This blog post centers on the question of whether life’s evolution truly possesses directionality. It explores diverse perspectives, from Darwin’s concepts to modern molecular time machine research, delving deeply into the relationship between evolution and progress.
“In the humanities classroom, where I arrived late after oversleeping, a discussion was in full swing about the revolutionary processes and changes in human society. One student presented, ‘Just as living organisms have evolved, human society has also changed to move toward more advanced forms and will continue to do so.’ Is that really the case? Can the changes in human society truly be called progress or advancement moving forward?”
As you may have noticed, this student’s argument contains a clear error. It stems from equating the concept of evolution with that of progress. The word ‘progress’ (進步), composed of ‘advance’ (進) and ‘step’ (步), and ‘evolution’ (進化), composed of ‘advance’ (進) and ‘become’ (化), both share a degree of meaning related to ‘moving forward’. Therefore, those who do not fully grasp the concept of evolution are prone to think the two terms carry very similar meanings. However, examining the terminology used by Charles Darwin, who first formally presented the concept of evolution, reveals this thinking is based on a significant misunderstanding.
Darwin described his theory as “The Theory of Descent with Modification.” Translated into Korean, this would be something like “Theory of Lineage with Modification.” He deliberately preferred the phrase “Descent with Modification” over the word “Evolution” to prevent his theory from being misunderstood as advocating for the ‘progress’ of life. In other words, he wanted people to clearly distinguish and understand evolution and progress as separate concepts.
This explanation should be relatively easy to accept for anyone with a basic understanding of life sciences or evolutionary biology. However, if we move beyond the anthropocentric concept of ‘progress’ and define progress in a broader sense as ‘moving in a certain direction,’ it becomes much harder to assert definitively that “evolution is not progress.” Even Darwin, who sought to understand evolution and progress as separate concepts, hesitated to claim that the entire process from bacteria to humans lacked any directionality whatsoever. In this context, many scholars have argued that the evolution of life has proceeded toward increasing complexity. They contend that over the long evolutionary process since life’s emergence, complexity has steadily and quite consistently increased.
Looking back at the entire evolutionary history of life, the later an organism appeared in time, the higher level of complexity it exhibited. This makes attempts to explain evolutionary directionality in terms of complexity seem quite plausible. However, there are also clearly opposing views that reject this perspective. A prime example is Stephen Jay Gould. In his seminal work, Full House, Gould argued with great force that evolution lacks any inherent directionality. To support his claim, he likened evolution to the drunken man’s walk, explaining:
“If one end of the road has a tavern and the other end has a ditch, the probability that a drunken stumble from the tavern will land in the ditch is practically 1. Even if the drunkard, disoriented by alcohol, has a 0.5 probability of walking in either direction, the path is blocked at one end by the bar, meaning he must eventually head toward the ditch.”
Gould states that the reason evolution appears to have a certain directionality is analogous to the situation in this analogy, where the drunkard inevitably ends up in the ditch. Life’s evolution originally proceeded without any specific purpose or direction. However, a wall of ‘complexity 0’—the complexity possessed by the first living beings—exists at one end of the complexity spectrum (like the tavern blocking the path in the analogy). This wall limits the direction of evolution, making it appear as if it progresses toward increasing complexity. In other words, just as a drunken stumble, whether left or right, inevitably leads to the ditch, the evolution of complexity also proceeded as a result of chance, without presupposing any destination or direction.
However, so-called adaptationists, who particularly emphasize the importance of natural selection, strongly object to the claim that evolution lacks any directionality. They cite as primary evidence the irreversible nature of several events that brought about major changes in life science, such as the emergence of eukaryotic cells and multicellular organisms. According to Gould’s argument, the evolution of life should be capable of reversing direction at any time—that is, regressing toward reduced complexity. Yet no known case exists where such an evolutionary upheaval was fully reversed, returning to a previous state. Unlike Gould, who argued that massive physical events like asteroid impacts could significantly alter evolutionary outcomes, adaptationists contend that evolution cannot retrace the evolutionary upheavals accumulated through adaptation under any circumstances. They maintain that the series of upheavals created by traits accumulated through adaptation has shaped the direction of evolution itself.
Thus, the debate over the directionality of evolution remains highly contentious today. While it is true that physical factors have influenced and altered the course of evolution, it is equally true that such changes have never completely reversed an already occurring evolutionary cataclysm. Therefore, this debate remains a question that cannot be easily resolved until the directionality of evolution is experimentally verified across the entire history of life on Earth. If we were to name the most certain method, it might be developing a true ‘time machine’ to travel back to the past. While this may sound like a far-fetched fantasy, there are actual examples where such an idea has been attempted in the form of research. A research team at the University of Chicago conducted a study using a so-called ‘molecular time machine’ to recreate the evolutionary process of ancient proteins in the laboratory.
The team applied deep mutation scanning technology to reconstructed ancient proteins, systematically analyzing the characteristics of a vast library of protein variants. The results revealed that over 800 alternative evolutionary pathways existed that were theoretically judged to be more efficient than the paths actual proteins had selected throughout history. They also confirmed that diverse evolutionary paths diverged significantly due to just a few mutations occurring in the initial proteins. This research demonstrates that the evolution of life we observe today is not necessarily the result of the ‘optimal’ adaptive process, and that the direction of evolution can be significantly altered by a single specific event. In other words, these findings clearly reveal that ‘chance’ plays a very significant role in the evolution of life. When turning back the clock of Earth’s history, there is a real possibility that humans in their present form would not reappear as an evolutionary product. Therefore, the conclusion drawn is that the direction of evolution is not inevitable but rather closer to non-existent.
Of course, it would be difficult to say that this single study completely ends the long-standing debate over the directionality of evolution. Rather, it is more accurate to view this research as a powerful reminder of the randomness of evolution and the importance of external events. Nevertheless, the true reason for introducing this study is not to definitively settle the scientific debate over the directionality of evolution itself, but to approach the initial question posed at the beginning of this essay—concerning the directionality of evolution, the changes in human society, and progress—from a new perspective.
Let us now return to the initial question: “Does human society progress with a sense of direction?” Compared to early primitive societies, modern human society has not only become increasingly complex but also significantly more organized and systematized. Furthermore, the shift in social institutions and values towards greater emphasis on individual human rights also suggests that human society has, in some sense, ‘progressed’. However, if the concepts of good and evil, and the values of right and wrong, are not absolute but relative—varying according to the era, culture, and perspective of the group—then human society may have merely moved in various directions based on the values of people in each era. So what about the evolution of life? Has evolution truly progressed with a sense of direction? As revealed in our examination thus far, this question too is a conundrum far from easily resolved. Yet, through molecular time machine research, at least one fact has become clear: the evolutionary path humanity has walked so far is by no means the only correct answer. And the insight that there is not just one single correct answer for the direction of change in any system is one that can be applied almost directly to human society in reality.
Our society is often called a ‘correct answer society’. It’s believed that only by excelling in exams where you must choose one correct answer from five options can you get into a good university, and only then can you land a job at a good company, save up for a house, and ultimately enjoy a relatively comfortable life. At first glance, it seems the correct answer for what constitutes a successful life is already predetermined. It’s difficult to definitively say whether human society is progressing with a clear direction, but it’s clear that many people are running in one direction only to live what is called a ‘correct answer life’. Even humanity, the product of a long evolutionary process, is merely one of the many efficient evolutionary paths that life systems could have chosen. Yet our current society pushes many people onto a standardized, one-size-fits-all life trajectory, as if it already knows the single correct answer.
My reason for studying life sciences isn’t solely to acquire theoretical knowledge. It also stems from a desire to gain life lessons and everyday wisdom by closely examining the survival strategies of diverse life forms that have existed as this planet’s masters far longer than humanity. From this perspective, the most crucial lesson humanity can learn from the evolutionary process of life, unfolding over billions of years, in a society where the answer to what constitutes a successful life is already predetermined, is likely this: “There is no single correct answer.” I conclude this piece hoping that a beautiful society, where diverse lives of different individuals can all be recognized as valid answers in their own ways, will one day become reality. I sincerely cheer on the countless people who struggle and wander because their chosen path differs from what our society demands as the so-called “right answer,” encouraging them to find a little more courage and walk their chosen path with greater pride and confidence.
