I am researching the origins of life as personal research. However, rather than from a chemical or biological perspective, I am leveraging my experience as a systems engineer to tackle this intriguing issue from a systems engineering standpoint.
In previous articles, I have explained the hypothesis I have in mind. In them, I pointed out that the formation of a self-reinforcing feedback loop plays a crucial role in chemical evolution regarding the origins of life.
Recently, I came up with the idea of modeling the loop of processing. Modeling, in this context, refers to the task of clarifying the abstract structure and behavior of a target system when designing it.
In this article, I will model the loop of processing and explain my hypothesis on the origins of life from a loop-centric perspective.
Modeling the Loop of Processing
While there are loops that dynamically change like whirlpools and do not have a fixed entity, the processing loop I am thinking of fundamentally possesses a static structure. I will refer to a unit of this static structure as a “catalyst.” Because of its static nature, its shape doesn’t change before or after processing. In this sense, it acts as a catalyst.
The catalysts forming the loop are fundamentally arranged in order. In the model, this will be represented as a circular list. The loop, thus, is fundamentally based on a circular list of catalysts.
Between these catalysts, input and output are exchanged. Moreover, there are links between catalysts. Following these links, some of the output from the previous catalyst is handed over as input to the next one.
Transfers between links require time, and sometimes the transported material can be lost. Also, some kind of carrier is needed to move the transported material along the link. When the carrier transports materials, it consumes energy.
Once all the necessary inputs for a catalyst are available, processing occurs, and output is produced. Energy is also used in this process.
The output includes not only materials used for the next processing but also materials that become catalysts or materials that are not used in that particular loop.
Energy and carriers can be supplied from outside or can be produced from stored internal resources.
It’s also possible to supply the input of some process from outside the loop or to release the output from the loop to the outside.
Temporary Closed-loop System
Advanced loops can borrow energy, input, and carriers from the outside while accumulating output inside the loop.
Moreover, even if the external supply temporarily stops, it’s possible for highly advanced loops to continue operating by using the accumulated output as an input for the loop.
Note that the output can also be broken down to produce energy, allowing the loop to be self-sufficient in terms of input, energy, and carriers.
However, this closed-loop system will only last until the accumulated output runs out. Once the output ceases, the loop will break.
If energy, input, and carriers are supplied again from outside before the loop breaks, this closed-loop can continue to accumulate output.
Such a loop, which can sustain processing in a temporary closed environment, becomes a model for life.
Mortality Stasis and the Riddle of Life
Here’s a point of note. Such a loop structure can be mechanically realized with, for example, a battery, a motor that runs on that battery, and a generator. Defining life is challenging, but the difference between such mechanical devices and living organisms is that when the process stops, their structure collapses. This happens both after they have started operating and even during their assembly.
I call this condition “mortality stasis,” meaning that stopping leads directly to death. Machines that can start again even after stopping are termed “dormant stasis.” Why Earth’s creatures exhibit mortality stasis is a significant mystery because dormant stasis would seem more conducive to survival. Why did life with mortality stasis emerge instead of mechanisms with dormant stasis? I refer to this mystery as the “riddle of life.”
Regarding the riddle of life, one answer I’ve found, or a significant clue even if it’s not a full answer, is that systems with mortality stasis can internally possess mechanisms of dormant stasis, while the reverse is not logically possible. From this perspective, while living organisms may internally have several mechanisms of dormant stasis, they possess mortality stasis as a whole. When viewed in this light, systems with mortality stasis are invariably more diverse and multifunctional than those with dormant stasis. I believe this is why systems with mortality stasis have an advantage in changing environments.
And I believe that when mechanisms like robots or AI, which are highly advanced, flexible, and capable of intelligent self-modification, emerge, only then will the era come when mechanisms with dormant stasis can continuously persist.
From Non-life to Life 1: The Loop Hypothesis on Early Earth
If we consider a loop that can sustain processes in a temporary closed environment and also possesses dormancy as one model of life, the establishment of this process would signify the origin of life.
Initially, the ancient Earth, devoid of life, had ample carriers. The prime example is the water cycle. Water seeping from mountains becomes rivers, circulating in ponds and lakes, and meandering into the sea through confluences and bifurcations. The sea water, once warmed, evaporates and rises, forms clouds, which are then blown to the land by wind, and pour down as rain on the mountains.
Various chemicals can circulate using this loop as a carrier. While it might be improbable for substances to dissolve into water vapor, it’s conceivable that volatile chemicals could be carried by rising air currents created by water vapor, reaching the clouds. It’s even known that many bacteria reside in today’s clouds, so it wouldn’t have been an issue for smaller chemical substances to reach them.
Merely the movement of chemicals riding on Earth’s water cycle isn’t close to the chain of processes catalyzed by the aforementioned loops. But what if, utilizing this circulating water as a carrier, catalytic chemicals began accumulating in surface ponds and puddles?
In a particular pond, accumulated catalysts process incoming chemicals from upstream using solar or geothermal energy, producing outputs. These outputs move along the river’s flow, reaching catalysts in another pond where they are processed in a similar manner, generating different outputs. This cycle continues until they reach the sea, then, carried by clouds, they return to the mountains.
It’s believed that the energy from the sun or geothermal sources, the water cycle as a carrier, and catalysts accumulating in ponds and puddles, could potentially form this basic loop.
From Non-life to Life 2: Hypothesis of Chemical Evolution Based on the Loop Model
Within this loop, new catalysts are produced as outputs, and these give rise to new loops, diversifying the overall system. This generation of new catalysts contrasts with biological amplification through genes, and is termed a “chemical evolution” process.
Given the vast river networks on Earth, and the possibility of virtually infinite chemical patterns created through synthesis, it’s conceivable that a plethora of loops were tested on Earth. This is how I perceive the initial phase of the emergence of life.
Further, if loops producing chemicals that can store energy, like sugars or lipids, came into existence, that would be a significant advancement. If these sugars or lipids could be broken down to extract energy in situations or timings devoid of solar or geothermal energy, it would be another big leap.
If a circulating loop could form within a single pond, without leveraging the vast water cycle of Earth, that would be further progress. And if the necessary catalysts for that loop were enveloped within lipid membranes, akin to cell membranes, enabling the loop to function within, we would be nearly at our goal.
What remains is a mechanism that allows the intake of necessary inputs or energy from outside through the cell membrane, and a system that, even if there’s a temporary period when external inputs or energy can’t be acquired, can break down internal sugars to maintain structure and prevent the loop from stopping. Once these are in place, it’s complete.
Thus, we’d have the creation of a loop that can sustain processes in a temporary closed environment and also possesses dormancy. If we consider this as one model of life, it signifies the birth of life in accordance with this model.
Hypothesis on Evolutionary Transition: A Baton Pass from Self-reinforcing Feedback Loops to Self-replication
While I’ve described the story of this loop as a model of a single life form, it is because I have not incorporated the self-replicating genes or DNA into this model. The definition and mysteries of the origins of life are profound and complex. Hence, I have deliberately set up a model here that excludes the topic of self-replication.
By deliberately thinking in terms of a model that excludes self-replication, I aim to demonstrate that chemical evolution at the origin of life can occur without DNA. If this loop model were a self-reinforcing feedback loop that autonomously produces the necessary catalysts, or if multiple loops interact to output catalysts required by each other, chemical evolution could progress through the mechanism described here, even without self-replicating DNA.
Considering the complex and advanced functions of DNA and RNA, it seems reasonable to believe that before the emergence and progression of DNA or RNA-driven evolution, chemical evolution driven by these self-reinforcing feedback loops played a significant role.
Through the chemical evolution driven by these self-reinforcing feedback loops, complex and self-reinforcing loops emerged. Within these loops, the appearance and growth of chemical substances with genetic information like RNA or DNA advanced. Eventually, this led to the possibility of self-replication, which we believe marked the emergence of prototypical cells.
At this point, the era of chemical evolution concluded, and the era of biological evolution began — this encapsulates the entirety of my hypothesis. Furthermore, upon reflection, even after the onset of the biological evolution era, where DNA replicates itself, the mechanism of the self-reinforcing feedback loop continues to function, promoting self-preservation and evolution. The food chain of organisms being structured as a loop supports this view, and there are various other loops existing within ecosystems.
In Conclusion
I have introduced my hypothesis on the origins of life from a new perspective centered on modeling loops. While many of the contents have been discussed in previous articles, the novel discovery here is the loop-centric modeling.
By modeling centered on loops, I’ve realized that temporary closed loops can serve as models for life.
Typically, the origin of life is up to the formation of cells. However, in the loop-centric model, it’s possible to view the emergence of life as the point when a temporary closed-loop forms, even without DNA. This perspective suggests that the appearance of DNA merely marks a baton pass from chemical evolution to biological evolution and that DNA isn’t essential for the phenomenon known as life.
While I based our discussion on a simple loop model, in reality, the loop structure of life isn’t just one loop but an amalgamation of many. I’ve found the loop-centric modeling approach promising in this article, and moving forward, I’d like to model multiple loops and delve deeper into the discussion.
