Life is the greatest miracle that exists on our planet. The problems of studying it currently occupy not only biologists, but also physicists, mathematicians, philosophers, and other scientists. Of course, the most difficult puzzle is the very origin of life on Earth.
So far, researchers have been arguing about how this happened. Strange as it may seem, a considerable contribution to the study of this phenomenon was made by philosophy: this science allows one to draw the right conclusions, summarizing huge amounts of information. What versions of scientists today are guided around the world? Here are the current theories of the origin of life on Earth:
- The concept of spontaneous generation.
- Creationism, or the theory of divine creation.
- The principle of stationary state.
- Panspermia, supporters of which argue about the natural "productivity" of any planet, where there are suitable conditions. In particular, this idea was developed in due time by the notorious academician Vernadsky.
- Biochemical evolution according to A. I. Oparin.
Let us consider all these theories of the origin of life on Earth in somewhat more detail.
Materialism and idealism
Even in the Middle Ages and earlier, in the Arab world, some scientists, even at the risk of their own lives, suggested that the world could have been created as a result of some natural processes, without the participation of the divine essence. These were the first materialists. Accordingly, all other points of view, which provided for Divine intervention in the creation of all things, were idealistic. Accordingly, it is quite possible to consider the origin of life on Earth from these two positions.
Creationists claim that life could only be created by God, while materialists promote the theory of the emergence of the first organic compounds and life from inorganic substances. Their version is based on the difficulty or impossibility of understanding those processes that resulted in life in its modern form. It is interesting, but the modern Church supports this hypothesis only partially. From the point of view of those most friendly to scientists, the main Thought of the Creator is really impossible to understand, but we can determine the phenomena and processes by which life arose. However, it is still very far from a truly scientific approach.
Currently prevailing point of view of the materialists. However, they did not always put forward modern theories of the origin of life. Thus, the hypothesis that the birth and evolution of life on Earth occurred spontaneously was initially popular, and supporters of this phenomenon were encountered at the beginning of the 19th century.
Proponents of this concept argued that there are some laws of natural nature, which determine the possibility of the arbitrary transition of inorganic compounds into organic with the subsequent arbitrary formation of life. This also includes the theory of creating a “homunculus,” an artificial person. In general, the spontaneous generation of life on Earth is still considered by some "specialists" seriously ... At least, it is good that they say about bacteria and viruses.
Of course, the erroneousness of such an approach was later proved, but it played an important role, giving a huge amount of valuable empirical material. Note that the final rejection of the version of the independent birth of life occurred only in the middle of the XIX century. In principle, the impossibility of such a process was proved by Louis Pasteur. For this, the scientist even received a considerable prize from the French Academy of Sciences. Soon, the main theories of the origin of life on Earth, which we describe below, come to the fore.
Theory of Academician Oparin
Modern ideas about the origin of life on Earth are based on a theory that was put forward by a domestic researcher, Academician Oparin, back in 1924. He refuted the principle of Redi, who spoke about the possibility of only biogenic synthesis of organic substances, stating that this concept is valid only for the modern state of affairs. The scientist pointed out that at the very beginning of its existence, our planet was a giant rocky ball, on which, in principle, there was no organic matter.
Oparin's hypothesis was that the origin of life on planet Earth is a long biochemical process, the raw materials for which are the usual compounds that can occur on any planet. The academician suggested that the transition of these substances to more complex ones turned out to be possible under the influence of extremely strong physical and chemical factors. Oparin first hypothesized the continuous transformation and interaction of organic and inorganic compounds. He called it "biochemical evolution." Below are the main stages of the birth of life on Earth according to Oparin.
Stage of chemical evolution
About four billion years ago, when our planet was a huge and lifeless stone in the depths of space, on its surface was already a process of non-biological synthesis of carbon compounds. During this period, volcanoes ejected titanic amounts of lava and hot gases. Cooling down in the primary atmosphere, the gases turned into clouds, from which torrential rains were incessant. All these processes took place over millions of years. But let me, when did the birth of life on Earth begin?
At the same time, the showers gave rise to huge primary oceans, whose waters were extremely saturated with salts. The first organic compounds, the formation of which took place in the atmosphere under the action of the strongest electric discharges and UV irradiation, fell there. Gradually their concentration increased until the seas turned into a sort of “broth” saturated with peptides. But what happened next and how did the first cells arise from this “soup”?
The formation of protein compounds, fats and carbohydrates
And only at the second stage in the "broth" there are true proteins and other compounds, of which life is built. Conditions on the Earth softened, carbohydrates, proteins and fats appeared, the first biopolymers, nucleotides. This was the formation of coacervate drops, which were the prototype of real cells. Roughly speaking, drops of protein, fats, carbohydrates (as in soup) were so called. These formations could absorb, absorb those substances that were dissolved in the waters of the primary oceans. At the same time, there was a peculiar evolution, the result of which was drops with enhanced stability and stability to the effects of the external environment.
Appearance of the first cells
Actually, at the third stage, this amorphous formation turned into something more “meaningful”. That is, in a living cell capable of the process of self-reproduction. The natural selection of drops, about which we have already spoken above, became more and more rigid. The first “advanced” coacervates already had a primitive, but metabolism. Scientists suggest that the drop, reaching a certain size, broke up into smaller formations that possessed all the features of the maternal "cell".
Gradually, a layer of lipids arose around the core of the coacervate, giving rise to a full-fledged cell membrane. This is how the primary cells, archaeta, were formed. It is this moment with the full right to be seen as the birth of life on Earth.
Is non-biological synthesis of organic matter real?
As for the hypothesis of the origin of life on Earth from Oparin ... For many, the question immediately arises: “How realistic is the formation of organic matter from inorganics under natural conditions at all?” Many researchers visited such thoughts!
In 1953, American scientist Miller modeled the primary atmosphere of the Earth, with its incredible temperatures and electrical discharges. Simple inorganic compounds were placed on this medium. As a result, acetic and formic acids, other organic compounds were formed there. This is how the birth of life on Earth took place. Briefly, this process can characterize the philosophical law “The Transition of Quantity to Quality”. Simply put, with the accumulation of a certain amount of proteins and other substances in the primary ocean, these compounds acquire other properties and the ability to self-organize.
The strengths and weaknesses of the Oparin theory
The concept we have considered has not only strong but also weak points. The strength of the theory is its logic and experimental confirmation of the abiotic synthesis of organic compounds. In principle, this could be the birth and development of life on Earth. The great weakness is the fact that so far no one can explain how the koatservats were able to transform into a complex biological structure. Even supporters of the theory recognize that the transition from a protein-fat drop to a full-fledged cell is very doubtful. Probably, we are missing something, not taking into account unknown factors. Currently, all scientists recognize that there has been a sharp leap, as a result of which self-organization of a substance has become possible. How could such a thing happen? It is still unclear ... What else are the basic theories of the origin of life on Earth?
Theory of Panspermia and Stationary State
As we have said, at one time this version was strongly supported and “promoted” by the famous academician Vernadsky. In general, the theory of panspermia cannot be discussed in isolation from the concept of a stationary state, since they consider the principle of the origin of life from the same point of view. You should know that for the first time this concept was proposed by the German Richter at the end of the 19th century. In 1907 he was supported by the Swedish explorer Arrhenius.
Scientists who adhere to this concept believe that life in the Universe simply existed and will always exist. It is transferred from planet to planet with the help of comets and meteorites, which play the role of original "seeds". The disadvantage of such a theory is that the Universe itself is believed to have been formed about 15-25 billion years ago. It doesn't look like “Eternity” at all. Considering the fact that the life of planets potentially suitable for education is many times smaller than ordinary stony planetoids, the question can be considered quite natural: “When and where did life form and how did it spread through the Universe with such speed, given unrealistic distances?”
It should be remembered that the age of our planet is no more than 5 billion years. Comets and asteroids fly much slower than the speed of light, so they simply would not have enough time to bring the "seeds" of life to Earth. Proponents of panspermia suggest that certain seeds (spores of microorganisms, for example) are transferred “on light rays” at a corresponding speed ... Only decades of spacecraft operation have shown that there are quite a few free particles in space. The probability of such a method of distribution of living organisms is too small.
Some researchers today suggest that on any planet that is suitable for life, protein bodies may eventually form, but the mechanism of this process is unknown to us. Other scientists say that there may be some “cradles” in the Universe, planets on which life can form. It sounds, of course, like some kind of science fiction ... However, who knows? In recent years, a theory has gradually begun to take shape in our country and abroad, the provisions of which speak of information originally encoded in atoms of substances ...
Allegedly, these data and give the same impetus, which leads to the transformation of the simplest koatservatov in archecell. Logically, this is the same theory of the spontaneous generation of life on Earth! In general, the concept of panspermia is difficult to consider as a completed scientific thesis. Its supporters can only say that life on Earth was brought from other planets. But how was it formed there? There is no answer to this.
"Gift" from Mars?
Today it is known for certain that there really was water on the Red Planet and there were all conditions conducive to the development of protein life. The data that confirms this was obtained by working on the surface of two descent vehicles at once: Spirit and Curiosity. But until now, scientists ardently argue: was there life there? The fact is that the information obtained from the same rovers speaks about the short-term (in geological aspect) existence of water on this planet. How high is the probability that, in principle, complete protein organisms have developed? Again, there is no answer to this question. Again, even if life came to our planet from Mars, this in no way explains the process of its development there (which we have already written about).
So, we have considered the basic concepts of the origin of life on Earth. Which of them is absolutely true, is unknown. The problem also lies in the fact that so far there is not a single experimentally confirmed test that could confirm or refute at least the concept of Oparin, not to mention other theses. Yes, we can synthesize protein without any problems, but we cannot get protein life. So the work of scientists is still in store for many decades to come.
There is another problem. The fact is that we are intensely looking for a life based on carbon, and are trying to understand exactly how it originated. And what if the concept of life is much broader? What if it can be based on silicon? In principle, such a point of view does not contradict the provisions of chemistry and biology. So, in the search for answers, we are met with new and new questions. Currently, scientists have put forward several fundamental theses, guided by which people are looking for potentially habitable planets. Here they are:
- The planet should turn in the so-called “comfort zone” around the star: on its surface there should be neither too hot nor too cold. In principle, at least one or two planets in each star system meet this requirement (Earth and Mars, in particular).
- The mass of such a body should be medium (within one and a half sizes of the Earth). Too big planets either have unrealistically high gravity, or are gas giants.
- A more or less highly organized life can exist only near fairly old stars (at least three or four billion years).
- A star should not seriously change its parameters. It is useless to search for life around white dwarfs or red giants: if it was there, it has already died a long time due to extremely unfavorable environmental conditions.
- It is desirable that the star system was single. In principle, modern researchers object to this thesis. It is possible that a binary system with two stars located at opposite ends may contain even more potentially habitable planets. Moreover, today they are increasingly saying that somewhere on the outskirts of the solar system there is a gas-dust cloud, the forerunner of the second-born unborn.
So what can be said in conclusion? First, we urgently lack data on the exact environmental conditions on the newly emerged Earth. To get this information, ideally, you should observe the development of the planet, which is similar to ours on other indicators. In addition, researchers still find it difficult to say exactly which factors stimulate the transition of archaequil coacervates into full-fledged cells. Perhaps further in-depth studies of the genome of living beings will give some answers.