What is the Origin of Life?

How did life originate? There are many speculations and hypotheses on this problem, and there are many controversies. It is a major problem that modern natural science is trying to solve. The theory of chemical origin, which is based on The Origin of Species and Miller's experiment, is generally accepted in the academic circles. With the deepening of knowledge and the discovery of various kinds of evidence, people will have a deeper study of the origin of life.

Theory of origin of life

The origin of life is an ancient mystery. When and where was life on earth born? How did it happen? For thousands of years, people have encountered many pitfalls while solving this mystery, and at the same time, they have seen unprecedented light. In the Spring and Autumn Period two thousand five hundred years ago, Lao Tzu wrote in the Tao Te Ching that the Tao has one life, two life, two life three, and three life. In current terms, life on earth has evolved from little to more. They have a common ancestor. This ancestor is one, and this one is born of heaven and earth. In today's words, it may be formed by the inorganic world.

The origin of life should be traced to the origin of elements and chemical molecules related to life. Therefore, the origin of life should start from the beginning of the formation of the universe through the so-called "Big Bang" which produced carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur and other main elements that constitute life.

About 6.6 billion years ago, a large explosion occurred in the Milky Way, and after a long period of agglomeration of debris and scattered materials, the solar system was formed about 4.6 billion years ago. The Earth, a member of the solar system, also formed 4.6 billion years ago. Next, the icy nebula material released a large amount of gravitational potential energy, which was then converted into kinetic energy and thermal energy, which caused the temperature to rise. In addition, the radioactive thermal energy of the elements inside the earth also increased the temperature. Therefore, the initial Earth was in a molten state. During the rotation of the high-temperature earth, the materials in it are differentiated. The heavy elements sink to the center and condense into the core. The lighter materials form the mantle and crust, and the cyclic structure gradually appears. This process took a long time, and the primitive crust appeared about 3.8 billion years ago, which is consistent with the age of rocks on the surface of most moons.

The origin and evolution of life are closely related to the origin and evolution of the universe. The constituent elements of life, such as carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur, are derived from the evolution of the elements after the "Big Bang." The data show that the chemical evolution of the pre-biological stage is not limited to the earth, and the products of chemical evolution exist widely in space. In interstellar evolution, certain biological single molecules, such as amino acids, purines, and pyrimidines, may form in interstellar dust or condensed nebulae, and then under certain conditions on the planet's surface, biological heights such as peptides and polynucleotides are generated. molecule. Through the transitional forms of several pre-biological evolutions, the most primitive biological system finally formed on the earth, that is, life with primitive cell structure. At this point, the evolution of biology has begun, and today countless complex life forms have been produced on Earth.

3.8 billion years ago, stable land masses formed on the earth, and various evidences show that the liquid hydrosphere is hot or even boiling. Some of the most thermophilic archaea and methanogens in existence are probably the closest to the oldest life forms on the planet, and their metabolism may be chemical inorganic autotrophic. The 3.5 billion-year-old microbe in the Wallawona Group in Western Australia may be the earliest evidence of life on Earth.

The emergence of the primitive crust marks that the earth has entered the era of geological development from the era of astronomical planets, and life with primitive cell structures has gradually begun to form. However, there have been no more organisms for a long time. It was not until the Cambrian 540 million years ago that there were a large number of metazoans with shells. Therefore, the geological age after the Cambrian is called epizoic. universe.

In the medieval West, the Bible's description of God's creation of all things within seven days is also very popular. The origin of life is not depicted in these ancient legends or myths. But how did the origin of life happen? How does science explore this eternal mystery? What progress have we made? What other issues remain unresolved?

First, the origin of life, the first mystery is the time of life, the origin of time. In the medieval West, people believed in the Bible's story of God's creation. Even in 1650, an Irish archbishop calculated that the exact time of God s creation was 4004 BC based on biblical descriptions, while another priest even calculated the creation time more accurately to October 23, 4004 At nine o'clock in the morning. That is to say, the origin of life is 6,000 years ago, so such a literal interpretation cannot of course be accepted by anyone advocating science. Science answers with fossils preserved in rocks. We know that after the death of living things, their remains are kept in the rocks under appropriate conditions. We call them fossils. The rock formation formed in the geological history is like a chronicle, and the evolutionary history of the earth's organisms is deeply buried in these rocks. The older fossils are preserved at the bottom of the rock formation.

To date, the oldest biological fossils found are rocks from Western Australia about 3.5 billion years ago. These fossils are similar to current cyanobacteria, they are some primitive life and are invisible to the naked eye. Its size is only a few microns to tens of microns. Therefore, it can be said that the origin of life is no later than 3.5 billion years. At the same time, the age of the formation of the earth was about 4.6 billion years ago. With these two data, we can see the age of the origin of life, which can be roughly defined between 4.6 billion and 3.5 billion years. Today, with the development of science, geologists believe that in the early days of the Earth's formation, the Earth was hit by a large number of asteroids and meteorite, which is not suitable for the survival of life. Rather than saying that there was life on the earth at the time, it was better to say that it was destroying life, so the origin of life on the earth was no earlier than 4 billion years. In addition, carbon was found in Greenland's 3.85 billion years of rock. We know that there are two types of carbon, one inorganic carbon and one organic carbon. In addition, carbon is divided into heavy carbon and light carbon, so the source of these carbons can be inferred from the ratio of light carbon to heavy carbon among carbons. Based on the isotope analysis of carbon, scientists speculate that these carbons are organic carbons and are derived from organisms. In other words, the time of the origin of life has been greatly shortened, that is, between 4 billion and 3.8 billion years ago. Since the origin of life on earth, it has been an uninterrupted history of life evolution.

First of all, there is the concept of time of the origin of life, which is between 4 billion and 3.8 billion years ago. How did life originate? Where did it originate? This has to review some hypotheses about the origin of life.

The first is creation. In the first chapter of the Old Testament, it was written that God created everything in the world within seven days. This idea was generally accepted by people in the Middle Ages in the West. It can be said that until now, this kind of Concepts are still accepted by many people, which is certainly not true, at least, it cannot be understood literally. Some people think that the "sky" here is not an actual day and night, but an era. This is not impossible: Since the origin of life is an unsolved mystery to this day, we cannot deny the possibility of God's creation.

The second is autonomy. For example, the Greeks believed that insects were born in the soil, vientiane renewed in spring, seeds germinated from the soil, and insects broke their shells from the egg shells left over last year. But this is not the origin of life, but the continuation of life. It can be said that this theory of autonomy has now been completely abandoned. Similar to this statement, there are also Egyptians who believe that life comes from the Nile River, and in ancient China, there was also a saying that rotten grasses were fluorescing.

The third hypothesis about the origin of life is the theory of origin, which was also quite popular in the West in the 19th century. The theory of origin says that life is inherent to the universe. How did the universe originate? How did matter come from? How does life come from matter? In fact, this is an agnostic theory. In the second half of the 20th century, the theory of biological origin gradually developed to the current theory of cosmological germ. Until now, many scientists believe that the formation of enzymes necessary for life, such as proteins and genetic materials, takes hundreds of millions of years. Early Earth did not have enough time to complete these processes, because it is only 200 million years old, so they believe that life must have come to Earth from somewhere in the universe in the form of spores or other life. Basis.

Since the 1940s, humans have used astrophysics to detect nearly a hundred organic molecules, such as formaldehyde and amino acids, outside the earth. Two of these celestial bodies may be related to life on earth, which may bring life or organic molecules to the earth. One is a comet, and the other is a meteorite. These two celestial bodies contain a large number of organic molecules. For example, some comets are called dirty snowballs. They not only contain solid water, but also organic compounds such as amino acids, irons, ethanol, purines, and pyrimidines. Life may be on the comet. Produced and brought to earth. Or when a comet and a meteorite hit the earth, these organic molecules undergo a series of synthesis to generate new life. Of course, this kind of embryo theory also has different ideas. It has two fatal weaknesses. One is whether life can migrate in the universe for a long time? Can it survive? The distance between celestial bodies is calculated in light years. Communication between celestial bodies may take tens of thousands of years, from one planet to another. Then in this vacuum, exposed to such a large number of cosmic rays, can living life continue to sprout for millions of years? This is the biggest problem. This process from inorganic molecules to organic compounds, such as the formation of small organic molecules on a comet, can also be formed on Earth, and there is no doubt about it.

In 1859, with the advent of Darwin's "The Origin of Species", unprecedented changes have taken place in biological sciences. At the same time, it has brought a dawn to the ancient mystery of revealing the origin of life. This is modern chemical evolution. The chemical evolution theory of the origin of life was first confirmed by an American scholar Miller in 1953. Since the early Earth temperature was relatively high and filled with many reducing gases, water, etc., then these gases and water Wait in a bottle to see if it can produce life or produce organic compounds. Miller put ammonia, hydrogen, water, carbon monoxide, etc. in a sealed bottle in 1953, plugged metal rods at both ends of the bottle, and turned on the power. Through this effect similar to lightning, it was indeed a few days later A large number of amino acids are produced. That is to say, on the earth, under lightning and normal temperature, organic molecules can also be synthesized from inorganic molecules. We know that amino acids are the most important substances that make up proteins, and can be said to be the most important substances that make up the origin of life. Therefore, the events of the origin of life described by Miller should be: on the early earth because of the large amount of reducing primitive atmosphere, such as methane, ammonia, water, hydrogen, etc., and the primitive ocean, when the early earth Lightning effects polymerize these gases into various amino acids, and these multiple amino acids may be locally concentrated under normal temperature and pressure, and then further evolved into proteins and other polysaccharides and polymer lipids. At a certain time, It is possible to conceive life, which is the process of life evolution described by Miller.

However, this warm pool said that it also encountered some problems. There were two problems. The first problem is that geologists now believe that the early Earth's atmosphere did not contain a large amount of reducing gas. It contained a large amount of carbon dioxide and nitrogen. There are more inert ingredients in this gas than Miller. In the case of lightning, a large number of amino acids cannot be formed. The second problem is that warm pools did not form for a long time in the early Earth. At that time, there were a large number of meteorites and meteors, plus the radioactivity of the earth itself. The temperature was very high. Once the warm pool produced life, a meteor Over time, the temperature may reach thousands or even thousands of degrees in an instant, and life will be extinct, and the origin of life can only be repeated once more. But let s think about it now, is there any higher temperature on the earth, reducing gas, and living beings? Well, there are two pieces of work that have epoch-making significance. One is American scholar Black in 1967, who found a large number of thermophilic organisms in the hot springs of Yellowstone Park. If the protein exceeds 60 degrees, it will solidify. Does the creature survive above 60? This was unthinkable before.

The second is that Chris also found a large number of thermophilic microorganisms in a hot spring at the bottom of the Pacific Ocean in 1977. This temperature is even higher, which may reach two hundred to three hundred Baidu. The pressure also has two hundred to three hundred atmospheres, and its environment does have a large amount of reducing gases, including hydrogen sulfide, methane, hydrogen, and carbon monoxide. This environment is indeed very similar to the environment of the earth in the early four billion years. Just at this time? This is what we see now. In addition, are there any microorganisms found in the volcanic vents or hot springs in the fossils? Indeed, we have also made very important progress in fossils. In 2000, Australian scientist Rose Masson found a large number of well-preserved filaments in volcanic sediments in Australia about 3.2 billion years ago. This shows that life 3.2 billion years ago lived near the hot springs. This is the latest, most popular, and most scientific scientific hypothesis about the origin of life, that is, life originated from hot springs, or underwater hot springs. , Commonly known as "black chimney" nearby.

Undersea hot springs and land hot springs share many characteristics. The first temperature is high. The second one contains a large amount of reducing gas. In addition to carbon dioxide, there are also carbon monoxide, hydrogen, ammonia, and hydrogen sulfide. The third is that they all contain a large number of organisms, such as cyanobacteria, photosynthetic bacteria, sulfur bacteria, especially a type of archaeal bacteria, which proliferate abnormally at high temperatures. It proliferated in large quantities when it exceeded one Baidu and left such The environment, for example, as soon as the temperature drops, it immediately goes to sleep and does not live normally. Do these creatures represent the original life forms of the earliest and most primitive life on earth?

In the early days, the temperature of the earth was very high, and the earliest life forms produced should be some organisms that can adapt to high temperatures. In the hot spring, the organisms are exactly thermophilic microorganisms. The environment of the hot spring has many similarities with the early global environment. For example, it has a high temperature and a large amount of reducing gases, carbon monoxide, hydrogen, ammonia, hydrogen sulfide, and so on. In the hot water environment of high temperature, it is beneficial for the dehydration of small molecule organic compounds to polymerize into organic polymers. For example, protein is now synthesized with organic small molecule amino acids, which is formed in hot water through this thermal polymerization reaction. Polymer. Especially near this hot water mouth, pyrite, commonly known as "fool gold", is composed of sulfur and iron. On its surface, it is very conducive to the synthesis of polymers, because the surface of iron sulfide is a Very good a natural catalyst. In addition, there is a gradient of temperature and water chemical identification between the hot spring mouth and the outer seawater. This gradient is also conducive to the continuous reflection of various chemistry. When the hot spring mouth spurts out, the temperature may reach two to three baidu, especially near the mid-ocean ocean ridge, and the temperature at the bottom of the sea is generally 0 to 4 degrees. From three Baidu to four Baidu, there is a temperature gradient. This temperature gradient has a continuous reflection on the synthesis of organic compounds. The most important point is that the creatures in the hot spring are indeed the most fundamental type of biological evolution speed, that is, its genes are the oldest type.

Modern biologists, through biomolecular research, have compared some thermophilic archaea in the hot spring with current common bacteria, and found that their genes share the same, not exceeding 60%. That is to say, these archaea contain a lot of ancient genes, that is to say, they are likely to be the type when life originated. The best evidence for the origin of life is the information contained in rocks and fossils on Earth between 4 billion and 3.8 billion years. However, after 4 billion years of change, the earth has changed beyond recognition. Even if the earth now has 4 to 3.8 billion years of rocks, it has entered a large number of variants and has almost no information.

So do nt just confine it to the earth. If life is a universal phenomenon in the universe, do other celestial bodies other than the earth have an environment similar to that of the early earth? If so, may we be able to open new windows for the study of the origin of life. What is our first goal? Not Mars but the moon. Geologists now believe that the moon was 4 billion years ago when a large planet hit the earth and burst out from it. The current moon has been formed. This time is exactly 4 billion years. If there is a life on the earth, let's take a look on the moon, willn't we solve this problem? In ancient Chinese myths, there is the saying that Chang'e ran to the moon. There are laurels, moon rabbits, and romantic love stories on the moon. The myth is completely destroyed. The moon is actually a desert star without life, without water, without oxygen, and not suitable for life.

Our second goal is Mars, because Mars may have a similar experience with the earth 4 billion years ago. The material composition of Mars is very similar to that of the earth, and its orbit is very similar to that of the earth. Is there life on Mars? When should we start looking for the origin of life? Generally it is three o'clock. The first one to find if there is living life on Mars? If there is living life, life may really have originated in the universe, or life on Earth may come from Mars, or from other comets. The second looks for liquid water, because water is the source of all things, and water is the source of life. Life on Earth is inseparable from water, so finding liquid water is a very important indicator. The third is to find compounds related to life. If there are no living creatures now, have they been in the past? Did compounds form in past organisms? Is it preserved among these rocks in the form of fossils?

In 1957, the message from the American Pirate spacecraft returned to Earth. There is no life on Mars and no liquid water exists. It is a barren and thirsty red planet. But in the 1990s, NASA stepped up its exploration of Mars, and pictures obtained from the Mars Rover, Mars Pioneer spacecraft and the Hubble Telescope, and other information about astrophysics showed that Liquid water was likely to have existed on Mars in the past. Some aerospace data show that Mars has a structure similar to an alluvial fan before the Great Flood, as well as water, river channels, dry riverbeds, and traces of water eroding rocks. In addition, at the poles of Mars, a situation similar to the thawing of frozen ground on Earth was found. This is information provided by aerospace data.

So is the study of Mars helpless? At least not at this stage, we have meteorite from Mars. In 1984, a meteorite was found above the ice cap of Antarctica. Elemental and gas chemical analysis of this meteorite found that the gas and isotopes of this meteorite are very similar to those on Mars. Therefore, it is believed that this meteorite came from Mars and fell on the ice cap of Antarctica 10,000 years ago.

By measuring the radioisotope age of this meteorite, this meteorite is 4 billion years old, about 4 billion years away, which is exactly the same as the age of life on Earth. For decades, scientists have done a lot of research, and some researchers believe that there are three aspects of evidence on this meteorite. First evidence: This meteorite contains several sedimentary minerals. Because sedimentary minerals are formed in the presence of water, scientists have inferred that there may have been water on Mars, especially one of these minerals was a magnetite mineral. This magnetite can only exist in the form of life. The second evidence: through chemical analysis of the surface of this meteorite, a variety of polycyclic aromatic hydrocarbons were obtained, which are related to life forms. Third evidence: Careful observation through scanning electron microscopy revealed biological fossils that looked very similar to bacteria. This fossil was only a few hundred nanometers. Therefore, in 1996, NASA announced to the world that there was life on Mars 4 billion years ago, and of course this is a family saying. Is the information about the existence of life in this meteorite true? Of course, many scholars have questioned this evidence. As far as magnetite is concerned, it is no doubt that this sedimentary mineral is produced by life and can only be deposited in the form of life with water. But know that this meteorite was found on the ice cap of Antarctica. The ice is all water. When the meteorite hits the ice cap, a lot of water may melt. When the meteorite hits the earth, many cracks may form. If liquid molten water enters through this crevice, isn't it possible to form a sedimentary mineral of its own? In addition, this magnetite is not unique to life, and can be formed under other material conditions. So the first piece of evidence is that many scientists think it is untenable. The problem of polycyclic aromatic hydrocarbons is also in the Antarctic ice sheet, which is minus 40 degrees or 50 degrees, etc. There are also a large number of bacteria and algae living. Is it polluting? Pollution now may be 10,000 years ago. Therefore, the second piece of evidence cannot be said to be a very reliable evidence. In particular, the third evidence is even more unreliable, that is, splitting the meteorite, and seeing these so-called bacterial fossils, these fossils are too small, only a few dozen nanometers in diameter, we know that an iron atom may have 0.6 nanometers, The diameter of this so-called biological fossil may be hundreds or even thousands of atomic nuclei. So the minimal morphology of this primitive cell with a cell membrane envelope now understood is unimaginable. Therefore, the existence of life on this meteorite, or the existence of life on Mars, needs further research.

The third celestial body we observe is the moon of Jupiter, especially the second moon called Europa. Its size is very similar to the diameter of the earth. In 1997, the Galileo spacecraft of the United States carried out Europa. Observation found that there are a large number of cracks on Europa's surface, and there are many cracks. Through the study of astrophysics methods, the planet is actually composed of water, which is solid ice. From these many fissures, the planet may have dissolved water in the past or at some time, that is to say, there was liquid water. Is there liquid water, or does life exist? This is still unknown and requires more in-depth research. In short, with the further development of aerospace technology and other related technologies, the exploration of extraterrestrial life has opened a new way for us to study the origin of life.

But no matter what, the origin of life has three processes: the first is from inorganic matter to small organic molecules, such processes as carbon monoxide, carbon dioxide, water, hydrogen, ammonia, methane, etc. These things synthesize small organic molecules, like Amino acids, purines, pyrimidines, nucleotides, high-energy compounds, fatty acids, porines, etc. Because the origin of Earth's life is from the inorganic world to the organic world, this process is essential no matter where it is-on the ocean floor, in a hot spring, on Mars, or on Europa.

The second is from small organic molecules to organic macromolecules, that is, amino acids, purines, pyrimidines and so on. Organic macromolecules are like proteins, polysaccharides, and nucleic acids, because proteins are the main substances that make up living organisms, and polysaccharides and sugars are the skeleton of many cells, the main components of cell walls, and nucleic acids. This is genetic material, so This process is also indispensable.

The macromolecules of the third organism evolved into primitive single-cell life. A primitive single cell with a membrane envelope on the outside and genetic material in it that needs to be exchanged for metabolism. So the process of the origin of life can actually be simply divided into these three processes: which step do we take to these three processes now? What else do we have to solve? The first process from inorganic matter to small organic molecules can be synthesized in hot springs, in the "black chimney" of the deep sea, or in the laboratory. This is the most classic experiment, which is The process of synthesizing inorganic small organic molecules is also essential.

The second process is the process from small organic molecules to organic macromolecules. This process is actually in hot springs, like the hot spring mouth of the sea, and on land, like Huangshi Park, and hot springs in Yunnan, China, because the temperature is very High, organic substances can undergo thermal polymerization and dehydration reactions inside, and can form proteins. In the laboratory, this process is also repeatable, so the second process of the origin of life is not difficult.

The most difficult is the third process of the origin of life, which is the process from biological macromolecules to primitive single cells. It can be said that this process is the biggest problem encountered by scientists so far, and it is also inorganic life to life, inorganic compounds to organic A gap that cannot be crossed by life. What parts of this process include? In other words, what parts should we start from studying biological macromolecules to primitive single-cell life? The first is to study the self-genetic system. A genetic system is the establishment of a biological macromolecular system capable of self-replication, and the establishment of such systems as DNA and RNA. How was it established? How is it synthesized? How do they have a genetic function? Second, the synthesis of proteins must be incorporated into the control of the self-replication system, that is, metabolism, which is the exchange of energy and matter in the cell, receives sunlight, receives chemical energy, produces organic matter, and then uses this organic matter to decompose to generate energy. This Energy acts like a motor to run this cell. This process is a very difficult process. The third process is the formation of biofilm systems, such as cell walls, cell membranes, and biofilm systems. Why is it important? Because we know that there is no isolation in the inorganic world, only a membrane inside the organism is isolated from the outside world. At the same time, this membrane is not absolutely isolated, but exchanges substances with the outside. It has some small gaps, so this biofilm system is a very precise biological mechanism. These three stages in the origin of life are indispensable and are also very difficult three steps.

So far, the origin of life can be described as: On the earth 4 billion years ago, small organic molecules synthesized from inorganic molecules gathered in hot water near the hot spring mouth or crater, and formed a large biological organism through polymerization. Molecules, these macromolecules make self-replication, self-selection, and then through the self-organization of the molecule, and copy and mutate to form nucleic acids and active proteins, at the same time, the separation structure is generated simultaneously, and finally the metabolic response under the control of the gene is the gene replication And the synthesis of proteins provides energy, and such a primitive cell that is self-replicating, wrapped in a biofilm, is created on earth. This primitive cell may be heterotrophic, or chemically autotrophic, and may resemble a thermophilic archaea of modern organisms near a hot spring. This short description basically describes the process of the origin of life. But it has four insurmountable divides. One is self-selection, because these molecules make up biological macromolecules or RNA and DNA. These molecules are very limited. Under inorganic conditions, or in the case of lightning, or in hot water, it forms many such molecules. How these molecules select themselves, synthesize DNA, RNA, and discard other large molecules, we do not know this process. The second is self-replication. DNA and RNA can replicate themselves and can be inherited for the next generation. We do not know this process. The third is the separation structure, that is, the cell membrane or the membrane structure inside the cell. In this process, we are not quite sure how it is formed? How phospholipids and fine biological structures are formed is not clear to us. The other is the problem of metabolism. First of all, we have not solved the process of absorbing external energy, but no matter how this hypothesis of the origin of life in the hot spring, there is indeed a lot of favorable evidence to support it. The most important progress.

The hot spring contains a large amount of carbon monoxide, hydrogen sulfide and sulfide metal minerals, especially pyrite minerals and sulfur. On the one hand, iron sulfide and sulfur have a metabolism. Iron sulfide is a very important catalyst. Many chemical reactions proceed very smoothly on its surface or in its crystal framework. Some important compounds have been found in hot springs. For example, an active substance such as sulfide is found in the hot spring. It is very similar to a very important compound and some complexes. This compound provides a way for energy metabolism.

Therefore, the metabolic pathway may be related to the pyrite and sulfur in the hot spring and their polymers. On the other hand, the emergence of genetic material RNA has a close relationship with the chemical processes of sulfide and sulfur. Deoxyribonucleic acid (DNA) can also be directly evolved from RNA deoxygenation. A polymer like pyrite is the pyrite polymer in this hot spring mouth. In fact, there are many important biochemical enzymes in the center, and those biochemical enzymes may be produced in a large amount of sulfur hot springs. From this point of view, life on Earth may have occurred in these sulfur-filled hot pools or sludges between 3.8 billion and 4 billion years ago. But we should clearly understand that we have a long way to go before we can unravel the ancient mystery of the origin of life. The evolution from inorganic matter to organic matter, to organic compounds, and to organic life forms also has a lot of contingencies. It is not because of such an environment and the conditions for its formation that it can produce life. Someone once metaphorically said that these inorganic things are like a garbage dump, which has everything in it, plastic, plastic bottles, iron, waste metal, oil, and life, a single cell, like a beautiful Mercedes-Benz car, after a typhoon passed The garbage was assembled into a Mercedes. It is conceivable that the origin of life is very difficult. Maybe our blue planet is the only paradise for life! Therefore, please protect our earth, cherish life on earth, and cannot expect the origin of the second life on earth.

Theory of origin of life

Obarin's theory of the origin of life

Researchers have discovered that under the conditions of certain concentration, temperature and pH, biological macromolecules dissolved in water can aggregate into small particles. Such small particles are known as agglomerates by the well-known originator of life. Obalin believes that the first morphological entity produced in the primitive ocean is this kind of aggregate, and his theory is called the model of aggregate life. ^[1]

Obalin

However, the macromolecular substances used in the research of aggregates are all biosynthesized. In this case, it is not possible to completely follow the evolutionary scenario under the paleogeological conditions, because under the simulation of the original conditions of the earth, so far, it has not been able to succeed. Ground to synthesize today's biological macromolecules through abiotic means.

In contrast, microsphere life models may be closer to the evolutionary scenario at the beginning of life. To simulate the volcanic environment of the primitive earth, scientists synthesized a protein-like substance, dissolved this substance in boiling saline or water, and formed a large number of pellets in the solution after cooling. This kind of ball is what the American scientist Fox said. Microspheres are stable in structure, similar in size to cells, have membranes like cells, and can multiply in the form of buds ... showing the original vitality of life, which shows that microspheres may be the common ancestor of all living things on earth today, so in the end Is this not the case?

All kinds of bacteria are the simplest in modern cells and the most primitive organisms that can survive and reproduce independently on the earth. Let's compare microspheres with E. coli. Microspheres sprout from one end to reproduce, and E. coli divides from the middle to reproduce; E. coli first replicates genetic material before dividing and transmits the exact same piece of life information to the offspring to ensure that children and parents have Identical blood, the microspheres are vacuoles, and there is no genetic material at all.

In fact, microspheres are relatively easy to make in the laboratory, but life can only be born on the earth after hundreds of millions of years of long history, so we try to get the original life in the laboratory in one step. Not too possible.

Although it is still unclear what the most primitive life was, the structure of life was very simple when it was just born, and there was no cell structure. After quite a long evolution, bacteria with a cell structure were born.

The oldest evidence of life on Earth was found in Western Australia, just northwest of the Australian mainland. (Shaffer, President, International Association for the Origin of Life)

The Australian continent is the oldest continent on earth, and here we can find clues left by primitive life. In this bay on the west coast, there are some stones that resemble stepping stones. They are soft and sticky to the touch. They are formed by the algae that live on them. They are called stromatolites. This is a stromatolite formed 3.5 billion years ago, covered with blue-green algae. They look like hairpins and are the oldest primitive life found so far.

Origin of life theory life and atmosphere

People used to think that life was born on the surface of the primitive ocean. However, when life was born, there was no ozone layer in the atmosphere, and the strong ultraviolet rays in the sun could directly shine on the earth's surface. How immature life escaped the pervasive killer of ultraviolet rays is still a mystery.

The Galapagos off the coast of Ecuador is where Darwin founded evolution. Here, the researchers dived into the volcanic cracks on the ocean floor, and were surprised to find a lot of strange creatures near the hot springs. The crater was filled with red hairy caterpillars, big crabs fed on bacteria, and the chemicals produced by high heat were It is a delicious meal of bacteria. This strange underwater world can not help but remind people that primitive life may have been born on the ocean floor.

On the primitive earth, the seafloor already had the conditions for the birth of life. Sulfur, hydrogen, methane, and carbon dioxide on the seafloor provided the material conditions for the birth of life. The volcanic eruptions on the seafloor generated heat and provided energy for the birth of life. Seawater blocks the damage of the sun's ultraviolet rays to primitive life.

Later, people found more evidence of life in extreme hot underwater environments. At a depth of 2,600 meters below the Pacific Ocean, researchers found a gushing volcanic spring. The temperature was as high as 350 ° C, but bacterial communities were also found.

In Tengchong County, bordering western Yunnan, China, there is a famous tourist area called Atami. There are many hot springs here, and there is a constant stream of gushing all year round. The most attractive of these is the large rolling pan, which has a beautiful blue color due to the dissolved minerals. The surface temperature of hot spring water is as high as over 100 ° C. However, even in this frightening environment, a large number of extremely thermophilic bacteria have also been found.

In the United States, scientists found a microorganism called thiosulfur bacteria in hot mud, which is slightly larger than one thousandth of a centimeter in diameter. It seems that the bacteria can swim freely. In fact, this is the water molecules surrounding the bacteria. During its movement, electron microscopy showed that the cells of these bacteria did not contain nucleus and looked ancient and primitive.

Here is the North Pole, where scientists have found distant past life in these humble rocks. Vaguely visible under the microscope are blue-green algae with a magnification of more than 1,000 times, which have maintained their original appearance 3.5 billion years ago. It appears that the cell structure is complex and life is normal.

This magical stone full of life is called stromatolite, not only in Australia, but also in the United States, South Africa and other parts of the world. Despite the age, traces of blue-green algae on stromatolites are still clearly visible, indicating that this creature was quite common on the earth at that time.

The prosperity of blue-green algae produced a large amount of oxygen, which profoundly changed the composition of the atmosphere. The ozone layer was born in the original atmosphere, blocking the ultraviolet killer in the sun, and life was able to reproduce and live on the ocean surface. The thick coat prevents the sun shining on the earth's surface from emitting, and gives life a warmth. It is precisely because of the meticulous care of the atmosphere that life in the cradle can survive.

The origin of life theory

As early as 1907, the famous Swedish chemist Arrhenius proposed that the seeds of life widely exist in the universe, and the first batch of life on Earth may come from outside the sky. By 1968, scientists had discovered interstellar molecules in space. Some interstellar molecules can be converted into amino acids under appropriate conditions, and amino acids are the basic molecules of life. This has led more scientists into the study of interstellar molecular observations.

So far, astronomers have found more than 100 molecules in interstellar clouds, and found the simplest amino acid, glycine, in the clouds that are forming stars near the center of the Milky Way. These novel discoveries have greatly inspired people to explore the world Passion for life.

Schematic diagram of the hypothesis of the origin of life in the original soup

The study of Meteorites from the sky outside proves the possibility of life in space from another aspect. Our earth receives tons of cosmic material from outside the earth every day. These materials enter the atmosphere to generate heat by friction and become ash, but large meteorites will rush into the atmosphere and have no time to burn completely and hit the earth. The crater is the best evidence that the earth meets the crater and the earth receives extraterrestrial material. Meteorites include stone and iron. There is also a meteorite called carbonaceous chondrite, which is very rare on earth. Some people think that it is composed of asteroid fragments, which are black because of higher carbon content. Extremely rich living matter has been found in carbonaceous chondrites, among which are amino acids.

There are more than 100 kinds of amino acids found in meteorites, while all the proteins on the earth are composed of only 20 amino acids (and all are composed of alpha amino acids). There are 10 amino acids found in Murchison meteorites that are the same as the amino acids of proteins on the earth: glycine , Alanine, serine, threonine, valine, leucine, isoleucine, aspartic acid and glutamic acid. Other organisms found in other meteorites and biospheres include: nicotinic acid (in the form of nicotinic acid, a coenzyme of a large class of redox enzymes), some monocarboxylic acids (such as formic acid, acetic acid, butyric acid), Sugar-like substances (composed of many polysaccharides on the earth) and complex amphiphilic substances (have both hydrophobic and hydrophilic ends), they are extracted from meteorite powder with chloroform and can form membrane vesicles in water . Meteorites have almost all of the core organic compound components used for primitive life and the origin of photosynthesis.

Soluble organic compounds in Murchison meteorite

Comet research seems even more tempting. As early as 1864, the famous cosmic chemist Huggins had speculated that spectroscopic observations of comets contained petroleum gas-like components. He said that although the comet was as cunning as the Sphinx, it finally leaked its secret. The famous Dutch astronomer Olt said that there is a comet warehouse on the outer edge of the solar system. Comets formed by primitive nebulae are between the sun and other stars.

Because of its irregular orbit, comets often hit solar system objects like moths flutter fire. The extremely spectacular horoscope that occurred in the summer of 1994 left a deep impression on people. A comet called Suvik-Levy-9, as predicted by astronomers, hit Jupiter as scheduled. This massive impact of the star was nicknamed the "Kiss of the Century" by the media.

Comets are extremely common objects in the vast universe, and French astronomer Kepler said, "Comets in the sky are like countless fish in the water.

After 76 years, Comet Halley returned to the inner solar system in 1986, enabling scientists to once again see the true appearance of the mysterious comet. Based on the results of this observation, scientists have proposed a comet dust model. They believe that a comet is composed of particles about 1 micron in size, with a silicate in the center, 25% organic matter on the outside, and water, ice, and free on the outside. The base and various particles are precisely these materials that have entered the earth and prepared rich material conditions for the origin of the earth's life. Some people assert that about 4.5 billion years ago, wandering comets in the universe accidentally hit the earth. It took 100 million years for the earth to drop thousands of degrees of high temperature, and hundreds of years later, the life of the comets The seeds germinated the first bacteria that could both reproduce and mutate. ^[4] But the question is, where does life in space come from? Such an answer simply moves the question elsewhere and does nothing to answer the ultimate question.

Life Origin Theory "Early Enzyme"

Before cells appeared on Earth, simple, tiny catalysts were most likely to have the chemical reactions necessary to accelerate and synchronize the creation of life. But how did these catalysts appear at the same time and how did they evolve into two modern superenzyme families? For the first time, researchers at the University of North Carolina School of Medicine have provided direct experimental evidence that shed light on how the original protein had the ability to accelerate the central chemical reactions necessary to synthesize the protein, thereby creating life. The research results are published in the journal "Biochemistry".

According to the Organization of Physicists Organization, the study provides evidence that the two major superenzyme families that transformed the genetic code in modern biological evolution evolved from opposite strands of the same ancestral gene.

Dr. Charles Carter of the University of North Carolina said: "We have discovered that an ancient gene may use its opposite two strands of DNA to encode two different active amino acid catalysts. One is responsible for activating the required amino acids in the protein and the other is responsible for Amino acids needed outside of protein. "

One of the main obstacles to creating life is how to accelerate various chemical reactions so that these reactions can occur at the same rate within the cell. Usually they not only respond slowly but also at different rates. The chemical reaction that binds amino acids to adenosine triphosphate or ATP, a molecule that transmits chemical energy in cells, is the key to life. This binding enables the protein to self-assemble. Without a catalyst, this binding reaction is about a thousand times slower than any other step in protein synthesis.

There is a synthetase called aminoacyl-tRNA in modern biological cells that can greatly accelerate this response. In the designed experiment, the Carter team physically disassembled the synthetase to show the catalytic activity necessary for all synthetase families-which part of the ability to bind to ATP. It was found that 46 amino acid chains, which accounted for only about 5% to 10% of the total number of enzymes, showed an activity of more than 40% of the total amount.

Carter called these enzyme fragments "primary enzymes." The research team found that the enzymatic activity of the "primary enzyme" focused on the activation reaction with ATP. This means that in the transformation of the chemical reactions that form proteins, these enzymes are able to combine with the most unstable, slow-forming structures to form tight complexes. Carter said that these enzyme complexes are necessary for the catalytic link in the process of protein formation, and then become the key to the formation of life on Earth. ^[5]