Life can only originate in liquid water. Life in the Earth

The origin of life on Earth is one of the most difficult and at the same time relevant and interest Ask in modern natural science.

Earth probably formed 4.5-5 billion years ago from a giant cloud space dust. particles of which are compressed into a hot ball. Water vapor was released from it into the atmosphere, and water fell from the atmosphere onto the slowly cooling Earth over millions of years in the form of rain. In the recesses of the earth's surface, the prehistoric Ocean was formed. In it, about 3.8 billion years ago, the original life was born.

Origin of life on earth

How did the planet itself come about and how did the seas appear on it? There is one widely accepted theory about this. In accordance with it, the Earth was formed from clouds of cosmic dust containing all known in nature chemical elements, which are compressed into a ball. Hot water vapor escaped from the surface of this red-hot ball, enveloping it in a continuous cloud cover. The water vapor in the clouds slowly cooled and turned into water, which fell in the form of abundant continuous rains on the still hot, burning Earth. On its surface, it again turned into water vapor and returned to the atmosphere. Over millions of years, the Earth gradually lost so much heat that its liquid surface began to harden as it cooled. This is how the earth's crust was formed.

Millions of years have passed, and the temperature of the Earth's surface has dropped even more. Storm water stopped evaporating and began to flow into huge puddles. Thus began the effect of water on earth's surface. And then, because of the drop in temperature, there was a real flood. Water that previously evaporated into the atmosphere and turned into its constituent part, continuously rushed down to the Earth, powerful showers fell from the clouds with thunder and lightning.

Little by little, in the deepest depressions of the earth's surface, water accumulated, which no longer had time to completely evaporate. There was so much of it that gradually a prehistoric Ocean was formed on the planet. Lightning cut the sky. But no one saw it. There was no life on Earth yet. The continuous downpour began to wash away the mountains. Water flowed from them in noisy streams and stormy rivers. Over millions of years, water flows have deeply corroded the earth's surface and in some places valleys have appeared. The content of water in the atmosphere decreased, and more and more accumulated on the surface of the planet.

The continuous cloud cover became thinner, until one day the first ray of the sun touched the Earth. The continuous rain is over. Most land covered prehistoric Ocean. From its upper layers, water washed out a huge amount of soluble minerals and salts that fell into the sea. Water from it continuously evaporated, forming clouds, and the salts settled, and over time there was a gradual salinization of sea water. Apparently, under some conditions that existed in antiquity, substances were formed from which special crystalline forms arose. They grew, like all crystals, and gave rise to new crystals, which attached more and more new substances to themselves.

Sunlight and possibly very strong electrical discharges served as a source of energy in this process. Perhaps the first inhabitants of the Earth were born from such elements - prokaryotes, organisms without a formed nucleus, similar to modern bacteria. They were anaerobes, that is, they did not use free oxygen for respiration, which was not yet in the atmosphere at that time. They served as a source of food organic compounds that arose on the still lifeless Earth as a result of exposure to ultraviolet radiation from the Sun, lightning discharges and heat from volcanic eruptions.

Life then existed in a thin bacterial film at the bottom of reservoirs and in humid places. This era of the development of life is called the Archean. From bacteria, and possibly in a completely independent way, tiny unicellular organisms also arose - the oldest protozoa.

What did the primitive earth look like?

Fast forward to 4 billion years ago. The atmosphere does not contain free oxygen, it is only in the composition of oxides. Almost no sounds, except for the whistle of the wind, the hiss of water erupting with lava and 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 been of concern to many researchers for a long time, their opinions on this matter differ greatly. The conditions on the Earth of that time could be evidenced by rocks, but they have long been destroyed as a result of geological processes and movements of the earth's crust.

Theories about the origin of life on Earth

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

There are several theories about the origin of life on Earth. For example, one of the long-standing hypotheses says that it was brought to Earth from space, but there is no conclusive evidence for this. In addition, the life that we know is surprisingly adapted to exist precisely in earthly conditions, so if it originated outside the Earth, then on the planet earth type. Most modern scientists believe that life originated on Earth, in its seas.

Theory of biogenesis

In the development of the doctrines of the origin of life, an important place is occupied by the theory of biogenesis - the origin of the living only from the living. But many consider it untenable, since it fundamentally opposes the living to the inanimate and affirms the idea of the eternity of life rejected by science. Abiogenesis - the idea of the origin of living things from non-living things - the initial hypothesis modern theory origin of life. In 1924, the famous biochemist A. I. Oparin suggested that with powerful electrical discharges in earth's atmosphere, which 4-4.5 billion years ago consisted of ammonia, methane, carbon dioxide and water vapor, the simplest organic compounds necessary for the emergence of life could arise. Academician Oparin's prediction came true. In 1955 American explorer S. Miller, passing electric charges through a mixture of gases and vapors, received the simplest fatty acid, urea, acetic and formic acid and a few amino acids. Thus, in the middle of the 20th century, the abiogenic synthesis of protein-like and other organic substances was experimentally carried out under conditions reproducing the conditions of the primitive Earth.

Panspermia theory

The theory of panspermia is the possibility of transferring organic compounds, spores of microorganisms from one cosmic body to another. But it does not at all give an answer to the question, how did life originate in the Universe? There is a need to justify the emergence of life at that point in the Universe, the age of which, according to the theory big bang, is limited to 12-14 billion years. Until now, there hasn't even been elementary particles. And if there are no nuclei and electrons, there is no chemical substances. Then, within a few minutes, protons, neutrons, electrons arose, and matter entered the path of evolution.

Multiple sightings of UFOs, rock carvings of things that look like rockets and "cosmonauts", as well as reports of alleged encounters with aliens are used to substantiate this theory. When studying the materials of meteorites and comets, many "precursors of life" were found in them - substances such as cyanogens, hydrocyanic acid and organic compounds, which may have played the role of "seeds" that fell on the bare Earth.

Supporters of this hypothesis were laureates Nobel Prize F. Creek, L. Orgel. F. Crick based on two indirect evidence: universality genetic code: necessary for the normal metabolism of all living beings of molybdenum, which is now extremely rare on the planet.

The origin of life on Earth is impossible without meteorites and comets

Researcher at Texas Tech University, after analyzing a huge volume collected information, put forward a theory of how life could form on Earth. The scientist is sure that the appearance of early forms the simplest life on our planet would be impossible without the participation of comets and meteorites that fell on it. The researcher shared his work at the 125th annual meeting of the Geological Society of America, held on October 31 in Denver, Colorado.

Author of the work, professor of geoscience at the Texas technological university(TTU) and curator of the museum of paleontology at the university, Sankar Chatterjee said that he came to this conclusion after analyzing information about the early geological history our planet and comparing these data with various theories chemical evolution.

The expert believes that this approach allows us to explain one of the most hidden and not fully understood periods in the history of our planet. According to many geologists, the bulk of space "bombardments" in which comets and meteorites participated occurred at a time of about 4 billion years ago. Chatterjee believes that the earliest life on Earth formed in craters left by impacts of meteorites and comets. And most likely this happened during the Late Heavy Bombardment (3.8-4.1 billion years ago), when the collision of small space objects with our planet has increased dramatically. At that time, there were several thousand cases of comets falling at once. Interestingly, this theory is indirectly supported by the Nice Model. According to it, the real number of comets and meteorites that should have fallen to the Earth at that time corresponds to the real number of craters on the Moon, which in turn was a kind of shield for our planet and did not allow the endless bombardment to destroy it.

Some scientists suggest that the result of this bombardment is the colonization of life in the oceans of the Earth. At the same time, several studies on this topic indicate that our planet has more inventory water than it should. And this surplus is attributed to comets that flew to us from the Oort Cloud, presumably located in one light year from U.S.

Chatterjee points out that the craters formed by these collisions were filled with melted water from the comets themselves, as well as the necessary chemical building blocks necessary for the formation of the simplest organisms. At the same time, the scientist believes that those places where life did not appear even after such a bombardment simply turned out to be unsuitable for this.

“When the Earth formed about 4.5 billion years ago, it was completely unsuitable for the appearance of living organisms on it. It was a real boiling cauldron of volcanoes, poisonous hot gas and meteorites constantly falling on it, ”writes the online journal AstroBiology, referring to the scientist.

“And after one billion years, it became a quiet and calm planet, rich in huge reserves of water, inhabited by various representatives microbial life - the ancestors of all living things."

Life on Earth could have originated from clay

A group of scientists led by Dan Luo from Cornell University came up with a hypothesis that ordinary clay could serve as a concentrator for the most ancient biomolecules.

Initially, the researchers were not concerned with the problem of the origin of life - they were looking for a way to increase the efficiency of cell-free protein synthesis systems. Instead of letting DNA and its supporting proteins float freely in the reaction mixture, the scientists tried to force them into hydrogel particles. This hydrogel, like a sponge, absorbed the reaction mixture, sorbed the necessary molecules, and as a result, all the necessary components were locked in a small volume - just as it happens in a cell.

The authors of the study then tried to use clay as an inexpensive substitute for hydrogel. Clay particles turned out to be similar to hydrogel particles, becoming a kind of microreactors for interacting biomolecules.

Having received such results, scientists could not help but recall the problem of the origin of life. Clay particles, with their ability to sorb biomolecules, could actually serve as the very first bioreactors for the very first biomolecules before they had membranes. This hypothesis is also supported by the fact that the leaching of silicates and other minerals from rocks with the formation of clay began, according to geological estimates, just before, according to biologists, the most ancient biomolecules began to combine into protocells.

In water, or rather in solution, little could happen, because the processes in solution are absolutely chaotic, and all compounds are very unstable. Clay modern science- more precisely, the surface of particles of clay minerals - is considered as a matrix on which primary polymers could form. But this is also only one of many hypotheses, each of which has its own strengths and weak sides. But in order to simulate the origin of life on a full scale, one must really be God. Although in the West today there are already articles with the titles "Cell Construction" or "Cell Modeling". For example, one of the last Nobel laureates, James Szostak, is now actively trying to create effective cell models that reproduce on their own, reproducing their own kind.

Water is integral part bodies of living beings. Blood, muscles, fat, brain and even bones contain water in large quantities. Usually water makes up 65-75% of the body weight of a living organism. The body of some marine animals, such as jellyfish, contains even 97-98% water. All processes that take place in the body of animals and plants occur only with the participation of aqueous solutions. Life is impossible without water.

The first concern of the emerging organism is nutrition. Finding food on land is much more difficult than at sea. Land plants need long roots to extract water and nutrients dissolved in it. Animals earn their livelihood with great effort. Another thing in the sea. dissolved in salty sea water nutrients. Thus, sea plants are surrounded on all sides by the nutrient solution and easily absorb it.

It is equally important for the body to maintain its body in space. On land, this is a very difficult task. Air environment very sparse. To stay on the ground, you must have special devices - strong limbs or strong roots. On land, the largest animal is the elephant. But a whale is 40 times heavier than an elephant. If such a huge animal began to move on land, then it would simply die, unable to withstand its own weight. Neither thick skin nor massive ribs would have been sufficient support for this 100-ton carcass. Water is a completely different matter. Everyone knows that in the water you can easily lift a heavy stone, which on land you can hardly move. This happens because every body in water loses as much weight as the water displaced by it weighs. That is why the whale has to expend 10 times less effort to move in the water than this giant would need on land. Its body, supported by water from all sides, acquires greater buoyancy, and whales, despite their enormous weight, can high speed overcome great distances. The largest plants also live in the sea. Algae macrocystis reaches 150-200 meters in length. On earth, such giants are rare even among trees. Water supports a huge mass of this algae. For attachment to the ground, it does not require strong roots, as ground plants.

In addition, the temperature in the sea is more constant than in the air. And this is very important, since you do not need to look for protection from the cold in winter and from the heat in summer. On land, the difference between the air temperature in winter and summer reaches 80-90 degrees in some areas. In a number of places in Siberia, the temperature in summer reaches 35-40 degrees of heat, and in winter there are frosts of 50-55 degrees. In water, seasonal differences in temperature usually do not exceed 20 degrees. To protect themselves from the cold, terrestrial animals are covered by winter with fluffy fur, a layer of subcutaneous fat, and hibernate in dens and burrows during winter. It is difficult for plants to deal with freezing soil. That is why, in a particularly cold winter, birds, animals and other land animals die in masses, and trees also freeze out.

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The origin of life inhotwater

1. Life on Earth could have originated in volcanic lakes

The first primitive living cells could appear in the waters of fresh lakes, which were heated and saturated with microelements by prehistoric geothermal springs. This is stated by Russian and American scientists in an article published in the journal Proceedings of the National Academy of Sciences. Most geologists and evolutionary biologists believe that life on Earth in its modern form originated in the waters of the primary ocean, which covered almost the entire surface of the planet. It is believed that this ocean was a thick broth of amino acids and other “building blocks of life”, from which the first living cells appeared. A group of geologists and evolutionary biologists led by a native of Russia, Evgeny Kunin from National Institute health in the city of Bethesda (USA) offered new argument in favor alternative theory- the origin of life in freshwater lakes, the water of which receives steam and hot water from geothermal sources. In recent years, there has been much evidence that volcanic activity and other geothermal processes have played a role important role in the origin of life. So, in February 2010, British and German geologists proposed a new theory of the origin of life, according to which the first cells appeared at the mouths of underwater volcanoes and only then populated the entire oceans. In October 2011, another group of scientists found evidence of this in the deposits of ancient rocks in Greenland. Kunin and his colleagues “transferred” volcanoes from the waters of the “salted” primary ocean to freshwater lakes on those patches of land that existed in early history Earth, comparing chemical composition cells with a set of elements in the waters of modern geothermal lakes. In their study, the authors of the article suggested that the primary cells should have developed in the area that was the least different from them in chemical composition. From this point of view, sea water is not an ideal environment for the development of life - the concentration of sodium, potassium, manganese, zinc and ions of other important bioelements in it differs significantly from cellular ones. Even the most primitive microorganisms have a complex system of special "pumps" that prevent the cytoplasm from mixing with sea water. It is unlikely that such defenses already existed in the first protocells. Scientists compared the chemical composition of the cytoplasm in the cells of many modern organisms and derived "average" concentrations of amino acids, biologically important metals, and other substances. They then compared them to typical micronutrient profiles in present-day oceans, estimated primordial ocean composition, and water in present-day geothermal lakes. It turned out that volcanic lakes were the most favorable "cradle" for the origin of life. As Kunin and his colleagues note, only in their waters enough favorable conditions for the formation of structures of basic proteins and other important molecules that form the basis of the cell. According to scientists, such lakes could be formed as a result of the interaction of water entering the Earth along with meteorites and hot rocks at depth. Water during its journey from the surface to the deep layers "collected" potassium, sodium and other important trace elements and returned with them in the form of geothermal steam, which was deposited in the lakes. As geologists believe, such conditions could have existed stably for many millions of years, which gave life a great chance to appear. The conclusions of scientists are confirmed by the fact that a similar chemical composition is characteristic of the waters of geothermal sources in the vicinity of the Mutnovsky volcano in Kamchatka.

2. Chemical evolution

Chemical evolution or prebiotic evolution - the stage that preceded the emergence of life, during which organic, prebiotic substances arose from not organic molecules under the influence of external energy and selection factors and due to the deployment of self-organization processes that are characteristic of everyone relatively complex systems, which undoubtedly are all carbon-containing molecules. Also, these terms denote the theory of the emergence and development of those molecules that are of fundamental importance for the emergence and development of living matter. Everything that is known about the chemistry of matter makes it possible to limit the problem of chemical evolution to the framework of the so-called "water-carbon chauvinism", postulating that life in our Universe is represented in the only possible option: as a "mode of existence of protein bodies", feasible due to the unique combination of the polymerization properties of carbon and the depolarizing properties of the liquid-phase aquatic environment, as jointly necessary and / or sufficient (?) conditions for the emergence and development of all forms of life known to us. This implies that, at least, within one formed biosphere, there can be only one code of heredity common to all living beings of a given biota, but so far there remains open question whether there are other biospheres outside the Earth and whether other variants of the genetic apparatus are possible. It is also unknown when and where chemical evolution began. Any time is possible after the end of the second cycle of star formation, which occurred after the condensation of the products of explosions of primary supernovae, supplying heavy elements to interstellar space (with atomic mass over 26). The second generation of stars, already with planetary systems, enriched in heavy elements, which are necessary for the implementation of chemical evolution, appeared 0.5-1.2 billion years after the Big Bang. Under certain quite probable conditions, almost any environment can be suitable for launching chemical evolution: the depths of the oceans, the interior of planets, their surfaces, protoplanetary formations, and even clouds. interstellar gas, which is confirmed by the widespread detection in space by astrophysics methods of many types of organic substances - aldehydes, alcohols, sugars, and even the amino acid glycine, which together can serve as the starting material for chemical evolution, which has as its end result the emergence of life.

3. Hypotheses of chemical evolution

The appearance in space or on Earth of conditions for the autocatalytic synthesis of large volumes and a significant variety of carbon-containing molecules, that is, the emergence in abiogenic processes of substances necessary and sufficient for the beginning of chemical evolution. The appearance of relatively stable closed aggregates from such molecules, allowing one to isolate themselves from environment that with it the selective exchange of matter and energy becomes possible, that is, the emergence of certain protocellular structures. The appearance in such aggregates of chemical compounds capable of self-change and self-replication information systems, that is, the occurrence elementary units hereditary code. The appearance of mutual dependence between the properties of proteins and the functions of enzymes with information carriers (RNA, DNA), that is, the emergence of the actual code of heredity, as necessary condition already for biological evolution.

A great contribution to the clarification of these issues, among others, was made by the following scientists:

Alexander Oparin: Coacervates.

Harold Urey and Stanley Miller in 1953: Emergence of simple biomolecules in a simulated ancient atmosphere.

Sydney Fox: Microspheres from protenoids.

Thomas Check (University of Colorado) and Sidney Altman (University of Yale New Haven Connecticut) in 1981: Autocatalytic RNA fission: "Ribozymes" combine catalysis and information in a molecule. They are able to cut themselves out of the longer RNA chain and join the remaining ends again.

Walter Gilbert (Harvard University of Cambridge) develops in 1986 the idea of an RNA world.

Gunther von Kiedrowski (Ruhr-University Bochum) presents in 1986 the first DNA-based self-replicating system, an important contribution to understanding the growth functions of self-replicating systems

Manfred Eigen (Max Planck Institute, Faculty of Biophysical Chemistry, Göttingen): Evolution of ensembles of RNA molecules. Hypercycle.

Julius Rebeck (Cambridge) creates an artificial molecule (Aminoadenosintriazidester) that self-replicates in chloroform solution. Copies are still identical to the pattern, so evolution is impossible for these molecules.

John Corlis (Goddard Center space flights- NASA): The thermal springs of the seas supply the energy and chemicals that make chemical evolution independent of the space environment possible. Even today they are the living environment for the archaeobacteria (Archaea), which were originally in many ways.

Günter Wächtershäuser (Munich) - hypothesis of the world of iron sulfides: the first self-replicating structures with metabolism arose on the surface of pyrite. Pyrite (iron sulfide) set for this the necessary energy. On growing and again decaying pyrite crystals, these systems could grow and multiply, and different populations confronted different environmental conditions (selection conditions).

A.G. Cairns-Smith (University of Glasgow) and David C. Mauerzall (Rockefeller-Universität New York, New York) see clay minerals as a system that is itself subject to chemical evolution at first, resulting in many different, self-replicating crystals. These crystals attract organic molecules with their electric charge and catalyze the synthesis of complex biomolecules, and the volume of information of crystal structures first serves as a matrix. These organic compounds become more and more complex until they can multiply without the help of clay minerals.

Wolfgang Weigand, Mark Derr et al. (Max Planck Institute Faculty of Biogeochemistry, Jena) showed in 2003 that iron sulfide can catalyze the synthesis of ammonia from molecular nitrogen.

4. Wächterhäuser's theory

geothermal chemical Wächterhäuser

Theory of the iron-sulphur world

A particularly intensive form of the contribution of minerals and rocks to the prebiotic synthesis of organic molecules must take place on the surface of iron sulfide minerals. The Miller-Urey theory has significant limitations, especially given the erroneous explanation for the polymerization of the monomeric constituents of a biomolecule. Anaerobic bacteria, the metabolism of which occurs with the participation of iron and sulfur, still exist today. Growth of crystals of iron sulfide FeS2 An alternative scenario has been developed since the early 1980s by Günter Wächterhäuser. According to this theory, life on Earth arose on the surface of iron-sulfur minerals, that is, sulfides, which are still formed today through geological processes, and on the young Earth should have been much more common. This theory, as opposed to the RNA world hypothesis, suggests that metabolism preceded the appearance of enzymes and genes. Suggested as a suitable place are black smokers at the bottom of the oceans where high pressure, high temperature, no oxygen and plentiful various connections that could serve building material"bricks of life" or a catalyst in a chain of chemical reactions. The great advantage of this hypothesis over its predecessors is that for the first time the formation of complex biomolecules is associated with a constant reliable source of energy. Energy is released during the reduction of partially oxidized iron-sulfur minerals, such as pyrite (FeS2), with hydrogen (reaction equation: FeS2 + H2 \;\overrightarrow(\leftarrow)\; FeS + H2S), and this energy is sufficient for the endothermic synthesis of monomeric structural elements biomolecules and their polymerization:

Fe2+ + FeS2 + H2 \;\overrightarrow(\leftarrow)\; 2 FeS + 2 H+ ДG°" = ?44.2 kJ/mol

Other metals, like iron, also form insoluble sulfides. In addition to this, pyrite and other iron-sulfur minerals have a positively charged surface, on which predominantly negatively charged biomolecules (organic acids, phosphoric esters, thiols) can be located, concentrated and react with each other. The substances necessary for this (hydrogen sulfide, carbon monoxide and ferrous salts) fall from solution onto the surface of this “iron-sulfur world”. Wächterhäuser draws on the existing fundamental mechanisms of metabolism for his theory and derives from them a closed scenario for the synthesis of complex organic molecules (organic acids, amino acids, sugar, nitrogenous bases, fats) from simple inorganic compounds found in volcanic gases (NH3, H2, CO, CO2, CH4, H2S). In contrast to the Miller-Urey experiment, no energy sources are involved from outside, in the form of lightning or ultraviolet radiation; in addition, the first stages of synthesis at high temperatures and pressures proceed much faster (for example, catalyzed by enzymes chemical reactions). At temperatures of underwater volcanoes up to 350°C, the emergence of life is quite conceivable. Only later, if sensitive to high temperatures catalysts (vitamins, proteins), evolution should have occurred at a lower temperature. The Wächterhäuser scenario is well suited to the conditions of deep-sea hydrothermal vents, since the temperature difference there allows a similar distribution of reactions. The oldest microorganisms living today are the most heat-resistant, the limit known temperature maximum for their growth is +122°C. In addition, iron-sulfur active centers are still involved in biochemical processes, which may indicate the primary involvement of Fe-S minerals in the development of life.

5. RNA World

The RNA world hypothesis was first put forward in 1986 by Walter Gilbert and stated that RNA molecules were the precursors of organisms. The hypothesis is based on the ability of RNA to store, transmit, and reproduce genetic information, as well as its ability to catalyze reactions as ribozymes. AT evolutionary environment RNA molecules that multiply predominantly themselves would be more common than others. The starting point is simple self-replicating RNA molecules. Some of them have the ability to catalyze the synthesis of proteins, which in turn catalyze the synthesis of RNA and their own synthesis (the development of translation). Some RNA molecules are connected into an RNA double helix, they develop into DNA molecules and carriers of hereditary information (transcriptional development). The basis is certain RNA molecules that can copy any RNA sample, including themselves. Jennifer A. Doudna and Jack W. Szostak used as a template for the development of this type of RNA that cuts and splices itself into a prokaryotic intron. unicellular organism Tetrahymena thermophila. This confirms that rRNAs themselves are catalytic molecules in ribosomes and thus RNA catalyzes protein synthesis. However, the limitations are that with self-replicating RNA, not mono-, but oligonucleotides are the constituent links and auxiliary substances are needed. In 2001, it was discovered that the important catalytic centers of ribosomes are RNA, and not, as was previously accepted, proteins. This shows that the catalytic function of RNA, as suggested by the RNA world hypothesis, is used by living beings today.

Since ribosomes are considered to be very primitive cellular organelles, this discovery is considered an important contribution to substantiating the RNA world hypothesis. It is already safe to say that RNA molecules can synthesize proteins from amino acids. In this regard, nucleoproteins (complexes nucleic acids with proteins) are also of interest as possible precursors of RNA. Another RNA precursor could be polycyclic aromatic hydrocarbons. Poly world hypothesis aromatic hydrocarbons tries to answer the question of how the first RNAs arose, offering a variant of chemical evolution from polycyclic aromatic hydrocarbons to RNA-like chains.

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