In this blog post, we examine why evolution is perceived not as mere change but as ‘progress,’ and the basis for this perception, from an adaptationist perspective.
Darwin first introduced the mechanism of evolution by natural selection in his book ⟪On the Origin of Species⟫. Over long periods, diverse species in nature adapted to their environments and passed on adaptable traits to their offspring. This process gave rise to new species or led to the evolution of existing ones. Many evolutionary biologists have built upon Darwin’s mechanism of ‘evolution by natural selection’ without denying it, developing evolutionary theory further. We refer to the outcome of this natural selection using the term ‘adaptation’. Furthermore, the school of evolutionary biologists who strongly believe in the power of natural selection is called ‘adaptationists’, and the representative adaptationist is none other than ‘Richard Dawkins’. ⟪The Selfish Gene⟫, ⟪The Extended Phenotype⟫, and ⟪The Blind Watchmaker⟫ are his seminal works. Through these, Richard Dawkins argued that genes are the starting point of evolution and the most crucial element driving it. From here on, we will explore thoughts on evolution and progress from the adaptationist perspective, as exemplified by Richard Dawkins.
First, the adaptationist position on the relationship between evolution and progress holds that life has progressed toward increasing complexity, as seen in the transformation of simple cells like bacteria into more complex organisms. Aristotle, in his ‘Great Chain of Being’, organized a hierarchy from inanimate matter through plants, animals, and humans, placing humans at the highest position in nature. Humans are composed of tens of thousands of cells and represent the culmination of highly evolved complexity in terms of intelligence and capabilities. Therefore, Dawkins views evolution as progress, arguing that life began with inferior bacteria and evolved toward greater complexity, culminating in the superior organism that is humanity.
This raises a question: bacteria are the simplest form of life. Life has merely increased in diversity, not complexity. This trend of evolution cannot be called progress. One example is the tapeworm, a parasite that lives within the human body. It is said that tapeworms originally had legs, but as they became parasites living within the human body, their legs became useless and degenerated, leading to their current form. Therefore, while tapeworms adapted to a new environment, they lost their legs and evolved in a direction of decreasing complexity; thus, this cannot be considered progress.
To represent Dawkins’ position on this, it can be summarized roughly as follows. Since the core keyword is the increase or decrease in ‘complexity,’ measuring complexity is crucial. Common sense suggests that increased complexity means more cells and enhanced functions the organism can perform. Returning to the tapeworm example, I don’t think we can say its complexity decreased simply because its legs degenerated. It’s possible that some other function developed in place of the degenerated legs. Animals like planaria, which can regenerate even if their bodies are severed, are called flatworms. Tapeworms also belong to this group of flatworms. Thus, while tapeworms lost their legs, they gained the new ability to regenerate even if their bodies are severed. Therefore, the claim that tapeworms evolved in a direction of decreasing complexity, and that this represents regression rather than progress, is incorrect. It is reasonable to view the trend of evolution as an increase in complexity.
A similar example to tapeworms is the human appendix. The human appendix once performed a function, but it can be seen as having degenerated because it is now useless and no longer necessary. However, a counterargument is that, of course, in the case of the appendix, it is thought to have degenerated and become useless. Nevertheless, when considering the human organism as a whole, many organs exist in pairs, and consequently, it is reasonable to view this as an increase in complexity. Therefore, even in this case, the trend of evolution is toward increasing complexity, which can indeed be called progress.
Next, a view that can counter Dawkins’ argument is the mass extinction events, such as asteroid impacts. The core claim is that we have experienced 20 mass extinction events so far, and these are the primary factors blocking the progress of life. If these mass extinction events had not occurred, we might currently be living under the rule of dinosaurs, and lifeforms entirely different from modern humans might exist on Earth.
From Dawkins’ perspective, this argument can be answered simply. Mass extinctions on Earth have already occurred, and no one can know what would have happened if they hadn’t. Even if that were the case, evolution would still proceed toward increasing complexity, and humans would emerge again. This debate seems to hinge on the question of who bears the burden of proof. In philosophy, it is said that the burden of proof lies with the party raising a claim that seems counterintuitive. For example, suppose someone asserts, “On average, cars are faster than airplanes.” Generally, most people believe airplanes are faster. This widely accepted view is precisely what constitutes “common sense.” Since this person made a claim contrary to common sense, unless they prove that cars are faster than airplanes (a claim contrary to common sense), airplanes will always be faster than cars. Returning to the mass extinction events, the idea in the above argument that “if these mass extinction events had not occurred” seems somewhat out of place. Therefore, this can be seen as a claim contrary to common sense. Unless one proves that ‘if these mass extinction events had not occurred, we might now be living under the rule of dinosaurs, or entirely different life forms might exist,’ this argument can be considered completely invalid. Consequently, the fact that humanity exists today despite experiencing mass extinction events suggests that while these events occurred, humanity ultimately survived and evolved in a direction characterized by increasing complexity.
Another perspective on progress from Dawkins is that the evolution of the capacity for evolution itself constitutes progress. For example, the emergence of chromosomes, prokaryotic cells, meiosis, eukaryotic cells, and multicellular organisms represents the evolution of evolutionary capacity itself, which signifies progress. Consequently, even if another mass extinction were to occur, the core of progress lies in evolutionary capacity itself. Therefore, life will evolve again through the evolution of its own capacity, ultimately rebirthing human society as we know it today.
Thus far, I have primarily argued Dawkins’ position on the relationship between evolution and progress. The core of this argument is that simple bacterial cells underwent increasingly complex transformations to reach humans, and that life has progressed in this direction of increasing complexity. Aristotle, as seen in his ‘Great Chain of Being,’ placed humans at the apex of the natural world. Furthermore, humans are the result of highly evolved life, exhibiting the greatest increase in complexity. Therefore, the evolution of life has proceeded in the direction of increasing complexity, and this is precisely ‘progress’. Regarding counterarguments using examples like tapeworms or the human appendix, the following rebuttal can be made. While some organs may degenerate, when viewed holistically, an organism’s functions develop, and evolution proceeds toward increased complexity. Thus, evolution moves toward greater complexity, which is progress. Furthermore, regarding skepticism about the progress of life due to random events like mass extinction events, the answer is as follows: Even if mass extinction events occur, the core of progress lies in the evolutionary capacity itself. Therefore, life itself will evolve again, ultimately giving rise to human society as we know it today. Furthermore, the claim that if mass extinction events had not occurred, entirely different life forms would exist instead of humanity as we know it today, while plausible-sounding, is entirely baseless. This is because the burden of proof lies with those making such counterintuitive claims; failing to prove them renders the argument untenable.
