When searching for information about the evolution of logic [1], I found curious that all accounts were limited to human thought, philosophy, and the rational management of premises, inference [2], validity, truth, and conclusions.
I agree that logic is a mental process, but limiting its study to the Bronze Age or classical antiquity [3], and human thought, is quite narrow in my opinion.
Therefore, given this limitation, and in the interest of expanding the subject matter’s area, in this article I will propose a hypothesis of what I see are the types of logic in nature, how it may have evolved in motile single-celled organisms – later multicellular animals- and what is its biological function.
Types of Logic
Although logic is a mental process, it is, in fact, an observation of nature.
Physical Logic
Whether humans or other organisms are present to observe it or not, logic is implicit in physics. For example, if there are two objects in space nearby, then they will attract each other. If infrared light hits an object, then it will heat up. And, if a photon energizes an electron in an atom, then it will change its orbital, and vice versa.
This if/then pattern in nature is what I call the basic unit of logic: “if p, then q”.
Chemical Logic
As chemistry is basically an observation of more complex physics, chemical processes also have implicit logic.
For example, if atoms of a solute are put in a solvent, then they will diffuse. If the same is done, but with a membrane in the middle, then the density of both the solute and the solvent will eventually be the same on both sides of the membrane. And, if water is added to an acid, then its pH will tend to neutral.
Mental Logic
As I wrote above, whether physical or chemical logic are observed by any mind is irrelevant, they occur in nature anyway. But, when they are observed, then the basic components of mental logic start to emerge.
As mentioned, “if p, then q” is the basic unit of logic as observed in nature, but that may be combined with more structures to form more complex mental operations, such as:
• If all p, are q
• And r is p
• Then r is q
The above kind of reasoning could be attributed to the evolution of the brain, and seems to be the main focus of “logic” as a human systematic discipline.
Evolution of Cell Computation
But, if the mechanics of nature are the basis for mental reasoning, how did logic originate from those processes?
By observing cell behavior and physiology, I think logic in living organisms was present very early in the evolution of life.
In the diagram below I present a model for the possible evolution of independent cell computation in the form of the basic “if p, then q” format. This may have been the first step for what we call thought, reason, and logic today.
The First Cell Computation
The model, represented in the diagram below, is a step by step trajectory of how the first if/then computation may have appeared in motile single-celled organisms. It is divided in five eras, which begin with a non-motile ancestor in the filter era, and ends with the evolution of an independent computing organelle, or cellular region, in the computational era.
1. Filter Era
In the filter era, single-celled organisms were very basic and only stayed stationary while the solution around them provided nutrients and resources by means of the electrochemical gradient [4], osmosis, diffusion, and charge.
In this era, it is likely that the environment was abundant in food, and safe in the sense that the density of food particles must have been prominent as compared to pathogens or toxic substances.
In the diagram, the cell is shown stationary, food input requires no effort, is metabolized, and a residue is generated.
2. Animated Era
However, in such a benevolent environment, at some point, population growth must have created some competitive pressure. In this animated era, it is likely that some cells evolved a mechanical system for motility to be able to compete for relatively scarcer resources.
In the diagram, the cell is seen moving constantly, which enabled it to reach more nutrients in this competitive scenario.
3. Sensory Era
The problem of motility is that it created a new cost: Additional energy was needed to set the cell in motion. This created the need to develop sensors that would direct the cell to move only if there were resources detected in the vicinity. Otherwise, energy would have been constantly wasted.
In this sensory era, the energy saving mechanism worked where the presence of food substances nearby naturally created a signal, either physical or chemical. This signal was detected by the sensor, and then the sensor stimulated the cell to move in that direction.
In the diagram, the cell is seen with a new green sensory device on the top right, where it receives the signal, and then moves and ingests the food.
In a way it could be said that a basic form of “if p, then q” had developed here, but it still could be regarded as a direct physical and chemical kind of logic, rather than some sort of proto-mental computation.
4. Blocking Era
Because, at some point, the ratio between pathogens, toxic substances, and food would change toward a higher density of dangerous materials, a new blocking system must have been needed to stop the indiscriminate ingestion of particles from the environment.
As the modern brain has different pathways and mechanisms for different functions; e.g. motor and sensory nerves, and the vision, hearing, smelling, taste, and touch senses are all different nerve channels; a new, separate blocking sensory system must have evolved at this time.
In this blocking era, the new sensor served as a way to prevent the single-celled organism from ingesting any kind of substance. The function of blocking, or regulation, is also observed in modern developed nervous systems, with components as the prefrontal cortex [5] regulating impulses from elsewhere in the brain. However, the system in this era must have been mechanical and very basic.
In the diagram, the cell is shown with a new red sensory device on the bottom right. It receives the signal to move, it moves to the location of the detected substance, but the red blocker detects potential toxic material so it sends a direct block signal to the digestive system. This means the particle is not eaten.
As in the previous era, this new device was an important addition to the process of logic, but was still physical or chemical, as it was only a direct, binary yes/no or true/false, blocking mechanism. No real computation or indirect “judgement” was present.
5. Computational Era
In a world of more scarcity, danger, and complexity, a more sophisticated mechanism was needed.
As single-celled organisms were competing for resources, moving around searching for food, the ones who could judge with more granularity, as opposed to a simple yes or no, which particles and substances were suitable for digestion, could extract more economic benefit from the same environment.
In this computational era, to be able to do this, the motile cell developed another separate organelle that could compute whether a particular substance was good or bad, and, more importantly, in what degree, for the organism.
This organelle had the basic function of receiving a signal from the blocking sensor, and, if the signal indicated a certain characteristic of the detected substance, e.g. acidity, alkalinity, charge, temperature, hardness, solubility, etc., below or above a certain threshold, then the computing organelle would send a yes or no signal to the digestive system to instruct it to ingest the substance or reject it.
In the diagram, the cell may be seen receiving the first signal; moving toward the target; sensing one of the particles in the substance; sending a signal to the computing organelle as to its physical or chemical characteristics; the computing organelle receiving and assaying the signal and checking (computing) whether it reaches a certain quantitive threshold (this process is represented by the % symbol) or not; and then sending a positive signal, in the form of an action potential [6], to the digestive system, which then proceeds to ingest the substance.
The computation made by a separate unit or section in the cell in this era may be regarded as the origin of true logic in living organisms, as it was the most basic “if p, then q” function performed by what now can be defined as an indirect mental process: A threshold computation, or judgement, in a separate computing organelle, as opposed to a direct physical or chemical reaction.
This kind of process is observed in animal neurons today. They have a region of the cell called the axon hillock [7] that receives signals from dendrites, makes a mathematical computation, and then sends an action potential to the rest of the axon if a threshold is reached.
Function of Logic
It is very likely that the very basic process shown in the model above eventually evolved [8] into the full nervous systems as we see them today in multicellular animal organisms.
These systems include a brain, made up of these kinds of cells, as the separate computing organ, diverse types of sensors distributed around the organism, incoming signaling systems, and outgoing action potential and motor, voluntary and involuntary, mechanisms.
After the evolution of computation as described in this article, the future was likely the development of memory and emotions. These enabled much more complex and sophisticated forms of computation and thought as observed in social animals today.
Indeed, math, logic, and language are social animal mental disciplines to effectively map and manage reality. The goal of living organisms is replication, and the process is a series of engineering problems and solutions. For example, the need to eat, walk, run, swim, see, fly, bite, or think are all engineering problems which are associated with their corresponding evolutionary solutions.
Many of these problems were solved by evolutionary traits in the body of organisms, e.g. wings or brains, but others had to be thought out and built artificially, e.g. the airplane or even philosophy, in the case of humans.
In other words, logic, and the other mental tools, helped animals solve those engineering problems. Nothing more.
Summary
Logic, as I have found in encyclopedias, university knowledge bases, and expert articles, currently has a limited explanation. There is a distinction between natural and mental logic, but the latter has a long history of evolution from the former here on earth.
Animals have evolved mental logic, and today is present, one way or another, in the large majority of species in Kingdom Animalia. However counterintuitive, social animals also have logic, math, and language.
The origin of logic can be traced to the origin of motile cells, which later formed part of multicellular animal organisms. In fact, the evolution of motility itself may be a primitive form of logical response in the form “if food is scarce, then move to get it”, but that sort of logic may be better categorized as a direct physical or chemical kind of reaction.
The first independent computing organelles may have eventually evolved into the brains of multicellular animals with more complex indirect mental computations. One of those animals divided its computational thought into subjects, and called one of those subjects “logic”.
References
[1] Logic – by Britannica: https://www.britannica.com/topic/logic
[2] Inference – by Wikipedia: https://en.wikipedia.org/wiki/Inference
[3] Ancient Logic – by Stanford Encyclopedia of Philosophy: https://plato.stanford.edu/entries/logic-ancient/
[4] Electrochemical Gradient – by Wikipedia: https://en.wikipedia.org/wiki/Electrochemical_gradient
[5] Prefrontal cortex – by Wikipedia: https://en.wikipedia.org/wiki/Prefrontal_cortex
[6] Action potential – by Wikipedia: https://en.wikipedia.org/wiki/Action_potential
[7] Axon hillock – by Wikipedia: https://en.wikipedia.org/wiki/Axon_hillock
[8] Early evolution of neurons – by William Kristan – Distinguished Professor Emeritus Section of Neurobiology – UC San Diego: https://www.sciencedirect.com/science/article/pii/S0960982216304894
Code Is Law
