The Origin of Life: Clearing Misunderstandings Through Systematic Exploration
The origin of life is considered to be shrouded in many mysteries. From the perspective of a systems engineer, I am advancing the exploration of this mystery.
In this article, I will provide an overview of my research findings so far, aiming to organize my own thoughts on the subject.
Three Aspects of the Origin of Life
When considering the origin of life on Earth, it is necessary to break it down into three main aspects.
The first aspect is the systematic understanding of general physical and chemical laws.
Understanding this aspect helps dispel the misconception that the emergence of life is an exceptional event. Instead, it allows us to grasp that the emergence of life is an extension of the simple natural laws we understand.
The second aspect is the systematic understanding of biochemical phenomena.
Understanding this aspect reveals that, for the birth of life, metabolism rather than genetic information forms the basis. Additionally, it is evident that the complex organic compounds and metabolic systems within biological cells are not unique to cells. This separation allows us to consider the birth of cells and the complexity of organic compounds and metabolic systems independently.
The third aspect involves hypotheses about the emergence of life on Earth.
In this aspect, based on the understanding of the first two aspects, hypotheses are proposed and reasonable processes are examined regarding how life emerged on Earth. The understanding gained from the first two aspects removes the assumption that the birth of life was a short-term and local phenomenon. This allows for the formulation of hypotheses from the perspective of long-term chemical evolution on a global scale.
From this perspective, various existing hypotheses about the origin of life can be reinterpreted not as contradictions, but as local elements or parallel evolutionary paths within the overall process of life’s origin. Additionally, possibilities overlooked in existing research can be incorporated into these hypotheses.
The first two aspects are merely a logical reconfiguration of well-known scientific knowledge. Therefore, please note that they are not hypotheses to be tested based on experiments or evidence. Objective validation is only important based on the presence of logical inconsistencies, misunderstandings, or oversights.
The third aspect is purely hypothetical and requires validation through experiments and evidence. While presenting sufficient evidence is challenging, it provides a sufficiently reasonable explanation as a hypothesis about the origin of life.
A hypothesis constructed from the perspective of long-term chemical evolution on Earth answers many fundamental questions about the basic mechanisms of life’s origin. In other words, it provides a framework that can explain the overall picture of life’s origin without contradiction based on fundamental theories.
General Evolution Theory
Now, let’s first outline the general theory of evolution, which is central to the first aspect.
Darwin’s theory of evolution explains that the diversity of species and the complexity of biological structures and functions are the results of genetic replication and mutation, and natural selection. This will be referred to here as biological evolution theory.
I generalize this concept of evolution to extend it to inanimate objects. This will be referred to as general evolution theory. General evolution theory can be explained in terms of the definition of evolution and the mechanisms of evolution.
Evolution, as a phenomenon, is defined as the repeated occurrence of new objects or substances with increasing complexity in space over time, resulting in cumulative increases in complexity and diversity of types. Additionally, the complexity of interactions between objects and the diversity of types of interactions also increase.
With this definition, evolution can occur with mechanisms simpler than biological evolution.
First, the formation of new substances through simple combinations of matter, and the cumulative increase in the number of combinations, can be considered evolution. A representative example is the increase in the types of elements in the universe. After the Big Bang, the universe contained only elements with small atomic numbers like hydrogen and helium, but over time, elements combined to form heavier elements with larger atomic numbers.
Similarly, it is considered possible that, before the emergence of life, atoms and molecules on Earth repeatedly combined to form more complex molecules.
However, elements in the universe and molecules on Earth can also be decomposed, not just combined. Generally, more complex substances tend to have a higher likelihood of decomposition, so with this simple combinatorial evolution, the complexity of the substances generated eventually reaches a limit.
An important point here is to dispel the misconception that complex molecules, if formed, would quickly be destroyed due to various factors, and that without special conditions, complex molecules cannot exist.
In reality, there is a period between the synthesis and destruction of molecules. Therefore, if the rate of formation exceeds the rate of destruction, even highly destructible complex molecules will increase in number over time. There will always be a quantity in space where the rate of destruction and formation are in balance.
In the absence of special conditions, the generation of complex substances progresses to the state where this balance is maintained.
To generate substances with higher complexity from this point, it is necessary for evolution to make combinations more likely or make decomposition less likely. Elements do not have such effects, so it is thought that there is a limit to the naturally synthesized elements in the universe. On the other hand, on Earth, molecules with catalytic properties exist.
Such catalytic molecules can potentially exceed the limits of complexity in synthesized molecules by promoting combinations or inhibiting decomposition. Furthermore, interactions between catalytic molecules can spread catalytic effects in a network, creating self-catalytic pathways. Molecules in these self-catalytic pathways can serve as a foundation for the synthesis of even more complex molecules.
If evolution progresses to such stages and new catalytic substances are synthesized, the upper limit of complexity will be significantly higher compared to evolution without catalysts.
Moreover, there is a possibility of complex catalysts that can generate multiple types of catalysts. Such catalysts would have the ability to form multiple catalytic networks with a single catalyst and possess numerous self-catalytic pathways. These complex catalysts not only increase the complexity and diversity of individual substances but also enhance the complexity and diversity of combinations of multiple substances, driving evolution in that aspect.
In biological evolution, genes function as complex catalysts that can generate multiple types of catalysts.
By organizing the definition of evolution and generalizing the mechanisms of evolution, it becomes possible to understand evolution, from the evolution of elements and molecules by physical laws to biological evolution, within a single conceptual framework. This perspective allows us to understand biological evolution not as a special phenomenon but as an extension of simple natural laws, similar to general phenomena in physics and chemistry.
Additionally, it is necessary to correct another misconception here. We have an understanding that complex substances or structures will eventually be destroyed. Thus, there is a misconception that complex substances or structures like organic compounds used by organisms or biological bodies cannot exist in natural states.
However, in reality, destruction of substances or structures is not necessarily inevitable. Therefore, as long as there are no destructive factors, even highly complex substances or structures can be maintained in their state. Thus, there is no inherent superiority of synthesis over destruction. If there are many opportunities for synthesis, substances will become more complex; if there are many opportunities for destruction, the complexity of substances will decrease. And, if the initial state consists of only simple substances, substances will inevitably evolve to a stage where synthesis and destruction balance each other.
Cell-Independent Biochemical Phenomena
Moving on to the second aspect, here I will outline cell-independent biochemical phenomena to understand whether complex chains of chemical reactions, similar to those carried out by living organisms, can be realized if chemicals evolve according to general evolution theory.
Typically, the characteristics of biological cells include self-replication through genetic information, encapsulation by lipid membranes, and complex and diverse metabolic systems.
These are functions or mechanisms that are achievable because of the existence of biological cells, and it is thought that they could not exist or function without special conditions prior to the emergence of the first single-celled organisms on Earth.
Because of this, there is an assumption that it is difficult to consider these functions or characteristics as having formed gradually and then giving rise to life. This assumption has led existing research on the origin of life to focus on searching for locations or mechanisms where chemical evolution occurs locally and over a short period.
However, this assumption is a misconception and can be explained by current observable biochemical phenomena.
First, self-replication through genetic information is a function that can be realized by viruses, which do not possess cells. Viruses can exist outside cells for a certain period. Of course, viruses alone cannot self-replicate, so they achieve self-replication by utilizing cells.
However, this understanding is not entirely accurate. What viruses need is a mechanism for producing copies of the original virus, including gene replication within the cell. If such a mechanism exists and functions, viruses do not necessarily need to be inside a cell.
The encapsulation mechanism by lipid membranes is a function that cells possess to encapsulate various organic compounds beyond just cell membranes. Lipid membrane capsules that enclose organic compounds are not only used within cells but can also be transferred between cells.
Thus, similar to viruses, lipid membrane capsules can persist outside cells for a certain period. Moreover, the function of encapsulating various organic compounds by lipid membranes does not necessarily need to be inside a cell.
Metabolic systems are a series of mechanisms that produce chains of chemical reactions beneficial for maintaining life. There are many types of metabolic systems, and their combinations enable organisms to sustain life.
Many metabolic systems are contained within cells. However, this is not the only possibility.
Some metabolic systems are completed through cooperation between cells. There are also systems where the mechanism of metabolism is completed by exchanging organic compounds with other organisms or interacting with the environment.
From this perspective, it is possible in principle for metabolic systems established through chains of chemical reactions to exist entirely within the environment, rather than exclusively within cells. In other words, these biochemical phenomena can be considered cell-independent.
Another important point is that the functions required by viruses for gene replication and creating copies of the virus, as well as the encapsulation function by lipid membranes, are both types of metabolic systems.
Therefore, based on observable biochemical phenomena, it can be said that all these functions and mechanisms could exist in the environment without relying on cells.
This perspective allows for separating the establishment of these functions and mechanisms from the emergence of the first single-celled organisms in the origin of life. It enables us to consider the birth of the first cells not as a short-term local phenomenon, but as a long-term, wide-scale phenomenon.
Hypothesis on the Origin of Life
Up to this point, I have outlined the first and second aspects, focusing on systemically reorganizing well-established knowledge in physics and chemistry. As stated initially, these reorganizations do not include specific hypotheses about the origin of life.
Based on this reorganized knowledge, I will now outline my perspective on the third aspect: the hypothesis regarding the origin of life on Earth.
This hypothesis can be divided into two levels. The first-level hypothesis provides an overarching view of the origin of life and represents the more probable aspects of the hypothesis. The second-level hypothesis complements the first-level hypothesis with more specific details.
Here, I will describe the first-level hypothesis regarding the overall picture of the origin of life. The second-level hypothesis will be addressed later, as it is more specific and therefore less certain.
Chemical Factory Network Hypothesis
The first-level hypothesis regarding the overall picture of the origin of life on Earth consists mainly of two hypotheses: the Chemical Factory Network Hypothesis and the Cell-Free Metabolic System Hypothesis.
The Chemical Factory Network Hypothesis is designed to explain how chemical evolution might have progressed on Earth by applying general evolution theory to the Earth environment.
This hypothesis posits that complex chemical evolution leading to the origin of life utilized the entire Earth as a vast network of chemical factories.
Earth comprises land, oceans, and the atmosphere. Land includes numerous isolated water bodies such as lakes, ponds, and marshes. Water cycles through these environments, mixing and circulating minerals, inorganic compounds, and organic compounds. However, many of these water bodies are relatively isolated, resulting in differing concentrations of substances and varying temperature and sunlight conditions.
This diverse environment functions as a platform for synthesizing various chemical substances through diverse combinations of material encounters. Moreover, the water cycle not only transports substances in one direction but also creates a catalytic network with self-catalyzing pathways.
The Chemical Factory Network Hypothesis suggests that chemical evolution necessary for the emergence of life progressed gradually by leveraging Earth’s environmental characteristics.
While this hypothesis is speculative, if it were to be disproven, it would logically imply the adoption of the reverse hypothesis: that the origin of life did not utilize a global chemical evolution mechanism.
Previous research on the origin of life has mainly focused on localized, short-term phenomena. However, understanding the general evolution theory outlined in the first aspect makes it challenging to support a view that chemical evolution occurred only locally and briefly.
Furthermore, the Chemical Factory Network Hypothesis can accommodate existing theories on the origin of life, such as those involving mineral surfaces, hot springs, and deep-sea hydrothermal vents. It suggests that rather than one specific location, each location might have contributed uniquely to the synthesis of specific chemical substances.
Thus, while a hypothesis, the Chemical Factory Network Hypothesis is difficult to completely dismiss or ignore when considering the origin of life.
Cell-Free Metabolic System Hypothesis
The Cell-Free Metabolic System Hypothesis naturally follows from the understanding of cell-independent biochemical phenomena described in the second aspect.
This hypothesis proposes that complex and diverse metabolic systems, including self-replication through genetic information and encapsulation by lipid membranes, were already functional on Earth before the emergence of the first single-celled organisms.
The hypothesis primarily makes two claims. First, it asserts that organic compounds with the complexity required for these systems existed in sufficient variety and quantity in an environment without life, and that these systems functioned using these compounds. Second, it proposes that these systems gradually integrated within the pre-existing environment and eventually functioned within a single lipid membrane, leading to the emergence of the first single-celled organisms.
This hypothesis is also difficult to disprove. Disproving it would mean supporting the view that some or all of these functions did not exist before the emergence of single-celled organisms, implying that these functions began simultaneously with the emergence of single-celled life.
This view was somewhat assumed in previous research on the origin of life. However, after considering cell-independent biochemical phenomena, it appears more rational to think that cells emerged by integrating pre-existing functional systems rather than these systems appearing simultaneously with the first cells.
The Cell-Free Metabolic System Hypothesis can incorporate existing theories on the origin of life, such as the DNA World Hypothesis, RNA World Hypothesis, Metabolism-First Hypothesis, and Self-Catalytic Sets. These theories could be considered sequential or concurrent, depending on the context.
In particular, combining it with the Chemical Factory Network Hypothesis suggests that localized or specific functions might have progressed through metabolism-first chemical evolution, while other locations or functions progressed around RNA. Additionally, early stages might have seen self-catalytic sets driving evolution through natural selection, transitioning to viral mechanisms for genetic information replication at later stages.
Therefore, like the Chemical Factory Network Hypothesis, the Cell-Free Metabolic System Hypothesis is a challenging hypothesis to dismiss or ignore.
Conclusion
In this article, I have approached the origin of life from a systems theory perspective by reorganizing the basic knowledge of general evolution theory and cell-independent biochemical phenomena. These are not hypotheses but logical constructions based on fundamental knowledge in physics and chemistry.
This reorganization addresses implicit misunderstandings in discussions about the origin of life.
The most significant misunderstanding is the notion that in a closed system, substances degrade over time, leading to a loss of complexity.
In reality, whether in closed or open systems, the complexity of substances is determined by the balance between the rates of synthesis and degradation. As long as the synthesis rate exceeds the degradation rate in a state of low complexity, the complexity of substances in the system increases.
This is vividly illustrated by the increasing complexity of elements in the universe.
Many discussions about life treat increasing complexity over time as a special phenomenon contrary to natural laws. In contrast, the increasing complexity of elements in the universe is not treated as special. This reveals a double standard in thinking depending on the subject.
In my exploration of the origin of life, I have realized that addressing such misunderstandings is crucial for approaching the answer. As shown in this article, clarifying misunderstandings based on basic knowledge allows for more coherent and less contradictory hypotheses.
