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Ministry of Education and Science of the Russian Federation

Federal State Educational Institution of Higher Professional Education

Bashkir State University

Department of Biology

Department of Human Physiology and Zoology

Essay

discipline: Philosophical problems of biology

subject:Basictheoriesoriginlife

Completed by: Demidova E.S.

Checked by: Shevchenko A.M.

Introduction

1. Early theories

2. Modern theories

Conclusion

List of used literature

Introduction

Relevance of the topic. The question of the origin of life on Earth is one of the most difficult questions in modern natural science, to which there is still no clear answer.

To move on to the problem of the origin of life on Earth, we first define what life is. Let us recall the definitions of the concept “life”.

“Life is a way of existence of protein bodies, and this way of existence consists essentially in the constant self-renewal of the chemical components of these bodies” - F. Engels. Life is a higher form of existence of matter compared to the physical and chemical.

Living objects differ from non-living ones in metabolism - the continuous condition of life, the ability to reproduce, grow, irritability, adaptability to the environment, etc.

There is still no final and strict definition of the concept “life”.

Living systems are characterized by a very high level of structural and functional organization at the molecular level, the highest information density, self-organization, and the ability to self-heal.

Degree of development. This topic has already been analyzed by various authors, such as: Vernadsky V.I., Oparin A.I., Voitkevich G.V., in various publications.

The purpose of the work is to consider the main theories of the origin of life.

The goal defined the main tasks:

1. Reveal the essence of early theories of the origin of life.

2. Reveal the essence of the theory of biochemical evolution I.A. Oparina.

3. Give an idea of the theory of holobiosis and genobiosis.

1. Early theories

Theory of spontaneous generation

The theory of spontaneous generation of life was widespread in the Ancient world - Babylon, China, Ancient Egypt and Ancient Greece.

Scientists of the Ancient World and Medieval Europe believed that living beings constantly arise from inanimate matter: worms from dirt, frogs from mud, fireflies from morning dew, etc. Thus, the famous Dutch scientist of the 17th century. Van Helmont quite seriously described in his scientific treatise an experience in which, over 3 weeks, he obtained mice directly from a dirty shirt and a handful of wheat in a locked dark closet. For the first time, the Italian scientist Francesco Redi (1688) decided to subject a widespread theory to experimental testing. He placed several pieces of meat in vessels and covered some of them with muslin. In open vessels, white worms - fly larvae - appeared on the surface of the rotting meat. In the vessels covered with muslin, there were no fly larvae. Thus, F. Redi was able 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 doctor Lazzaro Spalanzani boiled meat and vegetable broths in sealed glass flasks. Broths in sealed flasks did not spoil. He concluded that the high temperature killed all living creatures that could cause the broth to spoil. However, the experiments of F. Redi and L. Spalanzani did not convince everyone. Vitalist scientists believed that spontaneous generation of living beings does not occur in boiled broth, since a special “vital force” is destroyed in it, which cannot penetrate into a sealed vessel because it is carried through the air.

Disputes over the possibility of spontaneous generation of life intensified in connection with the discovery of microorganisms. If complex living things cannot spontaneously generate, perhaps microorganisms can too.

In this regard, in 1859, the French Academy announced the award of a prize to the one who would finally decide the question of the possibility or impossibility of the spontaneous generation of life. This prize was received in 1862 by the famous French chemist and microbiologist Louis Pasteur. Just like Spalanzani, he boiled the nutrient broth in a glass flask, but the flask was not an ordinary one, but with a neck in the form of an S-shaped tube. Air, and therefore the “life force,” could penetrate into the flask, but the dust, and with it the microorganisms present in the air, settled in the lower leg of the S-shaped tube, and the broth in the flask remained sterile. However, as soon as the neck of the flask was broken or the lower leg of the S-shaped tube was rinsed with sterile broth, 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, the brief formulation of which is “all living things are from living things.”

However, Pasteur's experiment does not at all prove that living things can never spontaneously arise from non-living things. The experiment only proves the impossibility of the emergence of microorganisms specifically in the nutrient media that were used, under a very limited range of conditions and for short periods of time. But it does not prove the impossibility of the spontaneous generation of life over hundreds of millions of years of chemical evolution, in a variety of environments and under different conditions (especially under the conditions of the early Earth: in an oxygen-free atmosphere filled with methane, carbon dioxide, ammonia and hydrogen cyanide, when passing electrical discharges, etc. .d.). This experiment, in principle, cannot concern the question of the original origin of life, if only because in his experiments Pasteur used meat and yeast broths (as well as urea and blood), and before the origin of life there was neither yeast nor meat. Moreover, Pasteur’s experiment in no way refutes modern scientific theories and hypotheses about the origin of life in deep-sea hot hydrothermal springs, in geothermal springs, on mineral crystals, in outer space, in the protoplanetary nebula from which the Solar System was formed, etc.

Theorystationarystate

According to the steady state theory, the Earth never came into being, but existed forever; it was always capable of supporting life, and if it changed, it was very little. According to this version, species also never arose, they always existed, and each species has only two possibilities - either a change in numbers or extinction.

However, the stationary state hypothesis fundamentally contradicts the data of modern astronomy, which indicate a finite lifetime of any stars and, accordingly, planetary systems around stars. According to modern estimates, based on taking into account the rates of radioactive decay, the age of the Earth, the Sun and the Solar System is ~4.6 billion years. Therefore, this hypothesis is not usually considered by academic science.

Proponents of this hypothesis do not recognize that the presence or absence of certain fossil remains may indicate the time of appearance or extinction of a particular species, and cite as an example a representative of lobe-finned fish - coelacanth. According to paleontological data, lobe-finned animals became extinct at the end of the Cretaceous period. However, this conclusion had to be reconsidered when living representatives of lobe-fins were found in the Madagascar region. Proponents of the steady-state theory argue that only by studying living species and comparing them with fossil remains can one draw a conclusion about extinction, and even then it is very likely that it will be incorrect. Using paleontological data to support the steady-state theory, its proponents interpret the occurrence of fossils in ecological terms. For example, they explain the sudden appearance of a fossil species in a certain layer by an increase in the size of its population or its movement to places favorable for the preservation of remains. The steady state theory is of only historical or philosophical interest, since the conclusions of this theory contradict scientific data.

Theorypanspermia

Almost simultaneously with Pasteur’s experiments, the German scientist G. Richter put forward a hypothesis about the introduction of living beings to Earth from space, which was later called the theory of panspermia. According to this hypothesis, life in the form of “seeds” is widespread in space, from where the embryos of simple organisms could enter terrestrial conditions along with meteorites and cosmic dust and give rise to the evolution of all living things, thus giving rise to all the diversity of terrestrial life. That is, this theory allowed for the possibility of the emergence of life at different times in different parts of the Galaxy and its transfer to Earth in one way or another. The main idea of the theory of panspermia was shared by the largest scientists of the late 19th century. W. Thomson, G. Helmholtz, V.I. Vernadsky.

In 1908, the Swedish chemist S. Arrhenius put forward a similar hypothesis about the origin of life from space. He expressed the idea that the germs of life eternally exist in the Universe, move in outer space under the influence of light rays and, settling on the surface of planets, give rise to life on them. Life on our Earth began its development when the germs of life fell on it from Space.

The theory of panspermia was supported by many famous scientists, which contributed to its widespread use. This theory still has quite a large number of supporters today. Thus, American astronomers, studying a gas nebula located 25 thousand light years from the Earth, found traces of amino acids and other organic substances in its spectrum. In the early 1980s. American researchers have discovered in Antarctica a fragment of rock that was once knocked out from the surface of Mars by a large meteorite. Using an electron microscope, fossilized remains of microorganisms similar to terrestrial bacteria were discovered in this stone. This suggests that primitive life existed on Mars in the past, and perhaps it still exists there now.

However, there are no serious arguments in favor of panspermia. However, there are serious arguments against it. The fact is that, although the range of possible conditions for the existence of living organisms is quite wide, it is still believed that they must die in space under the influence of ultraviolet and cosmic rays.

There have been attempts to refute this position. Thus, the Dutch scientist M. Greenberg believed that life was brought to our planet by comets. In his opinion, living cells originated in the gas tails of comets. Therefore, he tried to reproduce the cometary environment in the laboratory. To do this, Greenberg cooled a mixture of methane, carbon monoxide and water to a temperature of -269 ° C and subjected it to ultraviolet irradiation. As a result, he obtained complex organic compounds. However, Greenberg's experiments did not change the opinions of most scientists.

The cosmic hypothesis of the origin of life has now been continued in the research of F. Hoyle, who suggested that microorganisms are formed in outer space, captured by comets and scattered in the space of the planets they fly past. But the predetermination of such an origin of life is extremely small, and the possibility alone is not the most important condition for the origin of life in Space or on Earth.

Some scientists are inclined to the version of “directed” panspermia. Its essence is the recognition of the existence of a certain galactic supercivilization of sowers who create and distribute the seeds of life across different planets. Among its supporters is the English professor F. Crick, one of the discoverers of gene structure, who proposed his hypothesis back in 1971. Unfortunately, for all its attractiveness, this version does not withstand strict scientific criticism; we do not have a single argument in its favor.

In addition, all existing variants of panspermia ultimately do not solve the problem of the origin of life. They only take it beyond the Earth, but leave the question open: if life was brought to Earth from space, then where and how did it originate there?

Theorycreationism

The theory of creationism has the longest history, since in almost all religions the emergence of life is considered as an act of divine creation, evidence of which is the presence in living organisms of a special force that controls all biological processes. The process of divine creation of the world and living things is inaccessible to observation, and the divine plan is inaccessible to human understanding.

Interestingly, in creationism the question of the duration of the act of creation of the world was resolved. The Bible says that God created the world in six days. Some Christian theologians believe that these were ordinary days of 24 hours. Other theologians treated the biblical texts as allegories and believed that each day of creation took a thousand years. But in all cases, discussions about the origin of life are based only on faith in biblical revelations, which cannot be doubted. Scientific truths, in accordance with the principle of falsification, are always questioned.

Thus, the concept of creationism is essentially not scientific, because it arose within the framework of a religious worldview. She argues that life is the way it is because God made it that way. This practically eliminates the question of a scientific solution to the problem of the origin of life, since all religions require accepting this position on faith, without evidence. Nevertheless, the theory of creationism continued and continues to enjoy quite a lot of popularity.

2. Moderntheories

TheorybiochemicalevolutionA.I. ABOUTParina

One of the main obstacles that stood at the beginning of the 20th century. On the way to solving the problem of the origin of life, there was a prevailing belief in science and based on everyday experience that there was no relationship between organic and inorganic compounds. Until the middle of the 20th century. many scientists believed that organic compounds can only arise in a living organism, biogenically. That is why they were called organic compounds, as opposed to inanimate substances - minerals, which were called inorganic compounds. It was believed that the nature of inorganic substances was completely different, and therefore the emergence of even the simplest organisms from inorganic substances was fundamentally impossible. However, after the first organic compound was synthesized from ordinary chemical elements, the idea of two different essences of organic and inorganic substances turned out to be untenable. As a result of this discovery, organic chemistry and biochemistry emerged, which study chemical processes in living organisms.

In addition, this scientific discovery made it possible to create the theory of biochemical evolution, according to which life on Earth arose as a result of physical and chemical processes. The initial basis for this hypothesis was data on the similarity of substances that make up plants and animals, as well as on the possibility of synthesizing organic substances that make up protein in laboratory conditions.

These discoveries formed the basis of the theory of A.I. Oparin, published in 1924 in the book “The Origin of Life,” which presented a fundamentally new hypothesis of the origin of life. He stated that the Redi principle, which introduces a monopoly of 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 syntheses of carbon compounds and their subsequent prebiological evolution took place on it.

He viewed the emergence of life as a single natural process, which consisted of the initial chemical evolution that took place under the conditions of the early Earth, which gradually moved to a qualitatively new level - biochemical evolution. The essence of the hypothesis was as follows: the origin of life on Earth is a long evolutionary process of the formation of living matter in the depths of nonliving matter. And this happened through chemical evolution, as a result of which the simplest organic substances were formed from inorganic ones under the influence of strong physicochemical factors.

Considering the problem of the origin of life through biochemical evolution, Oparin identifies three stages of the transition from inanimate to living matter: evolution biochemical natural science

1. stage of synthesis of initial organic compounds from inorganic substances under the conditions of the primary atmosphere of the early Earth;

2. the stage of formation of biopolymers, lipids, hydrocarbons from accumulated organic compounds in the primary reservoirs of the Earth;

3. the stage of self-organization of complex organic compounds, the emergence on their basis and evolutionary improvement of the processes of metabolism and reproduction of organic structures, culminating in the formation of the simplest cell.

At the first stage, about 4 billion years ago, when the Earth was lifeless, 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 huge amounts of hot lava. As the planet cooled, water vapor in the atmosphere condensed and rained down on the Earth, forming huge expanses of water. Since the Earth's surface remained hot, the water evaporated and then, cooling in the upper layers of the atmosphere, fell back onto the surface of the planet. These processes continued for many millions of years. Thus, various salts were dissolved in the waters of the primary ocean. In addition, it also contained organic compounds: sugars, amino acids, nitrogenous bases, organic acids, etc., which were continuously formed in the atmosphere under the influence of ultraviolet radiation, high temperature and active volcanic activity.

The primordial ocean probably contained in dissolved form various organic and inorganic molecules that entered it from the atmosphere and surface layers of the Earth. The concentration of organic compounds constantly increased, and eventually the ocean waters became a “broth” of protein-like substances - peptides.

At the second stage, as conditions on Earth softened, under the influence of electrical discharges, thermal energy and ultraviolet rays on the chemical mixtures of the primary ocean, it became possible to form complex organic compounds - biopolymers and nucleotides, which, gradually combining and becoming more complex, turned into protobionts. The result of the evolution of complex organic substances was the appearance of coacervates, or coacervate drops.

Coacervates are 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 the coacervates changed, which led either to their disintegration or to the accumulation of substances, i.e. to growth and changes in chemical composition, 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. Coacervates turned out to be able to absorb various organic substances from the external environment, which provided the possibility of primary metabolism with the environment.

At the third stage, as Oparin assumed, natural selection began to act. In the mass of coacervate droplets, the selection of coacervates that were most resistant to given environmental conditions occurred. The selection process took place over many millions of years, resulting in only a small fraction of coacervates being preserved. However, the preserved coacervate droplets had the ability to undergo primary metabolism. And metabolism is the primary property of life. At the same time, having reached a certain size, the mother drop could break up into daughter drops, which retained the features of the mother 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 turned into the simplest living organisms.

Further evolution of these prebiological structures was possible only with the complication of metabolic and energy processes within the coacervate. Only a membrane could provide stronger isolation of the internal environment from external influences. Around the coacervates, rich in organic compounds, layers of lipids appeared, separating the coacervate from the surrounding aqueous environment. During the process of evolution, lipids were transformed into the outer membrane, which significantly increased the viability and stability of organisms. The appearance of the membrane predetermined the direction of further chemical evolution along the path of increasingly perfect self-regulation until the emergence of the first cells.

The popularity of Oparin's theory in the scientific world is very great. However, most of the experiments that developed the scientist’s ideas were carried out only in the 1950s and 1960s. Thus, in 1953, S. Miller, in a series of experiments, simulated the conditions that existed at the early stage of the Earth's evolution. In the installation he made, many amino acids, adenine, simple sugars and other substances of important biological significance were synthesized. After this, L. Orgel synthesized simple nucleic acids in a similar experiment. But, despite its experimental validity and theoretical persuasiveness, Oparin’s theory has both strengths and weaknesses.

The strength of the theory is its 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 theory is also the possibility of experimental verification of its main provisions. This concerns not only the laboratory reproduction of the supposed physicochemical conditions of the primordial Earth, but also coacervates that imitate precellular ancestors and their functional characteristics.

The weak side of the theory is the impossibility of explaining the very moment of the leap from complex organic compounds to living organisms, because in none of the experiments it was possible to obtain life. In addition, Oparin assumed the possibility of self-reproduction of coacervates in the absence of molecular systems with genetic code functions. In other words, without reconstructing the evolution of the mechanism of heredity, it is impossible to explain the process of the jump from nonliving to living. Therefore, today it is believed that it will not be possible to solve this most complex problem of biology without involving the concept of open catalytic systems, molecular biology, and cybernetics.

TheoryholobiosisAndgenobiosis

The difficulty of resolving the question of the origin of life is explained by a well-known fact: for the self-reproduction of nucleic acids - the basis of the genetic code - enzyme proteins are needed, and for the synthesis of proteins - nucleic acids. This situation is similar to what happens when building a house, which simultaneously requires both materials and drawings and plans.

Of course, the easiest way would be to assume that nucleic acids and enzyme proteins appeared simultaneously, united into a single system within the protobiont, after which their coevolution began - simultaneous and interconnected evolution. Unfortunately, this compromise option has not received scientific recognition. The fact is that protein and nucleic macromolecules are structurally and functionally deeply different. Because of this, they could not appear simultaneously, as a result of one jump in the course of chemical evolution. Thus, their coexistence in a protobiological system is also impossible.

As a result, throughout most of the 20th century. scientists debated what was primary - proteins or nucleic acids, as well as how and at what stage they were combined into a single system capable of transmitting genetic information and regulating protein biosynthesis, i.e. being a living organism. Depending on the answer to the question of what is primary - proteins or nucleic acids, all existing hypotheses and theories can be divided into two large groups - holobiosis and genobiosis.

Oparin's theory, discussed earlier, belongs to the group of theories of holobiosis - a methodological approach that asserts the primacy of structures capable of elementary metabolism with the participation of enzymatic proteins. The appearance of nucleic acids in this theory is considered the completion of evolution, the result of competition between protobionts. This point of view can be called substrate.

Proponents of genobiosis proceed from the belief in the primacy of a molecular system with the properties of the primary genetic code. This group of hypotheses and concepts can be called informational. An example of this point of view is the theory of the American geneticist J. Haldane, put forward by him in 1929. According to Haldane’s theory, the primary one was not a structure capable of exchanging substances with the environment, but a macromolecular system, similar to a gene and capable of self-reproduction (and therefore called "naked genome").

Up until the 1980s. There was a clearly expressed opposition between the hypotheses of holobiosis and genobiosis, after which the balance began to tip in favor of the theory of genobiosis. This was largely due to a new interpretation of the property of molecular chirality of living organisms, discovered by L. Pasteur, which is considered the original and fundamental sign of living matter. The property of molecular chirality is believed to have originated as early as the ability of genetic self-reproduction. Moreover, this coding is performed using DNA or RNA molecules.

But the question remained unresolved as to which of these information molecules appeared first and played the role of a matrix for primary complementary polymerization.

The answer to the question was received by the end of the 1980s. It stated that the primary molecule was RNA, not DNA. Recognition of this fact was associated with the discovery of unique properties of RNA. It turned out that it is endowed with the same genetic memory as a DNA molecule. Further, the true ubiquity of RNA was established - it became clear that there are no organisms that lack RNA, although there are many viruses whose genome does not contain DNA. Also, contrary to the established dogma, which stated that the transfer of genetic information occurs in the direction from DNA to RNA and protein, it turned out to be possible to transfer information from RNA to DNA with the participation of an enzyme discovered in the early 1970s.

In the early 1980s. the ability of RNA to self-reproduce in the absence of protein enzymes was established, i.e. its autocatalytic function has been discovered. This explained all previously unsolved questions.

Thus, today it is believed that the protobiont was an RNA molecule. Ancient RNA was transport and combined the features of both phenotype and genotype. In other words, it could be subject to both genetic transformations and natural selection. It is already obvious that the process of evolution went from RNA to protein, and then to the formation of a DNA molecule in which the C-H bonds are stronger than the C-OH bonds of RNA.

It is obvious that the emergence of chirality, as well as primary RNA molecules, could not have occurred during smooth evolutionary development. Apparently, there was a jump with all the characteristic features of the self-organization of matter, the features of which were discussed above.

In the 1990s. A number of other versions have appeared, according to which life could have appeared in geothermal springs, on the seabed, in thin films of organic matter adsorbed on the surface of pyrite or apatite crystals. Their appearance is caused by some shortcomings of the theory of genobiosis, but they have not yet received sufficient justification and development.

Conclusion

The mystery of the appearance of life on Earth has worried people since time immemorial. Over the centuries, views on this problem have changed and a large number of very diverse hypotheses and theories have been put forward. Some of them became widespread and dominated in certain periods of the development of natural science. These types of theories of the origin of life include:

Creationism, which states that life was created by a supernatural being through an act of creation;

The steady state theory, according to which life has always existed;

The theory of spontaneous generation of life, based on the idea of the repeated emergence of life from nonliving matter;

The theory of panspermia, which states that life was brought to Earth from space;

The theory of biochemical evolution.

This diversity of views is due to the fact that it is impossible today to accurately reproduce or experimentally confirm the process of the origin of life. The noted theories are predominantly based on speculative ideas of both natural science researchers and researchers adhering to theological views.

Today there is no one clearly defined theory of the origin of life on Earth. Perhaps the continuous development of science will lead to some new completely unexpected discoveries.

Listusedliterature

1. Vernadsky V.I. Living matter. M.: Nauka, 1978.

2. Voitkevich G.V. The emergence and development of life on Earth. M., 1988.

3. Markov A.V. The birth of complexity. M.: Astrel, CORPUS, 2012.

4. Naydysh V.M. Concepts of modern natural science: Textbook. allowance. - M.: Gardariki, 2000.

5. Oparin A.I. The emergence of life on Earth. M.-L.: Publishing House of the USSR Academy of Sciences, 1941.

6. Oparin A.I. Life, its nature, origin and development. Institute of Biochemistry. - M.: USSR Academy of Sciences, 1968.

7. Oparin A.I. Modern views on the origin of life. M.: Pravda, 1947.

8. Origin of life. Science and faith (Science, Evolution, and Creationism). M.: Astrel, CORPUS, 2010.

9. Yanovskaya M.I. "Pasteur" / Series "Life of Remarkable People". - M.: Young Guard, 1960.

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Creationist concept

Creationism (from the Latin creaсio - creation) is a philosophical and methodological concept within the framework of which the entire diversity of the organic world, humanity, planet Earth, as well as the world as a whole, are considered as intentionally created by some superbeing (Creator) or deity. There is no scientific evidence for this point of view: in religion, truth is comprehended through divine revelation and faith. The process of creation of the world is thought of as having taken place only once and therefore inaccessible to observation.

The theory of creationism is adhered to by followers of almost all the most common religious teachings (especially Christians, Muslims, Jews). According to this theory, the origin of life refers to some specific supernatural event in the past that can be calculated. In 1650, Archbishop Ussher of Armagh (Ireland) calculated that God created the world in October 4004 BC. e. and finished his work on October 23 at 9 a.m., creating man. Asher obtained this date by adding up the ages of all the people mentioned in the Biblical genealogy, from Adam to Christ. From an arithmetic point of view, this makes sense, but it means that Adam lived at a time when, as archaeological finds show, a well-developed urban civilization already existed in the Middle East.

The traditional Judeo-Christian view of creation, as set out in the Book of Genesis, has been and continues to be controversial. However, existing contradictions do not refute the concept of creation. The creation hypothesis can neither be proven nor disproved and will always exist along with scientific hypotheses of the origin of life.

Theory of spontaneous generation (self-organization)

This theory of the origin of life on earth was common in ancient China, Babylon and Egypt as an alternative to creationism, with which it coexisted. Religious teachings of all times and all peoples usually attributed the appearance of life to one or another creative act of a deity. The first researchers of nature also resolved this issue very naively. Aristotle (384 – 322 BC), often hailed as the founder of biology, adhered to the theory of the spontaneous origin of life. Even for such an outstanding mind of antiquity as Aristotle, it was not particularly difficult to accept the idea that animals - worms, insects and even fish - could arise from silt. On the contrary, this philosopher argued that every dry body, becoming wet, and, conversely, every wet body, becoming dry, will give birth to animals.

According to Aristotle's hypothesis of spontaneous generation, certain "particles" of matter contain a certain "active principle" that, under suitable conditions, can create a living organism. Aristotle was right in believing that this active principle was contained in the fertilized egg, but he erroneously believed that it was also present in sunlight, mud and rotting meat.

A number of works dating back to the 16th and 17th centuries describe in detail the transformation of water, stones and other inanimate objects into reptiles, birds and animals. Grindel von Ach even gives a picture of frogs being formed from the May dew, and Aldrovand gives drawings showing how birds and insects are born from the branches and fruits of trees.

Already in 1688, the Italian biologist and physician Francesco Redi, who lived in Florence, approached the problem of the origin of life more strictly and questioned the theory of spontaneous generation. Dr. Redi, through simple experiments, proved the unfoundedness of opinions about the spontaneous generation of worms in rotting meat. He established that the small white worms are fly larvae. After conducting a series of experiments, he obtained data supporting the idea that life can only arise from previous life (the concept of biogenesis).

Thus, with regard to living beings visible to the naked eye, the assumption of spontaneous generation turned out to be untenable. But at the end of the 17th century. Kircher and Leeuwenhoek discovered a world of tiny creatures, invisible to the naked eye and visible only through a microscope. These “smallest living animals” (as Leeuwenhoek called the bacteria and ciliates he discovered) could be found wherever decay occurred, in long-standing decoctions and infusions of plants, in rotting meat, broth, in sour milk, in feces, in dental plaque One has only to place perishable and easily rotting substances in a warm place for a while, and microscopic living creatures that were not there before immediately develop in them. The idea arose that in rotting decoctions and infusions the spontaneous generation of living microbes from inanimate matter occurs. This idea was strongly confirmed in the experiments of the Scottish priest Needham, who took meat broth or decoctions of plant substances, placed them in tightly closed vessels and boiled them for a short time, according to Needham, all new embryos should die. they could not enter from the outside, since the vessels were tightly closed. However, after some time, microbes appeared in the liquids. From this the said scientist concluded that it is present during the phenomenon of spontaneous generation.

Another scientist, the Italian Spallanzani, opposed this opinion. Repeating Needham's experiments, he became convinced that longer heating of vessels containing organic liquids completely sterilizes them. In 1765, Lazzaro Spallanzani conducted the following experiment: after boiling meat and vegetable broths for several hours, he immediately sealed them and then removed them from the heat. Having examined the liquids a few days later, Spallanzani did not find any signs of life in them. From this he concluded that high temperatures destroyed all forms of living beings and that without them nothing living could arise.

A fierce dispute broke out between representatives of two opposing views. Spallanzani argued that the liquids in Needham's experiments were not sufficiently heated and embryos of living beings remained there. To this, Needham objected that it was not he who heated the liquids too little, but, on the contrary, Spallanzani heated them too much and with such a crude method destroyed the “generative power” of organic infusions, which is very capricious and fickle.

Louis Pasteur took up the problem of the origin of life in 1860. By this time, he had already done a lot in the field of microbiology and managed to solve problems that threatened sericulture and winemaking. He also proved that bacteria are ubiquitous and that non-living materials can easily be contaminated by living things if they are not properly sterilized. Through a series of experiments, he showed that everywhere, and especially near human habitation, tiny embryos are floating in the air. They are so light that they float freely in the air, only very slowly and gradually falling to the ground.

As a result of a series of experiments based on Splanzani's methods, Pasteur proved the validity of the theory of biogenesis and finally refuted the theory of spontaneous generation.

Pasteur explained the mysterious appearance of microorganisms in the experiments of previous researchers either by incomplete sterilization of the environment, or by insufficient protection of liquids from the penetration of germs. If you thoroughly boil the contents of the flask and then protect it from germs that could get in with the air flowing into the flask, then in one hundred cases out of a hundred, rotting of the liquid and the formation of microbes will not occur.

To dehydrate the air flowing into the flask, Pasteur used a variety of techniques: he either calcined the air in glass and metal tubes, or protected the neck of the flask with a cotton plug, in which all the smallest particles suspended in the air are retained, or, finally, he passed the air through a thin glass tube , curved in the shape of the letter S - in this case, all the embryos were mechanically retained on the wet surfaces of the bends of the tube.

Wherever the protection was sufficiently reliable, the appearance of microbes in the liquid was not observed. But maybe prolonged heating chemically changed the environment and made it unsuitable for supporting life? Pasteur easily refuted this objection too. He threw a cotton plug into the liquid, deprived of heat, through which air was passed and which, therefore, contained embryos - the liquid quickly rotted. Consequently, boiled infusions are quite suitable soil for the development of microbes. This development does not occur just because there is no embryo. As soon as the embryo enters the liquid, it immediately germinates and produces a lush harvest.

Pasteur's experiments showed beyond doubt that spontaneous generation of microbes does not occur in organic infusions. All living organisms develop from embryos, that is, they originate from other living beings. However, confirmation of the biogenesis theory gave rise to another problem. Since another living organism is necessary for the emergence of a living organism, then where did the very first living organism come from? Only the steady state theory does not require an answer to this question, and all other theories imply that at some stage in the history of life there was a transition from nonliving to living.

Panspermia theory

The theory of the origin of life on earth panspermia (Greek panspermía - a mixture of all kinds of seeds, from pán - all, everyone and spérma - seed) does not offer any mechanism to explain the initial emergence of life, but puts forward a theory about its non-terrestrial origin, therefore it cannot be considered theory of the origin of life, since it transfers the problem of origin to some other place in the universe. The theory convinces that life could have arisen one or more times at different times and in different parts of the galaxy or in the universe, multiple appearances of UFOs, rock art similar to rockets, astronauts and encounters with aliens are used to substantiate this theory. Russian and American followers in space believe that the formation of life within our solar system is negligible. However, they do not provide any information about the possibility of life in this system. Cyanide genes, hydrocyanic acid, and organic compounds were found in meteorites and comets - precursors of life, which may have played the role of seeds falling on the bare ground.

One of the first to express the idea of cosmic rudiments was in 1865 the German doctor G. E. Richter, who argued that life is eternal and its rudiments can be transferred from one planet to another. This hypothesis is closely related to the stationary state hypothesis. Based on the idea that small particles of solid matter (cosmozoans), separated from celestial bodies, are floating around everywhere in the cosmos, this author assumed that simultaneously with these particles, perhaps clinging to them, viable germs of microorganisms are flying around. Thus, these embryos can be transferred from one celestial body inhabited by organisms to another, where there is no life yet. If favorable living conditions have already been created on this latter, in the sense of suitable temperature and humidity, then the embryos begin to germinate, develop and subsequently become the ancestors of the entire organic world of a given planet.

This theory gained many supporters in the scientific world, among whom there were even such outstanding minds as G. Helmholtz, S. Arrhenius, J. Thomson, P. P. Lazarev and others. Its defenders sought mainly to scientifically substantiate the possibility of such a transfer embryos from one celestial body to another, which would preserve the viability of these embryos. Indeed, in fact, in the end, the main question is precisely whether a spore can make such a long and dangerous journey as flying from one world to another without dying, retaining the ability to germinate and develop into a new organism.

In the late 60s, the popularity of this theory resumed. This was due to the fact that during the study of meteorites and comets, many “precursors of living things” were discovered - organic compounds, hydrocyanic acid, water, formaldehyde, cyanogens. In 1975, amino acid precursors were found in lunar soil and meteorites. Proponents of panspermia consider them "seeds sown on Earth."

Modern adherents of the concept of panspermia (including Nobel Prize winner English biophysicist F. Crick) believe that life was brought to Earth either accidentally or intentionally by space aliens using aircraft. Proof of this is the repeated appearances of UFOs.

The panspermia hypothesis is supported by the point of view of astronomers Ch. Wickramasinghe (Sri Lanka) and F. Hoyle (Great Britain). They believe that microorganisms are present in large numbers in outer space, mainly in gas and dust clouds. Next, these microorganisms are captured by comets, which then, passing near the planets, “sow the germs of life.”

In general, interest in the theory of panspermia has not waned to this day.

Evolutionist concept

The first scientific theory regarding the origin of living organisms on Earth was created by the Soviet biochemist A. I. Oparin (born 1894). In 1924, he published works in which he outlined ideas about how life on Earth could have arisen. According to this theory, life arose in the specific conditions of the ancient Earth and is considered by Oparin as a natural result of the chemical evolution of carbon compounds in the Universe.

According to Oparin, the process that led to the emergence of life on Earth can be divided into three stages:

The emergence of organic substances.
Formation of biopolymers (proteins, nucleic acids, polysaccharides, lipids, etc.) from simpler organic substances.
The emergence of primitive self-reproducing organisms.

The theory of biochemical evolution has the largest number of supporters among modern scientists. The earth originated about five billion years ago; Initially, its surface temperature was very high (4000 – 80000C). As it cooled, a solid surface (the earth's crust - lithosphere) formed. The atmosphere, originally consisting of light gases (hydrogen, helium), could not be effectively contained by the insufficiently dense Earth, and these gases were replaced by heavier ones: water vapor, carbon dioxide, ammonia and methane. When the Earth's temperature dropped below 1000C, water vapor began to condense, forming the world's oceans. At this time, in accordance with the ideas of A.I. Oparin, abiogenic synthesis took place, that is, in the original earth’s oceans, saturated with various simple chemical compounds, “in the primary broth” under the influence of volcanic heat, lightning discharges, intense ultraviolet radiation and other factors environment began the synthesis of more complex organic compounds, and then biopolymers. The formation of organic substances was facilitated by the absence of living organisms - consumers of organic matter - and the main... oxidizing agent... -... oxygen. Complex amino acid molecules randomly combined into peptides, which in turn created the original proteins. From these proteins, primary living beings of microscopic size were synthesized.

The theory was justified, except for one problem, to which almost all experts in the field of the origin of life had long turned a blind eye. If spontaneously, through random template-free syntheses, single successful designs of protein molecules arose in the coacervate (for example, effective catalysts that provide an advantage for a given coacervate in growth and reproduction), then how could they be copied for distribution within the coacervate, and even more so for transmission to descendant coacervates? The theory turned out to be unable to offer a solution to the problem of exact reproduction - within a coacervate and in generations - of single, randomly appearing effective protein structures.

Recently, mathematical research has dealt a crushing blow to the hypothesis of abiogenic synthesis. Mathematicians have calculated that the probability of spontaneous generation of a living organism from lifeless blocks is practically zero. Thus, L. Blumenfeld proved that the probability of the random formation of at least one DNA molecule during the entire existence of the Earth is 1/10800. Contemporary American astrophysicist C. Wickramasinghe expressed the impossibility of abiogenic synthesis in the following way: “It’s faster for a hurricane that sweeps over an old airplane cemetery to assemble a brand new superliner from pieces of scrap than for life to emerge from its components as a result of a random process.”

The theories of abiogenic synthesis and geological data contradict. No matter how far we penetrate into the depths of geological history, we find no traces of the “Azoic era,” that is, the period when life did not exist on Earth.

The terrestrial form of life is extremely closely related to the hydrosphere. This is evidenced by the fact that water is the main part of the mass of any terrestrial organism (a person, for example, consists of more than 70% water, and organisms such as jellyfish - 97-98%). It is obvious that life on Earth formed only when the hydrosphere appeared on it, and this, according to geological data, happened almost from the beginning of the existence of our planet. Many of the properties of living organisms are determined precisely by the properties of water, but water itself is a phenomenal compound. Thus, according to P. Privalov, water is a cooperative system in which any action spreads in a “relay race” way over thousands of interatomic distances, that is, “long-range action” takes place.

Some scientists believe that the entire hydrosphere of the Earth is, in essence, one giant “molecule” of water. It has been established that water can be activated by natural electromagnetic fields of terrestrial and cosmic origin (in particular artificial). The recent discovery by French scientists of the “memory of water” was extremely interesting. Perhaps the fact that the Earth's biosphere is a single superorganism is due to these properties of water? After all, all organisms are components, “drops” of this supermolecule of earthly water.

Thus, there is now reason to assert that life on Earth appeared from the very beginning of its existence and arose, in the words of Ch. Wickramasinghe, “from an all-pervasive pan-galactic living system.”

Conclusion

Do we have a logical right to recognize the fundamental difference between living and nonliving? Are there facts in the nature around us that convince us that life exists forever and has so little in common with inanimate nature that under no circumstances could it ever be formed or separated from it? Can we recognize organisms as entities completely, fundamentally different from the rest of the world?

Biology of the XX century. deepened the understanding of the essential features of living things, revealing the molecular basis of life. The modern biological picture of the world is based on the idea that the living world is a grandiose System of highly organized systems.

Undoubtedly, new knowledge will be included in models of the origin of life, and it will become increasingly valid. But the more qualitatively the new differs from the old, the more difficult it is to explain its emergence.

After review main theories of the origin of life on Earth, the theory of creation seemed most likely to me personally. The Bible states that God created everything out of nothing. Surprisingly, modern science admits that everything could have been created out of nothing. “Nothing” in scientific terminology is called a vacuum. Vacuum, which is the physics of the 19th century. considered emptiness, according to modern scientific concepts it is a unique form of matter, capable of “giving birth” to material particles under certain conditions. Modern quantum mechanics allows that the vacuum can come into an “excited state”, as a result of which a field can form in it, and from it - matter.

Bibliography

Bernal D. The emergence of life Appendix No. 1: Oparin A.I. "The Origin of Life". - M.: "Mir", 1969.
Vernadsky V.I. The beginning and eternity of life. - M., 1989.
Naydysh V. M. Concepts of modern natural science. – M., 1999.
Oparin A. N. The emergence of life on earth. – M., 1957.
Ponnamperuma S. Origin of life. - M.: "Mir", 1977.
Smirnov I.N., Titov V.F. Philosophy. Textbook for students of higher educational institutions. - M.: Russian Economic Academy named after. Plekhanov, 1998.
Yablokov A.V., Yusufov A.G. Evolutionary doctrine. - M.: Higher School, 1988.

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The history of life on Earth hides many secrets. Whether they will ever be discovered will be determined by the future development of science.

We will limit ourselves to a cultural and historical consideration of all hypotheses of the origin of life on Earth. Within the framework of the natural science concept, we will pay special attention to constructive theoretical models of the theory of biochemical evolution.

Since biological time - age has an “arrow of time” directed from the past to the future and is described by the triad: birth - aging - death, the evolutionary idea arose already in mythology and was formed in ancient natural philosophy in theory of spontaneous generation life from inanimate matter, while multiple generation was assumed on the basis of naive transformism through a random combination of individual organs (Empedocles, 495-435 BC), a sudden transformation of species (Anaximenes, 384-322 BC). Aristotle (384-322 BC) formalized the theory of the spontaneous origin of life into a theory of the gradual development of living forms (from simple to complex), which intersects in the Middle Ages with the theory of creationism.

Creationism(creation, creation) - contains the thesis about the divine creation of the world and man. According to this theory, life is the result of supernatural events in the past. Many scientists in the aesthetics of thinking actually combine the evolutionary idea with creationism. It seems to us that the aesthetics of thinking of the Russian philosopher of the twentieth century Merab Mamardashvili is justified, leading to the intersection of sacred and secular thinking at the “meeting point with which we thought a thought that cannot be had by the will or desire of thought. It will be thought or not thought. And if we think about it, if we are at this point of intersection in the fullness of our collected being, it will not pass us by. Then we are worthy of this thought or, in other words, worthy of the gift. The gift does not flow from our merits, we are worthy of it only when it happens to us, and this is a path along an arc, and not horizontally, since we are linked and fused with the highest, superconscious.”

In the seventeenth century there arose biogenesis theory, which boils down to the statement that life can only arise from a previous life, i.e. “living from living.” It was formed by the Italian physician and biologist F. Redi and is known in the literature as the “Redi principle”. In 1862, the French biologist Louis Pasteur, with convincing experiments, proved the impossibility of spontaneous generation of the simplest organisms under modern conditions and established the principle “all living things come from living things.” The aesthetics of thinking of the founder of modern microbiology and immunology, L. Pasteur, clearly intersects with creationism in the following statement: “The more I study nature, the more I stand in awe of the works of the Creator. I pray while I’m working in the laboratory.”

The principle of complementarity of evolutionary ideas with creationism is also characteristic of the principle of development of Zh.B. Lamarck (1744-1829), who postulated the following principles: organisms are changeable; species (and other taxonomic categories) are provisional and are gradually transformed into new species; the general trend of historical changes in organisms is the gradual improvement of their organization (gradation), the driving force of which is the original (established by the Creator) nature’s desire for progress. Lamarckism is characterized by two complementary features: teleologism - as the inherent desire for improvement in organisms, organismcentrism - recognition of the organism as an elementary unit of evolution.

Charles Darwin (1809 - 1882), having generalized individual evolutionary ideas, created a coherent, detailed theory of evolution. He considered the driving forces of evolution to be hereditary variability and natural selection, and the organism of each species, i.e., actually individual individuals, as the elementary unit of evolution. Surviving individuals give rise to the next generation, and thus “successful” positive changes are passed on to subsequent generations. Very often, Charles Darwin's theory of natural selection is contrasted with creationism. However, let us turn to the aesthetics of thinking of Charles Darwin: “The world rests on patterns and in its manifestations appears as a product of the mind - this is an indication of its Creator.”

“God, truly dues ex machine, allows us to jump over the abyss between the living and the dead, nature and spirit, while preserving the abyss.” God (the Creator) is a complex, creative construct of our mind, demonstrating the ability of civilizing humanity to think abstractly. In the Middle Ages, the theory of creationism was formalized in confessional philosophical theologies and religions, which are based on the thesis: “God is known only through faith,” thereby religion separated faith in the divine creation of the world from science, i.e., from the scientific method of knowing the world, based on on a set of empirical and theoretical methods. At the same time, good and evil receive sacred sanction in religion and a person finds inner peace and light for work in our imperfect world. This is most clearly expressed in the following teaching by M.V. Lomonosov: “A mathematician is not sane if he wants to measure the Divine will with a compass. Such is the teacher of theology if he thinks that one can learn astronomy and chemistry from the Psalter.”

They tried to explain the appearance of life on Earth by introducing it from other cosmic worlds. In 1865, the German physician G. Richter put forward the hypothesis of cosmozoans (cosmic rudiments), according to which life is eternal and the rudiments inhabiting cosmic space can be transferred from one planet to another. Arose steady state theory, according to which life has always existed, based to a certain extent on the “Redi principle”. This hypothesis was supported by many scientists of the 19th century - W. Thompson, G. Helmholtz and others. The theory of the stationary state was shared to a certain extent by our great scientist V.I. Vernadsky, who believed that life on Earth appeared simultaneously with the appearance of the Earth.

The steady state theory in the Richter model intersects with panspermia theory, which was put forward by the famous Swedish naturalist S. Arrhenius in 1907: “The embryos of life eternally exist in the Universe, which move in outer space under the pressure of light rays; falling into the sphere of gravity of the planet, they settle on its surface and lay the beginning of life on this planet.” Structurally, the theoretical possibilities of panspermia are confirmed by a number of experiments: the detection of traces of organic compounds in meteorite and cometary substances, amino acid precursors in lunar soil, traces of microorganisms in a meteorite presumably of Martian origin. It is obvious that these discoveries of the second half of the 20th century will be expanded as man explores outer space.

However, within the framework of the natural science principle of global evolution, the theory of the stationary state is not productive, and the theory of panspermia also does not offer any mechanism to explain the primary origin of life; it simply transfers the problem of the origin of life to some other place in the Universe.

So, within the framework of the evolutionary “arrows of time”, based on the principle of complementarity, there remain two mutually exclusive, and possibly complementary, theories of creationism and theory of biochemical evolution. In our opinion, in the intersection of these theories, both belief in religious fanaticism and scientific absolutism seems unjustified. It seems to us that the feeling of “religious faith in the higher, superconscious and admiration” for the harmony of nature on Earth and in Space and the belief that in the “conceptual fund (as in the gene pool) of the Earth” all elements are significant and important is the basis not only of the spiritual, but and material culture of human civilization.

The anthropic principle, formulated in the 70s of the 20th century, speaks in favor of the non-random nature of the process of both the origin and development of life. Its essence lies in the fact that even a slight deviation in the value of any of the fundamental constants makes it impossible for highly ordered structures to appear in the Universe. For example, an increase in Planck's constant by 10% makes it impossible for a proton to combine with a neutron, that is, nucleosynthesis becomes impossible. A decrease in Planck's constant by 10% would lead to the formation of a stable 2 He nucleus, which would result in the burning of all hydrogen in the early stages of the expansion of the Universe, or the collapse of stars in later stages. Science has encountered a large group of facts, the separate consideration of which creates the impression of inexplicable coincidences bordering on a miracle. (in more detail: Barron J.D., Tipler F.J. The antropic cosmological principle, Oxford, 2nd., ed., 1986). According to the physicist J. Wheeler: “The life-giving factor lies at the center of the entire mechanism and constructs the world.”

At the same time, constructive theoretical models of biochemical evolution are based on the hypothesis that life arose as a result of processes that obey chemical and physical laws. Thus, we place, justifiably or not, the laws of physics and chemistry at the center of “the entire mechanism that constructs the world.”

The first three stages belong to the period of chemical evolution; from the fourth, biological evolution begins. The idea of chemical evolution has been confirmed by a number of experiments. The beginning of this work was laid in 1953 by S. Miller and G. Urey, who, under the influence of a spark charge on a gas mixture of methane and water vapor, obtained a set of small organic molecules, for the first time showing the possibility of abiogenic synthesis of organic compounds in systems simulating the expected composition the primary earth's atmosphere.

The complex processes of chemical evolution, which develop into biochemical and biological evolution, can be expressed in a simple sequence: atoms
simple molecules
complex macromolecules and ultramolecular systems (probionts)

unicellular organisms.

The first cells are considered the prototype of all living organisms of plants, animals, and bacteria.

However, in this physical and chemical construction of all living things, the anthropic principle is naturally present, i.e. belief in the non-random nature of the process of both the origin and development of life on Earth. In addition, the possibility of intersection of the theory of biochemical evolution of earthly matter with the theory of panspermia is not removed. The theory of biochemical evolution itself acquired a scientific character of theoretical construction of models, confirmed experimentally by the geochronological history of the Earth only in the 20th century after the discovery of the molecular genetic level of the biological level of matter and the emergence of evolutionary chemistry.

The theory of biochemical evolution is based on the concept of abiogenesis - the formation of organic compounds common in living nature outside the body, without the participation of enzymes.

All the numerous hypotheses that were put forward in the 60-80s of the 20th century had clearly expressed opposition on the issue of the characteristics of the protobiological system, i.e., the precellular ancestor. The problem was that between the chemical form of matter, which is not yet life, and the biological form of matter, which is already life, there is a prebiotic structure associated with the transition from physico-chemical evolution to biological. It was necessary to find some kind of precellular structure that could evolve so that it would be subject to genetic transformations and natural selection. As a result, two hypotheses emerged - coacervant and genetic.

The basis of the coacervant hypothesis is the assertion that the initial stages of biogenesis were associated with the formation of protein structures from the “primary ocean” due to coacervation - the spontaneous separation of an aqueous solution of polymers into phases with different concentrations. The main provisions of this hypothesis were first formulated by A.I. Oparin in 1924 (see: Oparin A.I. Life, its nature, origin and development. M., 1968). Selection as the main reason for the improvement of coacervants to primary living beings is the most important provision of Oparin’s hypothesis.

Within the framework of the coacervant hypothesis, a methodological principle arose, called holobiosis, i.e. the primacy of cellular-type structures endowed with the ability for elementary metabolism, including enzyme catalysis.

However, if we rely on equilibrium thermodynamics, then the molecules of living beings do not arise spontaneously; their formation requires a complex mechanism of continuous and coordinated action of a “heater” and a “cooler” in accordance with the second law of thermodynamics. The probability that a protein molecule consisting of 20 types of amino acids will be randomly formed according to a certain pattern is equal to

The number in the denominator is too large to be comprehended by the mind. “The probability, as the astronomer Freud Hoyle claims, is blatantly small, so small that it would be unthinkable even if the entire Universe consisted of an organic soup.” However, if we move to nonequilibrium thermodynamics, then the entropy of radiation S emission. much more entropy of matter S thing. (S izable >> S real), then the probability of formation of ordered structures from crystals to proteins and nucleic acids increases sharply.

However, for this Natural selection alone is unlikely to suffice, which is aimed at cleansing the gene pool of a population from “defective” genes, modification occurs only within the existing genetic material, as an adaptive response to environmental changes.

Comes to the fore genetic hypothesis, according to which nucleic acids first emerged as the matrix basis for protein synthesis. This hypothesis was first put forward in 1929 by the American geneticist G. Meller.

Within the framework of the genetic hypothesis, a methodological principle arose, called genobiosis, which asserts the primacy of the emergence as a result of biochemical evolution of a molecular system with the properties of a genetic code.

The idea of discrete splitting of genetic characteristics was added to natural selection, to a certain extent based on the basic position of quantum mechanics: “Everything: matter, energy, quantum characteristics of particles - act as discrete quantities, and none of them can be measured without changing it.” The genetic hypothesis connects the theory of biochemical evolution with global evolutionism, and the theory of the origin of life on Earth is associated with the belief in the existence of a “superrational, superintelligent” teleologism - as an inherent desire for improvement throughout the Universe up to the creation of a “reasonable observer”.

The genetic concept is now widely accepted as a result of discoveries made in the 1980s. It has been experimentally proven that simple nucleic acids can be reduplicated without enzymes. The ability of nucleic acids to serve as templates in the formation of complementary chains is the most convincing argument in favor of the idea of the leading importance in the process of biogenesis of the hereditary mechanism and, consequently, in favor of the genetic hypothesis of the origin of life.

By the early 1980s, it became clear that only ribonucleic acid (RNA) could be the primary nucleic acid.

In other words, it was the RNA molecule that could constitute the macromolecular substrate of the precellular ancestor. The decisive discovery regarding the role of the RNA molecule in the origin of life is as follows. Firstly, this is the establishment of the ability of RNA to self-reproduce in the absence of protein enzymes. Secondly, establishing the fact that one of the small RNA molecules (ribosine) itself has the functions of an enzyme. Finally, thirdly, it was found that RNA has autocatalytic properties.

Thus, we can assume that ancient RNA combined both functions: catalytic and information-genetic, which provided the possibility of self-reproduction of a macromolecular object. In other words, it met all the requirements of the mechanism of evolution in combining the theory of natural selection with the hereditary (genetic) discrete splitting of characters (allelic genes), and with the theory of linkage of non-allelic genes. This contributed to the subsequent evolution of the RNA-based macromolecular system into a more efficient DNA-based macromolecular system from the point of view of protein synthesis. In the process of such evolution, in most cases, a separation of information-genetic and catalytic functions occurred. Particular attention should be paid to the significant role of “right-left” dissymmetry of both nucleic acid and protein molecules, the origin of which has many hypotheses and has not yet been experimentally substantiated. It is possible that the emergence of such dissymmetry had as profound consequences for the origin of life as the emergence of baryon-antibaryon dissymmetry for the evolution of the Universe.

The problem is also is the time and place of action- Earth about 4.5 billion years ago- a unique arena for biochemical evolution. Or this process occurred and is occurring spontaneously and at the same time on the basis of “superrational, superintelligent” teleologism in various parts of outer space, and the Earth only provided favorable conditions for the development of life that had already arisen.

Moving to the ontogenetic (organismal) level of living nature, the structural feature of a living organism, since the 1940s, has been considered a cell - the factory of life. In other words, The cell is recognized as the lowest object of living nature, either as an independent unicellular organism or as an autonomous part of a multicellular organism. Precellular life forms - viruses - occupy an intermediate place between living and nonliving.

Only in the early 60s of the 20th century did the genetic concept of the cellular organization of living matter appear, which made it possible to discretely divide all living things into two superkingdoms - prokaryotes And eukaryotes. The most fundamental differences between the two types of organisms concern the nature of organization and replication at the genetic level; structure of the apparatus that synthesizes proteins; the nature of the “trigger” mechanisms of protein biosynthesis; structure of the RNA molecule; organization and nature of the photosynthetic apparatus, etc. However, neither prokaryotes nor eukaryotes have certain evolutionary advantages. This suggests that both of these types of organisms descend from a common ancestor, or archaecells, combining the features of prokaryotes and eukaryotes.

In the 1970s, this point of view received serious confirmation thanks to the discovery archaebacteria, which, being prokaryotes according to the type of organization of the genetic apparatus, have characteristics that bring them closer to eukaryotes. Most popular currently symbiotic a hypothesis according to which a eukaryotic cell is the result of a symbiosis of several prokaryotic cells.

An important concept of the functioning of living nature at the ontogenetic level is its functional system. According to this concept, functional systematicity is due to the fact that the components of systems not only interact, but also interact.

The concept of functional systematicity is universal at all structural levels of living nature. It is based on the interaction of mutational (genetically hereditary splitting of alternative characteristics (allelic genes) and linkage of non-allelic genes in the genetics of sex) selection with natural selection, when processes at lower levels are, as it were, organized by functional connections at higher levels, and partly by specialized regulatory apparatuses (homeostasis) , such as hormonal and primary systems in the animal body.

The concept of functional systematicity could appear at the molecular genetic level and in the form of a symbiosis of the methodological principles of holobiosis and genobiosis.

This approach to a certain extent eliminates the problem of the primacy of protein or DNA/RNA in the emergence of probionts. It is believed that life evolved based on the dynamic play of small molecules (organic and inorganic) and the first biopolymers may have been the result of autocatalytic reactions of small molecules in raindrops illuminated by the ultraviolet light of the primordial Sun. However, the problem arises of the ripening of these drops into coacervant drops in accordance with the Oparin scenario of the “primary broth” or into primary double-stranded RNA in accordance with the genetic hypothesis and their subsequent symbiosis into an archecell.

In our opinion, if we proceed from the proposal put forward by N.V. Timofeev-Resovsky’s axiom that the evolution of living nature is fundamentally unpredictable, then this axiom points to a rather difficult path for studying the origin of life on Earth and the anthropological study of human ancestry, which, in our opinion, leads to the intersection of at least three theories (concepts) , namely the natural science concept of biochemical evolution with the concepts of panspermia and creationism based on the anthropic principle and the principle of global evolutionism.

The science

According to scientists, life on earth began about 3 billion years ago: During this time, simple organisms developed into complex life forms. However, it is still a mystery to scientists how life began on the planet, and they have put forward several theories to explain this phenomenon:

1. Electric sparks

In the famous Miller-Urey Experiment, scientists proved that lightning could contribute to the emergence of the basic substances necessary for the origin of life: electrical sparks form amino acids in an atmosphere consisting of huge quantities of water, methane, ammonia and hydrogen. More complex life forms then evolved from amino acids. This theory was changed somewhat after researchers discovered that the planet's atmosphere billions of years ago was poor in hydrogen. Scientists suggested that methane, ammonia and hydrogen were contained in volcanic clouds saturated with electrical charges.

2. Clay

Chemist Alexander Graham Cairns-Smith from the University of Glasgow, Scotland, put forward the theory that at the dawn of life, clay contained many organic components located close to each other, and that the clay helped organize these substances into structures similar to our genes.

DNA stores information about the structure of molecules, and DNA's genetic sequences indicate how amino acids should be built into proteins. Cairns-Smith suggests that clay crystals helped organize organic molecules into ordered structures, and later the molecules themselves began to do this, “without the help” of clay.

3. Deep sea vents

According to this theory, life began in underwater hydrothermal vents that spewed out hydrogen-rich molecules. On their rocky surface, these molecules could come together and become mineral catalysts for the reactions that led to the origin of life. Even now, such hydrothermal vents, rich in chemical and thermal energy, are home to quite a large number of living creatures.

4. Icy start

3 billion years ago, the Sun did not shine as brightly as it does now, and, accordingly, less heat reached the Earth. It is quite possible that the surface of the earth was covered with a thick layer of ice, which protected fragile organic matter, located in the water underneath, from ultraviolet rays and cosmic exposure. In addition, the cold helped the molecules to exist longer, as a result of which the reactions that led to the origin of life became possible.

5. RNA world

DNA needs proteins to form, and proteins need DNA to form. How could they have formed without each other? Scientists suggested that RNA, which, like DNA, stores information, was involved in this process. From RNA, proteins and DNA were formed, respectively., which replaced it due to their greater efficiency.

Another question arose: “How did RNA appear?” Some believe that it spontaneously appeared on the planet, while others deny this possibility.

6. "Simple" theory

Some scientists have suggested that life evolved not from complex molecules like RNA, but from simple ones that interacted with each other. They may have been contained in simple shells similar to cell membranes. As a result of the interaction of these simple molecules, complex, which reacted more efficiently.

7. Panspermia

In the end, life could not have originated on our planet, but was brought from space: In science this phenomenon is called panspermia. This theory has a very solid basis: due to cosmic influences, fragments of stones are periodically separated from Mars, which reach the Earth. After scientists discovered Martian meteorites on our planet, they assumed that these objects brought bacteria with them. If you believe them, then we are all martians. Other researchers have suggested that life was brought by comets from other star systems. Even if they are right, humanity will look for an answer to another question: “How did life originate in space?”

The question of when life appeared on Earth has always worried not only scientists, but also all people. Answers to it

almost all religions. Although there is still no exact scientific answer to this question, some facts allow us to make more or less reasonable hypotheses. Researchers have found a rock sample in Greenland

with a tiny splash of carbon. The age of the sample is more than 3.8 billion years. The source of carbon was most likely some kind of organic matter - during this time it completely lost its structure. Scientists believe this lump of carbon may be the oldest trace of life on Earth.

What did the primitive Earth look like?

Let's fast forward to 4 billion years ago. The atmosphere does not contain free oxygen; it is found only in oxides. Almost no sounds except the whistle of the wind, the hiss of water erupting with lava and the impacts of meteorites on the surface of the Earth. No plants, no animals, no bacteria. Maybe this is what the Earth looked like when life appeared on it? Although this problem has long been of concern to many researchers, their opinions on this matter vary greatly. Rocks could indicate the conditions on Earth at that time, but they were destroyed long ago as a result of geological processes and movements of the earth's crust.

In this article we will briefly talk about several hypotheses for the origin of life, reflecting modern scientific ideas. According to Stanley Miller, a well-known expert in the field of the origin of life, we can talk about the origin of life and the beginning of its evolution from the moment when organic molecules self-organized into structures that were able to reproduce themselves. But this raises other questions: how did these molecules arise; why they could reproduce themselves and assemble into those structures that gave rise to living organisms; what conditions are needed for this?

According to one hypothesis, life began in a piece of ice. Although many scientists believe that carbon dioxide in the atmosphere maintained greenhouse conditions, others believe that winter reigned on Earth. At low temperatures, all chemical compounds are more stable and can therefore accumulate in larger quantities than at high temperatures. Meteorite fragments brought from space, emissions from hydrothermal vents, and chemical reactions occurring during electrical discharges in the atmosphere were sources of ammonia and organic compounds such as formaldehyde and cyanide. Getting into the water of the World Ocean, they froze along with it. In the ice column, molecules of organic substances came close together and entered into interactions that led to the formation of glycine and other amino acids. The ocean was covered with ice, which protected the newly formed compounds from destruction by ultraviolet radiation. This icy world could melt, for example, if a huge meteorite fell on the planet (Fig. 1).

Charles Darwin and his contemporaries believed that life could have arisen in a body of water. Many scientists still adhere to this point of view. In a closed and relatively small reservoir, organic substances brought by the waters flowing into it could accumulate in the required quantities. These compounds were then further concentrated on the inner surfaces of layered minerals, which could catalyze the reactions. For example, two molecules of phosphaldehyde that met on the surface of a mineral reacted with each other to form a phosphorylated carbohydrate molecule, a possible precursor to ribonucleic acid (Fig. 2).

Or maybe life arose in areas of volcanic activity? Immediately after its formation, the Earth was a fire-breathing ball of magma. During volcanic eruptions and with gases released from molten magma, a variety of chemicals necessary for the synthesis of organic molecules were carried to the earth's surface. Thus, carbon monoxide molecules, once on the surface of the mineral pyrite, which has catalytic properties, could react with compounds that had methyl groups and form acetic acid, from which other organic compounds were then synthesized (Fig. 3).

For the first time, the American scientist Stanley Miller managed to obtain organic molecules - amino acids - in laboratory conditions simulating those that were on the primitive Earth in 1952. Then these experiments became a sensation, and their author gained worldwide fame. He currently continues to conduct research in the field of prebiotic (before life) chemistry at the University of California. The installation on which the first experiment was carried out was a system of flasks, in one of which it was possible to obtain a powerful electric discharge at a voltage of 100,000 V.

Miller filled this flask with natural gases - methane, hydrogen and ammonia, which were present in the atmosphere of the primitive Earth. The flask below contained a small amount of water, simulating the ocean. The electric discharge was close to lightning in strength, and Miller expected that under its action chemical compounds were formed, which, when they got into the water, would react with each other and form more complex molecules.

The result exceeded all expectations. After turning off the installation in the evening and returning the next morning, Miller discovered that the water in the flask had acquired a yellowish color. What emerged was a soup of amino acids, the building blocks of proteins. Thus, this experiment showed how easily the primary ingredients of life could be formed. All that was needed was a mixture of gases, a small ocean and a little lightning.

Other scientists are inclined to believe that the ancient atmosphere of the Earth was different from the one that Miller modeled, and most likely consisted of carbon dioxide and nitrogen. Using this gas mixture and Miller's experimental setup, chemists attempted to produce organic compounds. However, their concentration in water was as insignificant as if a drop of food coloring were dissolved in a swimming pool. Naturally, it is difficult to imagine how life could arise in such a dilute solution.

If indeed the contribution of earthly processes to the creation of reserves of primary organic matter was so insignificant, then where did it even come from? Maybe from space? Asteroids, comets, meteorites and even particles of interplanetary dust could carry organic compounds, including amino acids. These extraterrestrial objects could provide sufficient amounts of organic compounds for the origin of life to enter the primordial ocean or small body of water.

The sequence and time interval of events, starting from the formation of primary organic matter and ending with the appearance of life as such, remains and, probably, will forever remain a mystery that worries many researchers, as well as the question of what. in fact, consider it life.

Currently, there are several scientific definitions of life, but all of them are not accurate. Some of them are so wide that inanimate objects such as fire or mineral crystals fall under them. Others are too narrow, and according to them, mules that do not give birth to offspring are not recognized as living.

One of the most successful defines life as a self-sustaining chemical system capable of behaving in accordance with the laws of Darwinian evolution. This means that, firstly, a group of living individuals must produce descendants similar to themselves, which inherit the characteristics of their parents. Secondly, in generations of descendants the consequences of mutations must manifest themselves - genetic changes that are inherited by subsequent generations and cause population variability. And thirdly, it is necessary for a system of natural selection to operate, as a result of which some individuals gain an advantage over others and survive in changed conditions, producing offspring.

What elements of the system were necessary for it to have the characteristics of a living organism? A large number of biochemists and molecular biologists believe that RNA molecules had the necessary properties. RNA - ribonucleic acids - are special molecules. Some of them can replicate, mutate, thus transmitting information, and, therefore, they could participate in natural selection. True, they are not capable of catalyzing the replication process themselves, although scientists hope that in the near future an RNA fragment with such a function will be found. Other RNA molecules are involved in “reading” genetic information and transferring it to ribosomes, where the synthesis of protein molecules occurs, in which the third type of RNA molecules takes part.

Thus, the most primitive living system could be represented by RNA molecules duplicating, undergoing mutations and being subject to natural selection. In the course of evolution, based on RNA, specialized DNA molecules arose - the custodians of genetic information - and no less specialized protein molecules, which took on the functions of catalysts for the synthesis of all currently known biological molecules.

At some point in time, a “living system” of DNA, RNA and protein found shelter inside a sac formed by a lipid membrane, and this structure, more protected from external influences, served as the prototype of the very first cells that gave rise to the three main branches of life, which are represented in the modern world by bacteria , archaea and eukaryotes. As for the date and sequence of appearance of such primary cells, this remains a mystery. In addition, according to simple probabilistic estimates, there is not enough time for the evolutionary transition from organic molecules to the first organisms - the first simplest organisms appeared too suddenly.

For many years, scientists believed that it was unlikely that life could have emerged and developed during the period when the Earth was constantly subject to collisions with large comets and meteorites, a period that ended approximately 3.8 billion years ago. However, recently, traces of complex cellular structures dating back at least 3.86 billion years have been discovered in the oldest sedimentary rocks on Earth, found in southwestern Greenland. This means that the first forms of life could have arisen millions of years before the bombardment of our planet by large cosmic bodies stopped. But then a completely different scenario is possible (Fig. 4).

Space objects falling to Earth could have played a central role in the emergence of life on our planet, since, according to a number of researchers, cells similar to bacteria could have arisen on another planet and then reached Earth along with asteroids. One piece of evidence supporting the theory of extraterrestrial origins of life was found inside a meteorite shaped like a potato and named ALH84001. This meteorite was originally a piece of Martian crust, which was then thrown into space as a result of an explosion when a huge asteroid collided with the surface of Mars, which occurred about 16 million years ago. And 13 thousand years ago, after a long journey within the solar system, this fragment of Martian rock in the form of a meteorite landed in Antarctica, where it was recently discovered. A detailed study of the meteorite revealed rod-shaped structures resembling fossilized bacteria inside it, which gave rise to heated scientific debate about the possibility of life deep in the Martian crust. It will be possible to resolve these disputes no earlier than 2005, when the US National Aeronautics and Space Administration will implement a program to fly an interplanetary spacecraft to Mars to take samples of the Martian crust and deliver samples to Earth. And if scientists manage to prove that microorganisms once inhabited Mars, then we can speak with a greater degree of confidence about the extraterrestrial origin of life and the possibility of life being brought from outer space (Fig. 5).

Rice. 5. Our origin is from microbes.

What have we inherited from ancient life forms? The comparison below of single-celled organisms with human cells reveals many similarities.

1. Sexual reproduction
Two specialized algae reproductive cells - gametes - mate to form a cell that carries genetic material from both parents. This is remarkably reminiscent of the fertilization of a human egg by a sperm.

2. Eyelashes
Thin cilia on the surface of a single-celled paramecium sway like tiny oars and provide it with movement in search of food. Similar cilia line the human respiratory tract, secrete mucus and trap foreign particles.

3. Capture other cells
The amoeba absorbs food, surrounding it with a pseudopodia, which is formed by the extension and elongation of part of the cell. In an animal or human body, amoeboid blood cells similarly extend a pseudopodia to engulf a dangerous bacterium. This process is called phagocytosis.

4. Mitochondria
The first eukaryotic cells arose when an amoeba captured prokaryotic cells of aerobic bacteria, which developed into mitochondria. And although bacteria and mitochondria of a cell (pancreas) are not very similar, they have one function - to produce energy through the oxidation of food.

5. Flagella
The long flagellum of a human sperm allows it to move at high speed. Bacteria and simple eukaryotes also have flagella with a similar internal structure. It consists of a pair of microtubules surrounded by nine others.

The evolution of life on Earth: from simple to complex

At present, and probably in the future, science will not be able to answer the question of what the very first organism that appeared on Earth looked like - the ancestor from which the three main branches of the tree of life originated. One of the branches is eukaryotes, whose cells have a formed nucleus containing genetic material and specialized organelles: energy-producing mitochondria, vacuoles, etc. Eukaryotic organisms include algae, fungi, plants, animals and humans.

The second branch is bacteria - prokaryotic (prenuclear) single-celled organisms that do not have a pronounced nucleus and organelles. And finally, the third branch is single-celled organisms called archaea, or archaebacteria, whose cells have the same structure as prokaryotes, but a completely different chemical structure of lipids.

Many archaebacteria are able to survive in extremely unfavorable environmental conditions. Some of them are thermophiles and live only in hot springs with temperatures of 90 ° C or even higher, where other organisms would simply die. Feeling great in such conditions, these single-celled organisms consume iron and sulfur-containing substances, as well as a number of chemical compounds that are toxic to other life forms. According to scientists, the thermophilic archaebacteria found are extremely primitive organisms and, in evolutionary terms, close relatives of the most ancient forms of life on Earth.

It is interesting that modern representatives of all three branches of life, most similar to their ancestors, still live in places with high temperatures. Based on this, some scientists are inclined to believe that, most likely, life arose about 4 billion years ago on the ocean floor near hot springs, erupting streams rich in metals and high-energy substances. Interacting with each other and with the water of the then sterile ocean, entering into a wide variety of chemical reactions, these compounds gave rise to fundamentally new molecules. So, for tens of millions of years, the greatest dish - life - was prepared in this “chemical kitchen”. And about 4.5 billion years ago, single-celled organisms appeared on Earth, whose lonely existence continued throughout the Precambrian period.

The burst of evolution that gave rise to multicellular organisms occurred much later, a little over half a billion years ago. Although microorganisms are so small that a single drop of water can contain billions, the scale of their work is enormous.

It is believed that initially there was no free oxygen in the earth’s atmosphere and the oceans, and under these conditions only anaerobic microorganisms lived and developed. A special step in the evolution of living things was the emergence of photosynthetic bacteria, which, using light energy, converted carbon dioxide into carbohydrate compounds that served as food for other microorganisms. If the first photosynthetics produced methane or hydrogen sulfide, then the mutants that appeared once began to produce oxygen during photosynthesis. As oxygen accumulated in the atmosphere and waters, anaerobic bacteria, for which it is harmful, occupied oxygen-free niches.

Ancient fossils found in Australia dating back 3.46 billion years have revealed structures believed to be the remains of cyanobacteria, the first photosynthetic microorganisms. The former dominance of anaerobic microorganisms and cyanobacteria is evidenced by stromatolites found in shallow coastal waters of unpolluted salt water bodies. In shape they resemble large boulders and represent an interesting community of microorganisms living in the limestone or dolomite rocks formed as a result of their life activity. At a depth of several centimeters from the surface, stromatolites are saturated with microorganisms: photosynthetic cyanobacteria that produce oxygen live in the uppermost layer; deeper bacteria are found that are to a certain extent tolerant of oxygen and do not require light; in the lower layer there are bacteria that can only live in the absence of oxygen. Located in different layers, these microorganisms form a system united by complex relationships between them, including food relationships. Behind the microbial film is a rock formed as a result of the interaction of the remains of dead microorganisms with calcium carbonate dissolved in water. Scientists believe that when there were no continents on the primitive Earth and only archipelagos of volcanoes rose above the surface of the ocean, the shallow waters were replete with stromatolites.

As a result of the activity of photosynthetic cyanobacteria, oxygen appeared in the ocean, and approximately 1 billion years after that, it began to accumulate in the atmosphere. First, the resulting oxygen interacted with iron dissolved in water, which led to the appearance of iron oxides, which gradually precipitated at the bottom. Thus, over millions of years, with the participation of microorganisms, huge deposits of iron ore arose, from which steel is smelted today.

Then, when the bulk of the iron in the oceans was oxidized and could no longer bind oxygen, it escaped into the atmosphere in gaseous form.

After photosynthetic cyanobacteria created a certain supply of energy-rich organic matter from carbon dioxide and enriched the earth's atmosphere with oxygen, new bacteria arose - aerobes, which can exist only in the presence of oxygen. They need oxygen for the oxidation (combustion) of organic compounds, and a significant part of the resulting energy is converted into a biologically available form - adenosine triphosphate (ATP). This process is energetically very favorable: anaerobic bacteria, when decomposing one molecule of glucose, receive only 2 molecules of ATP, and aerobic bacteria that use oxygen receive 36 molecules of ATP.

With the advent of oxygen sufficient for an aerobic lifestyle, eukaryotic cells also made their debut, which, unlike bacteria, have a nucleus and organelles such as mitochondria, lysosomes, and in algae and higher plants - chloroplasts, where photosynthetic reactions take place. There is an interesting and well-founded hypothesis regarding the emergence and development of eukaryotes, expressed almost 30 years ago by the American researcher L. Margulis. According to this hypothesis, the mitochondria that function as energy factories in the eukaryotic cell are aerobic bacteria, and the chloroplasts of plant cells in which photosynthesis occurs are cyanobacteria, probably absorbed about 2 billion years ago by primitive amoebae. As a result of mutually beneficial interactions, the absorbed bacteria became internal symbionts and formed a stable system with the cell that absorbed them - a eukaryotic cell.

Studies of fossil remains of organisms in rocks of different geological ages have shown that for hundreds of millions of years after their origin, eukaryotic life forms were represented by microscopic spherical single-celled organisms such as yeast, and their evolutionary development proceeded at a very slow pace. But a little over 1 billion years ago, many new species of eukaryotes emerged, marking a dramatic leap in the evolution of life.

First of all, this was due to the emergence of sexual reproduction. And if bacteria and single-celled eukaryotes reproduced by producing genetically identical copies of themselves and without the need for a sexual partner, then sexual reproduction in more highly organized eukaryotic organisms occurs as follows. Two haploid sex cells of the parents, having a single set of chromosomes, fuse to form a zygote that has a double set of chromosomes with the genes of both partners, which creates opportunities for new gene combinations. The emergence of sexual reproduction led to the emergence of new organisms, which entered the arena of evolution.

Three quarters of the entire existence of life on Earth was represented exclusively by microorganisms, until a qualitative leap in evolution occurred, leading to the emergence of highly organized organisms, including humans. Let's trace the main milestones in the history of life on Earth in a descending line.

1.2 billion years ago there was an explosion of evolution, caused by the advent of sexual reproduction and marked by the appearance of highly organized life forms - plants and animals.

The formation of new variations in the mixed genotype that arises during sexual reproduction manifested itself in the form of biodiversity of new life forms.

2 billion years ago, complex eukaryotic cells appeared when single-celled organisms complicated their structure by absorbing other prokaryotic cells. Some of them - aerobic bacteria - turned into mitochondria - energy stations for oxygen respiration. Others - photosynthetic bacteria - began to carry out photosynthesis inside the host cell and became chloroplasts in algae and plant cells. Eukaryotic cells, having these organelles and a clearly distinct nucleus containing genetic material, make up all modern complex life forms - from molds to humans.

3.9 billion years ago, single-celled organisms appeared that probably looked like modern bacteria and archaebacteria. Both ancient and modern prokaryotic cells have a relatively simple structure: they do not have a formed nucleus and specialized organelles, their jelly-like cytoplasm contains DNA macromolecules - carriers of genetic information, and ribosomes on which protein synthesis occurs, and energy is produced on the cytoplasmic membrane surrounding cell.

4 billion years ago, RNA mysteriously emerged. It is possible that it was formed from simpler organic molecules that appeared on the primitive earth. It is believed that ancient RNA molecules had the functions of carriers of genetic information and protein catalysts, they were capable of replication (self-duplication), mutated and were subject to natural selection. In modern cells, RNA does not have or does not exhibit these properties, but plays a very important role as an intermediary in the transfer of genetic information from DNA to ribosomes, in which protein synthesis occurs.

A.L. Prokhorov
Based on an article by Richard Monasterski
in National Geographic magazine, 1998 No. 3