Feedback Loops in the Origin of Life: Transition from Macro to Micro
From a systems engineering perspective, I am conducting personal research into the systemic mechanisms in the origin of life.
In my research, I base it on the chemical evolution theory, which posits that before life appeared on Earth, non-living chemical substances gradually combined and evolved. I have come to believe that the formation of self-reinforcing feedback loops by chemical substances and reactions, combined in a multi-layered manner, is a key point in chemical evolution.
In this article, I will first create a rough model of feedback loops in chemical evolution and briefly organize the types of loops that are formed. Based on this, I will outline my hypothesis that chemical feedback loops were formed using the water cycle on ancient Earth.
In the latter half, I will look at the progression of chemical evolution in the origin of life from the perspective centered on feedback loops. This will depict the transition from macro feedback loops driven by Earth’s water cycle to micro feedback loops of chemical reactions within cells. And I’ll touch on the point that a phenomenon centered on feedback loops could become one definition of life.
Let’s delve deeper.
Amplifying Feedback Loops
First, I will explain the amplifying feedback loop as one form of feedback loops in chemical evolution.
Let’s assume that to produce substance A, raw material B, catalyst C, reaction conditions D, and energy E are required.
Methods to increase the production of A include increasing B and C, making D more appropriate, and increasing the acquisition of E.
If A is a substance that increases the production of B or C, there is a feedback loop structure of increasing production between substances. This leads to amplification of production.
In particular, if A acts as a catalyst for the production of B, or if A increases the production of catalyst C, the amplification effect grows exponentially.
Not only the amplification between substances, but if A optimizes D or increases the acquisition of E from the environment, amplification effects can also be obtained. This can be called amplification due to the interaction between substances and the environment.
However, typically, there are certain constraints or limits, and amplification will plateau at a certain point.
Stabilizer Feedback Loops
Next, I will describe the stabilizer feedback loop as another form of feedback loop.
In more advanced feedback loops, instead of simply amplifying, it forms stabilizers. This is a feedback loop where, when the amount of A in the environment decreases, it triggers a mechanism to increase the production of A.
If the amount of A increases and production of B or C is inhibited, or if D moves away from its optimum state, or the acquisition of E decreases, it will act as a stabilizer.
Chemical Evolution: Stacking of Water Cycle and Feedback Loops
The first life on Earth is believed to have appeared due to chemical evolution, where non-living chemicals were gradually and complexly synthesized.
Cells have intricate structures, so a myriad of stages in the chemical evolution process would have been necessary.
It is unlikely that this chemical evolution proceeded all at once by gathering materials in one place. It is more natural to think that chemical evolution progressed step by step over a vast span of time.
Considering this, a model where materials locally gather and chemical evolution progresses cannot explain the phenomenon.
There must have been ponds or lakes on Earth where chemicals condensed. Chemicals can move between these places via the water cycle. This includes not only the flow of terrestrial rivers but also the movement in the sky due to the evaporation of water vapor, the movement of clouds, and rainfall.
In this loop structure of the water cycle, it is possible to form feedback loops with amplifying or stabilizing effects. Once such feedback loops are formed, they have the power to continue existing self-preservingly, like life.
I believe that these feedback loops form one by one, stacking upon one another until countless feedback loops are formed on Earth. This is my model of chemical evolution.
Transition from Macro to Micro
In this manner, as countless feedback loops formed across vast domains, it’s believed that chemical substances also became more complex.
Initially, to produce a large number of substances or combinations thereof, ponds and lakes in extensive regions collaborated, leading to the formation of robust feedback loops with high sustainability.
However, this geographical distribution is not essential for feedback loops. If a group of chemical substances can form a feedback loop efficiently, then even in a narrower range with fewer ponds and lakes, a loop can still be established.
Moreover, as chemical evolution progresses, when groups of chemical substances with complex and advanced functions emerge, it’s likely that countless feedback loops can operate even within a single pond or lake.
And when groups of chemical substances, capable of forming numerous strong feedback loops, become enveloped in a membrane while retaining their functionality, it’s believed that the prototype of a cell was formed.
In this way, feedback loops that formed on a global scale have, over the process of chemical evolution, been geographically or spatially compacted, eventually becoming encapsulated in a microscopic membrane.
From macro to micro, it evolved.
Life as Seen from the Perspective of Feedback Loops
Currently, the ability to possess DNA and replicate oneself is cited as a criterion for living organisms.
Where DNA appeared in the chemical evolution process I’ve depicted is unclear. It might have been formed after becoming enveloped in a membrane, or perhaps DNA that wasn’t encapsulated existed within ponds or lakes.
On the other hand, in my depiction of chemical evolution, feedback loops are key, and their formation was a condition for the birth of life.
While my description of chemical evolution is purely hypothetical, based on this, life can be viewed as a composite of chemical feedback loops. Each amplifying or stabilizing feedback loop serves as a component of life, essentially representing the smallest unit of a living phenomenon.
Initially, macro loops utilizing the global circulation of water across land and sky played a significant role in forming the components of living phenomena. This probably miniaturized over time, eventually becoming encapsulated within cells.
In Conclusion
In this article, I explained my hypothesis regarding the origin of life, focusing on the conceptual model of feedback loops and how they underpin life.
Also, by moving away from a chemically centered viewpoint and focusing on feedback loops, I was able to depict the spatial aspect of chemical evolution, transitioning from macro to micro.
Considering that a cellular structure is packed with complex global macro feedback complexes, it’s easier to comprehend the complexity of the chemical structures constituting the cell and the chain of chemical reactions they trigger.
Moreover, this can explain why cells don’t form by simply shaking a flask in a laboratory. Assuming my hypothesis is accurate, instead of a flask, perhaps what’s needed is the Earth itself.
