How could life arise on earth? Origin of life on earth

The science

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

1. Electrical sparks

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

2. Clay

The chemist Alexander Graham Cairns-Smith of the University of Glasgow, Scotland, theorized that, at the dawn of life, clay contained many organic compounds that were close together and that clay helped organize these substances into structures similar to our genes.

DNA stores information about the structure of molecules, and the genetic sequence of DNA indicates how amino acids should be built into proteins. Cairns-Smith suggests that clay crystals helped to 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 originated in underwater hydrothermal vents that ejected molecules rich in hydrogen. On their rocky surface, these molecules could come together and become mineral catalysts for the reactions that led to the birth of life. Even now, such hydrothermal vents, rich in chemical and thermal energy, are home to a fairly large number of living beings.

4. Ice 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 that protected the fragile organic matter in the water below it from ultraviolet rays and cosmic exposure. In addition, the cold helped the molecules survive longer, allowing the reactions that led to the birth of life.

5. World of RNA

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

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

6. "Simple" theory

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

7. Panspermia

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

The generally accepted theory is that the entire universe was compressed to the size of a proton, but after a powerful explosion, it expanded to infinity. This event happened about 10 billion years ago and as a result, the resulting universe was filled with cosmic dust, from which stars and planets around them began to form. Earth, by space standards, is a very young planet, it formed about five billion years ago, but how did life originate on it? Scientists still cannot find a definite answer to this question.

According to Darwin's theory, life on Earth arose as soon as suitable conditions were established, that is, an atmosphere appeared, a temperature that ensured the flow of life processes and water. According to the scientist, the first simplest unicellular organisms appeared precisely under the influence of the Sun on water. Later, they evolved to brown algae and other plant species. Thus, if you follow this rule, all multicellular species on the planet have evolved from plants. The answer to the most important question has not yet been received: “How can life appear from nothing, even if under the influence of the Sun?”. It is enough to conduct a simple experiment - pour well water into a jar, then close it hermetically and put it in sunlight. In any case, the liquid will remain the same as it was, there may be microscopic changes in its composition, but microorganisms will not appear there. If, however, the same experiment is carried out with an open jar, then after a few days it will be possible to notice how the walls begin to become covered with a layer of unicellular algae.

Based on this, we can say that for the origin of life and even its simplest forms, outside interference is necessary. Of course, the version of the independent origin of species is very tempting in that it proves the supposed independence of mankind, which is not indebted to God or aliens from other planets.

Recently, there are more and more supporters of cosmic origin, both of man and of the entire biosphere. Oddly enough, however, researchers in their research combine not only the appeal to artifacts already found or being found, but also to the Bible. If we interpret what was written there, in ordinary language, then we can draw analogies not with miracles, but with quite explainable physical phenomena. Based on this material, there is a certain higher mind, which populated the planet with living beings, as well as the human race. The book says that God created man in his own image and likeness, that is, it is possible that we are a copy, in any case, outwardly we repeat our creator.

Man is a biorobot - that is, an artificially created organism with intelligence, with a built-in opportunity for self-improvement. It is possible that the moment of human settlement of the planet is just described in the episode when Adam and Eve were expelled from the Garden of Eden to Earth, where they had to independently adapt to harsh living conditions. It may well be that the Garden of Eden means the place where the biorobots made by the creator were tested in greenhouse conditions and, after checking their performance, they were released into harsh reality.

Of course, the question remains: “What about the diversity of animal species in this case? After all, the creator could not create species, subspecies and orders, up to single-celled creatures? It is assumed that evolution still took place here, but more accelerated and taking place under the control of the creators. It is impossible not to deny the fact that in each of the animal species, there are still signs of a species preceding the evolutionary ladder. Birds are very similar to reptiles, especially in the elongated shape of the beak and the skin of their paws. The outlines of reptiles, in turn, strongly resemble fish, but many mammals have absorbed the signs of several previous species at once. Looking at a cat, you can easily guess the signs of both reptiles and amphibians. Love for a warm place, most likely passed on to cats in the genes, and despite the fact that they are warm-blooded, they always prefer to live where there is a source of heat. The same sign is characteristic of cold-blooded animals that are unable to generate heat on their own. Studying carefully the cat's eye, you can see that it is very similar to the eyes of a crocodile, and the shape of the head, with slight changes, resembles that of a snake. Sometimes one gets the impression that someone worked on the creation of views, in the same way as, for example, the designers of an automaker work, taking the chassis of the previous car as a basis and adding a few changes.

If this is the case, then it is not surprising that some of the animal species are simply bewildering, associated with the situation when the assembly lacks parts and uses what is available. There are especially many examples of such animals in Australia. In addition to the kangaroo, which belongs to rodents, but has a powerful musculoskeletal system like a horse, there are other interesting species, such as the platypus. This animal belongs to mammals, but breeds like birds - it lays eggs and has a bone beak similar to a goose. The structure of his body is very similar to a beaver, and the born cubs feed on milk not through the mother's nipples, but by licking the liquid protruding from the surface of the belly. Whether the creators themselves performed such painstaking work, or whether they only set the basic direction in development, and the formation of individual subspecies already took place independently - today this question remains open.

Variants of evolution can be considered from different angles, but most researchers still agree that evolution itself, if it has taken place, is just a consequence, but the cause remains to be clarified. No less popular is the opinion that the cause of the appearance of life on Earth was the fall of a meteorite, on which the simplest unicellular organisms were in a frozen state. Since by that time a warm climate had already been established on the planet, and the ancient world ocean occupied most of the surface, all conditions were created for the subsequent development of life. There is also a version that the meteorite was actually sent by intelligent beings precisely for the purpose of populating the planet, which is also not deprived of the right to exist.

Instead of a meteorite, there could be just an optical information beam, for example, sent from another universe or even another dimension. Indeed, why would such highly developed beings send something material across billions of light years? With their level of development, they have long been able to discover the possibilities of teleportation and freely operate in space and time, appearing exactly where it is needed. The information transmitted with the help of the beam materialized here on earth, in the same organisms, and thus the process of evolution was launched.

Of course, life could not only be provoked by an accidentally flown meteorite, the version that Mars could become a donor also finds many supporters. The mystery of this planet still cannot be solved. All that scientists have in their hands is pictures of a red surface thinned out by deep depressions, a mysterious face, most likely a feature of the relief, and minor soil samples. Billions of dollars have been spent on the design and launch of vehicles, but most of these attempts have not yielded results. It seems that some force on this planet stubbornly refuses to have contact with earthlings.

It is assumed that once Mars was inhabited and rich in natural resources, like the Earth, but subsequently, its magnetic field has weakened. This led to the fact that most of the atmosphere and moisture escaped into space, as a result, the body of the planet was left without protection from harsh ultraviolet radiation. It is possible that the inhabitants of Mars had the necessary knowledge and were able to relocate some species of animals to a neighboring planet, relocate themselves, or send a capsule with microorganisms.

The search for the original source of life will continue for a very long time, because with each new discovery in science and especially genetics, it is only possible to slightly lift the veil of mystery about the origin of mankind, which in turn leads to the emergence of new hypotheses. Yet, whatever the answer to this question, it is unlikely to be destined to be known until a person learns to feel responsible for his unique planet on which he was lucky to live.

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Doctor of Geological and Mineralogical Sciences I. A. REZANOV

In the language of literature, life was born "when the Earth screamed." But for the Earth to scream, it turned out not enough experience of Professor Challenger and little imagination of Conan Doyle, who forced his hero to drill a well. Speaking scientifically, I believe that we owe our lives to two catastrophes on a cosmic scale. In my opinion, only one source of information is able to reliably tell what events led to the emergence of life - this is the "stone chronicle" of the planet.

It is difficult for a non-specialist to believe that radioactive analysis makes it possible not only to accurately date the episodes of the geological scenario, even of such unimaginable antiquity, but also to recreate pictures of the physical processes of that time. How did life arise from dead matter?

According to the latest geological data, in the first 600 million years of the Earth's existence (4.0-3.9 billion years ago), such extreme conditions reigned on the planet that life was impossible. The dense atmosphere consisted mainly of hydrogen with an admixture of helium. The vents of numerous volcanoes spewed carbon dioxide, methane, ammonia, hydrogen sulfide and other gases. An analysis of the patriarchal stones showed that the pressure reached six thousand atmospheres, the surface of the planet heated up to 600 ° C, that is, it was hotter in this hellish hell than it is now on Venus, where life has not been found.

But younger rocks, born 3.8 billion years ago and later, were already formed in conditions close to modern ones. These pages of the stone chronicle testify that by that time the dense and highly heated hydrogen atmosphere had left the planet. It was possible to understand what provoked this only after waiting for the return of spacecraft from the Moon. Studying samples of lunar soil, selenologists in this space supplement to the Earth's stone record read that 3.9 billion years ago a giant catastrophe occurred in the solar system. The lunar seas - crater-shaped funnels with a diameter of up to 1200 kilometers - were knocked out at that time during the bombardment by giant asteroids. Cosmic bodies, bombarding the Moon, gave her a powerful impulse of heat, which heated her bowels to melting. Since then, two types of relief have been distinguished on the surface of the Moon: light "continents" and dark "seas" filled with molten basalts.

Academician V. G. Fesenkov and many other astronomers believed that the most probable cause of the catastrophe was the explosion of a planet whose orbit coincided with the asteroid belt located between the orbits of Mars and Jupiter.

If measured by the scale of the solar system, then the Moon is not far from the Earth. Consequently, a flurry of asteroids and meteorites also hit the Earth. Everyone knows that sound is transmitted due to vibrations of molecules. If there was no atmosphere on the Moon even then, then all these cataclysms took place in terrible silence (for a person, of course, if he could be present there). But what kind of cyclopean symphony would a witness over our planet hear? It is perhaps weak to say, following Conan Doyle, that "the Earth cried out." She roared. Falling, fragments-asteroids caused powerful air currents, and it became 100 degrees hotter in hell. The extra heat was enough to rip off the Earth's hydrogen blanket. And only after that, suitable conditions appeared on Earth for the emergence of life. As they say, there would be no happiness, but misfortune helped.

It turns out that the catastrophe became a necessary condition for the birth of life, but was it enough? No, because neither the atmosphere nor the hydrosphere remained on the surface of the Earth, and the crust and mantle melted. The planet was enveloped in molten, viscous granite crust, which did not allow gases to pass through. Gases accumulated in a less viscous mantle. Only at a pressure of at least ten thousand atmospheres and a temperature of at least 1000°C, the gases CO, CO2, H2, CH4, and NH3, poorly soluble in magma, broke through the crust in the form of giant jets.

It is known that complex organic compounds (amino acids, sugars, porphyrins) are formed during a volcanic eruption. Thus, only during one eruption of the Tyatya volcano on the Kuril Islands in 1973, 200 tons of complex organic matter accumulated in the ashes. How much of it was formed on the planet after the breakdown of the primary hydrogen atmosphere from the Earth, when giant gas jets constantly gushed out with an intensity thousands of times greater than the strength of current volcanic eruptions? At that time, millions of tons of organic compounds were synthesized annually in the vents of gas volcanoes. In a geologically short time (the first million years), a layer cake several tens of meters thick was baked on the surface of the planet from alternating layers of ash and organic compounds.

The abundance of organics was the second necessary reason for the birth of life on Earth. But even this was not enough. What else?

More than a hundred years ago, the famous French naturalist Louis Pasteur discovered that organic compounds in plants and animals are optically asymmetric - they rotate the plane of polarization of the light falling on them. All amino acids that make up animals and plants rotate the plane of polarization to the left, and all sugars to the right. If we synthesize compounds of the same chemical composition, then each of them will have an equal number of left- and right-handed molecules.

Now imagine that the environment with left and right molecules has passed into a state with only left or only right molecules. Experts call such an environment chirally (from the Greek word "heira" - hand) ordered. The self-reproduction of the living (biopoiesis, as defined by D. Bernal) could arise and be maintained only in such an environment.

The Soviet scientist L. L. Morozov proved that the transition to chiral ordering could not occur evolutionarily, but only with a sharp phase change. Academician V. I. Gol'danskii called this transition a chiral catastrophe. Still, scientists differ from other people not only in knowledge. Everyone used to think that a catastrophe is something terrifying, and physicists called a catastrophe the phenomenon due to which life was born and, ultimately, they themselves.

How did the conditions for the phase catastrophe that caused the chiral transition arise?

The most important thing was that the lower layers of the growing ash-organic cake were fried on the earth's crust heated to 600, and the upper ones cooled to the temperature of space, that is, absolute zero. The temperature difference reached 1000°. It is clear that the bottom of the pie burned, that is, the organic molecules melted under the influence of high temperature and even completely destroyed, and the top of the pie remained unbaked for the time being, as the organic molecules were frozen. Of course, the gases and, possibly, water vapor that leaked from the earth's crust changed the chemical composition of organic compounds. The gases carried heat with them, causing the melting boundary of the organic layer to move up and down.

At very low pressures of the atmosphere, water was on the earth's surface only in the form of steam and ice. When the pressure reached the so-called triple point of water (0.006 atmospheres), water for the first time could be in the form of a liquid.

Of course, it is only experimentally possible to prove what exactly caused the chiral transition: terrestrial or cosmic causes. But one way or another, at some point, chirally ordered molecules (namely, left-handed amino acids and right-handed sugars) turned out to be more stable and an unstoppable increase in their number began - a chiral transition.

The stone chronicle also tells that at that time there were neither mountains nor depressions on Earth. The semi-molten granite crust was a surface as flat as the level of the modern ocean. However, within this plain there were still depressions due to the uneven distribution of masses inside. These lowerings have played an extremely important role. The fact is that flat-bottomed depressions with a diameter of hundreds and even thousands of kilometers and a depth of no more than a hundred meters, probably became the cradle of life. After all, the water that collected on the surface of the planet flowed into them. The water diluted the chiral organic compounds in the ash layer. The chemical composition of the compound gradually changed, and the temperature stabilized. The transition from the inanimate to the living, which began in anhydrous conditions, continued already in the aquatic environment.

Is that the plot the origin of life? Most likely yes. In the Isua geological section (West Greenland), which is 3.8 billion years old, gasoline- and oil-like compounds were found with the C12/C13 isotopic ratio, characteristic of photosynthetic carbon. If the biological nature of the carbonaceous compounds from the Isua section is confirmed, then it will turn out that the whole plot - from the emergence of chiral organics to the appearance of a cell capable of photosynthesis and reproduction - was played out in only a hundred million years.

A phenomenon of cosmic proportions, predicted at the tip of a pen by Soviet scientists, is waiting for its experimental confirmation in order to move from the category of daring hypotheses to the honorable category of theories.

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

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

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

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

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

Cosmogonic hypothesis

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

Symbiosis of organelles of nuclear organisms

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

Spontaneous generation

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

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

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

Creation of existence from ordinary clay

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

Theory of permanent catastrophes

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

Matter as an objective reality

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

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

Teachings of Charles Darwin

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

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

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

Creation of God

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

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

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

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