In this blog post, we will explore the concept and meaning of evolution biologically, focusing on the question, “Is evolution a progress or just the result of simple adaptation?”
It is no exaggeration to say that Charles Darwin’s advocacy of the theory of evolution has renewed the way we look at living things. However, unlike how we tend to think of Charles Darwin when we use the word “evolution” biologically, Darwin did not use the word “evolution” when he first wrote “On the Origin of Species.” He seems to have avoided using the word to avoid giving the impression of “progress” and making readers think that life is changing towards some goal. However, even today, the question of whether evolution is progress is constantly being raised. If we consider evolution to be progress, there is a risk that it will lead to eugenics or species supremacy. Then, let’s argue why evolution is not progress from a biological perspective.
The idea of seeing evolution as progress is rooted in the Western view of nature, which has been around since Aristotle’s time, called the “chain of being.” The idea was that there are simple and inferior animals at the bottom of a huge ladder, and as you go up the ladder, there are higher and higher animals, and then humans, and then gods. Also, since the word “evolution” is widely used to mean “development,” we tend to think that biological evolution is also moving in a certain direction, and in the extreme, it is moving towards perfection, that is, it is progressing. However, “evolution” as a biological definition refers to the change in the distribution of traits within a population as the environmental-adaptive variation is passed on to the next generation in a specific population of organisms with various variations. This definition, which states that evolution occurs as individuals with environmental-adaptive variation, that is, variations that are beneficial for survival, survive, is based on Darwin’s theory of natural selection. This definition does not include the direction of evolution. In fact, in order to understand that evolution is not progress, we need to look at the entire process of evolution at once. If evolution is progress, then a human being, which is a vertebrate that has undergone more evolution after diverging from its common ancestor with the invertebrate squid, should be more perfect than the squid.
However, if we compare the squid’s eye with the human eye, the human eye has the optic nerve and blood vessels distributed in front of the retina, and they pass through the hole in the retina and connect to the brain, unlike the squid, which has the optic nerve distributed behind the smooth retina. This hole is called the “blind spot,” which creates a blind spot in the human’s field of vision. This is because the structure of the human eye evolved from the form in which the optic nerves spread out over the retina to a round shape. The human eye can easily become fatigued because the entire eye vibrates slightly to resolve the shadows caused by the optic nerves and blood vessels that cover the retina where images are formed. As such, the more advanced human eye does not have a more perfect structure than the squid’s. This is because evolution is not a process of striving for perfection, but rather the selection of slightly better mutations in the environment in which the organism lives. In other words, at the time those mutations were selected, they were the best changes and were more advantageous for survival than other individuals, but they were not a process of striving for the best structure. Another example is that the human respiratory and digestive tracts do not have separate pathways but overlap. This structure is very inefficient, as food can easily enter the respiratory tract and cause death, but it was the best option for life forms when they developed lung breathing during the evolutionary process. It was not the process of creating a respiratory tract separate from the digestive tract that is considered perfect.
Those who claim evolution as progress argue that the current living organisms are increasingly structurally complex compared to when life first originated. Of course, if you look at the evidence of the fossil record in a row, you can intuitively feel the sense of progress as you see the long and majestic evolutionary process of life, in which the simplest structure of prokaryotic cells, through eukaryotic cells, to multicellular organisms, invertebrates and vertebrates, and creatures with outstanding intelligence such as humans, emerge. However, the claim that increased structural complexity is progress is premised on the idea that organisms with high structural complexity are better, or more survival-friendly, organisms. If this premise is correct, then nature should have selected organisms with structures better suited to their environments and eliminated organisms that were not. However, the existence of bacteria, a single-celled prokaryote with a very simple structure that is still thriving at this very moment, refutes this claim. If increasing structural complexity is progress, bacteria should have been pushed aside by eukaryotes and gradually extinguished since the appearance of eukaryotes. However, bacteria are still living in the midst of a huge variety of bacteria that have much more complex structures than themselves, and even infect and kill them. Comparing the complexity of structures, it is clear that complex organisms such as existing vertebrates have evolved from organisms with simpler structures. However, this is only the result of adaptation and natural selection, and nature does not make choices with any target or purpose. The claim that evolution occurs in a direction that increases structural complexity can also be criticized based on the existence of viruses. Viruses have only a protein shell and nucleic acid, which is a simpler structure than bacteria. The scientists who first isolated the virus thought that it might be the first life form because of its simple structure. However, viruses are not the first life form because they cannot reproduce on their own and can only multiply through the metabolism of host cells. In other words, it can be speculated that viruses have become simpler in structure as they have chosen to parasitize through evolution. Evolution has not occurred in a direction that increases structural complexity.
Heckel’s proposition that “individual development repeats phylogenetic development” has also been argued that structural complexity has increased through evolution, and this is evidence that evolution is progress. The embryos of vertebrates at the beginning of their development have a relatively simple structure. Even the embryos of mammals at this stage have gills, and as more and more complex organs develop, they finally develop into an individual. This process is similar to the process of phylogenetic evolution in which simple-structured organisms evolve into the complex vertebrates of today. However, the process of evolution that repeats itself from individual occurrence is not necessarily the basis for the claim that evolution is progress. The increase in the structural complexity of living organisms is due to the fact that living organisms are subject to the laws of physics and chemistry. There is a minimum, simple form that can be called a living organism, and anything less than that is not a living organism, so the structure must either become more complex as a result of evolution or maintain its structure. Stephen J. Gould describes this as the drunkard model. A drunkard leaving a bar stumbles to the right or left, with a ditch on the right and the wall of the bar on the left. At this point, the probability of the drunkard stumbling in the direction to the right and the left is the same, but if the drunkard hits the wall of the bar, he can no longer move to the left, so he eventually moves in the direction of the ditch on the right and falls into the ditch. From the results alone, it appears that the drunkard moved in the direction to the right, but this is a coincidental result that was unavoidable due to the presence of the wall on the left. Heckel’s embryological argument can be similarly refuted. Since the early embryo is quite unstable, if a mutation occurs early in the evolutionary process, the embryo will easily die, so it has evolved with the addition of new stages.
It was revealed why the evolutionary process that appears to be progressive is not progressive, and that the evolutionary process is simply a process of selecting the best conditions at the time, and that it is not a change toward a perfect structure when viewed over time. In addition, the increase in structural complexity is natural due to the passage of time and physical and chemical laws, and is not intended in any direction. Nature does not make choices with a will. It is only by chance that life seems to be progressing in some way, and the structures and functions of various existing organisms are only the result of natural selection. Hitler, a believer in the theory of evolution, and eugenicists believed that evolution was progress and that organisms with certain traits were superior to those without, leaving many people with indelible wounds. As such, any definition in science can have a significant impact on society, so it must be approached with caution and precision. This is also true for the definition of the relationship between evolution and progress.
