Thomas Kuhn’s paradigm theory has been applied mainly in physics, but it is worth discussing whether it is valid in biology. In genetics, the theory works well, but in the case of evolutionary theory, it may not be appropriate for reasons of invention.
In everyday life, the word “paradigm” is very common. When the way of explaining a situation changes significantly, people usually say that a paradigm has changed. The term paradigm was popularized by Thomas S. Kuhn’s book The Structure of Scientific Revolutions. The Structure of Scientific Revolutions gave philosophers of science a new perspective on the methodology of science. A “paradigm” is a scientific theory or framework that is officially recognized by an entire group of scientists at a particular time in the history of science. In practice, paradigms and the theory of scientific revolutions explain many examples from the history of science, such as the revolutionary shift from Newtonian mechanics to Einstein’s theory of relativity or Kepler’s years-long struggle with the motions of Mars. It’s worth noting, however, that the examples that support the book’s content are mostly limited to physics. This could be explained by the fact that Thomas Kuhn studied physics at Harvard University. However, in order to call Kuhn’s theory of normal science a philosophical theory of science, it is necessary to analyze whether Kuhn’s theory of normal science applies to other fields of science. Therefore, let’s consider whether Kuhn’s philosophy of science can be applied to biology, which is recognized as one of the pillars of modern science, and thus test the validity of Kuhn’s philosophy of science.
Since paradigms in biology have not been well studied, there may be controversy about which theories are paradigms in biology, so we will first define what Kuhn is talking about before proceeding with the discussion. In , Kuhn states that a paradigm is an achievement that satisfies two characteristics. First, the achievement must be so unprecedented that it separates a group of tenacious advocates from the competing ways of doing science. Second, the achievement must be sufficiently flexible to leave all sorts of problems open to be solved by reorganized groups of researchers. Theories that satisfy these two conditions are called paradigms.
The two most important in the history of modern biology are the theory of evolution and the study of heredity in molecular biology. In order to answer the two questions of the origin of life and the continuity of life, biologists have revised their theories through various studies. In genetics, the “gene particle theory” is currently the theory that has won the battle against the “gene mixing theory” and is accepted as the orthodoxy by many molecular biologists. It has contributed to major molecular biology discoveries in the history of biology, including Mendel’s law of inheritance and Watson and Crick’s discovery of the double helix structure of DNA. Darwin’s theory of evolution may have been criticized by many scientists in the past, but it is currently the best explanation of adaptation and change in life compared to other theories, and scientists use it to solve major problems in biology, such as the creation of new species and population genetics. Therefore, these two theories fulfill Kuhn’s definition of a paradigm.
According to Kuhn’s theory, the history of science is explained through a process of pre-science, the formation of paradigms, the process of normal science, crises, and scientific revolutions. Let’s analyze whether the history of genetics research follows Kuhn’s theory of normal science. Among the many theories that attempted to explain how traits are passed on to offspring, two of the most influential were the gene-mixing theory and the gene-particle theory. The gene mixing theory states that parents’ inherited traits are mixed together to produce a green color, just as blue and yellow paints are mixed to produce a green color. On the other hand, the gene particle theory argues that inheritance occurs because parents pass on certain particulate units that are heritable to their offspring. The gene-mixing theory was discarded because it concluded that offspring would inevitably have similar traits over generations, and the gene-particle theory gained paradigm status because it was found to be able to explain genetic laws such as the law of dominance, the law of independence, and the law of segregation. Once the paradigm was established, normal scientific research proceeded to identify what the gene particle was. Biologists discovered that the gene particle is DNA, not protein, and then focused on finding out how DNA is encoded and how it is structured. In addition, the behavior of chromosomes was studied based on the gene particle theory, which allowed biologists to understand what causes the laws of inheritance. If we look at the history of genetics research, we can see that it is still centered around the paradigm of the gene particle theory. In other words, we can find Kuhn’s philosophy of science in the history of genetics.
Darwin’s theory of evolution was proposed by Darwin in 1859 when he published The Origin of Species. However, evolutionary theory is not a theory that emerged to solve a problem at a particular moment. It came about through the accumulation of various facts. First, archaeologists’ findings that the Earth is older than the Bible indicates, Paley’s finding that populations were overproducing, and Malthus’ finding that resource limitations led to competition among individuals for survival. It would take nearly 80 years after this to establish evolution as a “paradigm. After Darwin published his theory of evolution in 1859, it was not accepted by many until the early 1900s, when genetics explained the possibility of variation. It was the observation of various phenomena that led to the acceptance of evolutionary theory. This shows that evolutionary theory has not undergone what Kuhn calls a “gestalt transformation” in the philosophy of science. The basis for acceptance of evolutionary theory has been accumulated from the past, and the theory that can explain this basis has been accepted. It is questionable whether the normal scientific process is occurring even after evolutionary theory has been recently established as a paradigm. While scientists use evolutionary theory to explain various phenomena, there are biologists like Gould who still claim to be Darwinists, but who argue against the theory of gradualism, which is one of the pillars of Darwin’s theory of evolution. This does not constitute a “theory clarification” or “crisis” in Kuhn’s sense. The clarification of a theory is a phenomenon that occurs in normal science that allows for a clearer explanation of a phenomenon that was not well explained by the theory. However, since the discontinuous equilibrium theory contradicts one part of Darwin’s theory of evolution, it is not a clarification. Furthermore, paradigm crises are caused by anomalous cases, which can lead to either the rejection of the theory or the fitting of the anomalous case into the theory. However, the case of discontinuous equilibrium theory falls into neither of these categories. There is some process that is not explained by Kuhn’s theory of the philosophy of science.
In the historical review of heredity and evolution presented in the previous section, the concept of emergence can be used to explain why the study of heredity seems to conform well to Kuhn’s paradigmatic theory and evolutionary theory does not. In general, life is said to be ’emergent’. Emergence is the property that the properties of microscopic parts cannot explain the whole, which can be described as “the whole is greater than the sum of its parts”. One discipline that is bound to discuss emergence is neuroscience. Neuroscience, the study of the brain and the consciousness it produces, does not simply explain that neurons, or the sum of neurons, are responsible for the brain’s consciousness. There are some emergent properties that scientists don’t yet understand that cause the sum of neurons to produce human consciousness. Neuroscience does not yet have what Kuhn calls a “paradigm,” and neuroscientists are interested in explaining individual neural phenomena, not in discovering laws that govern them all, and even when they do, it is not easy to discover them through experimentation. Rather, it is the domain of philosophers and psychologists. This is because it is not easy for an emergent discipline to have a paradigm. Inventive disciplines have complex characteristics that cannot be reduced to a few theories. In order to form a paradigm, theories that solve various problems must be created, but it is not easy to create a paradigm because it is impossible to solve problems with a single theory in the presence of originality. The lack of paradigms in most fields of biology can be attributed to the inventiveness of biology. Therefore, it is impossible to discuss paradigms in most fields of biology, so analyzing the history of biology through Kuhn’s philosophy of science theory is not very meaningful.
Genetics is a branch of molecular biology. Molecular biology is the discipline that introduced the classic reductionism that explains the laws of inheritance by the behavior of genes and chromosomes. However, the study of evolutionary theory has a generative nature that is not explained by a single law. Darwin’s theory of evolution alone consists of at least five different theories: the steady evolution of organisms, the theory of common descent, the theory of speciation, the theory of gradualism, and the theory of natural selection. This supports the statement above that Kuhn’s theory of the philosophy of science is not a good account of an emergent discipline.
So far, we have seen how Kuhn’s philosophy of science is applied differently in genetics and evolution, two fields that comprise biology, and what drives this difference. Kuhn’s philosophy of science is well applied in genetics, but it does not provide an adequate explanation for evolution. We have shown that this difference stems from differences in the “originality” of biology in the two fields. In sum, Kuhn’s philosophy of science is inadequate to account for the emergent nature of science, and therefore does not account for the emergent nature of biology. In order to apply Kuhn’s philosophy of science to biology, it seems necessary to consider whether the gradual change of theories in biology, or the various intertwined theories, can be explained by a simple paradigm. It is also necessary to develop a new philosophy of science theory to explain the history of biology. Although Kuhn’s theory of philosophy of science is not entirely rejected in biology, it is questionable whether it is meaningful to apply it in biology, where paradigms are rarely present due to their emergent nature. It seems necessary for philosophers of science and biologists to work together to derive a theory that can explain the history of biology.
