When did life first appear on the earth?

This question is a bit difficult to answer. Try to talk about it.

If you start from a single cell, the first life should be nearly 4 billion years old. Since the formation of the earth 46 years ago. At this time, the earth is a fireball. Hundreds of millions of years later, it was bombarded by the universe. A large number of extraterrestrial meteorites hit the earth and the temperature dropped. For millions of years, a lot of water vapor has fallen from the sky, and the earth has become a big water balloon. At this time, the temperature is suitable, and the seawater dissolves various elements to form the original life soup. It is said that the black chimney at the bottom of the sea is the place to synthesize DNA of life, and it is also said that shallow water puddles synthesize DNA under the sunlight. At first, they were a combination of molecules, lifeless, lifeless, drifting in the sea, and gradually they were covered with a film, which was relatively stable. Tens of millions of years have passed and nothing has changed. One day, one such molecular package began to split itself to form another identical molecular package. This disruption is called cell division, and it depends on solar energy. This single cell division rate is very slow, so there has been no change in the past two billion years, that is, about1500 million years ago, some cells began to lose patience and began to eat their own compatriots. This is faster than relying on the sun, gaining more energy and copying into the fast lane. That is, one cell ate another cell one day, and it was a little difficult to digest it. The eaten cells did not resist or make a sound, but gave their energy to their owners. This conscientious cooperation makes the host very happy. We have weathered the storm together. Cells rely on solar energy to get energy, some for their own use, and some for endogenous cells called mitochondria, so this is the only time on earth. This has undergone earth-shaking changes. With the engine of internal energy, cell division is greatly accelerated and eukaryotic cells are formed, leaving ancient and primitive cells, including today's viruses, behind. Eukaryotic cells, with the internal energy system of the engine, are constantly developing and growing, and they are only waiting for a godsend opportunity. Previously, billions of cyanobacteria cells produced a lot of oxygen as a by-product, which was mostly used in iron oxide in seawater in the early days, so the oxygen content in seawater was not high, and the cells divided slowly, so they could not be combined with adults. Now, after the iron in seawater is oxidized (which is our iron ore formation mechanism), the oxygen content increases. Coupled with the snowball earth event 600 million years ago, a large number of cells were killed and injured, and a large number of cyanobacteria cells died (stromatolites in Shayu Bay, Australia are witnesses). This is true. From a few cells to thousands of combinations, from spontaneous replication to heterosexual replication, we finally produced what we call Ediacara biota 560 million years ago, Maotianshan biota in Chengjiang, Yunnan, China 530 million years ago, and Burgess biota, a world-famous biological origin discovery site 520 million years ago. We collectively refer to the CAMBRIAN explosion of life! Thus, after billions of years of evolution of single cells, all our phyla have finally evolved, and most creatures, that is, phyla, are complete. Some of them have already left, such as shrimp, trilobite, oogway and so on. Some have gone through hardships before landing on land. Like all insects today, plants are the first pioneers of landing ships. Next, a descendant named Picafis landed. It is the ancestor of all vertebrates and produced a generation of dinosaurs that ruled the earth for10.6 billion years. If it weren't for the extinction of the sky, there wouldn't be us. It was 65 million years ago that meteorites bombed the earth, destroying a generation of dominant dinosaurs, and mammals came onto the stage, producing a biped that proudly called itself Homo sapiens. Ruling the earth has just begun for more than 40 thousand years. When we look back at the process of life, some of them have gone, some have come, and they are endless. They passed on the DNA of life to us, and we are their descendants, which makes you and I fear every life on the earth and the cradle of life: the earth!

Paleontologists tell us that the first living cell was produced about 3.6 billion years ago.

The study on the origin of life and cell has not only biological significance, but also a scientific world outlook. (1) The origin of eukaryotic cells that constitute all eukaryotes; (2) The origin of prokaryotic cells is accompanied by the origin of life; (3) The newly developed theory of three realms, that is, the origin of ancient nuclei.

The origin of life can be traced back 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. The so-called "Big Bang" produced carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur and other major elements that make up life.

About 6.6 billion years ago, there was a big explosion in the Milky Way. After a long time of gluing, its fragments and loose matter formed the solar system about 4.6 billion years ago. As a member of the solar system, the earth was also formed about 4.6 billion years ago. Then, the cold nebula material releases a lot of gravitational potential energy, which is converted into kinetic energy and heat energy, leading to temperature rise. In addition, the radioactive heat energy of elements in the earth has also warmed up. So the early earth was in a molten state. During the rotation of the high-temperature earth, the substances in it are differentiated, and the heavy elements sink to the center and condense into the core, while the lighter substances form the mantle and crust, and gradually the circle structure appears. This process takes a long time. The original crust appeared about 3.8 billion years ago, which is consistent with the age of most rocks on the surface of the moon.

The origin and evolution of life are closely related to that of the universe. The elements of life, such as carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur, come from the evolution of elements after the Big Bang. The data show that the chemical evolution in the pre-biological stage is not limited to the earth, but also the products of chemical evolution widely exist in space. In interstellar evolution, some biomolecules, such as amino acids, purines and pyrimidines, may form or condense in interstellar dust. Then, under the specific conditions on the planet surface, biopolymers such as peptides and polynucleotides are produced. The most primitive biological system, that is, life with primitive cell structure, was formed on the earth after several transitional forms of pre-biological evolution. At this point, the evolution of life began, and countless complex life forms have been produced on the earth until today.

3.8 billion years ago, a stable land mass was formed on the earth, and various evidences show that the liquid hydrosphere is hot and even boiling. Some extremely thermophilic archaea and methanogens may be the oldest life forms closest to the earth, and their metabolic patterns may be chemical and inorganic autotrophs. 3.5 billion years ago, microorganisms in the Wallawona group in Western Australia may be the earliest evidence of life on earth.

The appearance 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 structure has gradually formed. However, there were not many creatures for a long time. Until the Cambrian 540 million years ago, a large number of metazoans with shells appeared, so the geological era after the Cambrian was called Phanerozoic.

Archean is the oldest geological period. From a biological point of view, it is the primary stage of primitive life and biological evolution. There were few prokaryotes at that time, and only a few fossil records were left. From the abiotic point of view, the Archean crust is thin, the geothermal gradient is steep, the volcanic-magmatic activity is intense and frequent, the rock strata are generally deformed and deteriorated, and the atmosphere and hydrosphere lack free oxygen. It is also a period of formation and continuous growth of silicon-aluminum crusts and an important metallogenic period.

In early Proterozoic, some relatively stable continental plates appeared on the earth's surface. Therefore, in terms of lithospheric structure, Proterozoic is more stable than Archean. The atmosphere in the late Proterozoic already contained free oxygen. With the increasing prosperity of plants and the strengthening of photosynthesis, the oxygen content in the atmosphere increased continuously. Algae plants in the middle and late Proterozoic are very prosperous, which is obviously different from Archean.

Sinian is a unique stage of geological history at the end of Proterozoic. From the perspective of biological evolution, the Sinian system is obviously different from Proterozoic without crusted metazoan fossils. However, compared with CAMBRIAN, which is rich in crustacean fossils, the fossils contained in Sinian system are not only monotonous, few in number, but also very limited in distribution. Therefore, the animal fossils can not be used for effective biostratigraphic work. The most prominent feature of the Sinian biosphere is that there are many kinds of crustless metazoa in the later period, and there are a few crusted animals in the later period. Advanced algae flourished further, and some new types of micro-animals appeared. Stromatolites tended to flourish in the early Sinian, and the number and species suddenly decreased in the later period. Judging from the structure of lithosphere, several large and relatively stable continental plates appeared on the surface of Sinian, which were covered by typical caprock deposits, similar to Paleozoic. Therefore, Sinian can be considered as a transitional stage between Proterozoic and Paleozoic.

1977 10 scientists found more than 200 ancient cell fossils in ancient sediments of Swaziland, South Africa, 3.4 billion years ago, and set the origin of life at 3.4 billion years ago. Soon, scientists were surprised to find the most primitive biological cyanobacteria and green algae fossils in rocks of 3.5 billion years, and had to trace the source of life.

Because eukaryotes appeared on the earth 800 million years ago, it was the Sinian period, and there was enough oxygen on the earth to appear eukaryotic cells.

Before that, they were anaerobic prokaryotes.

Since Pangu opened heaven and earth, three emperors and five emperors have been born.

In ancient times, heaven and earth took shape, and microorganisms in water began to multiply!