The origin of life is a vast scientific problem. Over the past 10 years, there has been a huge amount of new data and research. To date, there are still unresolved questions, but the overall picture of how life could have arisen from inanimate matter is very quickly clearing up. But, as you know, in science, each answer gives rise to 10 new questions.

Models of gradual evolution from inorganic compounds to the first organisms are well developed today. But the history of this issue dates back to the famous author .

The English naturalist and researcher did not write anything about this in his scientific works and did not seriously deal with theories and hypotheses of the origin of life. This topic was beyond the understanding of 19th century science. Charles was only talking about how all the variety of biological forms that we see came out of the first living organisms already existing.

Only from his letters to his best friend do we know that Darwin tried to think about this topic, but of course, at that level of knowledge, he could not specifically assume anything, except for the most general ideas that somehow they could from inorganic chemistry, ammonium salts, phosphorus with the use of electricity in a small warm pond, organic matter is born.

But it should be noted that even in this letter he guessed a lot very accurately. For example, chemists have discovered a plausible way for the abiogenic synthesis of nucleotides, the building blocks of which RNA is made. It turned out that these nucleotides can be spontaneously synthesized under conditions similar to those of a small warm reservoir.

There are a huge number of versions of the origin of all life on Earth. Many of them are invented by conspiracy theorists and pseudoscientists. But still, the bulk of the theories are based on real facts and research.

The main theories of the origin of life:

- creationism;

- panspermia;

— steady state theory;

- spontaneous generation;

- biochemical evolution.

Creationist hypothesis adhere to people who believe that life was created by the creator, God, the universal mind. It has no evidence, and it is not scientists who are promoting it, but journalists, theologians and theologians. They are also joined by people who want to earn extra money through deception.

These same creationists continue to argue that there is a mystery in the question of the origin of people, since archaeologists cannot find some missing link, that is, a transitional form from ancient Cro-Magnon man to modern Homo sapiens. Extremely important articles to understand:

» 100% Human origin: theories and hypotheses

Steady State Theory lies in the fact that the living, together with the universe, and, accordingly, the whole world, has existed and will always exist, regardless of time. Along with this, the derivatives of the universe, bodies and formations like stars, planetary systems, living organisms are limited in time: they are born and die.

At the moment, this hypothesis has only historical significance, and has not been discussed in scientific circles for a long time, as it has been refuted by modern science at a key point: the universe arose due to the big bang and its subsequent expansion. An important article on this topic in simple and understandable language: 100% Origin and evolution of the universe.

Panspermia theory more scientific. It assumes the following: living organisms brought cosmic bodies to our planet like meteorites or comets. Some especially dreamy supporters are sure that UFOs and aliens did it consciously, pursuing their goals.

In our solar system, the probability of finding living organisms anywhere else is extremely small, but life could fly to us from another star system. Astronomical data show that, according to the biochemical composition of meteorites, meteors and comets, organic compounds, such as amino acids, can often be found in them. It was they who could become seeds upon contact of the cosmic body with the Earth, just as dandelion seeds scatter hundreds of meters around.

The main counterbalance to the assertions of the panspermists is the logical question, where did life come from on other planets from which this same asteroid or comet flew. Thus, the panspermic hypothesis of the alien origin of living organisms can only supplement the main version - the biochemical one.

Theory of Abiogenesis through biochemical evolution studies and successfully proves the formation of organic structures from inorganic matter, and outside the body and without the use of special enzymes.

The synthesis of the simplest organic compounds from inorganic matter can take place in a wide variety of natural conditions: on the planet or in space (for example, in a protoplanetary disk - proplid). In 1953, the famous classic Miller-Urey experiment was carried out, proving that such organic matter as amino acids can appear in a mixture of different gases that would imitate the atmospheric composition of the planet.

In nature, over time, it was formed and acquired the ability to (by the way, today its synthesis by man is very difficult). But this is the main brick, and the answer to the question of the origin of life on Earth lies precisely in it.

Now it is absolutely known how the deoxyribonucleic acid molecule arose. At first biological beings were based on another similar molecule called RNA. For a long time there was another living world in which organisms had hereditary information in the form of a molecule of ribonucleic acid, which acted as proteins. This molecule is able to store hereditary information like DNA and perform active work like proteins.

In modern cells, these functions are separated - DNA stores hereditary information, proteins do the work, and RNA serves as a kind of intermediary between them. In the very first ancient organisms, there was only RNA, which coped with both tasks by itself.

An interesting pattern in the question of the origin of all living things is that over the past few years, dozens of new scientific articles have appeared that bring the mystery as close as possible, and no other theories and hypotheses of the origin of life except abiogenic are currently required.

Hypotheses of the origin of life on Earth

The problem of life and the living is the object of study of many natural disciplines, starting with biology and ending with philosophy, mathematics, which consider abstract models of the living phenomenon, as well as physics, which defines life from the standpoint of physical laws. Centuries of research and attempts to resolve these issues have given rise to various hypotheses of the origin of life.

In accordance with two worldview positions - materialistic and idealistic - even in ancient philosophy, opposite concepts of the origin of life developed: creationism and the materialistic theory of the origin of organic nature from inorganic. Proponents of creationism argue that life arose as a result of an act of divine creation, evidence of which is the presence in living organisms of a special force that controls all biological processes. Proponents of the origin of life from inanimate nature argue that organic nature arose due to the action of natural laws. Later, this concept was concretized in the idea of ​​spontaneous generation of life.

So, there are the following hypotheses of the origin of life.

1. creationism . According to the concept of creationism, life arose as a result of supernatural, i.e., violating the laws of physics, events in the past. The concept of creationism is followed by followers of almost all the most common religions. According to the traditional Judeo-Christian ideas about the creation of the world, set out in the Book of Genesis, the world and all the organisms inhabiting it were created by the almighty Creator in 6 days lasting 24 hours. However, at present, many Christians do not treat the Bible as a scientific book and believe that it contains the theological revelation about the creation of all living beings by God in a form understandable to all people of all times.

Logically, there can be no contradiction between the scientific and theological explanations of the creation of the world. these two realms of thought are mutually exclusive. Theology recognizes truth through divine revelation and faith and recognizes things for which there is no evidence in the scientific sense of the word. Science makes extensive use of observation and experiment, scientific truth always contains an element of hypothesis, while for the believer theological truth is absolute. The process of the divine creation of the world is conceived as having taken place once, therefore it is not available for observation. The concept of the divine creation of the world is outside the scope of scientific research, so science dealing with phenomena that can be observed can never prove or disprove this concept.

The anthropic principle, formulated in the 70s of our century, speaks in favor of the non-random nature of the process of the origin and development of life. Its essence lies in the fact that even slight deviations in the value of any of the fundamental constants leads to the impossibility of the appearance in the Universe of highly ordered structures and, consequently, of life. Thus, an increase in Planck's constant by 10% makes it impossible for a proton to combine with a neutron, i.e. makes nucleosynthesis impossible. A decrease in Planck's constant by 10% would lead to the formation of a stable isotope 2 He, which would result in the burning out of all hydrogen in the early stages of the expansion of the Universe. The non-random nature of the values ​​of the fundamental constants may indicate the presence of a “creative plan” from the very beginning of the formation of the Universe, which implies the presence of the Creator, the author of this plan.

2. Hypothesis of spontaneous origin of life . According to Aristotle, certain “particles” of matter contain some kind of “active principle”, which, under suitable conditions, can create a living organism.

The hypothesis of spontaneous origin of life was widespread in ancient China, Babylon and Egypt as an alternative to creationism. Following Empedocles, one of the first to express the idea of ​​organic evolution, Aristotle adhered to the concept of spontaneous origin of life, linking all organisms into a single "ladder of nature". According to Aristotle, certain “particles” of matter contain some kind of “active principle”, which, under suitable conditions, can create a living organism. This beginning, according to Aristotle, is present in a fertilized egg, in sunlight, mud and rotting meat. In 1688, the Italian physician Francesco Redi questioned the theory of spontaneous generation of life and conducted a series of experiments in which he showed that life can only arise from a previous life (the concept of biogenesis). Louis Pasteur (1860) finally refuted the theory of spontaneous origin of life and proved the validity of the theory of biogenesis. The experiments of L. Pasteur showed that microorganisms appear in organic solutions due to the fact that their embryos were previously introduced there. If a vessel with a nutrient medium is protected from entering microbes into it, then no spontaneous generation of life occurs.

The concept of spontaneous generation, though fallacious, has played a positive role; experiments designed to confirm it provided rich empirical material for the developing biological science. The final rejection of the idea of ​​spontaneous generation occurred only in the 19th century.

Confirmation of the theory of biogenesis gave rise to the problem of the first living organism from which all the others arose. In all theories (except the steady state theory) it is assumed that at some stage in the history of life there has been a transition from the inanimate to the living. How did it happen?

3. Steady State Hypothesis . According to this hypothesis, the Earth never came into being, but existed forever; The earth has always been capable of supporting life. Species have always existed, each species has only two possibilities: change in numbers or extinction.

4. Panspermia hypothesis claims that life could have arisen one or more times at different times and in different places in the universe. This hypothesis arose in the 60s of the XIX century and is associated with the name of the German scientist G. Richter. Later, the concept of panspermia was shared by such prominent scientists as S. Arrhenius, G. Helmholtz, V.I. Vernadsky. To substantiate this theory, UFO sightings, rock paintings of ancient, rocket-like and aliens, etc. are used. Soviet and American space research allows us to consider the probability of finding extraterrestrial life within the solar system as negligible, but they do not provide grounds for confirming or refuting the existence of life outside it. When studying the material of meteorites and comets, many “precursors of the living” (cyanogens, hydrocyanic acid, etc.) were found in them, which could play the role of “seeds” of life. Be that as it may, the theory of panspermia is not a theory of the origin of life as such; it simply transfers the problem of the origin of life to another place in the universe.

At the beginning of the XX century. The idea of ​​the cosmic origin of biological systems on Earth and the eternity of the existence of life in space was developed by the Russian scientist Academician V.I. Vernadsky.

5. The hypothesis of the eternal existence of life . It was put forward in the 19th century. It has been suggested that life exists in space and travels from one planet to another.

6. Hypothesis of biochemical evolution. The age of the Earth is estimated at 4.5–5 billion years. In the distant past, the temperature on the surface of our planet was 4000-8000 degrees Celsius. As it cooled, carbon and more refractory metals condensed to form the earth's crust; as a result of volcanic activity, continuous movements of the crust and compression caused by cooling, the formation of folds and ruptures occurred. The atmosphere of the Earth in ancient times was obviously reducing (in the most ancient rocks of the Earth there are metals in a reducing form, for example, ferrous iron, younger rocks contain metals in an oxidized form, for example, ferric iron). There was practically no oxygen in the atmosphere. The emergence of life is closely related to the emergence of the Earth's oceans, which happened about 3.8 billion years ago. Paleontological data indicate that the water temperature in them was not too low, but did not exceed 58 °C. Traces of the most ancient organisms have been found in the strata, whose age is estimated at 3.2-3.5 billion years.

The hypothesis of biochemical evolution was presented by Academician A.I. Oparin (1894-1980) in the book "The Origin of Life", published in 1924. He made the statement that the Redi principle, which introduces a monopoly on the biotic synthesis of organic substances, is valid only for the modern era of the existence of our planet. At the beginning of its existence, when the Earth was lifeless, abiotic synthesis of carbon compounds and their subsequent prebiological evolution took place on it.

The essence of Oparin's hypothesis is as follows: the origin of life on Earth is a long evolutionary process of the formation of living matter in the depths of inanimate matter. This happened through chemical evolution, as a result of which the simplest organic substances were formed from inorganic substances under the influence of potent physicochemical factors.

The emergence of life A.I. Oparin considered it as a single natural process, which consisted of the initial chemical evolution taking place under the conditions of the early Earth, which gradually moved to a qualitatively new level - biochemical evolution. Considering the problem of the emergence of life through biochemical evolution, Oparin distinguishes three stages of the transition from inanimate to living matter.

First stage - chemical evolution . When the Earth was still lifeless (about 4 billion years ago), abiotic synthesis of carbon compounds and their subsequent prebiological evolution took place on it. This period of the Earth's evolution was characterized by numerous volcanic eruptions with the release of a huge amount of red-hot lava. As the planet cooled, the water vapor in the atmosphere condensed and fell on the Earth in showers, forming huge expanses of water (the primary ocean). These processes continued for many millions of years. Various inorganic salts were dissolved in the waters of the primary ocean. In addition, various organic compounds, which are continuously formed in the atmosphere under the influence of ultraviolet radiation, high temperature, and active volcanic activity, also entered the ocean. The concentration of organic compounds was constantly increasing, and, in the end, the waters of the ocean became " broth» from protein-like substances - peptides.

Figure 26 - Scheme of the origin of life according to Oparin

Second phase - appearance of proteins . As the conditions on Earth softened, under the influence of electrical discharges, thermal energy and ultraviolet rays on the chemical mixtures of the primary ocean, the formation of complex organic compounds - biopolymers and nucleotides, which, gradually combining and becoming more complex, turned into protobionts (precellular ancestors of living organisms). The result of the evolution of complex organic substances was the appearance of coacervates, or coacervate drops. coacervates - complexes of colloidal particles, the solution of which is divided into two layers: a layer rich in colloidal particles and a liquid almost free of them. Coacervates had the ability to absorb various substances dissolved in the waters of the primary ocean. As a result, the internal structure of coacervates changed in the direction of increasing their stability in constantly changing conditions. The theory of biochemical evolution considers coacervates as prebiological systems, which are groups of molecules surrounded by a water shell. So, for example, coacervates are able to absorb substances from the environment, interact with each other, increase in size, etc. However, unlike living beings, coacervate drops are not capable of self-reproduction and self-regulation, so they cannot be classified as biological systems.

The third stage is the formation of the ability to self-reproduce, appearance of a living cell . During this period, natural selection began to act, i.e. in the mass of coacervate drops, the selection of coacervates, the most resistant to given environmental conditions, took place. The selection process has been going on for many millions of years. The surviving coacervate drops already possessed the ability for primary metabolism, the main property of life. At the same time, having reached a certain size, the parent drop broke up into child droplets that retained the features of the parent structure. Thus, we can talk about the acquisition by coacervates of the property of self-reproduction - one of the most important signs of life. In fact, at this stage, coacervates have become the simplest living organisms. Further evolution of these prebiological structures was possible only with the complication of metabolic processes inside the coacervate.

The internal environment of the coacervate needed protection from environmental influences. Therefore, around the coacervates, rich in organic compounds, layers of lipids arose, separating the coacervates from the surrounding aquatic environment. In the process of evolution, lipids were transformed into the outer membrane, which significantly increased the viability and resistance of organisms. The appearance of the membrane predetermined the direction of further biological evolution along the path of more and more perfect autoregulation, culminating in the formation of the primary cell - the archecell. A cell is an elementary biological unit, the structural and functional basis of all living things. Cells carry out an independent metabolism, are capable of division and self-regulation, i.e. have all the properties of living things. The formation of new cells from non-cellular material is impossible, cell reproduction occurs only due to division. Organic development is considered as a universal process of cell formation.

In the structure of the cell, there are: a membrane that delimits the contents of the cell from the external environment; cytoplasm, which is a saline solution with soluble and suspended enzymes and RNA molecules; a nucleus containing chromosomes, consisting of DNA molecules and proteins attached to them.

Therefore, the beginning of life should be considered the emergence of a stable self-reproducing organic system (cell) with a constant sequence of nucleotides. Only after the emergence of such systems can we speak of the beginning of biological evolution.

The transition from the inanimate to the living took place after the rudiments of two fundamental life systems arose and developed on the basis of the predecessors: the system of metabolism and the system of reproduction of the material foundations of the living cell.

The probability that a protein molecule consisting of 100 amino acids of 20 types will be randomly formed according to a certain pattern is 1/20 100 ≈ 1/10 130 . A living cell is a complex of interacting proteins, lipids and nucleotides that form the genetic code. The simplest cell contains more than 2000 enzymes. The probability of random formation of such complex structures is small.

The possibility of abiogenic synthesis of biopolymers was experimentally proven in the middle of the 20th century. In 1953, the American scientist S. Miller modeled the primary atmosphere of the Earth and synthesized acetic and formic acids, urea and amino acids by passing electric charges through a mixture of gases (water, carbon dioxide, hydrogen, nitrogen, methane). Thus, it was demonstrated how the synthesis of complex organic compounds is possible under the action of abiogenic factors.

Despite the theoretical and experimental validity, Oparin's concept has both strengths and weaknesses. The strength of the concept is a fairly accurate experimental substantiation of chemical evolution, according to which the origin of life is a natural result of the prebiological evolution of matter. A convincing argument in favor of this concept is also the possibility of experimental verification of its main provisions. The weak side of the concept is the impossibility of explaining the very moment of the jump from complex organic compounds to living organisms.

One of the versions of the transition from prebiological to biological evolution is offered by the German scientist M. Eigen. According to his hypothesis, the origin of life is explained by the interaction of nucleic acids and proteins. Nucleic acids are carriers of genetic information, and proteins serve as catalysts for chemical reactions. Nucleic acids reproduce themselves and transmit information to proteins. A closed chain appears - a hypercycle, in which the processes of chemical reactions are self-accelerated due to the presence of catalysts. In hypercycles, the reaction product simultaneously acts as both a catalyst and an initial reactant. Such reactions are called autocatalytic.

Another theory that can explain the transition from prebiological to biological evolution is synergy . The patterns discovered by synergetics make it possible to clarify the mechanism of the emergence of organic matter from inorganic matter in terms of self-organization through the spontaneous emergence of new structures during the interaction of an open system with the environment.

The question of the origin of life on Earth is one of the most difficult questions of modern natural science, to which there is no unambiguous answer to date.

There are several theories about the origin of life on Earth, the most famous of which are:

• theory of spontaneous (spontaneous) generation;
• the theory of creationism (or creation);
• steady state theory;
• theory of panspermia;
• theory of biochemical evolution (the theory of A.I. Oparin).

Consider the main provisions of these theories.

Theory of spontaneous (spontaneous) generation

The theory of spontaneous generation of life was widespread in the ancient world - Babylon, China, Ancient Egypt and Ancient Greece (Aristotle, in particular, adhered to this theory).

Scientists of the ancient world and medieval Europe believed that living beings constantly arise from inanimate matter: worms from mud, frogs from mud, fireflies from morning dew, etc. So, the famous Dutch scientist of the 17th century. Van Helmont quite seriously described in his scientific treatise an experience in which he got mice in a locked dark closet directly from a dirty shirt and a handful of wheat in 3 weeks. For the first time, the Italian scientist Francesco Redi (1688) decided to subject a widely accepted theory to experimental verification. He placed several pieces of meat in vessels and covered some of them with muslin. In open vessels, white worms appeared on the surface of rotting meat - fly larvae. There were no fly larvae in the vessels covered with muslin. Thus, F. Redi managed to prove that fly larvae do not appear from rotting meat, but from eggs laid by flies on its surface.

In 1765, the famous Italian scientist and physician Lazzaro Spalanzani boiled meat and vegetable broths in sealed glass flasks. Broths in sealed flasks did not spoil. He concluded that under the influence of high temperature all living creatures capable of causing spoilage of the broth died. However, the experiments of F. Redi and L. Spalanzani did not convince everyone. Vitalist scientists (from lat. vita- life) believed that spontaneous generation of living beings does not occur in a boiled broth, since a special “life force” is destroyed in it, which cannot penetrate into a sealed vessel, since it is transported through the air.

Disputes about the possibility of spontaneous generation of life intensified in connection with the discovery of microorganisms. If complex living beings can't reproduce spontaneously, perhaps microorganisms can?

In this regard, in 1859, the French Academy announced the award of a prize to the one who finally decides the question of the possibility or impossibility of spontaneous generation of life. This award was received in 1862 by the famous French chemist and microbiologist Louis Pasteur. Just like Spalanzani, he boiled nutrient broth in a glass flask, but the flask was not ordinary, but with a neck in the form of a 5-shaped tube. Air, and hence the "life force", could penetrate into the flask, but the dust, and with it the microorganisms present in the air, settled in the lower elbow of the 5-shaped tube, and the broth in the flask remained sterile (Fig. 1). However, it was worth breaking the neck of the flask or rinsing the lower knee of the 5-shaped tube with sterile broth, as the broth began to quickly become cloudy - microorganisms appeared in it.

Thus, thanks to the work of Louis Pasteur, the theory of spontaneous generation was recognized as untenable and the theory of biogenesis was established in the scientific world, a brief formulation of which is - "everything living is from living things."

Rice. 1. Pasteur flask

However, if all living organisms in the historically foreseeable period of human development originate only from other living organisms, the question naturally arises: when and how did the first living organisms appear on Earth?

Creation theory

Creation theory assumes that all living organisms (or only their simplest forms) were created (“designed”) in a certain period of time by some supernatural being (deity, absolute idea, supermind, supercivilization, etc.). It is obvious that the followers of most of the leading religions of the world, in particular the Christian religion, adhered to this point of view from ancient times.

The theory of creationism is still quite widespread, not only in religious, but also in scientific circles. It is usually used to explain the most complex, unresolved issues of biochemical and biological evolution associated with the emergence of proteins and nucleic acids, the formation of the mechanism of interaction between them, the emergence and formation of individual complex organelles or organs (such as the ribosome, eye or brain). The acts of periodic “creation” also explain the absence of clear transitional links from one type of animals
to another, for example, from worms to arthropods, from monkeys to humans, etc. It must be emphasized that the philosophical dispute about the primacy of consciousness (supermind, absolute idea, deity) or matter is fundamentally unsolvable, however, since an attempt to explain any difficulties of modern biochemistry and evolutionary theory by fundamentally incomprehensible supernatural acts of creation takes these issues beyond the scope of scientific research, the theory of creationism can not be attributed to the category of scientific theories of the origin of life on Earth.

Steady state and panspermia theories

Both of these theories are complementary elements of a single picture of the world, the essence of which is as follows: the universe exists forever and life exists in it forever (stationary state). Life is carried from planet to planet by "seeds of life" traveling in outer space, which can be part of comets and meteorites (panspermia). Similar views on the origin of life were held, in particular, by Academician V.I. Vernadsky.

However, the theory of the stationary state, which assumes an infinitely long existence of the universe, is not consistent with the data of modern astrophysics, according to which the universe arose relatively recently (about 16 billion years ago) by means of a primary explosion.

It is obvious that both theories (panspermia and stationary state) do not offer an explanation of the mechanism of the primary origin of life at all, transferring it to other planets (panspermia) or moving it to infinity in time (the theory of a stationary state).

Theory of biochemical evolution (theory of A.I. Oparin)

Of all theories of the origin of life, the most common and recognized in the scientific world is the theory of biochemical evolution, proposed in 1924 by the Soviet biochemist Academician A.I. Oparin (in 1936 he described it in detail in his book The Emergence of Life).

The essence of this theory is that biological evolution - i.e. the emergence, development and complication of various forms of living organisms, was preceded by chemical evolution - a long period in the history of the Earth, associated with the emergence, complication and improvement of the interaction between elementary units, "bricks" that make up all living things - organic molecules.

Prebiological (chemical) evolution

According to most scientists (primarily astronomers and geologists), the Earth was formed as a celestial body about 5 billion years ago. by condensation of particles of a gas and dust cloud rotating around the Sun.

Under the influence of compressive forces, the particles from which the Earth is formed release a huge amount of heat. Thermonuclear reactions begin in the bowels of the Earth. As a result, the Earth gets very hot. Thus, 5 billion years ago The earth was a hot ball rushing through outer space, the surface temperature of which reached 4000-8000°C (laugh. 2).

Gradually, due to the radiation of thermal energy into outer space, the Earth begins to cool. About 4 billion years ago The earth cools so much that a hard crust forms on its surface; at the same time, light, gaseous substances escape from its bowels, rising up and forming the primary atmosphere. The composition of the primary atmosphere was significantly different from the modern one. Apparently, there was no free oxygen in the atmosphere of the ancient Earth, and its composition included substances in a reduced state, such as hydrogen (H 2), methane (CH 4), ammonia (NH 3), water vapor (H 2 O ), and possibly also nitrogen (N 2), carbon monoxide and carbon dioxide (CO and CO 2).

The reducing nature of the Earth's primary atmosphere is extremely important for the origin of life, since substances in a reduced state are highly reactive and, under certain conditions, are able to interact with each other, forming organic molecules. The absence of free oxygen in the atmosphere of the primary Earth (practically all of the Earth's oxygen was bound in the form of oxides) is also an important prerequisite for the emergence of life, since oxygen easily oxidizes and thereby destroys organic compounds. Therefore, in the presence of free oxygen in the atmosphere, the accumulation of a significant amount of organic matter on the ancient Earth would have been impossible.

About 5 billion years ago- the emergence of the Earth as a celestial body; surface temperature — 4000-8000°C

About 4 billion years ago - formation of the earth's crust and primary atmosphere

At 1000°C- in the primary atmosphere, the synthesis of simple organic molecules begins

The energy for synthesis is given by:

The temperature of the primary atmosphere is below 100 ° C - the formation of the primary ocean -

Synthesis of complex organic molecules - biopolymers from simple organic molecules:

• simple organic molecules - monomers
• complex organic molecules - biopolymers

Scheme. 2. Main stages of chemical evolution

When the temperature of the primary atmosphere reaches 1000°C, the synthesis of simple organic molecules begins in it, such as amino acids, nucleotides, fatty acids, simple sugars, polyhydric alcohols, organic acids, etc. The energy for synthesis is supplied by lightning discharges, volcanic activity, hard space radiation and, finally, the ultraviolet radiation of the Sun, from which the Earth is not yet protected by the ozone screen, and it is ultraviolet radiation that scientists consider the main source of energy for abiogenic (that is, passing without the participation of living organisms) synthesis of organic substances.

The recognition and wide dissemination of the theory of A.I. Oparin was greatly facilitated by the fact that the processes of abiogenic synthesis of organic molecules are easily reproduced in model experiments.

The possibility of synthesizing organic substances from inorganic substances has been known since the beginning of the 19th century. Already in 1828, the outstanding German chemist F. Wöhler synthesized an organic substance - urea from inorganic - ammonium cyanate. However, the possibility of abiogenic synthesis of organic substances under conditions close to those of the ancient Earth was first shown in the experiment of S. Miller.

In 1953, a young American researcher, a graduate student at the University of Chicago, Stanley Miller, reproduced in a glass flask with electrodes soldered into it the primary atmosphere of the Earth, which, according to scientists of that time, consisted of hydrogen, methane CH 4, ammonia NH, and water vapor H 2 0 (Fig. 3). Through this gas mixture, S. Miller passed electric discharges simulating thunderstorms for a week. At the end of the experiment, α-amino acids (glycine, alanine, asparagine, glutamine), organic acids (succinic, lactic, acetic, glycocolic), γ-hydroxybutyric acid and urea were found in the flask. When repeating the experiment, S. Miller managed to obtain individual nucleotides and short polynucleotide chains of five to six links.

Rice. 3. Installation by S. Miller

In further experiments on abiogenic synthesis conducted by various researchers, not only electrical discharges were used, but also other types of energy characteristic of the ancient Earth, such as cosmic, ultraviolet and radioactive radiation, high temperatures inherent in volcanic activity, as well as various options for gas mixtures, imitating the original atmosphere. As a result, almost the entire spectrum of organic molecules characteristic of living things was obtained: amino acids, nucleotides, fat-like substances, simple sugars, organic acids.

Moreover, abiogenic synthesis of organic molecules can also occur on Earth at the present time (for example, in the course of volcanic activity). At the same time, not only hydrocyanic acid HCN, which is a precursor of amino acids and nucleotides, but also individual amino acids, nucleotides, and even such complex organic substances as porphyrins can be found in volcanic emissions. Abiogenic synthesis of organic substances is possible not only on Earth, but also in outer space. The simplest amino acids are found in meteorites and comets.

When the temperature of the primary atmosphere dropped below 100 ° C, hot rains fell on the Earth and the primary ocean appeared. With streams of rain, abiogenically synthesized organic substances entered the primary ocean, which turned it, but in the figurative expression of the English biochemist John Haldane, into a dilute "primary soup". Apparently, it is in the primordial ocean that the processes of formation of simple organic molecules—monomers of complex organic molecules—biopolymers begin (see Fig. 2).

However, the processes of polymerization of individual nucleoside, amino acids and sugars are condensation reactions, they proceed with the elimination of water, therefore, the aqueous medium does not contribute to polymerization, but, on the contrary, to the hydrolysis of biopolymers (i.e., their destruction with the addition of water).

The formation of biopolymers (in particular, proteins from amino acids) could take place in the atmosphere at a temperature of about 180°C, from where they were washed into the primary ocean with atmospheric precipitation. In addition, it is possible that on the ancient Earth, amino acids were concentrated in drying up reservoirs and polymerized in a dry form under the influence of ultraviolet light and the heat of lava flows.

Despite the fact that water promotes the hydrolysis of biopolymers, the synthesis of biopolymers in a living cell occurs precisely in an aqueous medium. This process is catalyzed by special catalytic proteins - enzymes, and the energy necessary for synthesis is released during the breakdown of adenosine triphosphoric acid - ATP. It is possible that the synthesis of biopolymers in the aquatic environment of the primary ocean was catalyzed by the surface of certain minerals. It has been experimentally shown that a solution of the amino acid alanine can polymerize in an aqueous medium in the presence of a special type of alumina. In this case, the peptide polyalanine is formed. The polymerization reaction of alanine is accompanied by the breakdown of ATP.

The polymerization of nucleotides is easier than the polymerization of amino acids. It has been shown that in solutions with a high salt concentration, individual nucleotides spontaneously polymerize, turning into nucleic acids.

The life of all modern living beings is a process of continuous interaction between the most important biopolymers of a living cell - proteins and nucleic acids.

Proteins are the "working molecules", "engineer molecules" of a living cell. Describing their role in metabolism, biochemists often use such figurative expressions as "the protein works", "the enzyme leads the reaction." The most important function of proteins is catalytic. As you know, catalysts are substances that speed up chemical reactions, but they themselves are not included in the final products of the reaction. Tanks-catalysts are called enzymes. Enzymes in bend and thousands of times accelerate metabolic reactions. Metabolism, and hence life without them, is impossible.

Nucleic acids- these are "molecules-computers", molecules are the keepers of hereditary information. Nucleic acids do not store information about all the substances of a living cell, but only about proteins. It is enough to reproduce in the daughter cell the proteins characteristic of the mother cell so that they accurately recreate all the chemical and structural features of the mother cell, as well as the nature and rate of metabolism inherent in it. Nucleic acids themselves are also reproduced due to the catalytic activity of proteins.

Thus, the mystery of the origin of life is the mystery of the emergence of the mechanism of interaction between proteins and nucleic acids. What information does modern science have about this process? What molecules were the primary basis of life - proteins or nucleic acids?

Scientists believe that despite the key role of proteins in the metabolism of modern living organisms, the first "living" molecules were not proteins, but nucleic acids, namely ribonucleic acids (RNA).

In 1982, American biochemist Thomas Check discovered the autocatalytic properties of RNA. He experimentally showed that in a medium containing high concentrations of mineral salts, ribonucleotides spontaneously (spontaneously) polymerize, forming polynucleotides - RNA molecules. On the original polynucleotide chains of RNA, as on a matrix, RNA copies are formed by pairing of complementary nitrogenous bases. The RNA template copying reaction is catalyzed by the original RNA molecule and does not require the participation of enzymes or other proteins.

What happened next is fairly well explained by what might be called "natural selection" at the molecular level. During self-copying (self-assembly) of RNA molecules, inaccuracies and errors inevitably arise. The erroneous RNA copies are copied again. When copying again, errors may occur again. As a result, the population of RNA molecules in a certain part of the primary ocean will be heterogeneous.

Since RNA decay processes are also taking place in parallel with the synthesis processes, molecules with either greater stability or better autocatalytic properties will accumulate in the reaction medium (i.e., molecules that copy themselves faster, “multiply” faster).

On some RNA molecules, as on a matrix, self-assembly of small protein fragments - peptides can occur. A protein "sheath" is formed around the RNA molecule.

Along with autocatalytic functions, Thomas Check discovered the phenomenon of self-splicing in RNA molecules. As a result of self-splicing, RNA regions that are not protected by peptides are spontaneously removed from RNA (they are, as it were, “cut out” and “ejected”), and the remaining RNA regions encoding protein fragments “grow together”, i.e. spontaneously combine into a single molecule. This new RNA molecule will already code for a large complex protein (Figure 4).

Apparently, initially protein sheaths performed primarily a protective function, protecting RNA from destruction and thereby increasing its stability in solution (this is the function of protein sheaths in the simplest modern viruses).

Obviously, at a certain stage of biochemical evolution, RNA molecules, which encode not only protective proteins, but also catalytic proteins (enzymes) that sharply accelerate the rate of RNA copying, gained an advantage. Apparently, this is how the process of interaction between proteins and nucleic acids, which we now call life, arose.

In the process of further development, thanks to the appearance of a protein with the functions of an enzyme, reverse transcriptase, on single-stranded RNA molecules, molecules of deoxyribonucleic acid (DNA) consisting of two strands began to be synthesized. The absence of an OH group in the 2" position of deoxyribose makes DNA molecules more stable with respect to hydrolytic cleavage in slightly alkaline solutions, namely, the reaction of the medium in primary reservoirs was slightly alkaline (this reaction of the medium was also preserved in the cytoplasm of modern cells).

Where did the development of a complex process of interaction between proteins and nucleic acids take place? According to the theory of A.I. Oparin, the so-called coacervate drops became the birthplace of life.

Rice. 4. Hypothesis of the emergence of interaction between proteins and nucleic acids: a) in the process of self-copying of RNA, errors accumulate (1 - nucleotides corresponding to the original RNA; 2 - nucleotides that do not correspond to the original RNA - errors in copying); b) due to its physicochemical properties, amino acids “stick” to a part of the RNA molecule (3 - RNA molecule; 4 - amino acids), which, interacting with each other, turn into short protein molecules - peptides. As a result of self-splicing inherent in RNA molecules, the parts of the RNA molecule that are not protected by peptides are destroyed, and the remaining ones "grow" into a single molecule encoding a large protein. The result is an RNA molecule covered with a protein sheath (the most primitive modern viruses, for example, the tobacco mosaic virus, have a similar structure)

The phenomenon of coacervation consists in the fact that under certain conditions (for example, in the presence of electrolytes) macromolecular substances are separated from the solution, but not in the form of a precipitate, but in the form of a more concentrated solution - coacervate. When shaken, the coacervate breaks up into separate small droplets. In water, such drops are covered with a hydration shell (a shell of water molecules) that stabilizes them - fig. 5.

Coacervate drops have some semblance of metabolism: under the influence of purely physical and chemical forces, they can selectively absorb certain substances from the solution and release their decay products into the environment. Due to the selective concentration of substances from the environment, they can grow, but when they reach a certain size, they begin to "multiply", budding small droplets, which, in turn, can grow and "bud".

The coacervate droplets resulting from the concentration of protein solutions in the process of mixing under the action of waves and wind can be covered with a lipid shell: a single membrane resembling soap micelles (with a single detachment of a drop from the surface of water covered with a lipid layer), or a double membrane resembling a cell membrane ( when a drop covered with a single-layer lipid membrane falls again onto the lipid film covering the surface of the reservoir - Fig. 5).

The processes of the emergence of coacervate droplets, their growth and "budding", as well as "dressing" them with a membrane from a double lipid layer are easily modeled in the laboratory.

For coacervate droplets, there is also a process of "natural selection" in which the most stable droplets remain in solution.

Despite the outward resemblance of coacervate drops to living cells, coacervate drops lack the main sign of a living thing - the ability for accurate self-reproduction, self-copying. Obviously, the precursors of living cells were such coacervate drops, which included complexes of replicator molecules (RNA or DNA) and the proteins they encode. It is possible that RNA-protein complexes existed for a long time outside the coacervate droplets in the form of the so-called “free-living gene”, or it is possible that their formation took place directly inside some coacervate droplets.

Possible path of transition from coacervate drops to primitive flares:

a) the formation of a coacervate; 6) stabilization of coacervate drops in an aqueous solution; c) - formation of a double lipid layer around the drop, similar to a cell membrane: 1 - coacervate drop; 2 - monomolecular layer of lipid on the surface of the reservoir; 3 — formation of a single lipid layer around the drop; 4 — formation of a double lipid layer around the drop, similar to a cell membrane; d) - a coacervate drop surrounded by a double lipid layer, with a protein-nucleotide complex included in its composition - a prototype of the first living cell

From a historical point of view, the extremely complex process of the origin of life on Earth, which is not fully understood by modern science, passed extremely quickly. For 3.5 billion years, the so-called. chemical evolution ended with the appearance of the first living cells and biological evolution began.

There is a hypothesis about the possible introduction of bacteria, microbes and other tiny organisms through the introduction of celestial bodies. Organisms developed and as a result of long-term transformations, life gradually appeared on Earth. The hypothesis considers organisms that can function even in an anoxic environment and at abnormally high or low temperatures.

This is due to the presence of migrant bacteria on asteroids and meteorites, which are fragments from collisions of planets or other bodies. Due to the presence of a wear-resistant outer shell, as well as due to the ability to slow down all life processes (sometimes turning into a spore), this kind of life is able to move for a very long time and over very long distances.

When getting into more hospitable conditions, “intergalactic travelers” activate the main life-supporting functions. And without realizing it, they form, over time, life on Earth.

The fact of the existence of synthetic and organic substances today is undeniable. Moreover, back in the nineteenth century, the German scientist Friedrich Wöhler synthesized organic matter (urea) from inorganic matter (ammonium cyanate). Then hydrocarbons were synthesized. Thus, life on planet Earth quite likely originated by synthesis from inorganic material. Through abiogenesis, theories of the origin of life are put forward.

Since the main role in the structure of any organic organism is played by amino acids. It would be logical to assume that they were involved in the settlement of the Earth with life. Based on the data obtained from the experiment of Stanley Miller and Harold Urey (the formation of amino acids by passing an electric charge through gases), we can talk about the possibility of the formation of amino acids. After all, amino acids are the building blocks with which complex systems of the body and any life, respectively, are built.

Cosmogonic hypothesis

Probably the most popular interpretation of all, which every student knows. The Big Bang Theory has been and remains a hot topic of discussion. The Big Bang came from a singular point of energy accumulation, as a result of which the Universe expanded significantly. Cosmic bodies were formed. Despite all the consistency, the Big Bang Theory does not explain the formation of the universe itself. As a matter of fact, no existing hypothesis can explain it.

Symbiosis of organelles of nuclear organisms

This version of the origin of life on Earth is also called endosymbiosis. The clear provisions of the system were drawn up by the Russian botanist and zoologist K. S. Merezhkovsky. The essence of this concept lies in the mutually beneficial cohabitation of the organelle with the cell. Which, in turn, suggests endosymbiosis, as a symbiosis beneficial for both parties with the formation of eukaryotic cells (cells in which a nucleus is present). Then, with the help of the transfer of genetic information between bacteria, their development and population increase were carried out. According to this version, all further development of life and life forms is due to the previous ancestor of modern species.

Spontaneous generation

This kind of statement in the nineteenth century, could not be taken without a share of skepticism. The sudden appearance of species, namely the formation of life from non-living things, seemed like a fantasy for people of that time. At the same time, heterogenesis (the method of reproduction, as a result of which individuals are born that are very different from the parents) was recognized as a reasonable explanation of life. A simple example would be the formation of a complex viable system from decaying substances.

For example, in the same Egypt, Egyptian hieroglyphs report the appearance of a diverse life from water, sand, decaying and rotting plant remains. This news would not have surprised the ancient Greek philosophers. There, the belief about the origin of life from the inanimate was perceived as a fact that did not require substantiation. The great Greek philosopher Aristotle spoke of the visible truth in this way: “aphids are formed from rotten food, Crocodile is the result of processes in rotting logs under water.” Mysteriously, but despite all sorts of persecution from the church, the conviction under the bosom of mystery lived for a century.

Debates about life on Earth cannot go on forever. That is why, at the end of the nineteenth century, the French microbiologist and chemist Louis Pasteur carried out his analyzes. His research was strictly scientific. The experiment was carried out in 1860-1862. Thanks to the removal of disputes from a sleepy state, Pasteur was able to solve the problem of the spontaneous generation of life. (For which he was awarded the prize by the French Academy of Sciences)

Creation of existence from ordinary clay

It sounds like madness, but in reality this topic has the right to life. After all, it is not in vain that the Scottish scientist, A.J. Cairns-Smith, put forward a protein theory about life. Strongly forming the basis of similar studies, he talked about the interaction at the molecular level between organic constituents and simple clay ... Being under its influence, the components formed stable systems in which changes occurred in the structure of both components, and then the formation of a sustainable life. In such a unique and original way, Kearns-Smith explained his position. Clay crystals, with biological inclusions in it, gave birth to life together, after which their “cooperation” ended.

Theory of permanent catastrophes

According to the concept developed by Georges Cuvier, the world that you can see right now is not at all primary. And what he is, so it's just another link in a consistently torn chain. This means that we live in a world that will eventually undergo a mass extinction of life. At the same time, not everything on Earth was subjected to global destruction (for example, there was a flood). Some species, in the course of their adaptability, survived, thereby populating the Earth. The structure of species and life, according to Georges Cuvier, remained unchanged.

Matter as an objective reality

The main theme of the teaching is various spheres and areas that bring closer to understanding evolution from the point of view of the exact sciences. (materialism is a worldview in philosophy that reveals all causal circumstances, phenomena and factors of reality. Laws are applicable to man, society, the Earth). The theory was put forward by well-known adherents of materialism, who believe that life on Earth originated from transformations at the level of chemistry. Moreover, they occurred almost 4 billion years ago. The explanation of life is directly related to DNA, (deoxyribonucleic acid) RNA (ribonucleic acid), as well as to some HMCs (high molecular weight compounds, in this case proteins.)

The concept was formed through scientific research, revealing the essence of molecular and genetic biology, genetics. The sources are authoritative, especially given their youth. After all, studies of the hypothesis about the world of RNA began to be carried out at the end of the twentieth century. A huge contribution to the theory was made by Carl Richard Woese.

Teachings of Charles Darwin

Speaking about the origin of species, it is impossible not to mention such a truly brilliant person as Charles Darwin. His life's work, natural selection, laid the foundation for mass atheist movements. On the other hand, it gave an unprecedented impetus to science, an inexhaustible ground for research and experimentation. The essence of the doctrine was the survival of species throughout history, by adapting organisms to local conditions, the formation of new features that help in a competitive environment.

Evolution refers to some processes aimed at changing the life of an organism and the organism itself over time. Under hereditary traits, they mean the transfer of behavioral, genetic, or other kind of information (transmission from maternal to child.)

The main forces of the movement of evolution, according to Darwin, is the struggle for the right to exist, through the selection and variability of species. Under the influence of Darwinian ideas, at the beginning of the twentieth century, research was actively carried out in terms of ecology, as well as genetics. The teaching of zoology has changed radically.

Creation of God

Many people from all over the globe still profess faith in God. Creationism is an interpretation of the formation of life on Earth. The interpretation consists of a system of statements based on the Bible and considers life as a being created by a creator god. The data is taken from the "Old Testament", "Gospel" and other sacred writings.

Interpretations of the creation of life in different religions are somewhat similar. According to the Bible, the earth was created in seven days. The sky, the celestial body, water and the like, were created in five days. On the sixth day, God created Adam from clay. Seeing a bored, lonely man, God decided to create another miracle. Taking Adam's rib, he created Eve. The seventh day was recognized as a day off.

Adam and Eve lived without trouble, until the malevolent devil in the form of a snake decided to tempt Eve. After all, in the middle of paradise stood the tree of the knowledge of good and evil. The first mother invited Adam to share the meal, thereby violating the word given to God (he forbade touching the forbidden fruits.)

The first people are expelled into our world, thereby starting the history of all mankind and life on Earth.

Hypotheses of the origin of life on Earth.

Currently, there are several concepts considering the origin of life on earth. Let us dwell only on some of the main theories that help to compose a fairly complete picture of this complex process.

Creationism (lat. cgea - creation).

According to this concept, life and all species of living beings inhabiting the Earth are the result of a creative act of a higher being at some specific time.

The main provisions of creationism are set out in the Bible, in the Book of Genesis. The process of the divine creation of the world is conceived as having taken place only once and therefore inaccessible to observation.

This is enough to take the whole concept of divine creation out of the scope of scientific research. Science deals only with observable phenomena and therefore will never be able to either prove or reject this concept.

Spontaneous(spontaneous) generation.

The ideas of the origin of living beings from inanimate matter were widespread in Ancient China, Babylon, and Egypt. The largest philosopher of ancient Greece, Aristotle, suggested that certain “particles” of matter contain some kind of “active principle”, which, under suitable conditions, can create a living organism.

Van Helmont (1579–1644), a Dutch physician and natural philosopher, described an experiment in which he allegedly created mice in three weeks. For this, a dirty shirt, a dark closet and a handful of wheat were needed. Van Helmont considered human sweat to be the active principle in the process of the birth of a mouse.

In the 17th-18th centuries, thanks to successes in the study of lower organisms, fertilization and development of animals, as well as the observations and experiments of the Italian naturalist F. Redi (1626-1697), the Dutch microscopist A. Leeuwenhoek (1632-1723), the Italian scientist L. Spallanzani ( 1729-1799), Russian microscopist M. M. Terekhovsky (1740-1796) and others, belief in spontaneous generation was thoroughly undermined.

However, until the appearance in the middle of the tenth century of the work of the founder of microbiology, Louis Pasteur, this doctrine continued to find adherents.

The development of the idea of ​​spontaneous generation refers, in essence, to the era when religious ideas dominated the public consciousness.

Those philosophers and naturalists who did not want to accept the Church's teaching on the "creation of life", with the then level of knowledge, easily came to the idea of ​​its spontaneous generation.

To the extent that, in contrast to the belief in creation, the idea of ​​the natural origin of organisms was emphasized, the idea of ​​spontaneous generation was at a certain stage of progressive significance. Therefore, this idea was often opposed by the Church and theologians.

The panspermia hypothesis.

According to this hypothesis, proposed in 1865. by the German scientist G. Richter and finally formulated by the Swedish scientist Arrhenius in 1895, life could be brought to Earth from space.

The most likely hit of living organisms of extraterrestrial origin with meteorites and cosmic dust. This assumption is based on data on the high resistance of some organisms and their spores to radiation, high vacuum, low temperatures, and other influences.

However, there are still no reliable facts confirming the extraterrestrial origin of microorganisms found in meteorites.

But even if they got to Earth and gave rise to life on our planet, the question of the original origin of life would remain unanswered.

Hypothesis biochemical evolution.

In 1924, the biochemist A. I. Oparin, and later the English scientist J. Haldane (1929), formulated a hypothesis that considers life as the result of a long evolution of carbon compounds.

The modern theory of the origin of life on Earth, called the theory of biopoiesis, was formulated in 1947 by the English scientist J. Bernal.

Currently, in the process of the formation of life, four stages are conventionally distinguished:

• 1. Synthesis of low molecular weight organic compounds (biological monomers) from gases of the primary atmosphere.
• 2. Formation of biological polymers.
• 3. Formation of phase-separated systems of organic substances separated from the external environment by membranes (protobionts).
• 4. The emergence of the simplest cells with the properties of the living, including the reproductive apparatus, which ensures the transfer of the properties of the parent cells to the daughter cells.

The first three stages are attributed to the period of chemical evolution, and from the fourth, biological evolution begins.

Let us consider in more detail the processes as a result of which life could have arisen on Earth. According to modern concepts, the Earth was formed about 4.6 billion years ago. Its surface temperature was very high (4000-8000°C), and as the planet cooled and gravitational forces acted, the earth's crust was formed from compounds of various elements.

Degassing processes led to the creation of an atmosphere enriched, possibly, with nitrogen, ammonia, water vapor, carbon dioxide and carbon monoxide. Such an atmosphere was, apparently, reducing, as evidenced by the presence in the most ancient rocks of the Earth of metals in reduced form, such as, for example, ferrous iron.

It is important to note that in the atmosphere there were hydrogen, carbon, oxygen and nitrogen atoms, which make up 99% of the atoms that make up the soft tissues of any living organism.

However, in order for atoms to turn into complex molecules, their simple collisions were not enough. Additional energy was needed, which was available on Earth as a result of volcanic activity, electrical lightning discharges, radioactivity, and ultraviolet radiation from the Sun.

The absence of free oxygen was probably not a sufficient condition for the emergence of life. If free oxygen were present on the Earth in the prebiotic period, then, on the one hand, it would oxidize the synthesized organic substances, and on the other hand, forming an ozone layer in the upper horizons of the atmosphere, it would absorb the high-energy ultraviolet radiation of the Sun.

During the considered period of the emergence of life, which lasted approximately 1000 million years, ultraviolet radiation was probably the main source of energy for the synthesis of organic substances.

Oparin A.I.

From hydrogen, nitrogen and carbon compounds, in the presence of free energy on Earth, simple molecules (ammonia, methane and similar simple compounds) should first have arisen.

In the future, these simple molecules in the primary ocean could enter into reactions with each other and with other substances, forming new compounds.

In 1953, the American researcher Stanley Miller in a series of experiments simulated the conditions that existed on Earth approximately 4 billion years ago.

Passing electrical discharges through a mixture of ammonia, methane, hydrogen and water vapor, he received a number of amino acids, aldehydes, lactic, acetic and other organic acids. American biochemist Cyril Ponnaperuma achieved the formation of nucleotides and ATP. In the course of such and similar reactions, the waters of the primary ocean could be saturated with various substances, forming the so-called "primary soup".

The second stage consisted of further transformations of organic substances and the abiogenic formation of more complex organic compounds, including biological polymers.

The American chemist S. Fox composed mixtures of amino acids, subjected them to heating, and obtained proteo-like substances. On primitive earth, protein synthesis could take place on the surface of the earth's crust. In small depressions in the solidifying lava, reservoirs appeared containing small molecules dissolved in water, including amino acids.

When the water evaporated or splashed onto the hot rocks, the amino acids reacted to form proteoids. The rains then washed the proteoids into the water. If some of these proteoids had catalytic activity, then the synthesis of polymers, i.e., protein-like molecules, could begin.

The third stage was characterized by the release of special coacervate drops in the primary "nutrient broth", which are groups of polymeric compounds. It has been shown in a number of experiments that the formation of coacervate suspensions, or microspheres, is typical of many biological polymers in solution.

Coacervate drops have some properties that are also characteristic of living protoplasm, such as selectively adsorbing substances from the surrounding solution and, due to this, "grow", increase their size.

Due to the fact that the concentration of substances in coacervate drops was ten times greater than in the surrounding solution, the possibility of interaction between individual molecules increased significantly.

It is known that the molecules of many substances, in particular polypeptides and fats, consist of parts that have a different relationship to water. The hydrophilic parts of the molecules located at the boundary between the coacervates and the solution turn towards the solution, where the water content is higher.

The hydrophobic parts are oriented inside the coacervates, where the water concentration is less. As a result, the surface of coacervates acquires a certain structure and, in connection with this, the property of letting some substances pass in a certain direction and not others.

Due to this property, the concentration of some substances inside the coacervates increases even more, while the concentration of others decreases, and the reactions between the components of the coacervates acquire a certain direction. Coacervate drops become systems isolated from the medium. Protocells, or protobionts, arise.

An important step in chemical evolution was the formation of a membrane structure. In parallel with the appearance of the membrane, there was an ordering and improvement of metabolism. Catalysts should have played a significant role in the further complication of metabolism in such systems.

One of the main features of living things is the ability to replicate, that is, to create copies that are indistinguishable from parent molecules. This property is possessed by nucleic acids, which, unlike proteins, are capable of replication.

A protenoid capable of catalyzing the polymerization of nucleotides with the formation of short RNA chains could form in coacervates. These chains could play the role of both a primitive gene and messenger RNA. Neither DNA, nor ribosomes, nor transfer RNAs, nor enzymes of protein synthesis have yet participated in this process. All of them appeared later.

Already at the stage of formation of protobionts, natural selection probably took place, i.e., the preservation of some forms and the elimination (death) of others. Thus, progressive changes in the structure of protobionts were fixed due to selection.

The appearance of structures capable of self-reproduction, replication, and variability apparently determines the fourth stage in the development of life.

So, in the late Archean (approximately 3.5 billion years ago), at the bottom of small reservoirs or shallow, warm and nutrient-rich seas, the first primitive living organisms arose, which were heterotrophs by type of nutrition, i.e., fed on ready-made organic substances, synthesized in the course of chemical evolution.

Fermentation, a process of enzymatic transformation of organic substances, in which other organic substances serve as electron acceptors, served as a means of metabolism.

Part of the energy released in these processes is stored in the form of ATP. It is possible that some organisms also used the energy of redox reactions for life processes, that is, they were chemosynthetics.

Over time, there was a decrease in the reserves of free organic matter in the environment, and organisms capable of synthesizing organic compounds from inorganic ones gained an advantage.

In this way, probably about 2 billion years ago, the first phototrophic organisms of the cyanobacteria type arose, capable of using light energy for the synthesis of organic compounds from CO2 and H2O, while releasing free oxygen.

The transition to autotrophic nutrition was of great importance for the evolution of life on Earth, not only in terms of creating reserves of organic matter, but also for saturating the atmosphere with oxygen. At the same time, the atmosphere began to acquire an oxidizing character.

The appearance of the ozone screen protected the primary organisms from the harmful effects of ultraviolet rays and put an end to the abiogenic (non-biological) synthesis of organic substances.

These are the modern scientific ideas about the main stages of the origin and formation of life on Earth.

A visual diagram of the development of life on Earth (clickable)

Addition:

The wonderful world of "black smokers"

In science, it has long been believed that living organisms can exist only from the energy of the Sun. Jules Verne in his novel Journey to the Center of the Earth described the underworld with dinosaurs and ancient plants. However, this is fiction. But who would have thought that there would be a world isolated from the energy of the Sun with absolutely different living organisms. And he was found at the bottom of the Pacific Ocean.

Back in the fifties of the twentieth century, it was believed that there could be no life in the ocean depths. The invention of the bathyscaphe by Auguste Picard dispelled these doubts.

His son, Jacques Picard, together with Don Walsh, descended in the Trieste bathyscaphe into the Mariana Trench to a depth of more than ten thousand meters. At the very bottom, the participants of the dive saw a live fish.

After that, oceanographic expeditions from many countries began to comb the deep ocean abyss with deep-sea nets and discover new animal species, families, orders, and even classes!

Submersions in bathyscaphes improved. Jacques-Yves Cousteau and scientists from many countries made costly dives to the bottom of the oceans.
In the 70s, a discovery was made that turned many ideas of scientists upside down. Faults were discovered near the Galapagos Islands at a depth of two to four thousand meters.
And at the bottom were discovered small volcanoes - hydrotherms. Sea water, falling into the faults of the earth's crust, evaporated along with various minerals through small volcanoes up to 40 meters high.
These volcanoes were called "black smokers" due to the black water coming out of them.

However, the most incredible thing is that in such water, filled with hydrogen sulfide, heavy metals and various toxic substances, a stormy life flourishes.

The temperature of the water coming out of the black smokers reaches 300°C. The sun's rays do not penetrate to a depth of four thousand meters, and therefore there cannot be a rich life.
Even in shallower depths, benthic organisms are very rare, not to mention deep abysses. There, animals feed on organic debris that falls from above. And the greater the depth, the less poorer the bottom life.
On the surfaces of black smokers, chemoautotrophic bacteria have been found that break down sulfur compounds erupted from the planet's interior. Bacteria cover the bottom surface in a continuous layer and live in aggressive conditions.
They have become food for many other animal species. In total, about 500 species of animals living in extreme conditions of "black smokers" have been described.

Another discovery was vestimentifera, which belong to the class of bizarre animals - pogonophores.

These are small tubes from which protrude long tubes at the ends with tentacles. The unusual thing about these animals is that they don't have a digestive system! They entered into symbiosis with bacteria. Inside the vestimentifer there is an organ - the trophosome, where many sulfurous bacteria live.

Bacteria receive hydrogen sulfide and carbon dioxide for life, the excess of breeding bacteria is eaten by vestimentifera itself. In addition, bivalve mollusks of the genera Calyptogena and Bathymodiolus were found nearby, which also entered into symbiosis with bacteria and ceased to depend on the search for food.

One of the most unusual creatures of the deep-sea world of hydrotherms is Alvinella pompeii worms.

They are named because of the analogy with the eruption of the Pompeii volcano - these creatures live in a zone of hot water reaching 50 ° C, and ash from sulfur particles constantly falls on them. Worms, together with vestimentifera, form real "gardens" that provide food and shelter for many organisms.

Crabs and decapods live among colonies of vestimentifera and pompeii worms, which feed on them. Also among these "gardens" there are octopuses and fish from the eelpout family. The world of black smokers also harbored long-extinct animals that were driven out of other parts of the ocean, such as Neolepas barnacles.

These animals were widespread 250 million years ago, but then became extinct. Here, representatives of barnacles feel calm.

The discovery of the ecosystems of "black smokers" has become the most significant event in biology. Such ecosystems have been found in different parts of the World Ocean and even at the bottom of Lake Baikal.

Pompeii worm. Photo life-grind-style.blogspot.com