Problem origin of life on earth has long been of interest and concern to man. There are several hypotheses about the origin of life on our planet:

life is created by God;
life on Earth is brought from outside;
living things on the planet have repeatedly spontaneously generated from non-living things;
life has always existed;
life arose as a consequence of the biochemical revolution.

The whole variety of different hypotheses comes down to two mutually exclusive points of view. Proponents of the theory of biogenesis believed that all living things come only from living things. Their opponents defended the theory of abiogenesis - they considered it possible for the living to originate from the non-living.

Many scientists admitted the possibility of spontaneous generation of life. The impossibility of spontaneous generation of life was proved by Louis Pasteur.

The second stage is the formation of proteins, fats, carbohydrates, nucleic acids from simple organic compounds in the waters of the primary ocean. The disparate molecules of these compounds were concentrated and formed coacervates, acting as open systems, capable of exchanging substances with the environment and growing.

The third stage - as a result of the interaction of coacervates with nucleic acids, the first living beings were formed - probionts, capable, in addition to growth and metabolism, of self-reproduction.

MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUS

BSPU IM. M. TANKA

FACULTY OF SPECIAL EDUCATION

DEPARTMENT OF THE FUNDAMENTALS OF DEFECTOLOGY

Essay

in the discipline "Natural Science"

on the topic of:

"Basic hypotheses about the origin of life on Earth".

Performed:

1st year student of group 101

correspondence department (budget

form of education)

……… Irina Anatolyevna

INTRODUCTION…………………………………………………………………..….1

1. CREATIONISM……………………………………………………….…….1

2. STATION STATE THEORY…………..……………….….2

3. THE THEORY OF SPONTANEOUS GENERATION…………..…3

4. THE THEORY OF PANSPERMIA………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

5. A. I. OPARIN’S THEORY………………………………………………..……10

6. MODERN VIEWS ON THE ORIGIN OF LIFE ON EARTH……………………………………………………………………………....12

CONCLUSION…………………………………………………………...……..14

LITERATURE …………………………………………………………...……...15

INTRODUCTION

The problem of the origin of life on Earth and the possibility of its existence in other areas of the Universe has long attracted the attention of both scientists and philosophers, as well as ordinary people. In recent years, interest in this "eternal problem" has increased significantly.

This is due to two circumstances: firstly, significant progress in laboratory modeling of some stages of the evolution of matter, which led to the origin of life, and, secondly, the rapid development of space research, making it increasingly possible to directly search for any life forms on the planets of the solar system. and in the future and beyond.

The origin of life is one of the most mysterious questions, the exhaustive answer to which is unlikely to ever be received. Many hypotheses and even theories about the origin of life, explaining various aspects of this phenomenon, are still unable to overcome the essential circumstance - to experimentally confirm the fact of the appearance of life. Modern science does not have direct evidence of how and where life arose. There are only logical constructions and indirect evidence obtained through model experiments, and data in the field of paleontology, geology, astronomy, etc.

Theories regarding the origin of life on Earth are varied and far from reliable. The most common theories for the origin of life on Earth are as follows:

1. Life was created by a supernatural being (Creator) at a specific time (creationism).

2. Life has always existed (the theory of a stationary state).

3. Life arose repeatedly from inanimate matter (spontaneous generation).

4. Life is brought to our planet from the outside (panspermia).

5. Life arose as a result of processes that obey chemical and physical laws (biochemical evolution).

1. Creationism.

Creationism (from Latin creacio - creation) is a philosophical and methodological concept, within 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 confirmation of this point of view: in religion, the truth is comprehended through divine revelation and faith. The process of creation of the world is conceived as having taken place only once and therefore inaccessible to observation.

The followers of almost all the most common religious teachings adhere to theories of creationism (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 o'clock in the morning, creating man. Asher got this date by adding up the ages of all the people mentioned in the Biblical genealogy, from Adam to Christ (“who bore whom”). From the point of view of arithmetic, this makes sense, but it turns out 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 idea of ​​the creation of the world, set forth in the Book of Genesis, has caused and continues to cause controversy. However, the existing contradictions do not refute the concept of creation. The hypothesis of creation can neither be proved nor disproved and will always exist together with scientific hypotheses of the origin of life.

Creationism is thought of as God's Creation. However, at present, some consider it as the result of the activities of a highly developed civilization that creates various forms of life and monitors their development.

2. THE THEORY OF A STATIONARY STATE.

According to this theory, the Earth never came into being, but existed forever; it has always been capable of sustaining life, and if it has changed, it has changed 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.

According to modern estimates based on the rate of radioactive decay, the age of the Earth is estimated at 4.6 billion years. Improved dating methods give increasingly higher estimates of the age of the Earth, which allows the proponents of the steady state theory to believe that the Earth has always existed.

Proponents of this theory 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 the cross-finned fish - coelacanth (coelacanth). It was believed that the brush-finned fish (coelacanth) is a transitional form from fish to amphibians and died out 60-90 million years ago (at the end of the Cretaceous period). However, this conclusion had to be revised when, in 1939, off the coast of about. Madagascar, the 1st live coelacanth was caught, and then other specimens. Thus, coelacanth is not a transitional form.

Many other animals that were considered extinct were found, for example, lingula - a small marine animal, allegedly extinct 500 million years ago, is still alive today and like other "living fossils": solendon - a shrew, tuatara - a lizard. For millions of years, they have not undergone any evolutionary changes.

Another example of delusion is Archeopteryx - a creature that binds birds and reptiles, a transitional form on the way to turning reptiles into birds. But in 1977, fossils of birds were discovered in Colorado, the age of which is commensurate with and even exceeds the age of the remains of Archeopteryx, i.e. it is not a transitional form.

Proponents of the steady state theory argue that only by studying living species and comparing them with fossil remains can one conclude about extinction, and in this case it is very likely that it will turn out to be wrong. Using paleontological data to support the steady state theory, its proponents interpret the appearance of fossils in an ecological sense.

Thus, for example, the sudden appearance of a fossil species in a particular stratum is explained by an increase in its population or its movement to places favorable for the preservation of remains.

Much of the argument in favor of this theory has to do with obscure aspects of evolution, such as the significance of gaps in the fossil record, and it has been most elaborate in this direction.

The hypothesis of a stationary state is sometimes called the hypothesis of eternism (from Latin eternus - eternal). The hypothesis of eternism was put forward by the German scientist W. Preyer in 1880.

Preyer's views were supported by Academician Vladimir Ivanovich Vernadsky (1864 - 1945), the author of the doctrine of the biosphere. Vernadsky believed that life is the same eternal basis of the cosmos, which are matter and energy. “We know, and we know this scientifically,” he repeated, “that the Cosmos cannot exist without matter, without energy. And is there enough matter even without revealing life - to build the Cosmos, that Universe, which is accessible to the human mind? He answered this question in the negative, referring precisely to scientific facts, and not to personal sympathies, philosophical or religious convictions. “... You can talk about the eternity of life and the manifestations of its organisms, just as you can talk about the eternity of the material substrate of celestial bodies, their thermal, electrical, magnetic properties and their manifestations. From this point of view, the question of the beginning of life will be just as far from scientific research as the question of the beginning of matter, heat, electricity, magnetism, motion.

Proceeding from the idea of ​​the biosphere as an earthly, but at the same time, a cosmic mechanism, Vernadsky connected its formation and evolution with the organization of the Cosmos. “It becomes clear to us,” he wrote, “that life is a cosmic phenomenon, and not purely earthly.” Vernadsky repeated this thought many times: “... there was no beginning of life in the Cosmos that we observe, since there was no beginning of this Cosmos. Life is eternal, because the eternal Cosmos.

3. THE THEORY OF SPONTANEOUS GENERATION.

This theory was circulated in ancient China, Babylon, and Egypt as an alternative to the 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 the deity. Very naively solved this question and the first researchers of nature. Aristotle (384-322 BC), often hailed as the founder of biology, held to the theory of the spontaneous generation of life. Even for such an outstanding mind of antiquity as Aristotle, it was not difficult to accept the idea that animals - worms, insects, and even fish - could arise from mud. On the contrary, this philosopher argued that every dry body, becoming wet, and, conversely, every wet body, becoming dry, give birth to animals.

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

“These are the facts - living things can arise not only by mating animals, but also by the decomposition of the soil. It is the same with plants: some develop from seeds, while others, as it were, spontaneously generate under the action of all nature, arising from the decaying earth or certain parts of plants ”(Aristotle).

The authority of Aristotle had an exceptional influence on the views of medieval scholars. The opinion of this philosopher in their minds was intricately intertwined with the teachings of the Church Fathers, often giving absurd and even ridiculous ideas from a modern point of view. The preparation of a living person or his likeness, "homunculus", in a flask, by mixing and distilling various chemicals, was considered in the Middle Ages, although very difficult and lawless, but no doubt doable. Obtaining animals from inanimate materials seemed so simple and common to scientists of that time that the famous alchemist and physician Van Helmont (1577 - 1644) directly gives a recipe, following which mice can be artificially prepared by covering a vessel with grain with wet and dirty rags. This very successful scientist described an experiment in which he allegedly created mice in three weeks. For this, a dirty shirt, a dark closet and a handful of wheat were needed. Van Helmont considered human sweat to be the active principle in the process of the birth of a mouse.

A number of works belonging 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 formed from May dew, and Aldrovand gives drawings showing how birds and insects are born from branches and fruits of trees.

The further natural science developed, the more important accurate observation and experience became in the knowledge of nature, and not just reasoning and sophistication, the more narrowed was the scope of the theory of spontaneous generation. 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, by simple experiments, proved the groundlessness of opinions about the spontaneous generation of worms in rotting meat. He found that the little white worms were fly larvae. After conducting a series of experiments, he received data confirming the idea that life can only arise from a previous life (the concept of biogenesis).

“Conviction would be futile if it could not be confirmed by experiment. So in the middle of July I took four large, wide-mouthed vessels, put earth in one of them, some fish in another, Arno eels in the third, and a piece of veal in the fourth, closed them tightly and sealed them. Then I placed the same in four other vessels, leaving them open... Soon the meat and fish in the unsealed vessels were wormed; flies could be seen flying freely into and out of the vessels. But I did not see a single worm in the sealed vessels, although many days had passed after the dead fish had been placed in them” (Redi).

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 XVII century. Kircher and Leeuwenhoek discovered the world of the smallest creatures, invisible to the naked eye and distinguishable only through a microscope. These “tiniest living animals” (this is how 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 plaque . “In my mouth,” Leeuwenhoek wrote, “there are more of them (germs) than there are people in the United Kingdom.” One has only to put perishable and easily rotting substances in a warm place for some time, as microscopic living creatures immediately develop in them, which were not there before. Where do these creatures come from? Could they really come from embryos that accidentally fell into the rotting liquid? How many of these germs must be everywhere! The thought involuntarily appeared that it was here, in rotting decoctions and infusions, that spontaneous generation of living microbes from inanimate matter took place. This opinion in the middle of the XVIII century. received strong confirmation in the experiments of the Scottish priest Needham. Needham took meat broth or decoctions of vegetable substances, placed them in tightly closed vessels and boiled them for a short time. At the same time, according to Needham, all the embryos should have died, while new ones could not get in from the outside, since the vessels were tightly closed. However, after a while, microbes appeared in the liquids. From this, the said scientist concluded that he was present at the phenomenon of spontaneous generation.

However, this opinion was opposed by another scientist, the Italian Spallanzani. Repeating Needham's experiments, he became convinced that a longer heating of vessels containing organic liquids completely dehydrates them. In 1765, Lazzaro Spallanzani conducted the following experiment: having boiled meat and vegetable broths for several hours, he immediately sealed them, after which he removed them from the fire. After examining the liquids a few days later, Spallanzani found no signs of life in them. From this, he concluded that the high temperature destroyed all forms of living beings and that without them, nothing living could have arisen.

A fierce dispute broke out between representatives of two opposing views. Spallanzani argued that the liquids in Needham's experiments were not heated enough and the embryos of living beings remained there. To this, Needham objected that he did not heat the liquids too little, but, on the contrary, Spallanzani heated them too much and by such a rude method destroyed the "generating force" of organic infusions, which is very capricious and fickle.

Thus, each of the disputants remained unconvinced, and the question of the spontaneous generation of microbes in decaying liquids was not resolved either way for a whole century. During this time, many attempts have been made empirically to prove or disprove spontaneous generation, but none of them has led to definite results.

The question became more and more confused, and only in the middle of the 19th century. it was finally resolved thanks to the brilliant research of the brilliant French scientist Pasteur.

LOUIS PASTER

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 was able to solve the 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. In a number of experiments, he showed that everywhere, and especially near human habitation, the smallest germs rush in the air. They are so light that they float freely in the air, only very slowly and gradually sinking to the ground.

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

The mysterious appearance of microorganisms in the experiments of previous researchers was explained by Pasteur either by incomplete desolvation of the medium, or by insufficient protection of liquids from the penetration of germs. If the contents of the flask are thoroughly boiled and then protected from germs that could get into the flask with air flowing into the flask, then in a hundred cases out of a hundred the liquid will not rot and the formation of microbes does not occur.

Pasteur used a wide variety of methods to dehydrate the air flowing into the flask: 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 were trapped, or, finally, passed the air through a thin glass tube. , bent in the form of the letter S; in this case, all the nuclei were mechanically retained on the wet surfaces of the tube bends.

S-necked flasks used in Louis Pasteur's experiments:

A - in a flask with a curved neck, the broth remains transparent (sterile) for a long time; B - after removal of the S-shaped neck in the flask, a rapid growth of microorganisms is observed (the broth becomes cloudy).

Wherever the protection was sufficiently reliable, the appearance of microbes in the liquid was not observed. But perhaps prolonged heating has chemically changed the environment and made it unsuitable for supporting life? Pasteur easily refuted this objection as well. He threw a cotton plug into a liquid that had not been heated, through which air was passed and which, consequently, contained germs - the liquid quickly rotted. Therefore, boiled infusions are quite suitable soil for the development of microbes. This development does not take place just because there is no germ. As soon as the embryo enters the liquid, it immediately germinates and gives a lush harvest.

Pasteur's experiments showed with certainty that spontaneous generation of microbes in organic infusions does not occur. All living organisms develop from embryos, that is, they originate from other living beings. However, the confirmation of the theory of biogenesis gave rise to another problem. Since another living organism is needed 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 in all other theories it is assumed that at some stage in the history of life there was a transition from inanimate to living. So how did life originate on Earth?

4. THEORY OF PANSPERMIA.

Pasteur is rightly considered the father of the science of the simplest organisms - microbiology. Thanks to his work, an impetus was given to the most extensive studies of the world invisible to the naked eye of the smallest creatures inhabiting the earth, water and air. These studies were no longer directed, as before, to a mere description of the forms of microorganisms; bacteria, yeast, ciliates, amoeba, etc. studied from the point of view of their living conditions, their nutrition, respiration, reproduction, from the point of view of the changes that they produce in their environment, and, finally, from the point of view of their internal structure, their finest structure. The further these studies went, the more and more it was discovered that the simplest organisms are not at all as simple as they thought before.

The body of any organism - a plant, a snail, a worm, a fish, a bird, an animal, a person - consists of the smallest bubbles visible only under a microscope. It is made up of these bubble cells, just as a house is made of bricks. Different organs of various animals and plants contain cells that differ from each other in their appearance. Adapting to the work that is assigned to this organ, the cells, its components, one way or another, change, but in principle all cells of all organisms are similar to each other. Microorganisms differ only in that their entire body consists of only one single cell. This fundamental similarity of all organisms confirms the now generally accepted idea in science that everything living on Earth is connected, so to speak, by blood relationship. More complex organisms evolved from simpler ones, gradually changing and improving. Thus, one has only to explain to oneself the formation of some simple organism - and the origin of all animals and plants becomes clear.

But, as already mentioned, even the simplest, consisting of only one cell, are very complex formations. Their main component, the so-called protoplasm, is a semi-liquid, viscous gelatinous substance saturated with water, but insoluble in water. The composition of protoplasm includes a number of extremely complex chemical compounds (mainly proteins and their derivatives), which are not found anywhere else, only in organisms. These substances are not simply mixed, but are in a special state, little studied until now, due to which the protoplasm has the thinnest, poorly distinguishable even with a microscope, but extremely complex structure. The suggestion that such a complex formation with a well-defined fine organization could spontaneously arise within a few hours in structureless solutions, such as broths and infusions, is as wild as the suggestion that frogs form from May dew or mice from grain.

The exceptional complexity of the structure of even the simplest organisms so struck the minds of some scientists that they came to the conclusion that there was an impassable abyss between the living and the non-living. The transition of the inanimate into the living, organized seemed to them absolutely impossible either in the present or in the past. “The impossibility of spontaneous generation at any time,” says the famous English physicist W. Thomson, “should be considered as firmly established as the law of universal gravitation.”

But how, then, did life occur on Earth? After all, there was a time when the Earth, according to the now generally accepted view in science, was a white-hot ball. This is supported by the data of astronomy, and geology, and mineralogy, and other exact sciences - this is undoubtedly. This means that on Earth there were such conditions under which life was impossible, unthinkable. Only after the globe had lost a significant part of its heat, dissipating it into cold interplanetary space, only after the first thermal seas were formed by cooled water vapor, did the existence of organisms like those that we now observe become possible. To clarify this contradiction, a theory was created that bears a rather complicated name - the theory of panspermia (Greek panspermía - a mixture of all seeds, from pán - all, everyone and spérma - seed).

One of the first to express the idea of ​​cosmic rudiments was the German physician G. E. Richter in 1865, 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. Proceeding from the idea that small particles of solid matter (cosmozoans), separated from celestial bodies, are everywhere in the world space, the above author assumed that simultaneously with these particles, perhaps, having stuck to them, viable germs of microorganisms are carried. In this way, 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 a suitable temperature and humidity, then the embryos begin to germinate, develop and subsequently become the ancestors of the entire organic world of this planet.

This theory has acquired 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, in which the viability of these embryos would be preserved. After all, in fact, in the end, the main question is precisely whether a spore can make such a long and dangerous journey as a flight from one world to another without dying, retaining the ability to germinate and develop into a new organism. Let us analyze in detail what dangers are encountered on the way of the embryo.

First of all, it is the coldness of interplanetary space (220° below zero). Separated from its home planet, the embryo is doomed to rush for many years, centuries and even millennia in such terrifying temperatures before a lucky chance gives it the opportunity to descend to a new earth. Involuntarily there is a doubt whether the embryo is capable of withstanding such a test. To resolve this issue, we turned to the study of resistance to cold of modern spores. Experiments carried out in this direction have shown that the germs of micro-organisms endure cold very well. They remain viable even after six months at 200° below zero. Of course, 6 months is not 1000 years, but nevertheless experience gives us the right to assume that at least some of the embryos can endure the terrible cold of interplanetary space.

A much greater danger to the embryos is their complete exposure to light rays. Their path between the planets is permeated with the rays of the sun, which are detrimental to most microbes. Some bacteria die from the action of direct sunlight within a few hours, others are more resistant, but very strong lighting affects all microbes without exception. However, this unfavorable effect is greatly weakened in the absence of atmospheric oxygen, and we know that there is no air in interplanetary space, and therefore we can reasonably assume that the germs of life will also pass this test.

But a lucky chance gives the embryo the opportunity to fall into the sphere of attraction of some planet with favorable temperature and humidity conditions for the development of life. The only thing left for the wanderer, obeying the force of gravity, is to fall to his new Earth. But just here, almost already in a peaceful harbor, a formidable danger awaits him. Previously, the embryo hovered in a vacuum, but now, before falling to the surface of the planet, it must fly through a rather thick layer of air that envelops this planet on all sides.

Everyone, of course, is well aware of the phenomenon of “shooting stars” - meteors. Modern science explains this phenomenon as follows. In interplanetary space, solid bodies and particles of various sizes are worn, perhaps fragments of planets or comets that have flown into our solar system from the most remote places in the Universe. Flying near the globe, they are attracted by this latter, but before falling on its surface, they must fly through the air atmosphere. Due to air friction, a rapidly falling meteorite heats up to a white heat and becomes visible in the dark firmament. Only a few of the meteorites reach the earth, most of them burn out from the intense heat still far from its surface.

The embryos must also undergo a similar fate. However, various considerations show that this kind of death is not necessary. There is reason to believe that at least some of the embryos that enter the atmosphere of a particular planet will reach its surface viable.

At the same time, one should not forget about those colossal astronomical periods of time during which the Earth could be sown with germs from other worlds. These intervals are calculated in millions of years! If during this time, out of many billions of embryos, at least one reached the surface of the Earth safely and found conditions suitable for its development here, then this would already be enough for the formation of the entire organic world. This possibility, in the present state of science, seems unlikely, but admissible; in any case, we have no facts that directly contradict it.

However, the theory of panspermia is only an answer to the question of the origin of life on earth, and by no means to the question of the origin of life in general, transferring the problem to another place in the Universe.

“One of the two,” says Helmholtz. “Organic life has either ever begun (originated), or exists forever.” If we admit the first, then the theory of panspermia loses all logical meaning, since if life could originate somewhere in the Universe, then, based on the uniformity of the world, we have no reason to assert that it could not originate on Earth. Therefore, supporters of the theory under consideration accept the position of the eternity of life. They admit that "life only changes its form, but is never created from dead matter."

In the late 60s, the popularity of this theory resumed. This was due to the fact that in the study of meteorites and comets, many "precursors of the living" 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 the Earth." In 1992, the works of American scientists appeared, where, based on a study of material collected in Antarctica, they describe the presence in meteorites of the remains of living beings resembling bacteria.

Modern adherents of the concept of panspermia (including the Nobel Prize winner English biophysicist F. Crick) believe that life on Earth was brought to Earth by accident or intentionally by space aliens using aircraft. Evidence of this is the repeated appearances of UFOs, rock carvings of objects similar to spaceports, as well as reports of meetings with aliens.

The point of view of astronomers C. Wickramasingh (Sri Lanka) and F. Hoyle (Great Britain) adjoins the panspermia hypothesis. They believe that in outer space, mainly in gas and dust clouds, microorganisms are present in large numbers. Further, these microorganisms are captured by comets, which then, passing near the planets, "sow the germs of life."

Other scientists express the idea of ​​transferring the "spores of life" to Earth by light (under the pressure of light).

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

5. THE THEORY OF A. I. OPARIN.

The first scientific theory regarding the origin of living organisms on Earth was created by the Soviet biochemist A. I. Oparin (b. 1894). In 1924, he published works in which he outlined ideas about how life could have arisen on Earth. 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:

1. The emergence of organic substances.

2. The formation of biopolymers (proteins, nucleic acids, polysaccharides, lipids, etc.) from simpler organic substances.

3. Emergence of primitive self-reproducing organisms.

The theory of biochemical evolution has the largest number of supporters among modern scientists. The earth arose about five billion years ago; Initially, its surface temperature was very high (4000 - 80000C). As it cooled, a solid surface was formed (the earth's crust - the lithosphere). The atmosphere, which originally consisted of light gases (hydrogen, helium), could not be effectively retained by the insufficiently dense Earth, and these gases were replaced by heavier gases: 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 soup" 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, the primary living creatures of microscopic size were synthesized.

The most difficult problem in the modern theory of evolution is the transformation of complex organic substances into simple living organisms. Oparin believed that the decisive role in the transformation of the inanimate into the living belongs to proteins. Apparently, protein molecules, attracting water molecules, formed colloidal hydrophilic complexes. Further merging of such complexes with each other led to the separation of colloids from the aqueous medium (coacervation). On the border between the coacervate (from Latin coacervus - clot, heap) and the environment, lipid molecules were lined up - a primitive cell membrane. It is assumed that colloids could exchange molecules with the environment (a prototype of heterotrophic nutrition) and accumulate certain substances. Another type of molecule provided the ability to reproduce itself.

A. I. Oparin’s system of views was called the “coacervate hypothesis”.

The theory was substantiated, except for one problem, which for a long time turned a blind eye to almost all experts in the field of the origin of life. If spontaneously, by random template-free syntheses in a coacervate, single successful constructions of protein molecules arose (for example, effective catalysts that provide an advantage for this 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 has been unable to offer a solution to the problem of exact reproduction - within the coacervate and in generations - of single, randomly appearing effective protein structures.

6. MODERN VIEWS ON THE ORIGIN OF LIFE ON EARTH.

The theory of A.I. Oparin and other similar hypotheses have one significant drawback: there is not a single fact that would confirm the possibility of abiogenic synthesis on Earth of at least the simplest living organism from lifeless compounds. Thousands of attempts at such a synthesis have been made in numerous laboratories around the world. For example, the American scientist S. Miller, based on assumptions about the composition of the Earth's primary atmosphere, passed electrical discharges through a mixture of methane, ammonia, hydrogen and water vapor in a special device. He managed to obtain molecules of amino acids - those basic "building blocks" that make up the basis of life - proteins. These experiments were repeated many times, some of the scientists managed to get quite long chains of peptides (simple proteins). But only! No one has been lucky enough to synthesize even the simplest living organism. Nowadays Redi's principle is popular among scientists: "The living - only from the living."

But suppose that such attempts will someday be crowned with success. What will such an experience prove? Only that for the synthesis of life, the human mind, complex advanced science and modern technology are needed. None of this existed on the original Earth. Moreover, the synthesis of complex organic compounds from simple ones contradicts the second law of thermodynamics, which prohibits the transition of material systems from a state of greater probability to a state of lesser probability, and the development from simple organic compounds to complex ones, then from bacteria to humans, took place in this direction. Here we observe nothing but the creative process. The second law of thermodynamics is an immutable law, the only law that has never been questioned, violated or refuted. Therefore, the order (gene information) cannot spontaneously arise from the disorder of random processes, which is confirmed by the theory of probability.

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. So, L. Blumenfeld proved that the probability of random formation of at least one DNA molecule (deoxyribonucleic acid - one of the most important components of the genetic code) during the entire existence of the Earth is 1/10800 Think about the negligibly small value of this number! Indeed, in its denominator there is a figure, where after one there is a series of 800 zeros, and this number is an incredible number of times greater than the total number of all atoms in the Universe. The modern American astrophysicist C. Wickramasinghe so figuratively expressed the impossibility of abiogenic synthesis: “It is faster that a hurricane that sweeps over a cemetery of old aircraft will assemble a brand new superliner from pieces of scrap than life will arise from its components as a result of a random process.”

Contradict the theory of abiogenic synthesis and geological data. No matter how far we penetrate into the depths of geological history, we do not find traces of the "Azoic era", that is, the period when life did not exist on Earth.

Now paleontologists in rocks whose age reaches 3.8 billion years, that is, close to the time of the formation of the Earth (4-4.5 billion years ago, according to recent estimates), have found fossils of rather complexly organized creatures - bacteria, blue-green algae, simple fungi. V. Vernadsky was sure that life is geologically eternal, that is, there was no era in geological history when our planet was lifeless. “The problem of abiogenesis (spontaneous generation of living organisms),” the scientist wrote in 1938, “remains fruitless and paralyzes really overdue scientific work.”

The terrestrial form of life is extremely closely related to the hydrosphere. This is evidenced by at least 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%). Obviously, life on Earth was formed only when the hydrosphere appeared on it, and this, according to geological information, happened almost from the beginning of the existence of our planet. Many of the properties of living organisms are due precisely to the properties of water, while water itself is a phenomenal compound. So, according to P. Privalov, water is a cooperative system in which any action is distributed by a "relay" way over thousands of interatomic distances, that is, there is a "far action".

Some scientists believe that the entire hydrosphere of the Earth, in essence, is 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 constituent parts, “drops” of this supermolecule of terrestrial water.

Although we still know only the terrestrial protein-nucleic-aquatic life, this does not mean that its other forms cannot exist in the boundless Cosmos. Some scientists, in particular American ones, G. Feinberg and R. Shapiro, model such hypothetically possible variants of it:

plasmoids - life in stellar atmospheres due to magnetic forces associated with groups of mobile electric charges;

radiobes - life in interstellar clouds based on aggregates of atoms that are in different states of excitation;

lavabobs - life based on silicon compounds, which can exist in lakes of molten lava on very hot planets;

waterfowl - life that can exist at low temperatures on planets covered with "reservoirs" of liquid methane, and draw energy from the conversion of orthohydrogen to parahydrogen;

thermophages are a type of cosmic life that derives energy from the temperature gradient in the atmosphere or oceans of planets.

Of course, such exotic life forms so far exist only in the imagination of scientists and science fiction writers. Nevertheless, the possibility of the real existence of some of them, in particular plasmoids, is not ruled out. There are some reasons to believe that on Earth, in parallel with "our" form of life, there is another kind of it, similar to the mentioned plasmoids. These include some types of UFOs (unidentified flying objects), formations similar to ball lightning, as well as invisible to the eye, but fixed by color photographic film, energy “clots” flying in the atmosphere, which in some cases showed reasonable behavior.

Thus, now there is reason to assert that life on Earth appeared from the very beginning of its existence and arose, according to C. Wickramasinghe, "from an all-penetrating general galactic living system."

CONCLUSION.

Do we have a logical right to recognize the fundamental difference between the living and the non-living? 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 form, stand out from it? Can we recognize organisms as formations completely, fundamentally different from the rest of the world?

Biology of the 20th century deepened the understanding of the essential features of the living, revealing the molecular foundations of life. At the heart of the modern biological picture of the world lies the idea that the living world is a grandiose system of highly organized systems.

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

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

LITERATURE.

1. Bernal D. "The Emergence of Life" Appendix No. 1: Oparin A.I. "The Origin of Life". - M.: "Mir", 1969.

2. Vernadsky V.I. Living substance. - M., 1978.

3. Naydysh V. M. Concepts of modern natural science. - M., 1999.

4. General biology./ Ed. N. D. Lisova. - Mn., 1999.

5. Ponnamperuma S. "The Origin of Life". - M.: "Mir", 1977.

6. Smirnov I.N., Titov V.F. Philosophy. Textbook for students of higher educational institutions. - M.: Russian Economic Academy. Plekhanov, 1998.

Tutoring

Need help learning a topic?

Our experts will advise or provide tutoring services on topics of interest to you.
Submit an application indicating the topic right now to find out about the possibility of obtaining a consultation.

Hypotheses of the origin of life on Earth

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The main hypotheses of the origin of life on earth.

Biochemical evolution

Among astronomers, geologists and biologists, it is generally accepted that the age of the Earth is approximately 4.5 - 5 billion years.

According to many biologists, in the past the state of our planet was little like the current one: probably the temperature on the surface was very high (4000 - 8000 ° C), and as the Earth cooled, carbon and more refractory metals condensed and formed the earth's crust ; the surface of the planet was probably bare and uneven, since as a result of volcanic activity, shifts and contractions of the crust caused by cooling, folds and ruptures formed on it.

It is believed that the gravitational field of the still insufficiently dense planet could not hold light gases: hydrogen, oxygen, nitrogen, helium and argon, and they left the atmosphere. But simple compounds containing among others these elements (water, ammonia, CO2 and methane). Until the Earth's temperature dropped below 100°C, all water was in a vapor state. The absence of oxygen was probably a necessary condition for the origin of life; as laboratory experiments show, organic substances (the basis of life) are much easier to form in an oxygen-poor atmosphere.

In 1923 A.I. Oparin, based on theoretical considerations, expressed the opinion that organic substances, possibly hydrocarbons, could be created in the ocean from simpler compounds. The energy for these processes was supplied by intense solar radiation, mainly ultraviolet radiation, which fell on the Earth before the ozone layer formed, which began to trap most of it. According to Oparin, the variety of simple compounds found in the oceans, the surface area of ​​the Earth, the availability of energy and time scales suggest that organic matter gradually accumulated in the oceans and formed a "primordial soup" in which life could arise.

It is impossible to understand the origin of man without understanding the origin of life. And to understand the origin of life is possible only by understanding the origin of the Universe.

First there was a big bang. This explosion of energy took place fifteen billion years ago.

Evolution can be thought of as the Eiffel Tower. At the base - energy, above - matter, planets, then life. And finally, at the very top - a man, the most complex and the last animal to appear.

The course of evolution:

15 billion years ago: the birth of the universe;

5 billion years ago: birth of the solar system;

4 billion years ago: birth of the Earth;

3 billion years ago: the first traces of life on Earth;

500 million years ago: first vertebrates;

200 Ma: First mammals;

70 million years ago: the first primates.

According to this hypothesis, proposed in 1865. by the German scientist G. Richter and finally formulated by the Swedish scientist Arrhenius in 1895, life could be brought to Earth from space. The most likely hit of living organisms of extraterrestrial origin with meteorites and cosmic dust. This assumption is based on data on the high resistance of some organisms and their spores to radiation, high vacuum, low temperatures, and other influences.

In 1969, the Murchison meteorite was found in Australia. It contained 70 intact amino acids, eight of which are part of the human protein!

Many scientists could argue that the squirrels that petrified upon re-entry into the atmosphere were dead. However, a prion, a protein that can withstand very high temperatures, has recently been discovered. The prion is stronger than the virus and is able to transmit the disease much faster. According to the Panspermia theory, man somehow originates from a virus of extraterrestrial origin that struck monkeys, which mutated as a result.

Theory of spontaneous generation of life

This theory was circulated in ancient China, Babylon, and Egypt as an alternative to the creationism with which it coexisted.

Aristotle (384-322 BC), often hailed as the founder of biology, held to the theory of the spontaneous generation of life. Based on his own observations, he developed this theory further, linking all organisms in a continuous series - the "ladder of nature." “For nature makes the transition from lifeless objects to animals with such a smooth succession, placing between them creatures that live, while not being animals, that between neighboring groups, due to their close proximity, one can hardly notice the differences” (Aristotle).

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

“These are the facts - living things can arise not only by mating animals, but also by decomposition of the soil. The same is the case with plants: some develop from seeds, while others, as it were, spontaneously generate under the action of all nature, arising from the decaying earth or certain parts of plants ”(Aristotle).

With the spread of Christianity, the theory of the spontaneous origin of life was not honored: it was recognized only by those who believed in witchcraft and worshiped evil spirits, but this idea continued to exist somewhere in the background for many more centuries.

Steady State Theory

According to this theory, the Earth never originated, but existed forever, it is always capable of supporting life, and if it has changed, then very little. Species have also always existed.

Estimates of the age of the earth have varied greatly, from about 6,000 years according to Archbishop Ussher's calculations, to 5,000 106 years according to modern estimates based on radioactive decay rates. Improved dating methods give increasingly higher estimates of the age of the Earth, which allows the proponents of the steady state theory to believe that the Earth has existed forever. According to this theory, species also never arose, they have always existed, and each species has only two alternatives - either a change in numbers or extinction.

Proponents of this theory do not recognize that the presence or absence of certain fossil remains may indicate the time of the appearance or extinction of a particular species, and cite as an example a representative of lobe-finned fish - coelacanth. Proponents of the steady state theory argue that only by studying living species and comparing them with fossil remains, one can conclude about extinction, and in this case it is very likely that it will turn out to be wrong. Using paleontological data to confirm the steady state theory, its few supporters interpret the appearance of fossils in an ecological aspect (increase in abundance, migration to places favorable for the preservation of remains, etc.). Much of the argument in favor of this theory has to do with obscure aspects of evolution, such as the significance of gaps in the fossil record, and it has been most elaborate in this direction.

creationism

Creationism (lat. sgea - creation). According to this concept, life and all species of living beings inhabiting the Earth are the result of a creative act of a higher being at some specific time. The main provisions of creationism are set out in the Bible, in the Book of Genesis. The process of the divine creation of the world is conceived as having taken place only once and therefore inaccessible to observation. This is enough to take the whole concept of divine creation out of the scope of scientific research. Science deals only with observable phenomena and therefore will never be able to either prove or reject this concept.

The theory of water origin of man

It says: man came directly from the water. Those. we were once something like marine primates, or humanoid fish.

The "Water Theory" of human origins was put forward by Alistair Hardy (1960) and developed by Elaine Morgan. After that, the idea was broadcast by many popularizers, for example, Jan Lindblad and the legendary submariner Jacques Maillol. According to Hardy and Morgan, one of our ancestors was a Miocene great ape of the proconsul family, which lived in the water for many millions of years before becoming terrestrial.

In favor of the origin of the "water monkey", the following human features are given:

1. The ability to hold your breath, apnea (including during vocalization) makes a person a diver.

2. Working with dexterous brushes and using tools is similar to the behavior of the raccoon and sea otter.

3. When wading water bodies, primates stand on their hind limbs. The semi-aquatic lifestyle contributed to the development of bipedal locomotion.

4. The loss of hair and the development of subcutaneous fat (in humans it is normally thicker than in other primates) are characteristic of aquatic mammals.

5. Large breasts helped keep the body in the water and warm the heart.

6. Hair on the head helped keep the baby.

7. An elongated foot helped swim.

8. There is a skin fold between the fingers.

9. By wrinkling the nose, a person can close the nostrils (monkeys - no)

10. The human ear takes in less water.

And for example, if a newborn is placed in water immediately after he leaves the mother's womb, he will feel great. He already knows how to swim. After all, in order for a newborn to move from the stage of a fish to the stage of an air-breathing mammal, it needs to be patted on the back.

The problem of the origin and evolution of life is one of the most interesting and at the same time the least studied issues related to philosophy and religion. Almost throughout almost the entire history of the development of scientific thought, it was believed that life is a self-generating phenomenon.

Main theories:

1) life was created by the Creator at a certain time - creationism (from lat. creation- creation);

2) life arose spontaneously from non-living matter;

3) life has always existed;

4) life was brought to Earth from space;

5) life arose as a result of biochemical evolution.

According to the theory creationism , the origin of life refers to a specific event in the past that can be calculated. The organisms that inhabit the Earth today are descended from separately created basic types of living beings. The created species were from the very beginning excellently organized and endowed with the capacity for some variability within certain boundaries (microevolution).

Theory of spontaneous origin of life existed in Babylon, Egypt and China as an alternative to creationism. It goes back to Empedocles and Aristotle: certain “particles” of matter contain some kind of “active principle”, which, under certain conditions, can create a living organism. Aristotle believed that the active principle is in a fertilized egg, sunlight, rotting meat. For Democritus, the beginning of life was in silt, for Thales, in water, for Anaxagoras, in air.

With the spread of Christianity, the ideas of spontaneous generation were declared heretical, and for a long time they were not remembered. But Helmont came up with a recipe for getting mice from wheat and dirty laundry. Bacon believed that decay is the germ of a new birth. The ideas of spontaneous generation of life were supported by Copernicus, Galileo, Descartes, Harvey, Hegel, Lamarck, Goethe, Schelling.

L. Pasteur in 1860 finally showed that bacteria can appear in organic solutions only if they were brought there earlier. And to get rid of microorganisms, sterilization is necessary, called pasteurization . Hence, the idea was strengthened that a new organism can only be from a living one.

Supporters theories of the eternal existence of life believe that on the ever-existing Earth, some species were forced to become extinct or dramatically change their numbers in certain places due to changes in external conditions. A clear concept on this path has not been developed, since there are some gaps and ambiguities in the paleontological record of the Earth.

The hypothesis about the appearance of life on Earth as a result of the transfer of certain germs of life from other planets was called panspermia (from Greek. pan- all, everyone and sperma- seed). The panspermia theory offers no mechanism for explaining the origin of life and moves the problem elsewhere in the universe. Having originated in space, life was preserved for a long time in anabiosis almost at T= O K and was brought to Earth by meteorites. At the beginning of the XX century. Arrhenius came up with the idea of ​​radiopanspermia. He described how particles of matter, dust particles and living spores of microorganisms leave the inhabited planets into the world space. They, while maintaining their viability, fly in the Universe due to light pressure and, when they land on a planet with suitable conditions, begin a new life.

In the last century, when studying the substance of meteorites and comets, many "precursors of the living" were discovered - organic compounds, water, formaldehyde, cyanogens. Modern adherents of the concept of panspermia believe that life on Earth was brought by accident or intentionally by space aliens. The point of view of astronomers C. Wickramasingh (Sri Lanka) and F. Hoyle (Great Britain) adjoins the panspermia hypothesis. They believe that in outer space, mainly in gas and dust clouds, microorganisms are present in large numbers, where, according to scientists, they are formed. Further, these microorganisms are captured by comets, which then, passing near the planets, "sow the germs of life."

The first scientific theory regarding the origin of living organisms on Earth was created by the Soviet biochemist A.I. Oparin. In 1924, he published works in which he outlined ideas about how life could have arisen on Earth. According to this theory, life arose in the specific conditions of the ancient Earth, and is considered as a natural result of the chemical evolution of carbon compounds in the Universe. According to this theory, the process that led to the emergence of life on Earth can be divided into three stages:

1) The emergence of organic substances.

2) The formation of biopolymers (proteins, nucleic acids, polysaccharides, lipids, etc.) from simpler organic substances.

3) The emergence of primitive self-reproducing organisms.

In ideas about the origin of life as a result of biochemical evolution the evolution of the planet itself plays an important role. The earth has existed for almost 4.5 billion years, and organic life for about 3.5 billion years. The young Earth was a hot planet with a temperature of 5 ... 8 10 3 K. As it cooled, refractory metals and carbon condensed, forming the earth's crust. The atmosphere of the primitive Earth was very different from the modern one. Light gases - hydrogen, helium, nitrogen, oxygen, argon, etc. - were not yet retained by the insufficiently dense planet, while heavier compounds remained (water, ammonia, carbon dioxide, methane).

When the Earth's temperature dropped below 100ºC, water vapor began to condense, forming the oceans. At this time, abiogenic synthesis took place, that is, in the primary terrestrial oceans saturated with various simple chemical compounds, “in the primary soup”, under the influence of volcanic heat, lightning discharges, intense ultraviolet radiation and other environmental factors, the synthesis of more complex organic compounds began, 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, the primary living creatures of microscopic size were synthesized.

The most difficult problem in the modern theory of evolution is the transformation of complex organic substances into simple living organisms. Oparin believed that the decisive role in the transformation of the inanimate into the living belongs to proteins. Apparently, protein molecules, attracting water molecules, formed colloidal hydrophilic complexes. Further merging of such complexes with each other led to the separation of colloids from the aqueous medium (coacervation). On the border between the coacervate (from lat. coacervus- clot, heap) and the environment lined up lipid molecules - a primitive cell membrane. It is assumed that colloids could exchange molecules with the environment (a prototype of heterotrophic nutrition) and accumulate certain substances.

The first organisms on earth were single-celled - prokaryotes. After several billion years, eukaryotes were formed, and with their appearance there was a choice of a plant or animal way of life, the difference between which lies in the method of nutrition and is associated with the process of photosynthesis. It is accompanied by the entry of oxygen into the atmosphere; the current oxygen content in the atmosphere of 21% was reached 25 million years ago as a result of the intensive development of plants.