The question of the origin of life on Earth is one of the most difficult questions modern natural science, to which there is no unambiguous answer so far.
There are several theories about the origin of life on Earth, the most famous of which are:
- theory of spontaneous (spontaneous) generation;
- the theory of creationism (or creation);
- steady state theory;
- theory of panspermia;
- theory of biochemical evolution (the theory of A.I. Oparin).
Consider the main provisions of these theories.
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 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 deteriorate. 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 lat. vita- life) believed that spontaneous generation of living beings does not occur in a boiled broth, since a special “life force” is destroyed in it, which cannot penetrate into a sealed vessel, since it is carried 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. 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 the theory of biogenesis was established in the scientific world, a brief formulation of which is - "everything living is from living things."
Rice. 1. Pasteur flask
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
Creation theory 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 the scope of scientific research, the theory of creationism cannot be classified as 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).
Theory of biochemical evolution (theory of A.I. Oparin)
Of all theories of the origin of life, the most common and recognized in the scientific world is the theory of biochemical evolution, proposed in 1924 by the Soviet biochemist Academician A.I. Oparin (in 1936 he described it in detail in his book The Emergence of Life).
The essence of this theory is that biological evolution - i.e. The appearance, development and complication of various forms of living organisms was preceded by chemical evolution - a long period in the history of the Earth, associated with the emergence, complication and improvement of the interaction between elementary units, "bricks" that make up all living things - organic molecules.
Prebiological (chemical) evolution
According to most scientists (primarily astronomers and geologists), the Earth was formed as a celestial body about 5 billion years ago. by condensation of particles of a gas and dust cloud rotating around the Sun.
Under the influence of compressive forces, the particles from which the Earth is formed release a huge amount of heat. Thermonuclear reactions begin in the bowels of the Earth. As a result, the Earth gets very hot. Thus, 5 billion years ago The earth was a hot ball rushing through outer space, the surface temperature of which reached 4000-8000°C (laugh. 2).
Gradually, due to the radiation of thermal energy into outer space, the Earth begins to cool. About 4 billion years ago The earth cools so much that a hard crust forms on its surface; at the same time, light, gaseous substances escape from its bowels, rising up and forming the primary atmosphere. The composition of the primary atmosphere was significantly different from the modern one. Apparently, there was no free oxygen in the atmosphere of the ancient Earth, and its composition included substances in a reduced state, such as hydrogen (H 2), methane (CH 4), ammonia (NH 3), water vapor (H 2 O ), and possibly also nitrogen (N 2), carbon monoxide and carbon dioxide (CO and CO 2).
The reducing nature of the Earth's primary atmosphere is extremely important for the origin of life, since substances in a reduced state are highly reactive and, under certain conditions, are able to interact with each other, forming organic molecules. The absence of free oxygen in the atmosphere of the primary Earth (practically all of the Earth's oxygen was bound in the form of oxides) is also an important prerequisite for the emergence of life, since oxygen easily oxidizes and thereby destroys organic compounds. Therefore, in the presence of free oxygen in the atmosphere, the accumulation of ancient earth a significant amount of organic matter would be impossible.
About 5 billion years ago- the emergence of the Earth as a celestial body; surface temperature — 4000-8000°C
About 4 billion years ago - formation earth's crust and primary atmosphere
At 1000°C- in the primary atmosphere, the synthesis of simple organic molecules
The energy for synthesis is given by:
The temperature of the primary atmosphere is below 100 ° C - the formation of the primary ocean -
Synthesis of complex organic molecules - biopolymers from simple organic molecules:
- simple organic molecules - monomers
- complex organic molecules - biopolymers
Scheme. 2. Main stages of chemical evolution
When the temperature of the primary atmosphere reaches 1000°C, the synthesis of simple organic molecules begins in it, such as amino acids, nucleotides, fatty acids, simple sugars, polyhydric alcohols, organic acids, etc. Energy for synthesis is supplied by lightning discharges, volcanic activity, hard cosmic radiation, and, finally, ultraviolet radiation The Sun, from which the Earth is not yet protected by an ozone screen, and it is ultraviolet radiation that scientists consider the main source of energy for abiogenic (i.e., passing without the participation of living organisms) synthesis of organic substances.
The recognition and wide dissemination of the theory of A.I. Oparin was greatly facilitated by the fact that the processes of abiogenic synthesis of organic molecules are easily reproduced in model experiments.
The possibility of synthesizing organic substances from inorganic substances has been known since the beginning of the 19th century. Already in 1828, the outstanding German chemist F. Wöhler synthesized an organic substance - urea from inorganic - ammonium cyanate. However, the possibility of abiogenic synthesis of organic substances under conditions close to those of the ancient Earth was first shown in the experiment of S. Miller.
In 1953, a young American researcher, a graduate student at the University of Chicago, Stanley Miller, reproduced in a glass flask with electrodes soldered into it the primary atmosphere of the Earth, which, according to scientists of that time, consisted of hydrogen, methane CH 4, ammonia NH, and water vapor H 2 0 (Fig. 3). Through this gas mixture, S. Miller passed electric discharges simulating thunderstorms for a week. At the end of the experiment, α-amino acids (glycine, alanine, asparagine, glutamine), organic acids (succinic, lactic, acetic, glycocolic), γ-hydroxybutyric acid and urea were found in the flask. When repeating the experiment, S. Miller managed to obtain individual nucleotides and short polynucleotide chains of five to six links.
Rice. 3. Installation by S. Miller
In further experiments on abiogenic synthesis, conducted by various researchers, not only electrical discharges were used, but also other types of energy characteristic of the ancient Earth - cosmic, ultraviolet and radioactive radiation, high temperatures inherent in volcanic activity, as well as a variety of options gas mixtures simulating the primordial atmosphere. As a result, almost the entire spectrum of organic molecules characteristic of living things was obtained: amino acids, nucleotides, fat-like substances, simple sugars, organic acids.
Moreover, abiogenic synthesis of organic molecules can also occur on Earth at the present time (for example, in the course of volcanic activity). At the same time, not only hydrocyanic acid HCN, which is a precursor of amino acids and nucleotides, can be found in volcanic ejecta, but also individual amino acids, nucleotides, and even such complex structures. organic matter like porphyrins. Abiogenic synthesis of organic substances is possible not only on Earth, but also in outer space. The simplest amino acids are found in meteorites and comets.
When the temperature of the primary atmosphere dropped below 100 ° C, hot rains fell on the Earth and the primary ocean appeared. With streams of rain, abiogenically synthesized organic substances entered the primary ocean, which turned it, but figurative expression English biochemist John Haldane, into a diluted "primordial broth". Apparently, it is in the primordial ocean that the processes of formation of simple organic molecules—monomers of complex organic molecules—biopolymers begin (see Fig. 2).
However, the processes of polymerization of individual nucleoside, amino acids and sugars are condensation reactions, they proceed with the elimination of water, therefore, the aqueous medium does not contribute to polymerization, but, on the contrary, to the hydrolysis of biopolymers (i.e., their destruction with the addition of water).
The formation of biopolymers (in particular, proteins from amino acids) could take place in the atmosphere at a temperature of about 180°C, from where they were washed into the primary ocean with atmospheric precipitation. In addition, it is possible that on the ancient Earth, amino acids were concentrated in drying up reservoirs and polymerized in a dry form under the influence of ultraviolet light and the heat of lava flows.
Despite the fact that water promotes the hydrolysis of biopolymers, the synthesis of biopolymers in a living cell occurs precisely in an aqueous medium. This process is catalyzed by special catalytic proteins - enzymes, and the energy necessary for synthesis is released during the breakdown of adenosine triphosphoric acid - ATP. It is possible that the synthesis of biopolymers in the aquatic environment of the primary ocean was catalyzed by the surface of certain minerals. It has been experimentally shown that a solution of the amino acid alanine can polymerize in an aqueous medium in the presence of a special type of alumina. In this case, the peptide polyalanine is formed. The polymerization reaction of alanine is accompanied by the breakdown of ATP.
The polymerization of nucleotides is easier than the polymerization of amino acids. It has been shown that in solutions with a high salt concentration, individual nucleotides spontaneously polymerize, turning into nucleic acids.
The life of all modern living beings is a process of continuous interaction between the most important biopolymers of a living cell - proteins and nucleic acids.
Proteins are the "working molecules", "engineer molecules" of a living cell. Describing their role in metabolism, biochemists often use such figurative expressions as "the protein works", "the enzyme leads the reaction." The most important function of proteins is catalytic. As you know, catalysts are substances that accelerate chemical reactions, but they do not enter into the final products of the reaction. Tanks-catalysts are called enzymes. Enzymes in bend and thousands of times accelerate metabolic reactions. Metabolism, and hence life without them, is impossible.
Nucleic acids- these are "molecules-computers", molecules are the keepers of hereditary information. Nucleic acids do not store information about all the substances of a living cell, but only about proteins. It is enough to reproduce in the daughter cell the proteins characteristic of the mother cell so that they accurately recreate all the chemical and structural features of the mother cell, as well as the nature and rate of metabolism inherent in it. Nucleic acids themselves are also reproduced due to the catalytic activity of proteins.
Thus, the mystery of the origin of life is the mystery of the emergence of the mechanism of interaction between proteins and nucleic acids. What information does modern science have about this process? What molecules were the primary basis of life - proteins or nucleic acids?
Scientists believe that despite the key role of proteins in the metabolism of modern living organisms, the first "living" molecules were not proteins, but nucleic acids, namely ribonucleic acids (RNA).
In 1982, American biochemist Thomas Check discovered the autocatalytic properties of RNA. He experimentally showed that in a medium containing high concentrations of mineral salts, ribonucleotides spontaneously (spontaneously) polymerize, forming polynucleotides - RNA molecules. On the original polynucleotide chains of RNA, as on a matrix, RNA copies are formed by pairing of complementary nitrogenous bases. The RNA template copying reaction is catalyzed by the original RNA molecule and does not require the participation of enzymes or other proteins.
What happened next is fairly well explained by what might be called "natural selection" at the molecular level. During self-copying (self-assembly) of RNA molecules, inaccuracies and errors inevitably arise. The erroneous RNA copies are copied again. When copying again, errors may occur again. As a result, the population of RNA molecules in a certain part of the primary ocean will be heterogeneous.
Since RNA decay processes are also taking place in parallel with the synthesis processes, molecules with either greater stability or better autocatalytic properties will accumulate in the reaction medium (i.e., molecules that copy themselves faster, “multiply” faster).
On some RNA molecules, as on a matrix, self-assembly of small protein fragments - peptides can occur. A protein "sheath" is formed around the RNA molecule.
Along with autocatalytic functions, Thomas Check discovered the phenomenon of self-splicing in RNA molecules. As a result of self-splicing, RNA regions that are not protected by peptides are spontaneously removed from RNA (they are, as it were, “cut out” and “ejected”), and the remaining RNA regions encoding protein fragments “grow together”, i.e. spontaneously combine into a single molecule. This new RNA molecule will already code for a large complex protein (Figure 4).
Apparently, initially protein sheaths performed primarily a protective function, protecting RNA from destruction and thereby increasing its stability in solution (this is the function of protein sheaths in the simplest modern viruses).
Obviously, at a certain stage of biochemical evolution, RNA molecules, which encode not only protective proteins, but also catalytic proteins (enzymes) that sharply accelerate the rate of RNA copying, gained an advantage. Apparently, this is how the process of interaction between proteins and nucleic acids, which we now call life, arose.
In the process of further development, due to the appearance of a protein with the functions of an enzyme, reverse transcriptase, on single-stranded RNA molecules, molecules of deoxyribonucleic acid (DNA) consisting of two strands began to be synthesized. The absence of an OH group in the 2" position of deoxyribose makes DNA molecules more stable with respect to hydrolytic cleavage in slightly alkaline solutions, namely, the reaction of the medium in primary reservoirs was slightly alkaline (this reaction of the medium was also preserved in the cytoplasm of modern cells).
Where did the development of a complex process of interaction between proteins and nucleic acids take place? According to the theory of A.I. Oparin, the so-called coacervate drops became the birthplace of life.
Rice. 4. Hypothesis of the emergence of interaction between proteins and nucleic acids: a) in the process of self-copying of RNA, errors accumulate (1 - nucleotides corresponding to the original RNA; 2 - nucleotides that do not correspond to the original RNA - errors in copying); b) due to its physicochemical properties, amino acids “stick” to a part of the RNA molecule (3 - RNA molecule; 4 - amino acids), which, interacting with each other, turn into short protein molecules - peptides. As a result of self-splicing inherent in RNA molecules, the parts of the RNA molecule that are not protected by peptides are destroyed, and the remaining ones "grow" into a single molecule encoding a large protein. The result is an RNA molecule covered with a protein sheath (the most primitive modern viruses, for example, the tobacco mosaic virus, have a similar structure)
The phenomenon of coacervation consists in the fact that under certain conditions (for example, in the presence of electrolytes) macromolecular substances are separated from the solution, but not in the form of a precipitate, but in the form of a more concentrated solution - coacervate. When shaken, the coacervate breaks up into separate small droplets. In water, such drops are covered with a hydration shell (a shell of water molecules) that stabilizes them - fig. 5.
Coacervate drops have some semblance of metabolism: under the influence of purely physical and chemical forces, they can selectively absorb certain substances from the solution and release their decay products into the environment. By selectively concentrating substances from environment they can grow, but when they reach a certain size, they begin to "multiply", budding small droplets, which, in turn, can grow and "bud".
The coacervate droplets resulting from the concentration of protein solutions in the process of mixing under the action of waves and wind can be covered with a lipid shell: a single membrane resembling soap micelles (with a single detachment of a drop from the surface of water covered with a lipid layer), or a double membrane resembling a cell membrane ( when a drop covered with a single-layer lipid membrane falls again onto the lipid film covering the surface of the reservoir - Fig. 5).
The processes of the emergence of coacervate droplets, their growth and "budding", as well as "dressing" them with a membrane from a double lipid layer are easily modeled in the laboratory.
For coacervate droplets, there is also a process of "natural selection" in which the most stable droplets remain in solution.
Despite the outward resemblance of coacervate drops to living cells, coacervate drops lack the main sign of a living thing - the ability for accurate self-reproduction, self-copying. Obviously, the precursors of living cells were such coacervate drops, which included complexes of replicator molecules (RNA or DNA) and the proteins they encode. It is possible that RNA-protein complexes existed for a long time outside coacervate droplets in the form of the so-called “free-living gene”, or it is possible that their formation took place directly inside some coacervate droplets.
Possible path of transition from coacervate drops to primitive flares:
a) the formation of a coacervate; 6) stabilization of coacervate drops in an aqueous solution; c) - formation of a double lipid layer around the drop, similar to a cell membrane: 1 - coacervate drop; 2 - monomolecular layer of lipid on the surface of the reservoir; 3 — formation of a single lipid layer around the drop; 4 — formation of a double lipid layer around the drop, similar to a cell membrane; d) - a coacervate drop surrounded by a double lipid layer, with a protein-nucleotide complex included in its composition - a prototype of the first living cell
Extremely complex, not fully understood modern science From a historical point of view, the process of the emergence of life on Earth was extremely fast. For 3.5 billion years, the so-called. chemical evolution ended with the appearance of the first living cells and biological evolution began.
Creationism is a trend that originated among scientists and philosophers who did not deny Christianity and all its dogmas. It consists in the fact that everything material that exists in our world was born by the Creator - God. All teachings based on theology completely reject the theory of the evolution of the world. It is worth noting that over time, creationism finds more and more supporters. They come both from philosophers and priests, and from professors and researchers.
How it works?
In philosophy, creationism is primarily the main opponent of evolution. He denies the self-development of all living things, the transformation of the simple into the complex, improvement and other knowledge that is often taught to us in schools and institutes. Two sources serve as the basis for this: Christian Holy Scriptures and those related to nature, the development of people and animals, and various phenomena. Hence, we have a creationist hypothesis. To a greater extent, it has a biblical beginning, based on the Holy Scriptures. They say that in six days God created the sky, water, earth, people, animals, plants and everything else that surrounds us.
Fundamentals of Doctrine
An important role in the formation of this philosophical trend is played by facts that are not amenable to any explanation from the point of view of evolution. Among them, a place of honor is occupied by the problem of the origin of human spirituality, his ability to think abstractly and dream. Also a mystery is the emergence of structured grammar, which is present in any language.
Creationism and science
Based on this, many scientists claim that creationism is the same Second. There is no connection between the laws of biology and physics in the world, and also there is nothing in common between physical and chemical processes. In the course of such studies, scientists have repeatedly questioned the spontaneous generation of living organisms on the planet.
It is important to note that the most popular right now is young earth creationism. which involves literally following the words of the Bible. That is, our whole world was created really in a week. In contrast, there is old-earth creationism, which claims that six days is a metaphor that characterizes various time intervals in the history of being. At first, people learned the sky, the earth, then they delved into the study of plants and animals, and then their own kind became their subject of study.
Despite these internal divisions, the principle of creationism remains the same. He confirms the theory big bang and the expanding universe, but at the same time rejects Marxism as we understand it. Nowadays, this teaching is based on intricate principles that also consider aspects such as extraterrestrial intelligence, parallel worlds and, of course, God's participation in all this.
Creationism today
Modern creationism is a complex mix of science, religion, myths and facts. It is not studied in universities, but everyone can get acquainted with it, it is enough just to get the necessary literature and try to comprehend the nature of the world around us.
Introduction……………………………………………………………………………………....3
1. The concept of creationism…………………………………………………………………….4
2. The concept of spontaneous generation of life…………………………………………………………..5
3. The concept of a stationary state………………………………………………………...7
4. The concept of panspermia………………………………………………………………………8
5. The concept of the origin of life on Earth in the historical past as a result of processes that obey physical and chemical laws (abiogenesis)…………….10
Conclusion………………………………………………………………………………….12
List of literature used………………………………………………………….13
Introduction
Questions about the origin of nature and the essence of life have long been the subject of human interest in his desire to understand the world around him, understand himself and determine his place in nature. The origin of life is one of the three most important worldview problems along with the problem of the origin of our Universe and the problem of the origin of man.
This question not only attracts the close attention of scientists from different countries and specialties, but is of interest to all people in the world in general.
Today in the world there are a huge number of theories of the origin of life, some of them are more true, some less, but each of them has a grain of truth. However, this greatest mystery of mankind has not yet been solved, new theories are still appearing, there are disputes about their correctness.
Centuries of research and attempts to resolve these issues have given rise to different concepts of the origin of life. The most common are:
The concept of creationism - the divine creation of the living
The concept of spontaneous generation of life (vitalism)
Steady state concept
Panspermia concept - extraterrestrial origin of life
The concept of the origin of life on Earth in the historical past as a result of processes that obey physical and chemical laws (Oparin's hypothesis)
These theories will be considered in this paper.
1. The concept of creationism
She has the most ancient history, since in almost all polytheistic religions the emergence of life is regarded as an act of divine creation, evidence of which is the presence in living organisms of a special force that controls all biological processes. These views are shared by many religious teachings of European civilization. The process of the divine creation of the world and the living is inaccessible to observation, and the divine plan is inaccessible to human understanding.
According to creationism, the emergence of life on Earth could not be realized in a natural, objective, regular way; life is the result of a divine creative act. The origin of life refers to a specific event in the past that can be calculated. In 1650, Archbishop Asher of Ireland calculated that God created the world in October 4004 BC, and at 9 o'clock in the morning on October 23, man. He obtained this number from an analysis of the ages and family ties of all persons mentioned in the Bible. However, by that time there was already a developed civilization in the Middle East, which is proved by archaeological research. However, the issue of the creation of the world and man is not closed, since the texts of the Bible can be interpreted in different ways.
2. The concept of spontaneous generation of life (vitalism)
The theory of spontaneous origin of life originated in Babylon, Egypt and China as an alternative to creationism. It is based on the concept that under the influence of natural factors, the living can arise from the inanimate, the organic from the inorganic. It goes back to Empedocles and Aristotle.
Based on the information about animals that came from the soldiers of Alexander the Great and merchant travelers, Aristotle formed the idea of a gradual and continuous development of the living from the inanimate and created the idea of the "ladder of nature" in relation to the animal world. He did not doubt the spontaneous generation of frogs, mice and other small animals. Plato spoke of the spontaneous generation of living beings from the earth in the process of decay.
The idea of spontaneous generation became widespread in the Middle Ages and the Renaissance, when the possibility of spontaneous generation of not only simple, but also rather highly organized creatures, even mammals (for example, mice made of rags) was allowed. For example, in W. Shakespeare's tragedy "Antony and Cleopatra" Leonid says to Mark Antony: "Your Egyptian reptiles start up in the mud from the rays of your Egyptian sun. Here, for example, a crocodile ... ". There are known attempts by Paracelsus to develop recipes for an artificial person (homunculus).
Helmont came up with a recipe for getting mice from wheat and dirty laundry. Bacon also believed that decay is the germ of a new birth. The ideas of spontaneous generation of life were supported by Galileo, Descartes, Harvey, Hegel,
Against the theory of spontaneous generation in the 17th century. the Florentine doctor Francesco Redi spoke. Putting the meat in a closed pot, F. Redi showed that the larvae of blowflies do not spontaneously generate in rotten meat. Supporters of the theory of spontaneous generation did not give up, they argued that spontaneous generation of larvae did not occur for the sole reason that air did not enter the closed pot. Then F. Redi placed the pieces of meat in several deep vessels. He left some of them open, and covered some with muslin. After some time, in the open vessels, the meat swarmed with fly larvae, while in the vessels covered with muslin, there were no larvae in the rotten meat.
In the XVIII century. The German mathematician and philosopher Leibniz continued to defend the theory of spontaneous generation of life. He and his supporters argued that there is a special "life force" in living organisms. According to the vitalists (from the Latin "vita" - life), "life force" is present everywhere. Just breathe it in, and the inanimate becomes alive.”
The microscope opened the microworld to people. Observations showed that in a tightly closed flask with meat broth or hay infusion, microorganisms are detected after a while. But as soon as the meat broth was boiled for an hour and the neck was sealed, nothing appeared in the sealed flask. Vitalists suggested that prolonged boiling kills the "life force" that cannot penetrate the sealed flask.
The Paris Academy of Sciences appointed a prize for solving this issue, and in 1860 Louis Pasteur was able to prove that spontaneous generation of microorganisms does not occur. To do this, he used a flask with a long curved neck and boiled infusions at a temperature of 120 degrees. At the same time, microbes and their spores died, when cooling, the air passed into the flask, and with it the microorganisms, but they settled on the walls of the curved neck of the flask and did not fall into the infusion. Thus, the inconsistency of the theory of spontaneous generation was finally proved.
3. The concept of a steady state
According to this concept, the Earth never came into being and exists forever and is always capable of supporting life. If there have been changes to the Earth, it has been very minor.
As the main argument, the supporters of this concept put forward the existing uncertainties in physical, chemical, geological theories in determining the age of the Earth and the Universe as a whole.
Species, according to this concept, have always existed and for them there are only two possibilities: to survive at the expense of numbers or die out.
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 the cross-finned fish - coelacanth. 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.
Comparison of paleontological data with modern views can have, according to the supporters of this concept, only an ecological meaning: the movement of a species, an increase in its numbers, or extinction in adverse conditions.
The existing gaps in the paleontological record of species, which the French scientist J. Cuvier (1769 - 1832) drew attention to, and the explanation of their occurrence by periodically occurring catastrophes on Earth, are used by supporters of this concept as arguments in favor of the eternal, non-arising and non-disappearing phenomenon of life.
4. The concept of panspermia
According to this hypothesis, life was brought from space either in the form of spores of microorganisms, or by deliberately "populating" the planet with intelligent aliens from other worlds. There is no direct evidence for this. And the theory of panspermia itself does not offer any mechanism for explaining the primacy of the origin of life and transfers the problem to another place in the Universe. Liebig believed that the atmosphere celestial bodies, as well as rotating cosmic nebulae - these are repositories of an animated form, like eternal plantations of organic germs, from where life is scattered in the form of these germs in the Universe.
In 1865, the German physician G. Richter put forward the hypothesis of cosmozoans (cosmic germs), according to which life is eternal and the germs inhabiting the world space can be transferred from one planet to another. His hypothesis was supported by many eminent scientists. Kelvin, Helmholtz and others thought in a similar way.
In 1908, the Swedish chemist Svante Arrhenius put forward a similar hypothesis. He suggested that the germs of life exist in the Universe forever, move in outer space under the influence of light rays and, settling on the surface of planets, in particular the Earth, give rise to life there.
Quite a large number of supporters have this concept today. Thus, American astronomers, studying a gaseous nebula 25,000 light years away from the Earth, found traces of amino acids and other organic substances in its spectrum.
In the early 1980s, American researchers found a piece of rock in Antarctica that had once been knocked out from the surface of Mars. large meteorite. The fossilized remains of microorganisms similar to terrestrial bacteria were found in this stone. This may indicate that primitive life existed on Mars in the past, maybe it is there today.
To justify panspermia, cave paintings resembling living organisms or the appearance of UFOs are usually used. Supporters of the theory of the eternity of life (de Chardin and others) believe that on the ever-existing Earth, some species were forced to die out or drastically change their numbers in certain places of the planet due to changes 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. According to Chardin, at the moment of the origin of the universe, God merged with matter and gave it a vector of development. Thus, we see that this concept interacts closely with creationism.
The concept of panspermia is usually reproached for the fact that it does not provide a fundamental answer to the question of the ways of the origin of life, and only postpones the solution of this problem for an indefinite period. At the same time, it is tacitly implied that life should have occurred at a certain specific point (or several points) of the Universe, and then spread throughout outer space - just as newly emerged species of animals and plants spread across the Earth from their area of origin; in this interpretation, the panspermia hypothesis really looks like just a departure from the solution of the problem. However, the real essence of this concept is not at all in the romantic interplanetary wanderings of the “germs of life”, but in the fact that life as such is simply one of the fundamental properties of matter, and the question of the “origin of life” is in the same row as, for example, , the question of the "origin of gravity".
Thus, at least the position concerning the ubiquity of the spread of life in the Universe has not been confirmed.
5. The concept of the origin of life on Earth in the historical past as a result of processes that obey physical and chemical laws (abiogenesis)
Until the middle of the XX century. many scientists believed that organic compounds can only occur in a living organism. That is why they were called organic compounds, as opposed to substances of inanimate nature - minerals, which were named inorganic compounds. It was believed that organic substances arise only biogenically, and the nature of inorganic substances is completely different, so the emergence of even the simplest organisms from inorganic substances is completely impossible. However, after the usual chemical elements the first organic compound was synthesized, the concept of two different essences of organic and inorganic substances turned out to be untenable. As a result of this discovery, organic chemistry and biochemistry, which study the chemical processes in living organisms.
In addition, this scientific discovery allowed to create the concept of biochemical evolution, according to which life on Earth arose as a result of physical and chemical processes. This hypothesis was based on data on the similarity of substances that make up plants and animals, on the possibility of synthesizing organic substances that make up protein in laboratory conditions.
Academician A.I. Oparin published his work "The Origin of Life" in 1924, where a fundamentally new hypothesis of the origin of life was presented. The essence of the hypothesis boiled down to the following: the origin of life on Earth is a long evolutionary process of the formation of living matter in the depths of inanimate matter. And this happened through chemical evolution, as a result of which the simplest organic substances were formed from inorganic substances under the influence of potent physical and chemical factors, and thereby chemical evolution gradually rose to a qualitative level. new level and passed into 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:
synthesis of initial organic compounds from inorganic substances in the conditions of the primary atmosphere of the primitive Earth;
formation of biopolymers, lipids, hydrocarbons from the accumulated organic compounds in the primary reservoirs of the Earth;
self-organization of complex organic compounds, the emergence on their basis and evolutionary improvement of the process of metabolism and reproduction of organic structures, culminating in the formation of a simple cell.
Despite all the experimental validity and theoretical persuasiveness, Oparin's concept has both strengths and weaknesses.
The strength of the concept is a fairly accurate correspondence of its 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. This concerns the laboratory reproduction not only of the supposed physicochemical conditions of the primary Earth, but also of coacervates imitating the precellular ancestor and its functional features.
The weak side of the concept is the impossibility of explaining the very moment of the jump from complex organic compounds to living organisms - after all, none of the experiments set up managed to get life. In addition, Oparin admits the possibility of self-reproduction of coacervates in the absence of molecular systems with the functions of the genetic code. In other words, without reconstructing the evolution of the mechanism of heredity, it is impossible to explain the process of the jump from the inanimate to the living. Therefore, today it is believed that to solve this the hardest problem biology without involving the concept of open catalytic systems, molecular biology, and cybernetics will not work.
Conclusion
The question of the origin of life is one of the most burning questions in modern science. Organic life perfectly knows how to reproduce itself, but after all, once it had to appear from inanimate, inert matter. How this happened is still unclear.
All the theories and hypotheses presented here are only a small part of the huge number of supposed answers to the greatest mystery of mankind - the mystery of the origin of life on Earth, that exist today in the world. We can only hope for a speedy resolution of this problem. Perhaps, having found the answer to the question, we will discover another world for ourselves, reveal the missing links in the chain of the emergence and development of mankind, and finally find out our past. Unfortunately, so far each person can only choose which idea is better for him to adhere to, which is closer to him.
To date, the Oparin-Haldane theory seems to be the most realistic, but no one knows how plausible it is. After all, the evolutionary theory of Charles Darwin was also irrefutable for a long period of time, but now there is a huge amount of facts and evidence of its incorrectness.
Despite such a variety and a huge number of different hypotheses and theories about the cause of the origin of life on Earth, none of them has yet been proven and finally approved. It follows from this that there are still gaps in the history of mankind, there is a lot of unexplored. There are such secrets and riddles, the meaning of which we cannot comprehend.
Bibliography
- Voitkevich G.V., Origin and development of life on Earth, Moscow, 1988
- Sadokhin A.P., Concepts of modern natural science: Textbook. - M.: UNITY-DANA Publishing House, 2009
- A.A. Gorelov, Concepts of modern natural science, M.: Center, 2005
- Semenov E.V., Mamontov S.G., Kogan V.L., Biology, M.: graduate School, 1984
- Ponnamperuma S., Origin of life, M.: Mir, 2001
The evolutionary doctrine of Zh.B. Lamarck.
J. B. Lamarck (1744-1829) - the creator of the first evolutionary doctrine. He reflected his views on the historical development of the organic world in the book Philosophy of Zoology (1809).
J. B. Lamarck created a natural animal system based on the principle of kinship between organisms. Being engaged in the classification of animals, Lamarck came to the conclusion that species do not remain constant, they change slowly and continuously. According to the level of their organization, Lamarck divided all animals known at that time into 14 classes. In his system, in contrast to the Linnaean system, animals are placed in ascending order - from ciliates and polyps to highly organized creatures (birds and mammals). Lamarck believed that the classification should reflect the "order of nature itself", that is, its progressive development. All 14 classes of animals Lamarck divided into 6 gradations, or successive stages of complication of their organization:
I (1. Ciliates, 2. Polyps);
II (3. Radiant, 4. Worms);
III (5. Insects, 6. Arachnids);
IV (7. Crustaceans, 8. Annelids, 9. Barnacles, 10. Mollusks);
V (11. Fishes, 12. Reptiles);
VI (13. Birds, 14. Mammals).
According to Lamarck, the complication of the animal world has a stepped character and therefore he called it gradation. In the fact of gradation, Lamarck saw a reflection of the course of the historical development of the organic world. Lamarck, for the first time in the history of biology, formulated the position on the evolutionary development of living nature: life arises by spontaneous generation of the simplest living bodies from substances of inanimate nature. Further development follows the path of progressive complication of organisms, i.e., the path of evolution. In an attempt to find the driving forces of progressive evolution, Lamarck came to the arbitrary conclusion that in nature there is a certain initial law of the internal desire of organisms to improve. According to these ideas, all living things, starting with spontaneous ciliates, constantly strive to complicate their organization in a long series of generations, which in ultimately leads to the transformation of some forms of living beings into others (for example, ciliates gradually turn into polyps, polyps into radiant ones, etc.).
Lamarck considered the main factor in the variability of organisms to be the influence external environment: conditions change (climate, food), and after that, species change from generation to generation. In organisms lacking a central nervous system (plants, lower animals), these changes occur directly. So, for example, in the hard-leaved ranunculus, the underwater leaves are strongly dissected in the form of filaments (direct influence of the aquatic environment), and the surface leaves are lobed (direct influence of the air environment). In animals with a central nervous system, the influence of the environment on the body, according to Lamarck, is carried out indirectly: a change in living conditions changes the needs of the animal, which causes a change in its actions, habits and behavior. As a result, some organs are used more and more often in work (exercise), while others less and less often (do not exercise). At the same time, during exercise, organs develop (a long neck and front legs in a giraffe, wide swimming membranes between the fingers in waterfowl, long tongue in anteater and woodpecker, etc.), and if not exercised, they are underdeveloped (underdevelopment of eyes in a mole, wings in an ostrich, etc.). Lamarck called this mechanism of changes in organs the law of exercise and non-exercise of organs.
There are serious shortcomings in Lamarck's interpretation of the causes of species change in nature. Thus, the influence of exercise or non-exercise of the organs cannot explain the changes in such characteristics as the length of the hairline, the thickness of the coat, the fat content of milk, the color of the integument of animals that cannot exercise. In addition, as is now known, not all changes that occur in organisms under the influence of the environment are inherited.
The development of comparative embryology, the work of K. Behr.
Like many others natural Sciences Embryology originated in antiquity. In the writings of Aristotle there are quite detailed descriptions of the development of the chicken embryo. At the same time, two main points of view on developmental processes arose - preformism and epigenesis. These two views of development were fully formed by the 17th century, and a struggle began between them. Then, in connection with the advent of the microscope, factual data began to accumulate on the structure of the embryos and the processes of development of various organisms.
The formation of embryology as a science and the systematization of factual material are associated with the name of Professor of the Medico-Surgical Academy K. Baer. He revealed that in the process of embryonic development, common typical characters are first revealed, and then particular characters of a class, order, family, and, last of all, characters of a genus and species appear. This conclusion was called Baer's rule. According to this rule, the development of the organism proceeds from the general to the particular. K. Baer pointed out the formation of two germ layers in embryogenesis, described the notochord, and others.
Karl Baer showed that the development of all organisms begins with the egg. In this case, the following patterns are observed that are common to all vertebrates: at the early stages of development, a striking similarity is found in the structure of the embryos of animals belonging to different classes (in this case, the embryo of the highest form does not look like an adult animal form, but like its embryo); in the embryos of each large group of animals, common characters are formed earlier than special ones; in the process of embryonic development, there is a divergence of signs from more general to special.
Karl Baer in his writings on embryology formulated patterns that were later called "Baer's Laws":
The most common characters of any large group of animals appear in the embryo earlier than the less common characters;
After the formation of the most general signs, less common ones appear, and so on until the appearance of special signs characteristic of this group;
The embryo of any kind of animal, as it develops, becomes less and less like the embryos of other species, and does not pass through the later stages of their development;
The embryo of a highly organized species may resemble the embryo of a more primitive species, but never resembles the adult form of that species.
Elimination, its forms. Examples.
In biology, elimination is the death of some individuals, organisms or their groups, populations, species due to various natural causes, that is, the influence of environmental factors. Most often, these individuals are not adapted to the process of fighting for existence, being the weakest among the rest. The very death of representatives of a particular species is physical, when death occurs due to the impact of ecology, as well as genetic, when the genotype changes, which leads to a decrease in the number of offspring and their viability, to a decrease in their contribution to the gene pool of the next generation. Distinguish E. non-selective (general) and selective. Indiscriminate E. occurs when a population is exposed to environmental factors that exceed the adaptive capabilities of a given group of individuals (population, species), usually natural disasters and catastrophic anthropogenic interventions (floods, droughts, changes in the nature of the landscape). Mass E. can lead to the complete extinction of a species. Of leading importance in evolution is the selective death of some individuals in a population, which is due to their lower relative fitness. Only selective E. leads to differentiated survival and reproduction of more adapted individuals, that is, to natural selection.
Modern understanding of the struggle for existence. Forms of relationships between organisms. Examples.
Modern understanding of natural selection. Selection form. Examples.
In the modern sense natural selection- this is selective (differential) reproduction of genotypes, or differential reproduction. Differential reproduction is the end result of numerous processes: survival of gametes, success in fertilization, survival of zygotes, embryos, birth, survival in young age and during puberty, the desire to mate, the success of mating, fertility. Differences in these processes are the result of differences in traits and properties, differences in the genetic program. Objects of selection: individuals, families, populations, groups of populations, species, communities, ecosystems. Scope of natural selection: SW affects all traits of an individual. Selection proceeds according to phenotypes - the results of the realization of the genotype in the process of ontogenesis in specific environmental conditions, i.e., selection acts only indirectly on genotypes. The field of action of natural selection is populations. The point of application of natural selection is a trait or property. EO has two sides: differential (selective) survival and differential mortality, that is, natural selection has positive and negative sides. Negative EO side - elimination. Positive side- preservation of phenotypes most appropriate to the conditions of the ecosystem in this moment. EO increases the frequency of these phenotypes, and hence the frequency of the genes that form these phenotypes. The mechanism of natural selection 1. Changes in genotypes in a population are diverse, they affect any signs and properties of organisms. 2. Among the many changes, there are random ones that are better suited to specific natural conditions at this time. 3. Those with these beneficial traits leave more surviving and breeding offspring than the rest of the population. 4. From generation to generation, useful changes are summed up, accumulated, combined and turned into adaptations - adaptations. Forms of natural selection. EO in the process of evolution takes various forms . There are three main forms: stabilizing selection, driving selection and disruptive selection. Stabilizing selection is a form of SW aimed at maintaining and increasing the stability of the implementation in a population of an average, previously established trait or property. With stabilizing selection, individuals with an average expression of a trait get an advantage in reproduction (in a figurative expression, this is “survival of mediocrities”). This form of selection, as it were, protects and strengthens the new trait, eliminating from reproduction all individuals that phenotypically noticeably deviate in one direction or another from the established norm. Example: after a snowfall and strong winds, 136 stunned and half-dead sparrows were found; 72 of them survived and 64 died. The dead birds had very long or very short wings. Individuals with medium - "normal" wings turned out to be more hardy. Stabilizing selection over millions of generations protects the established species from significant changes, from the destructive effect of the mutation process, rejecting deviations from the adaptive norm. This form of selection operates as long as the living conditions in which the given traits or properties of the species are developed do not change significantly. Driving (directed) selection - selection that contributes to a shift in the average value of a trait or property. Such selection contributes to the consolidation of the new norm in place of the old one, which has come into conflict with the changed conditions. The result of such selection is, for example, the loss of some feature. So, in conditions of functional unsuitability of an organ or part of it, natural selection contributes to their reduction, i.e. decrease, disappearance. Example: loss of fingers in ungulates, eyes in cave animals, limbs in snakes, etc. The material for the action of such selection is supplied by various kinds of mutations. Disruptive (tearing) selection - a form of selection that favors more than one phenotype and acts against medium, intermediate forms. This form of selection manifests itself in those cases when none of the groups of genotypes receives an absolute advantage in the struggle for existence due to the variety of conditions simultaneously encountered in one territory. In some conditions, one quality of the trait is selected, in others, another. Disruptive selection is directed against individuals with an average, intermediate nature of characters and leads to the establishment of polymorphism, i.e. many forms within one population, which, as it were, is “torn” into parts. Example: In forests where soils are brown, earth snails often have brown and pink shells, in areas with coarse and yellow grass, yellow color prevails, etc. .
Similar and homologous organs. Examples.
Analogous organs are organs that are different in origin, have an external similarity and perform similar functions. Similar are the gills of crayfish, tadpole and gills of dragonfly larvae. The dorsal fin of killer whales (cetacean mammals) is similar to the dorsal fin of a shark. Elephant tusks (overgrown incisors) and walrus tusks (hypertrophied fangs), wings of insects and birds, cactus spines (modified leaves) and barberry spines (modified shoots), as well as dogrose thorns (skin outgrowths) are similar.
Similar organs arise in distant organisms as a result of their adaptation to the same environmental conditions or the performance of organs of the same function.
Homologous organs - organs that are similar in origin, structure, location in the body. The limbs of all terrestrial vertebrates are homologous, because they meet the criteria of homology: they have a common structural plan, occupy a similar position among other organs, and develop in ontogeny from similar embryonic rudiments. Homologous nails, claws, hooves. The venom glands of snakes are homologous salivary glands. Mammary glands are homologues of sweat glands. Pea tendrils, cactus needles, barberry needles are homologues, they are all leaf modifications.
The similarity in terms of the structure of homologous organs is a consequence of the common origin. The existence of homologous structures is a consequence of the existence of homologous genes. Differences arise due to changes in the functioning of these genes under the influence of evolutionary factors, as well as due to retardations, accelerations, and other changes in embryogenesis leading to divergence of forms and functions.
Rudiments and atavisms. Examples.
Rudiments are usually called organs or their parts that do not function in the human body and, in principle, are superfluous, sometimes they can perform some secondary functions, but in any case, their original meaning was lost during evolutionary development;
Atavisms are signs that arise in a person that were characteristic of his distant ancestors, the appearance of these in our time is explained by the fact that any human DNA contains genes responsible for this sign, but they are suppressed by others and do not function. A genetic failure at some level of development contributes to the manifestation of these genes, which results in some kind of unusual for modern man property.
Examples of human rudiments:
A classic example human rudiment can be called ear muscles.
These are the anterior, superior, temporoparietal and posterior auricular muscles, which ensure the movement of the auricle in different directions.
As is known, in modern world a person does not need moving ears, and, nevertheless, this possibility exists, and in some people it is especially pronounced.
Examples of rudiments: wisdom tooth The rudiments of a person are also wisdom teeth.
The shape of the crown of such a tooth suggests that in the distant past, people ate a large amount of hard and tough food, which is why these teeth were needed.
Today we have a completely different diet, and therefore the need for such teeth has disappeared.
By the way, people from latest generations, who have reached the age of thirty, wisdom teeth began to erupt less and less, which confirms this hypothesis.
The vermiform appendix, also called the appendix, can also be attributed to the rudiments of a person.
However, having lost its original function (digestive), it continues to perform secondary ones, namely: protective, secretory and hormonal.
But, despite the important role in the body, many consider it an absolutely useless organ, which is fundamentally wrong.
Another example of a vestigial organ that our body continues to use is the coccyx (the fused vertebrae of the lower spine is a vestigial tail).
Nowadays, it serves to attach the muscles and ligaments that are involved in the functioning of the organs of the reproductive system.
As you can see, there are a huge number of examples of rudiments in our body.
Examples of human atavisms:
Examples of atavisms and rudiments A manifestation of atavism is considered to be increased hairline on the human body.
Rarely, but there were such cases that the human body was more than 95 percent covered with thick hair, like a primate, only the soles of the feet and palms remained unaffected.
This sends us back to the common ancestor of man and ape.
Also, there were often cases of the formation of an extra pair of mammary glands or nipples (both in men and women), the development of a caudal appendage in humans.
Moreover, the latter case is clearly visible already in the first ultrasound images.
Microcephaly photoSome scientists refer to atavism and microcephaly - this is a decrease in the size of the skull and brain with normal body proportions.
As a rule, such people express mental insufficiency. And yet, whether it is worth attributing this pathology to atavisms is a moot point and has no unequivocal answer.
24. Theory of phylembryogenesis A.N. Severtsov. Types of phylembryogenesis. Significance for evolution. One of the main tasks of evolutionary theory was to find out how changes in individual organisms become features of a species and larger taxa, in other words, how ontogenetic changes correlate with phylogenetic ones. According to E. Haeckel's biogenetic law, ontogenesis is a quick and concise repetition of phylogenesis (recapitulation). Severtsov revised the generally static Haeckel scheme of recapitulation and put forward the thesis that ontogeny does not simply copy phylogeny, but that all stages of ontogenesis undergo changes in the process of evolution, and, accordingly, phylogenetic transformations (phylembryogenesis) occur. At the early stages of embryonic development, major evolutionary innovations (archallaxis) appear, at later stages, changes of a smaller scale (deviations), and at the final stages, transformations of an even smaller rank. An extension of ontogeny can also occur by adding stages (anabolism). A clear illustration of Severtsov's theory of phylembryogenesis is the origin and evolution of multicellular animals. According to the scientist, there is no ontogeny as such in unicellular organisms, it appears in their multicellular descendants, which first develop through anabolism, and then through changes in primary rudiments based on archallaxis and deviations. Within the framework of the theory of phylembryogenesis, the doctrine of the correlation of organs, their reduction, and other issues of evolutionary phylogenetics was developed.
Creationism. Basic ideas. Representatives (C. Linnaeus, Cuvier).
Creationism is a direction in biology that explains the origin of the world by an act of divine creation and the denial of the variability of species in their historical development. The formation of K-ma in biology is associated with con. 18 - beg. 19th centuries Supporters of the idea of the constancy of species (C. Linnaeus, J. Cuvier, C. Lyell).
However, even during the period of domination of metaphysics and creationism in biology, individual natural scientists fixed their attention on the facts of variability, the transformation of forms of plants and animals. A trend known as transformism was born and developed. Transformism, which undermined the foundations of metaphysics and creationism, is considered the forerunner of evolutionary doctrine.
One of the main merits of Linnaeus was the definition of the concept species, the introduction into active use of binominal (binary) nomenclature and the establishment of a clear subordination between systematic (taxonomic) categories. He compiled descriptions of about 7,500 species of P and 4,000 species of Zh. He developed a set of botanists. terms. But most importantly, he built a clear system of plants, consisting of 24 classes, which made it possible to quickly and accurately determine their species. He took the form as the basis for the classification, divided the plants into subordinate taxonomic groups, orders, genera, and species. He took the structure of the reproductive system as the basis for the classification of plants.
The animals were divided into 6 cells. according to the structure of the circulatory system. mammals, birds, reptiles (amphibians and reptiles), fish, insects and worms (he attributed sponges to worms).
Advantages of the Linnaean system:
1. Considered the species as a real-life unit of wildlife
2. Entered the binary name of the species.
3. A person was classified as mammals by a detachment of primates, and cetaceans were classified as mammals.
The most prominent spokesman and defender of the creationist doctrine was J. Cuvier. J. Cuvier - French naturalist, naturalist. Considered the founder of comparative anatomy and paleontology. He was a member of the French Geographical Society.
According to his views, any living being is a closed static system that meets two basic principles - correlation and conditions of existence. That is, all organs and systems of the body are mutually connected and mutually conditioned, and all of them are created for a specific purpose, carried out through their functions, and the body is arranged in such a way that its organs are correlated with each other and are pre-adapted to life in certain conditions of existence. Organisms may perish if conditions change, entire faunas and floras may disappear from the face of the Earth forever, but they cannot change. This concept had a pronounced creationist character (the world was created by the creator and cannot be changed).
In search of harmonization of this concept with the accumulated early XIX in. paleontological data suggesting that animal world changed over geological time, Cuvier in 1812 developed the theory of catastrophes.
He explained these catastrophes as follows: the sea was advancing on land and swallowing up all life, then the sea receded, the seabed became dry land, which was populated by new Zh., who moved from distant places where they lived before.
The theory of catastrophes has become widespread. However, a number of scientists expressed their critical attitude towards it. The stormy disputes between adherents of the immutability of species and supporters of spontaneous evolutionism were put to an end by the deeply thought-out and fundamentally substantiated theory of the formation of species, created by Charles Darwin and A. Wallace.
2. Transformation. Basic ideas. Representatives (Saint-Hilaire, Buffon, Lomonosov). Saint-Hilerfranz zoologist, member of the Institute of France, predecessor of the British evolutionist C. Darwin. Saint-Hilaire was the first to express the idea of the need to distinguish organs according to their structure and action; partially foresaw the biogenetic law, according to which certain stages of evolutionary development and changes in organs appear and pass at a certain time during the development of the embryo, as if indicating the development of organs in predecessors. The scientist was one of the first to suggest the idea of great importance embryology in the matter of morphological and comparative research. On the basis of comparative anatomical evidence of the unity of the structure of organisms within certain classes of vertebrates, Zhiv-y S.-I. undertook a search for the morphological unity of animals of different classes, using the method of comparative study of embryos. Zh. S.'s doctrine of a single plan for the organization of all types of the animal world was subjected to severe attacks by scientific supporters of the immutability of the species. Defending the doctrine of the unity of the animal world, J. S. sharply criticized Cuvier's theory of 4 isolated types of structure of the animal world, devoid of commonality in organization and transitions. Despite the cruel attacks of reactionary circles, he came out with a direct defense of the evolutionary idea. To substantiate his views, S.-I drew on extensive material from various biological sciences (embryology, paleontology, comparative anatomy, taxonomy). S.-I. created the doctrine of deformities as natural phenomena of nature, laid the foundation for experimental teratology, having received a number of artificial deformities in experiments on chicken embryos. He created the science of animal acclimatization. Transformists opposed the metaphysical idea of the constancy of species and against the creationist "theory of creation." They proved the natural origin of the organic world. However, transformism is not yet an evolutionary doctrine. He affirms only the transformation, the transformation of species, without rising to a consistent understanding of development as historical process. Among the progressive naturalists of the XVIII century. a special place is occupied by J. Buffon (1707-1788) - a versatile and fruitful scientist who paid much attention to the development of transformist ideas. Buffon had at his disposal the richest collections of animals, which were constantly replenished with new exhibits delivered from all over the world. Buffon's materialistic views led him to the idea of the natural origin of animals and plants. Moreover, he tried to create a general picture of the origin of the Earth. According to him, the Earth broke away from the Sun in the form of a fiery liquid ball. Rotating in world space, it gradually cooled down. Life on Earth appeared at a time when the entire surface of the Earth was covered by the oceans. Who were the first inhabitants of the sea? According to Buffon, these were mollusks and fish, that is, complex organisms. They arose suddenly, directly from living particles of matter that were in the ocean. With further cooling of the Earth, land arose due to the activity of volcanoes. The climate of the Earth was hot, and the first inhabitants of the land were tropical animals that arose from marine organisms, like modern elephants, ungulates and predators. Thus, according to Buffon, a relatively small number of main families arose from which all other animals descended by transformation. Buffon believed that main reason variability and "rebirth" of animals were factors such as climate, food, and hybridization. As the animals spread the globe they fell into different environmental conditions and, changing, formed all that diverse animal world that exists in our time. Buffon's views were advanced for his time. Materialist traditions developed in Russian science in the 18th century under the influence of the philosophical ideas of M. V. Lomonosov. Lomonosov was a consistent materialist. Lomonosov's main contribution to natural science was associated with the development of physics, chemistry and geology. Lomonosov was the first to put forward the idea of development to explain the processes of mountain building, the emergence of layered rocks, peat, and coal. The factors causing geological processes, he considered erosion, weathering and volcanic activity. Studying the layers of the earth, Lomonosov met with the remains of extinct animals and, unlike most scientists of his time, saw in them not the "play of nature", but the petrified remains of organisms.
3. Preformism. main ideas. Representatives. The theory of epigenesis. The question of individual development - ontogenesis - has attracted attention since the time of Aristotle. Thanks to the efforts of many researchers by the XVII century. extensive material has been accumulated on the changes that occur with the embryos of vertebrates at the macro level. The appearance of the microscope in the 17th century brought embryology to a qualitatively new level, although the imperfection of the first microscopes and the extremely primitive technique for making micropreparations made the early stages of embryonic development practically inaccessible for study. In the XVII-XVIII centuries. Two views on ontogenesis took shape - preformism and epigenesis. Supporters of preformism believed that embryonic development is reduced to the growth of a fully formed embryo. It was assumed that the embryo - a smaller version of the complex adult organism - existed in this form from the moment of creation. The Preformists, in turn, divided into two groups. Owists - J. Swammerdam, A. Vallisneri, M. Malpighi, S. Bonnet, A. Galler, L. Spalanzani and others believed that the already formed embryo is in the egg, and the male sexual principle only gives impetus to development. Animalculists A. Leeuwenhoek , N. Hartseker, I.N. Lieberkühn et al. argued that the embryo is contained in a spermatozoon, which develops at the expense of the egg's nutrients. A. Leeuwenhoek admitted the existence of male and female spermatozoa. An extreme expression of preformism was the theory of embeddings. According to it, germ cells of embryos, like nesting dolls, already carry the embryos of the next generation, those contain the embryos of subsequent generations, and so on. The views of the preformists were based on some factual data. So, J. Swammerdam, having opened the chrysalis of a butterfly, found a fully formed insect there. The scientist took this as evidence that the later stages of development are hidden in the earlier ones and are not visible for the time being. The preformists explained the similarity of children with both parents by the fact that the embryo, which originated from an egg or from a seminal animal, is formed in the image and likeness of its parents under the influence of the mother's imagination during uterine life. However, some supporters of this concept admitted that nested embryos are not necessarily identical with each other, to the extent that the very progress of living forms could be preformed at the time of creation. Adherents of an alternative trend - epigenetics - believed that in the process of ontogenesis, new structures are formed and organs of the embryo from a structureless substance. For the first time, the idea of epigenesis is found in the work of V. Harvey's Research on the birth of animals in 1651, but the corresponding views were fully expressed by K.F. Wolf 1733-1794. K.F. Wolff proceeded from the premise that if the preformists are right, then all the organs of the fetus, as soon as we can see them, should be fully formed. In his work Theory of Origin in 1759, the scientist describes the pictures of the gradual emergence of various organs from an unorganized mass in animals and plants. Unfortunately, K.F. Wolf worked with a rather poor microscope, which gave rise to many factual inaccuracies, but this does not detract from the significance of the theory of epigenesis he created. The epigenetic point of view in the 18th century. adhered to P. Maupertuis, J. Needham, D. Diderot, and partly J. Buffon. The decisive turning point in the dispute between representatives of the two currents occurred in the 19th century. after the work of K.M. Baer 1792-1876, who managed to remove the alternative - either preformism or epigenesis.K.M. Baer believed that no neoplasms occur anywhere in the embryo, only transformations take place. At the same time, the transformation of K.M. Baer did not understand it in the spirit of preformism, but viewed it as a genuine development, with profound qualitative transformations from the simpler and undifferentiated to the more complex and differentiated.
The human worldview is by nature anthropocentric. How many people exist, so much they ask themselves: “Where are we from?”, “What is our place in the world?” Man is the central object in the mythology and religions of many peoples. It is the main one in modern science. At different peoples At different times there were different answers to these questions.
There are three global approaches, three main points of view on the emergence of man: religious, philosophical and scientific. The religious approach is based on faith and tradition, usually it does not require any additional confirmation of its correctness. The philosophical approach is based on a certain initial set of axioms, from which the philosopher builds his picture of the world by reasoning.
Scientific approach relies on facts established in the course of observations and experiments. To explain the connection between these facts, a hypothesis is put forward, which is tested by new observations and, if possible, experiments, as a result of which it is either rejected (then a new hypothesis is put forward), or confirmed and becomes a theory. In the future, new facts can refute the theory, in which case the following hypothesis is put forward, which better corresponds to the entire set of observations.
And religious, and philosophical, and scientific views changed over time, influenced each other and intricately intertwined. Sometimes it is extremely difficult to figure out which area of culture to attribute a particular concept to. The number of existing views is enormous. Impossible in summary consider at least a third of them. Below we will try to deal with only the most important of them, the ones that most influenced the worldview of people.
Power of the Spirit: creationism
Creationism (lat. creatio - creation, creation) is a religious concept, according to which a person was created by some higher being - God or several gods - as a result of a supernatural creative act.
The religious world view is the oldest attested in the written tradition. Tribes with a primitive culture usually chose different animals as their ancestors: the Delaware Indians considered the eagle to be their ancestor, the Osage Indians - the snail, the Ainu and Papuans from Moresby Bay - the dog, the ancient Danes and Swedes - the bear. Some peoples, for example, the Malays and Tibetans, had ideas about the emergence of man from apes. On the contrary, the southern Arabs, the ancient Mexicans and the Negroes of the Loango coast considered the monkeys to be feral people with whom the gods were angry. The specific ways of creating a person, according to different religions, are very diverse. According to some religions, people appeared on their own, according to others, they were created by the gods - from clay, from breath, from reeds, from their own bodies and with a single thought.
There are a huge variety of religions in the world, but in general, creationism can be divided into orthodox (or anti-evolutionary) and evolutionary. Theologians-anti-evolutionists believe that the only true point of view stated in the tradition, in Christianity, is in the Bible. Orthodox creationism requires no other evidence, relies on faith, and ignores scientific evidence. According to the Bible, man, like other living organisms, was created by God as a result of a one-time creative act and did not change in the future. Supporters of this version either ignore the evidence for long-term biological evolution, or consider them the results of other, earlier and possibly unsuccessful creations (although can the Creator be unsuccessful?). Some theologians recognize the existence in the past of people different from those living now, but deny any continuity with the modern population.
Evolutionary theologians recognize the possibility of biological evolution. According to them, animal species can turn into one another, but the guiding force in this is the will of God. Man could also arise from lower organized beings, but his spirit remained unchanged from the moment of the initial creation, and the changes themselves took place under the control and at the will of the Creator. Western Catholicism officially stands on the positions of evolutionary creationism. The 1950 encyclical of Pope Pius XII "Humani generis" admits that God could create not a ready-made person, but an ape-like creature, putting, however, an immortal soul into him. After this position was confirmed by other popes, for example, John Paul II in 1996, who wrote in a message to the Pontifical Academy of Sciences that "new discoveries convince us that evolution should be recognized as more than a hypothesis." It's funny that for millions of believers, the opinion of the Pope in this matter means incomparably more than the opinion of thousands of scientists who have devoted their whole lives to science and rely on the research of thousands of other scientists. In Orthodoxy, there is no single official point of view on the issues of evolutionary development. In practice, this leads to the fact that different Orthodox priests interpret the moments of the emergence of a person in completely different ways, from a purely orthodox version to an evolutionary-creationist one similar to the Catholic one.
Modern creationists conduct numerous studies in order to prove the absence of continuity between ancient people and modern people, or the existence of completely modern people in ancient times. To do this, they use the same materials as anthropologists, but they look at them from a different angle. As practice shows, creationists in their constructions rely on paleoanthropological finds with unclear dates or conditions of location, ignoring most of the rest of the materials. In addition, creationists often operate with scientifically incorrect methods. Their criticism falls on those areas of science that are not yet fully covered - the so-called "white spots of science" - or unfamiliar to the creationists themselves; usually such reasoning impresses people who are not sufficiently familiar with biology and anthropology. For the most part, creationists are engaged in criticism, but you can’t build on criticism of your concept, and they don’t have their own independent materials and arguments. However, it must be admitted that there is some benefit to scientists from creationists: the latter serve as a good indicator of the comprehensibility, accessibility and popularity of the results of scientific research to the general public, an additional incentive for new work.
It is worth noting that the number of creationist currents, as well as philosophical and scientific ones, is very large. In Russia, they are almost not represented, although a significant number of natural scientists are inclined to such a worldview.