The modern concept of the origin of life on Earth is the result of a broad synthesis natural sciences, many theories and hypotheses put forward by researchers of various specialties.
For the emergence of life on Earth, the primary atmosphere (of the planet) is important.
Earth's primary atmosphere contained methane, ammonia, water vapor, and hydrogen. By acting on a mixture of these gases with electric charges and ultraviolet radiation, scientists managed to obtain complex organic substances that make up living proteins. The elementary "building blocks" of the living are such chemical elements like carbon, oxygen, nitrogen and hydrogen.
In a living cell, by weight, it contains 70% oxygen, 17% carbon, 10% hydrogen, 3% nitrogen, followed by phosphorus, potassium, chlorine, calcium, sodium, magnesium, and iron.
So, the first step towards the emergence of life is the formation organic matter from inorganic. It is associated with the presence of chemical "raw materials", the synthesis of which can occur under certain radiation, pressure, temperature and humidity.
The emergence of the simplest living organisms was preceded by a long chemical evolution. From a small number of compounds (as a result of natural selection), substances with properties suitable for life arose. Compounds that arose on the basis of carbon formed the "primary soup" of the hydrosphere. Substances containing nitrogen and carbon arose in the molten depths of the Earth and were brought to the surface during volcanic activity.
The second step in the emergence of compounds is associated with the emergence of biopolymers in the Earth's primary ocean: nucleic acids, proteins. Assuming that during this period organic compounds were in the primary ocean of the Earth, then complex organic compounds could form on the surface of the ocean in the form of a thin film and in shallow water heated by the sun. The anaerobic environment facilitated the synthesis of polymers from inorganic compounds. Simple organic compounds began to combine into large biological molecules.
Enzymes were formed - protein substances - catalysts that contribute to the formation or disintegration of molecules. As a result of the activity of enzymes, the "primary elements" of life arose - nucleic acids, complex polymeric substances consisting of monomers.
Monomers in nucleic acids are arranged in such a way that they carry certain information, a code,
consisting in the fact that each amino acid included in the protein corresponds to a certain protein of 3 nucleotides (triplet). Proteins can be built on the basis of nucleic acids and exchange of matter and energy with the external environment can take place.
The symbiosis of nucleic acids formed "molecular genetic control systems".
At this stage, nucleic acid molecules acquired the properties of self-reproduction of their own kind, began to control the process of formation of protein substances.
At the origins of all living things were revertase and matrix synthesis from DNA to RNA, the evolution of the r - RNA - molecular system into DNA - nova. This is how the “genome of the biosphere” arose.
Heat and cold, lightning, ultraviolet reaction, atmospheric electric charges, gusts of wind and water jets - all this provided the beginning or attenuation of biochemical reactions, the nature of their course, gene "bursts".
By the end of the biochemical stage, such structural formations as membranes appeared, limiting the mixture of organic substances from the external environment.
membranes played leading role in the construction of all living cells. The bodies of all plants and animals are made up of cells.
Modern scientists have come to the conclusion that the first organisms on Earth were single-celled prokaryotes. In their structure, they resembled bacteria or blue-green algae that currently exist.
For the existence of the first "living molecules", prokaryotes, as for all living things, an influx of energy from the outside is necessary. Each cell is a small "energy station". ATP and other compounds containing phosphorus serve as a direct source of energy for cells. Cells receive energy from food, they are able not only to spend, but also to store energy.
Scientists suggest that many of the first lumps of living protoplasm arose on Earth. About 2 billion years ago, a nucleus appeared in living cells. Eukaryotes evolved from prokaryotes. There are 25-30 species of them on Earth. The simplest of them are amoeba. In eukaryotes, there is a decorated nucleus in the cell with a substance containing the code for protein synthesis.
By this time, there was a “choice” of a plant or animal lifestyle. The difference between these lifestyles is related to the mode of nutrition and the occurrence of photosynthesis, which consists in the creation of organic substances (for example, sugars from carbon dioxide and water using light energy).
Thanks to photosynthesis, plants produce organic matter, due to which an increase in the mass of plants occurs, and produce a large amount of organic matter.
With the advent of photosynthesis, oxygen began to enter the Earth's atmosphere, and a secondary Earth atmosphere with a high oxygen content was formed.
The appearance of oxygen and the intensive development of land plants - greatest stage in the development of life on earth. From that moment, a gradual modification and development of living forms began.
Life with all its manifestations has produced profound changes in the development of our planet. Improving in the process of evolution, living organisms spread more and more widely on the planet, taking a great part in the redistribution of energy and substances in the earth's crust, as well as in the air and water shells of the Earth.
The emergence and spread of vegetation led to a fundamental change in the composition of the atmosphere, initially containing very little free oxygen, and consisting mainly of carbon dioxide and probably methane and ammonia.
Plants assimilating carbon from carbon dioxide have created an atmosphere containing free oxygen and only traces of carbon dioxide. Free oxygen in the composition of the atmosphere served not only as an active chemical agent, but also as a source of ozone, which blocked the path of short ultraviolet rays to the Earth's surface (ozone screen).
At the same time, carbon, accumulated for centuries in the remains of plants, formed energy reserves in the earth's crust in the form of deposits of organic compounds ( coal, peat).
The development of life in the oceans led to the creation of sedimentary rocks consisting of skeletons and other remains of marine organisms.
These deposits, their mechanical pressure, chemical and physical transformations have changed the surface earth's crust. All this testified to the presence of a biosphere on Earth, in which life phenomena unfolded and continue to this day.
It has long history. It all started about 4 billion years ago. The Earth's atmosphere does not yet have an ozone layer, the concentration of oxygen in the air is very low and nothing is heard on the surface of the planet, except for erupting volcanoes and wind noise. Scientists believe that this is what our planet looked like when life began to appear on it. It is very difficult to confirm or deny this. Rocks that could give more information to people collapsed a long time ago, thanks to the geological processes of the planet. So, the main stages of the evolution of life on Earth.
The evolution of life on earth. unicellular organisms.
Life got its start with the advent of the simplest forms of life - single-celled organisms. The first unicellular organisms were prokaryotes. These organisms first appeared after the Earth became suitable for the beginning of life. would not allow even the simplest forms of life to appear on its surface and in the atmosphere. This organism did not require oxygen for its existence. The concentration of oxygen in the atmosphere increased, which led to the appearance of eukaryotes. For these organisms, oxygen became the main thing for life, in an environment where the oxygen concentration was low, they did not survive.
The first organisms capable of photosynthesis appeared 1 billion years after the appearance of life. These photosynthetic organisms were anaerobic bacteria . Life gradually began to develop, and after the content of nitrogenous organic compounds fell, new living organisms appeared that could use nitrogen from the Earth's atmosphere. Such creatures were blue-green algae. The evolution of unicellular organisms took place after terrible events in the life of the planet and all stages of evolution were protected under magnetic field earth.
Over time, the simplest organisms began to develop and improve their genetic apparatus and develop methods of their reproduction. Then, in the life of unicellular organisms, there was a transition to the division of their generative cells into male and female.
The evolution of life on earth. multicellular organisms.
After the emergence of unicellular organisms, more complex forms of life appeared - multicellular organisms. The evolution of life on planet Earth has acquired more complex organisms, characterized by a more complex structure and complex transitional stages of life.
The first stage of life Colonial unicellular stage. The transition from unicellular organisms to multicellular organisms, the structure of organisms and the genetic apparatus becomes more complicated. This stage is considered the simplest in the life of multicellular organisms.
Second stage of life Primary differentiated stage. A more complex stage is characterized by the beginning of the principle of "division of labor" between the organisms of one colony. At this stage, there was a specialization of body functions at the tissue, organ and system-organ levels. Thanks to this, a nervous system began to form in simple multicellular organisms. The system did not yet have a nerve center, but there is a coordination center.
Third stage of life Centralized-differentiated stage. During this stage, the morphophysiological structure of organisms becomes more complicated. The improvement of this structure occurs through the strengthening of tissue specialization. The food, excretory, generative and other systems of multicellular organisms become more complicated. At nervous systems a well-defined nerve center appears. The methods of reproduction are improving - from external fertilization to internal.
The conclusion of the third stage of life of multicellular organisms is the appearance of man.
Vegetable world.
The evolutionary tree of the simplest eukaryotes was divided into several branches. Multicellular plants and fungi appeared. Some of these plants could float freely on the surface of the water, while others were attached to the bottom.
psilophytes- plants that first mastered the land. Then other groups of land plants arose: ferns, club mosses and others. These plants reproduced by spores, but preferred aquatic environment a habitat.
Plants reached a great diversity in the Carboniferous period. Plants developed and could reach a height of up to 30 meters. In this period, the first gymnosperms appeared. Lycosform and cordaites could boast of the greatest distribution. Cordaites resembled coniferous plants in the form of a trunk and had long leaves. After this period, the surface of the Earth was diverse with various plants that reached 30 meters in height. After a large amount of time, our planet became similar to the one we know now. Now on the planet there is a huge variety of animals and plants, man has appeared. Man, as a rational being, after getting "on his feet" devoted his life to studying. Riddles began to interest a person, as well as the most important thing - where did a person come from and why does he exist. As you know, there are still no answers to these questions, there are only theories that contradict each other.
Since childhood, I have had an interesting book about the history of our planet on my shelf, which my children are already reading. I will try to briefly convey what I remember, and I will tell you when living organisms appeared.
When did the first living organisms appear?
The origin occurred due to a number of favorable conditions no later than 3.5 billion years ago - in archean era. The first representatives of the living world had the simplest structure, but gradually, as a result of natural selection, conditions developed for complicating the organization of organisms. This led to the emergence of completely new forms.
So, the subsequent periods of development of life are as follows:
- Proterozoic - the beginning of the existence of the first primitive multicellular organisms, for example, mollusks and worms. In addition, algae, the ancestors of complex plants, developed in the oceans;
- the Paleozoic is the time of the flood of the seas and significant changes in the outlines of the land, which led to the partial extinction of most of the animals and plants;
- Mesozoic - a new round in the development of life, accompanied by the emergence of a mass of species with subsequent progressive modification;
- Cenozoic - especially milestone- the emergence of primates and the development of man from them. At this time, the planet acquired the outlines of land familiar to us.
What did the first organisms look like?
The first creatures were small lumps of proteins, completely unprotected from any impact. Most died, but the survivors were forced to adapt, which marked the beginning of evolution.
Despite the simplicity of the first organisms, they had important abilities:
- reproduction;
- absorption of substances from the environment.
We can say that we were lucky - in the history of our planet there were practically no radical climate changes. Otherwise, even a small change in temperature could destroy a small life, which means that a person would not appear. The first organisms did not have a skeleton or shells, so it is quite difficult for scientists to trace history from geological deposits. The only thing that allows us to assert about life in the Archean is the content of gas bubbles in ancient crystals.
The origin of life on Earth is one of the most difficult and at the same time topical and interesting question in modern natural science.
Earth probably formed 4.5-5 billion years ago from a giant cloud space dust. particles of which are compressed into a hot ball. Water vapor was released from it into the atmosphere, and water fell out of the atmosphere onto the slowly cooling Earth over millions of years in the form of rain. In the recesses of the earth's surface, the prehistoric Ocean was formed. In it, about 3.8 billion years ago, the original life was born.
Origin of life on earth
How did the planet itself come about and how did the seas appear on it? There is one widely accepted theory about this. In accordance with it, the Earth was formed from clouds of cosmic dust, containing all chemical elements known in nature, which were compressed into a ball. Hot water vapor escaped from the surface of this red-hot ball, enveloping it in a continuous cloud cover. The water vapor in the clouds slowly cooled and turned into water, which fell in the form of abundant continuous rains on the still hot, burning Earth. On its surface, it again turned into water vapor and returned to the atmosphere. Over millions of years, the Earth gradually lost so much heat that its liquid surface began to harden as it cooled. This is how the earth's crust was formed.
Millions of years have passed, and the temperature of the Earth's surface has dropped even more. Storm water stopped evaporating and began to flow into huge puddles. Thus began the effect of water on earth's surface. And then, because of the drop in temperature, there was a real flood. Water, which had previously evaporated into the atmosphere and turned into its constituent part, continuously rushed down to the Earth, powerful showers fell from the clouds with thunder and lightning.
Little by little, in the deepest depressions of the earth's surface, water accumulated, which no longer had time to completely evaporate. There was so much of it that gradually a prehistoric Ocean was formed on the planet. Lightning cut the sky. But no one saw it. There was no life on Earth yet. The continuous downpour began to wash away the mountains. Water flowed from them in noisy streams and stormy rivers. Over millions of years, water flows have deeply corroded the earth's surface and in some places valleys have appeared. The content of water in the atmosphere decreased, and more and more accumulated on the surface of the planet.
The continuous cloud cover became thinner, until one day the first ray of the sun touched the Earth. The continuous rain is over. Most of the land was covered by the prehistoric Ocean. From its upper layers, water washed out a huge amount of soluble minerals and salts that fell into the sea. The water from it continuously evaporated, forming clouds, and the salts settled, and over time there was a gradual salinization. sea water. Apparently, under some conditions that existed in antiquity, substances were formed from which special crystalline forms arose. They grew, like all crystals, and gave rise to new crystals, which attached more and more new substances to themselves.
Sunlight and possibly very strong electrical discharges served as a source of energy in this process. Perhaps the first inhabitants of the Earth were born from such elements - prokaryotes, organisms without a formed nucleus, similar to modern bacteria. They were anaerobes, that is, they did not use free oxygen for respiration, which was not yet in the atmosphere at that time. The source of food for them was organic compounds that arose on the still lifeless Earth as a result of exposure to ultraviolet radiation from the Sun, lightning discharges and heat generated during volcanic eruptions.
Life then existed in a thin bacterial film at the bottom of reservoirs and in humid places. This era of the development of life is called the Archean. From bacteria, and possibly in a completely independent way, tiny unicellular organisms also arose - the oldest protozoa.
What did the primitive Earth look like?
Fast forward to 4 billion years ago. The atmosphere does not contain free oxygen, it is only in the composition of oxides. Almost no sounds, except for the whistle of the wind, the hiss of water erupting with lava and the impact of meteorites on the surface of the Earth. No plants, no animals, no bacteria. Maybe this is what the Earth looked like when life appeared on it? Although this problem has been of concern to many researchers for a long time, their opinions on this matter differ greatly. The conditions on the Earth of that time could be evidenced by rocks, but they have long been destroyed as a result of geological processes and movements of the earth's crust.
Theories about the origin of life on Earth
In this article, we will briefly talk about several hypotheses for the origin of life, reflecting modern scientific ideas. According to Stanley Miller, a well-known expert in the field of the origin of life, one can talk about the origin of life and the beginning of its evolution from the moment when organic molecules organized themselves into structures that could reproduce themselves. But this raises other questions: how did these molecules come about; why they could reproduce themselves and assemble into those structures that gave rise to living organisms; what are the conditions for this?
There are several theories about the origin of life on Earth. For example, one of the long-standing hypotheses says that it was brought to Earth from space, but there is no conclusive evidence for this. In addition, the life that we know is surprisingly adapted to exist precisely in terrestrial conditions, therefore, if it originated outside the Earth, then on a terrestrial-type planet. Most modern scientists believe that life originated on Earth, in its seas.
Theory of biogenesis
In the development of the teachings on the origin of life, an important place is occupied by the theory of biogenesis - the origin of the living only from the living. But many consider it untenable, since it fundamentally opposes the living to the inanimate and affirms the idea of the eternity of life rejected by science. Abiogenesis - the idea of the origin of living things from non-living things - the initial hypothesis modern theory origin of life. In 1924, the famous biochemist A.I. Oparin suggested that with powerful electrical discharges in earth's atmosphere, which 4-4.5 billion years ago consisted of ammonia, methane, carbon dioxide and water vapor, the simplest organic compounds necessary for the emergence of life could arise. Academician Oparin's prediction came true. In 1955, the American researcher S. Miller, passing electric charges through a mixture of gases and vapors, obtained the simplest fatty acid, urea, acetic and formic acids and several amino acids. Thus, in the middle of the 20th century, the abiogenic synthesis of protein-like and other organic substances was experimentally carried out under conditions reproducing the conditions of the primitive Earth.
Panspermia theory
The theory of panspermia is the possibility of transferring organic compounds, spores of microorganisms from one cosmic body to another. But it does not at all give an answer to the question, how did life originate in the Universe? There is a need to justify the emergence of life at that point in the Universe, the age of which, according to the theory big bang, is limited to 12-14 billion years. Until that time, there were not even elementary particles. And if there are no nuclei and electrons, there is no chemical substances. Then, within a few minutes, protons, neutrons, electrons arose, and matter entered the path of evolution.
This theory is based on multiple sightings of UFOs, rock carvings of things that look like rockets and "astronauts", and reports of alleged encounters with aliens. When studying the materials of meteorites and comets, many "precursors of life" were found in them - substances such as cyanogens, hydrocyanic acid and organic compounds, which, possibly, played the role of "seeds" that fell on the bare Earth.
Supporters of this hypothesis were laureates Nobel Prize F. Creek, L. Orgel. F. Crick based on two indirect evidence: universality genetic code: necessary for the normal metabolism of all living beings of molybdenum, which is now extremely rare on the planet.
The origin of life on Earth is impossible without meteorites and comets
A researcher from Texas Tech University, after analyzing the vast amount of information collected, put forward a theory of how life could form on Earth. The scientist is sure that the appearance of early forms the simplest life on our planet would be impossible without the participation of comets and meteorites that fell on it. The researcher shared his work at the 125th annual meeting of the Geological Society of America, held on October 31 in Denver, Colorado.
Author of the work, professor of geoscience at the Texas technological university(TTU) and curator of the museum of paleontology at the university, Sankar Chatterjee said that he came to this conclusion after analyzing information about the early geological history of our planet and comparing these data with various theories of chemical evolution.
The expert believes that this approach allows us to explain one of the most hidden and not fully understood periods in the history of our planet. According to many geologists, the bulk of space "bombardments" involving comets and meteorites occurred at a time of about 4 billion years ago. Chatterjee believes that the earliest life on Earth formed in craters left by impacts of meteorites and comets. And most likely this happened during the period of the "Late Heavy Bombardment" (3.8-4.1 billion years ago), when the collision of small space objects with our planet increased dramatically. At that time, there were several thousand cases of comets falling at once. Interestingly, this theory is indirectly supported by the Nice Model. According to it, the real number of comets and meteorites that should have fallen to the Earth at that time corresponds to the real number of craters on the Moon, which in turn was a kind of shield for our planet and did not allow the endless bombardment to destroy it.
Some scientists suggest that the result of this bombardment is the colonization of life in the oceans of the Earth. At the same time, several studies on this topic indicate that our planet has more water reserves than it should. And this surplus is attributed to comets that flew to us from the Oort Cloud, which is presumably one light year away from us.
Chatterjee points out that the craters formed by these collisions were filled with melted water from the comets themselves, as well as the necessary chemical building blocks necessary for the formation of the simplest organisms. At the same time, the scientist believes that those places where life did not appear even after such a bombardment simply turned out to be unsuitable for this.
“When the Earth formed about 4.5 billion years ago, it was completely unsuitable for the appearance of living organisms on it. It was a real boiling cauldron of volcanoes, poisonous hot gas and meteorites constantly falling on it, ”writes the online journal AstroBiology, referring to the scientist.
“And after one billion years, it became a quiet and calm planet, rich in huge reserves of water, inhabited by various representatives of microbial life - the ancestors of all living beings.”
Life on Earth could have originated from clay
A group of scientists led by Dan Luo from Cornell University came up with a hypothesis that ordinary clay could serve as a concentrator for the most ancient biomolecules.
Initially, the researchers were not concerned with the problem of the origin of life - they were looking for a way to increase the efficiency of cell-free protein synthesis systems. Instead of letting DNA and its supporting proteins float freely in the reaction mixture, the scientists tried to force them into hydrogel particles. This hydrogel, like a sponge, absorbed the reaction mixture, sorbed the necessary molecules, and as a result, all the necessary components were locked in a small volume - just as it happens in a cell.
The authors of the study then tried to use clay as an inexpensive substitute for hydrogel. Clay particles turned out to be similar to hydrogel particles, becoming a kind of microreactors for interacting biomolecules.
Having received such results, scientists could not help but recall the problem of the origin of life. Clay particles, with their ability to sorb biomolecules, could actually serve as the very first bioreactors for the very first biomolecules before they had membranes. This hypothesis is also supported by the fact that the leaching of silicates and other minerals from rocks with the formation of clay began, according to geological estimates, just before, according to biologists, the most ancient biomolecules began to combine into protocells.
In water, or rather in solution, little could happen, because the processes in solution are absolutely chaotic, and all compounds are very unstable. Clay by modern science - more precisely, the surface of particles of clay minerals - is considered as a matrix on which primary polymers could form. But this is also only one of many hypotheses, each of which has its own strengths and weak sides. But in order to simulate the origin of life on a full scale, one must really be God. Although in the West today there are already articles with the titles "Cell Construction" or "Cell Modeling". For example, one of the last Nobel laureates James Szostak is now actively trying to create efficient cell models that reproduce on their own, reproducing their own kind.
Theory of spontaneous (spontaneous) generation
The theory of spontaneous generation of life was widespread in the ancient world - Babylon, China, Ancient Egypt And Ancient Greece(This theory was followed, in particular, by Aristotle).
Scientists ancient world And medieval Europe they believed that living beings constantly arise from inanimate matter: worms - from mud, frogs - from mud, fireflies - from morning dew, etc. So, the famous Dutch scientist of the 17th century. Van Helmont quite seriously described in his scientific treatise an experience in which he got mice in a locked dark closet directly from a dirty shirt and a handful of wheat in 3 weeks. For the first time, the Italian scientist Francesco Redi (1688) decided to subject a widely accepted theory to experimental verification. He placed several pieces of meat in vessels and covered some of them with muslin. In open vessels, white worms appeared on the surface of rotting meat - fly larvae. There were no fly larvae in the vessels covered with muslin. Thus, F. Redi managed to prove that fly larvae do not appear from rotting meat, but from eggs laid by flies on its surface.
In 1765, the famous Italian scientist and physician Lazzaro Spalanzani boiled meat and vegetable broths in sealed glass flasks. Broths in sealed flasks did not spoil. He concluded that under the influence of high temperature all living creatures capable of causing spoilage of the broth died. However, the experiments of F. Redi and L. Spalanzani did not convince everyone. Vitalist scientists (from Latin vita - life) believed that spontaneous generation of living beings does not occur in boiled broth, since a special “life force” is destroyed in it, which cannot penetrate into a sealed vessel, since it is transported through the air.
Disputes about the possibility of spontaneous generation of life intensified in connection with the discovery of microorganisms. If complex living beings can't reproduce spontaneously, perhaps microorganisms can?
In this regard, in 1859, the French Academy announced the award of a prize to the one who finally decides the question of the possibility or impossibility of spontaneous generation of life. This award was received in 1862 by the famous French chemist and microbiologist Louis Pasteur. Just like Spalanzani, he boiled nutrient broth in a glass flask, but the flask was not ordinary, but with a neck in the form of a 5-shaped tube. Air, and hence the "life force", could penetrate into the flask, but the dust, and with it the microorganisms present in the air, settled in the lower elbow of the 5-shaped tube, and the broth in the flask remained sterile (Fig. 2.1.1 ). However, it was worth breaking the neck of the flask or rinsing the lower knee of the 5-shaped tube with sterile broth, as the broth began to quickly become cloudy - microorganisms appeared in it.
Thus, thanks to the work of Louis Pasteur, the theory of spontaneous generation was recognized as untenable and in scientific world the theory of biogenesis was established, the brief formulation of which is “everything living is from living things”.
However, if all living organisms in the historically foreseeable period of human development originate only from other living organisms, the question naturally arises: when and how did the first living organisms appear on Earth?
Creation theory
The theory of creationism assumes that all living organisms (or only their simplest forms) were created (“designed”) in a certain period of time by some supernatural being (deity, absolute idea, supermind, supercivilization, etc.). It is obvious that the followers of most of the leading religions of the world, in particular the Christian religion, adhered to this point of view from ancient times.
The theory of creationism is still quite widespread, not only in religious, but also in scientific circles. It is usually used to explain the most complex, unresolved issues of biochemical and biological evolution associated with the emergence of proteins and nucleic acids, the formation of the mechanism of interaction between them, the emergence and formation of individual complex organelles or organs (such as the ribosome, eye or brain). Acts of periodic "creation" also explain the absence of clear transitional links from one type of animal
to another, for example, from worms to arthropods, from monkeys to humans, etc. It must be emphasized that the philosophical dispute about the primacy of consciousness (supermind, absolute idea, deity) or matter cannot be resolved in principle, however, since an attempt to explain any difficulties of modern biochemistry and evolutionary theory fundamentally incomprehensible supernatural acts of creation takes these questions beyond scientific research, the theory of creationism cannot be attributed to the category of scientific theories of the origin of life on Earth.
Steady state and panspermia theories
Both of these theories are complementary elements of a single picture of the world, the essence of which is as follows: the universe exists forever and life exists in it forever (stationary state). Life is carried from planet to planet by "seeds of life" traveling in outer space, which can be part of comets and meteorites (panspermia). Similar views on the origin of life were held, in particular, by Academician V.I. Vernadsky.
However, the theory of the stationary state, which assumes an infinitely long existence of the universe, is not consistent with the data of modern astrophysics, according to which the universe arose relatively recently (about 16 billion years ago) by means of a primary explosion.
It is obvious that both theories (panspermia and stationary state) do not offer an explanation of the mechanism of the primary origin of life at all, transferring it to other planets (panspermia) or moving it to infinity in time (the theory of a stationary state).
Living on earth - where are we from? There is no shortage of versions - from purely scientific to the most fantastic. Mankind has been looking for an answer to this question for thousands of years. The well-known Russian biophysicist Vsevolod Tverdislov tried to answer it during a lecture held in educational center"Sirius". He explained why there is only one living organism on Earth, what is common between the slime mold and railways in Tokyo and how to look for aliens. "Lenta.ru" gives the main theses of his speech.
Three questions
In science, for enlightened humanity, there are only three questions: how the Universe appeared, how life originated in it, and how living things learned to think. To understand such global topics, you need to think on a large scale, not within the framework of any one particular science.
Many processes can be explained with the help of such a concept as “self-organization of active media”. The active medium energetically and informationally combines heterogeneous processes in space and time. Such seemingly different phenomena as the spread of fire in a steppe fire, the spread of rumors and infections, currencies or languages are explained in the same way, if we consider them from the standpoint of biophysics.
Biophysics is a branch of biology that studies the physical aspects of the existence of living nature at all its levels, from molecules and cells to the biosphere as a whole, as well as the science of physical processes occurring in biological systems different levels organization and the influence of various physical factors on biological objects. Biophysics is called upon to reveal the links between the physical mechanisms that underlie the organization of living objects and the biological characteristics of their life activity.
In other words, the mechanisms of self-organization in physicochemical, biological, ecological, and social systems can be considered from a general standpoint. Having an understanding of the self-organization of active media, it is possible to create models that describe such seemingly dissimilar processes as the operation of a laser, blood coagulation, chemical reactions, heartbeat or the appearance of annual rings in a tree.
Even Aristotle stated: “It is correct in philosophy to consider similarities even in things that are far apart from each other.” modern science proceeds from the fact that this statement is true not only for philosophy.
We are local
How many organisms are there on Earth? One: the biosphere. This is the only self-sufficient organism, under its feet is the periodic table, ash nu falls from above, that is, light quanta. Well, the conditions of the Earth, of course, must be taken into account.
The active medium self-organizes according to the same principles, regardless of its size. As an example, consider how a slime mold spreads along the bark of an oak tree. The simplest organism, a cell half a millimeter in size, a piece of mucus that can grow so large that it will cover meters of a tree.
Scientists conducted an experiment based on geographical map Tokyo and surroundings. Around the slime mold, which, as it were, is located on the site of the Japanese capital, they laid out food in those places where the cities and towns neighboring Tokyo are located. The slime mold began to move towards food, laying channels to it - "paths". When the researchers compared the movement pattern of the experimental organism and the real map of the Japanese transport arteries, they matched. All active media self-organize, obeying the same laws.
Self-organization is the basis of all life on earth. At the same time, it is important to take into account that this self-organization is determined primarily physical laws- even in biology, although people are used to interpreting biology through chemical compounds. If we are talking about heredity, then remember DNA. When talking about biological working tools, they mean proteins and enzymes. If you hear about the cell membrane, then lipid membranes come to mind.
As a result, even astronomers look for carbon compounds that resemble amino acids when looking for life in the universe. If something resembling nucleic acids is encountered, then the assumption is made that life forms exist there. But it is not at all obvious that outside the Earth there will be the same DNA as here.
How does natural selection work on Earth? Nature prefers certain acids and rejects others not because she likes or dislikes them. And not even the amino acids themselves are selected - nature chooses the principles of efficiency among different physical forms: the most effective wins. This means that extraterrestrial civilizations must be sought not through the DNA that we, people, are made of, but through the physical forms of energy consumption.
This is the basis of the concept of the Dyson sphere, developed by the American astrophysicist Freeman Dyson. By the way, he borrowed the idea from the book "The Starmaker" by science fiction writer Olaf Stapledon. How did he suggest looking for alien intelligence? It is necessary to create in space a thin spherical shell of large radius, comparable to the radius of planetary orbits, with a star in the center. It is assumed that an advanced civilization of aliens can use the sphere to fully utilize the energy of a star or to solve the problem of living space. By energy fluctuations aliens will be discovered.
So far, not a single even the most primitive compound has been found outside the Earth, which could not be synthesized on our planet. Everything that is found in space is produced by the Earth itself now. In other words, there is no evidence that life on Earth was introduced from outside. This refutes the panspermia hypothesis, which suggests that the germ of life (for example, spores of microorganisms) was brought to our planet from space, say, by a meteorite.
If five amino acids arrive on a meteorite, you still need to make a cell out of them. Imagine that you have a violin, a drum, and a bassoon, but just because you have these musical instruments does not mean you have an orchestra. This is the main secret of the origin of life. No one brought this orchestra to us on Earth. All compounds that are found in space are also produced on Earth - with the help of lightning and natural catalysts.
Avoid balance
You can often hear the expression "this organism is in equilibrium with environment". The physicist interprets this phrase unambiguously: "this organism is dead." We are fundamentally non-equilibrium and removed from thermodynamic equilibrium, and if we talk about our relations with the environment, then we are in thermodynamic, energy and material balance. It can be stationary relations or non-stationary, but not equilibrium. We can only have balance in the graveyard.
The very essence of life is the interaction of differences in chemical and electrical potentials, concentrations, and so on. Only in the case of inequality and disequilibrium can a chemical process take place. From the point of view of a biophysicist, energy life is a parabola. At the bottom, life stops, in a sense it is not there. The processes of self-organization of the active medium begin when the equilibrium ends and the system moves away from it.
If we take two systems with the same electric potential - no matter how great it is - then there can be no movement of charges. We need asymmetry. This is the main condition for starting processes. Chemical processes driven by physics. Modern systems biology and biophysics are built on this. And now one of the most promising areas is science, which, on the one hand, includes biophysics, and, on the other, synergetics.
Synergetics, or theory complex systems- an interdisciplinary area of science that studies the general patterns of phenomena and processes in complex non-equilibrium systems (physical, chemical, biological, environmental, social, and others) based on their inherent principles of self-organization. Synergetics is an interdisciplinary approach, since the principles governing the processes of self-organization appear to be the same regardless of the nature of the systems, and a common mathematical apparatus should be suitable for their description.
The famous French physicist, Nobel Prize winner Pierre Curie said that nature is driven by the violation of symmetry, the movement itself is essentially a distortion of symmetry, because symmetry is static.
It must be borne in mind that nature often does not obey what physicists traditionally call "law". For example, Hooke's law is a statement according to which the deformation that occurs in an elastic body is directly proportional to the force applied to it. But this law is not applicable to large deformations - it is impossible to stretch a spring, for example, by 10 kilometers. So, not every law of physics is a law of nature. You have to understand proportions. linear dependencies. Here it becomes obvious that systems far from equilibrium can pass through smooth sections and fall into the so-called bifurcation points - that is, bifurcations.
Very often (especially politicians) they say that development should follow the path of evolution, not revolution. But evolution, including biological evolution, after a smooth development goes just through a bifurcation, and it is very difficult to predict what it will be like after passing the bifurcation point. The degree of accuracy of the forecast is about the same as that of weather forecasters. The probability of a 100% match is unlikely, since even nature itself does not know how it will behave after passing the bifurcation point.
Extremely simplifying, we can say that life on Earth is a system consisting of two conjugated subsystems - the biosphere and the human "economy". Each of them is a hierarchically organized active environment, none of them can exist on its own.
It is in this direction that the science of the living is now developing - in the search for a relationship between the energy flows of matter and information and spatio-temporal self-organization. For example, why do fish often swim in large schools? In this way they reduce the water resistance for each individual moving fish. But suddenly a shark appears, and the joint falls apart. It's functional, but it's also a change in symmetry. And if you look at what happened from the point of view of a biophysicist, this is a bifurcation.
On the verge of a new breakthrough
By the beginning of the 20th century, almost all the classical fundamental sciences seemed to have been completed. Geographic discoveries made, astronomers all the nearest constellations and device solar system described, geologists explored everything, physics and chemistry are completed, Maxwell's equations are written, electromagnetism is understood, theoretical mechanics is mastered, there is a periodic table, people understand how organic compounds are arranged. Everything seemed to be known - there was nowhere to go further.
And suddenly a breakthrough: appears quantum mechanics, the theory of relativity appears, quantum mechanics comes to chemistry and gives it a new powerful impetus. By the middle of the 20th century, the classical sciences had a huge number of branches: physics solid body, macromolecular physics, space physics and so on. The sciences scattered over a huge number of applied areas. Vladimir Ivanovich Vernadsky, the famous Russian and Soviet natural scientist, wrote: “The growth of scientific knowledge of the 20th century is rapidly blurring the lines between individual sciences. We are increasingly specializing not in sciences, but in problems.”
Thanks to this, there was a strong breakthrough of civilization, a powerful breakthrough. But humanity, rejoicing at a strong start, spent the second half of the 20th century and the beginning of the 21st very mediocre. Applied areas of science have not given the world anything essentially new, they are constantly updating the shell of old ideas. For example, nuclear power plants have become much more reliable, but the very principle of their operation has not changed since the 1950s. Gadgets are getting thinner, we say that they are more modern, but the principles of their operation remain the same.
For a new civilizational breakthrough, the time has come to focus not on applied areas of science, but on fundamental ones, in order to give the world a new breakthrough, which then applied areas will exploit for another hundred years.
A new combination of sciences is taking place. Physics began to connect its two extreme wings, combining the ideas of the smallest and the largest, that is elementary particles and the universe. Scientists are closely involved in the Big Bang theory. The same processes take place in biology. Researchers are consolidating their knowledge about the big (biosphere) and small (genome).
By the way, the inability to teach to see the picture of the world as a whole is one of the weak points and modern education: pupils and students receive a lot of disparate information that exists separately in the minds, without turning into a single knowledge. The often used expression “clip thinking” describes this situation in the best possible way.
What will the unification of sciences give? We will soon find out and perhaps be surprised. The famous English writer Arthur Clarke, one of the so-called "big three science fiction writers" whose influence was not limited to literature, in his book "Future Features" (1962) formulated "Clark's laws", and the first of them reads: "If deserved , the wise scientist says that something in science is possible, he is almost certainly right. If he says something is impossible, he is almost certainly wrong.”
