another controversial aspect of evolutionary theory is the speed of evolution. There are two main positions: gradualism, which holds that life evolves slowly, and punctuated equilibrium, which holds that there are plateaus and cataclysmic periods in evolution. Gradualism points to the incompleteness of the fossil record and argues that evolution must have occurred slowly. On the other hand, piecemeal equilibrium argues that the fossil record is intermittent, with periods of rapid evolution alternating with periods of relative stasis. This debate is far from settled and requires a deeper understanding of the mechanisms of evolution.
In addition to disciplines that focus on the principles of evolution, there are many other fields of study that are derived from evolutionary theory. For example, taxonomic phylogenetics aims to identify the flexible relationships of organisms and understand their evolutionary history. It utilizes the fossil record, anatomical similarities, embryological evidence, and molecular biology data to construct a phylogenetic tree of living things, with the goal of revealing key events in the evolutionary process. Taxonomic phylogeny is a practical application of evolutionary biology that plays an important role in understanding the birth and divergence of different species.
Through these studies, biologists understand the origins of life and explore how each species has differentiated and adapted. For example, the three-region, six-phase classification system divides life into three domains: bacteria, archaea, and eukaryotes, which are further subdivided into plants, animals, fungi, and protists. This classification serves as an important tool for systematically understanding the evolutionary history of life and forms the basis of biological research.
However, evolutionary theory is not limited to biological evolution; it also challenges questions about the origin of life. One of the disciplines that studies the origin of life is chemical evolution. Chemical evolution studies how the first life forms arose in the mineralized environment of the primordial Earth. Miller’s and Fox’s experiments provided clues to the origin of life by showing how organic matter could form from inorganic matter, and even complex organisms such as microspheres capable of self-replication.
While the theory of evolution is still incomplete, the phenomenon of evolution is supported by so much evidence that it has become almost orthodox. This research now extends beyond biology into a variety of fields, including evolutionary psychology and cultural evolution. Evolutionary theory plays a key role in understanding the complexity and diversity of life, and is an important pillar of modern science. The development of evolutionary theory continues to be studied as an essential tool for understanding the past and present of life, and even for predicting the future.
