The Greatest Show from Darwin. 12. origin of eye

To the beginning: http://proza.ru/2022/06/26/1108

12. The origin of the eye.

Let's return to the question of the origin of the eye. Let's look into the encyclopedia, from where we learn that the eye is just a part of the visual system, which includes the following anatomical formations:
- peripheral paired organ of vision — the eye itself (with its light—perceiving photoreceptors - rods and cones of the retina);

- nervous structures and formations of the central nervous system: optic nerves, chiasm, optic tract, visual pathways — a pair of cranial nerves, oculomotor nerves, block nerves and diverting nerves;

- lateral cranial body of the intermediate brain (with subcortical visual centers), anterior tubercles of the quadriplegia of the midbrain (primary visual centers);

- subcortical (and stem) and cortical visual centers: the lateral cranial body and the cushions of the visual hillock, the upper mounds of the roof of the midbrain (quadrilateral) and the visual cortex.

Vision, as we can see, is a very complex system in which the eye itself plays an important, but far from universal role. All the components of the system are equally important for vision and the defeat (absence) of any of them equally deprives a living being of a chance to see the light.

It's hard not to agree with Charles Darwin. How can it not seem absurd synchronous mutation of such different organs? What is the probability of such a coincidence when the subcortical visual centers, the lateral cranial body of the intermediate brain (with subcortical visual centers), the anterior tubercles of the quadrilateral of the midbrain (primary visual centers), all these paired nerve structures and formations of the central nervous system, and, finally, the eye itself with all its rods, cones and a bunch of other devices?

Someone will say: synchronously is not necessary at all, a sequence of random mutations of each individual anatomical formation will suit perfectly. First, let the cones of the right eye evolve, then some chiasm, then the visual pathways of the left eye, then something in the brain clicks, etc., etc. until the turn comes to the cones of the eye from which we started.

OK, but what about the theory? You can't turn a blind eye to the theory of evolution for the sake of the visual system? After all, like it or not, any of the components of the system is energy-consuming. Any improvement of the eye, nervous structures or brain requires an increase in the flow of blood and nutrients, not to mention the appearance of some lateral knee bodies, pillows of the visual hillock or something else in the same spirit.

The benefits of all these successive mutations will arise only after the completion of the entire cycle of transformations, and natural selection should consistently - from generation to generation - turn a blind eye to useless structures that require significant energy costs?

I do not dare to say that this is impossible, but only agree with Charles Darwin and confirm that, specifically, my frail brain is unable to overcome the contradiction between such a course of events and his theories.

Here is one of the most famous quotes from the first edition of The Origin of Species: "We can say that natural selection daily and hourly investigates the smallest variations around the world, discarding the bad ones, preserving and composing the good ones..."

In the context of "good" are useful, and "bad" are useless, not giving advantages in survival. Anyway, all successive mutations of the visual system are useless until the full cycle of transformations is completed.
It is easy to see this with a simple example from modern life. What is the use of a high-resolution screen or 4K video if your computer device has some kind of antediluvian processor of the early nineties of the last century, RAM, measured not even in megabytes, but in kilobytes and first-generation networks may need a couple of years to transmit a picture of such high resolution.

Even if someone suddenly invented high-resolution screens or 4K video at the end of the twentieth century, no company would launch such screens or promote such a video format, since no device existing at that time could reproduce it.
The opposite is contrary to the laws of the market. A business cannot benefit from an innovation ahead of time until the entire infrastructure is tightened up. Consequently, such inventions will not be in demand for the time being.
I believe that in a nature governed by natural selection and in a business governed by the market, the principles of utility and uselessness will not differ much from each other. And if so, then all successive mutations of the visual system when passing through the control of natural selection should be recognized as bad and discarded.

Let's not dwell on this for too long, but rather look at the beginning of the evolutionary chain at the moment when vision was born. The encyclopedia says the following about the evolution of the eye:

"In general, several thousand genes are involved in the development of the eye, but a single "trigger gene" ("master gene") launches the entire gene network."
Indeed, in the beginning there had to be some random mutation that marked the beginning of the great path to enlightenment. One gene appeared, then, as a result of a series of mutations, hundreds and hundreds more others.

The English-language Wikipedia reports that: "the first eye fossils found to date date back to the Ediacaran period (about 555 million years ago). In the lower Cambrian there was an explosion, apparently of rapid evolution, called the "Cambrian explosion"... Before the Cambrian explosion, animals may have sensed light, but did not use it for rapid movement or navigation by sight."
The earliest precursor of the eye are photoreceptor proteins, single-celled organisms that perceive light, and are called "eye spots". "Eye spots can only sense ambient brightness: they can distinguish light from darkness, sufficient for photoperiodism and circadian rhythms daily synchronization. They are not sufficient for vision, as they cannot distinguish shapes or determine the direction from which the light comes."

Euglena is given as an example of such a unicellular organism. "The eyesight of euglena, called the stigma, is located at its anterior end. This is a small spot of red pigment that shades the collection of photosensitive crystals. Together with the leading flagellum, the eyespot allows the body to move in response to light, often towards light, to aid in photosynthesis, and to predict day and night- the main function of circadian rhythms."

Here is a perfect example! Why didn't we turn to Darwin right away? One mutation, an undeniable advantage. Natural selection triumphs! Everything is self-evident and there is nothing to worry about.

I'm afraid you won't forgive me if I don't consider this bright moment of evolution at least for form's sake. Not completely relying on my own analysis tool, I will try to look at the world with Euglena's "eye spot". It shouldn't be too difficult, since we are distant relatives. Although we are separated by millions of mutations, we still have something in common. It is possible that the similarity in mental abilities.

How can I imagine myself in Euglena's place? After all, vision is such a familiar thing for us, bestowed from birth. It is even difficult for most people to imagine how to live without the ability to see.

I'll try to imagine that as a result of a random mutation, I have a new sensory ability. Let it be, for example, echolocation, like in bats.
We are not bats, and the feeling that has arisen is not a picture on the sonar monitor. This is not a visual sensation at all, it is a completely unusual sensation that manifests itself incomprehensibly and therefore frighteningly. It may be a burning sensation in the intestines, tingling on the tongue or something painful in the ears trying to perceive certain sound signals beyond the limits of human perception. Why painful and unpleasant? Because the nervous system is not able to recognize the new sensory ability and will most likely signal this with pain signals.

What are the options for the development of events? If I don't panic and run to the doctors, who almost certainly diagnose an acute mental disorder burdened with hallucinations, then sooner or later the psyche must adapt to new sensations. And if I am patient and inquisitive enough, then after a few years I will most likely be able to compare unusual sensations with the environment and then I will get a new ability that will give me an invaluable advantage over other people.

If you discard all these "ifs", then everything looks pretty simple. What can prevent Euglena from doing the same? There may be a lack of a highly developed analytical mechanism, usually called the brain. I don't mean myself here. My brain would most likely have panicked, and echolocation would have led me eventually straight to one of the psychiatric hospitals.
The English Wikipedia reports that: "the functional unit of the eye is a photoreceptor cell that contains opsin proteins and reacts to light by initiating a nerve impulse."

That is, along with the ability to distinguish light, Euglena must learn to respond correctly to nerve impulses. "Actual excretion may be more complicated, as some microvilli contain traces of cilia, but other observations seem to confirm the fundamental difference between protostomes and deuterostomes. These considerations focus on the reaction of cells to light – some use sodium to trigger an electrical signal that will form a nerve impulse, while others use potassium; further, protostomes as a whole create a signal, allowing more sodium to pass through their cell walls, whereas deuterostomes pass less."

Oh, there are also electrical signals generated by someone with sodium, someone with potassium. I'm afraid it may take hundreds of pages to analyze the entire difficult path of mutations that have formed nerve impulses and, most importantly, an adequate response to them. After all, without mutations that help to respond correctly to a nerve impulse, the advantage becomes a serious disadvantage. Isn't that right?

How to react to a new signal? A reasonable person will need life experience or, at worst, a clear instruction, a computer will need a program code, and euglena will need a record in DNA that will appear after a series of random mutations. But what is the probability of Euglena to live up to that bright moment when she will be able to respond to light with benefit if the gloomy world is full of false signals and harmful mutations?

The same encyclopedia reports that it was possible to calculate the time of the complete evolution of the eye. "How quickly a round spot of photoreceptor cells can evolve into a fully functional vertebrate eye has been estimated based on the mutation rate, relative advantage to the body and natural selection.
 However, the time required for each condition was constantly overestimated, and the generation time was set to one year, which is often found in small animals. Even with such pessimistic estimates, the vertebrate eye would still have evolved from a spot of photoreceptor cells in less than 364,000 years."

I would like to see these calculations. No, not because I doubt their accuracy, but to admire. Despite the fact that I am remotely familiar with the periodic table of Mendeleev, it would probably take me the lion's share of this time just to select sodium or potassium from all the known elements, then select their correct proportion in order to eventually synthesize an electrical signal.

Professor Dawkins states that: "Huge leaps in one generation ... are almost as incredible as the divine creation of the world, and are excluded from consideration for the same reason: it's statistically too unlikely..."

If we accept the logic of Dawkins, then we face a difficult alternative. Either exclude this case from consideration due to statistical low probability, or recognize the divine creation of the world. I ask you to pay attention that this is not my suggestion, but a logical conclusion to which the esteemed professor pushes us. After all, here we see not just a big leap in one generation, but a truly grandiose one.

In my opinion, Euglena deserves the Nobel Prize. Judge for yourself, in 2019, the American physicist John Goodenough, the British chemist Stanley Whittingham and the Japanese chemist Akira Esino won the Nobel Prize in Chemistry for the improvement of lithium-ion batteries. It took the bright minds of mankind more than twenty years to improve the components of the device that is changing the world before our eyes.

This is the greatest invention of our time, and it was made by three people, despite the fact that many millions of people on our planet are familiar with both physics and chemistry. And a single-celled organism in complete darkness and without hope of ever appearing at the award ceremony in Stockholm, managed to make an incredibly complex transformation at the intersection of physics, chemistry, biology and genetics in one single-celled generation: to create a visual system.

This is a fact of evolution theory of Darwin that cannot be disputed and deserves universal admiration.

next: http://proza.ru/2022/07/10/514