What is the origin of life on earth?

The chemical origin theory is a hypothesis about the origin of life that is generally accepted by scholars. This hypothesis holds that life on earth evolved step by step from non-living substances through extremely complex chemical processes over an extremely long period of time after the earth's temperature gradually dropped. The theory of chemical origin divides the origin of life into four stages: the first stage is the stage in which organic small molecules are generated from inorganic small molecules, that is, the chemical evolution process of the origin of life was carried out under primitive earth conditions. This process textbook It has already been described in and will not be repeated here. What needs to be highlighted is Miller's simulation experiment. In this experiment, a flask containing an aqueous solution represents the primitive ocean, and its upper spherical space contains "reducing atmosphere" such as hydrogen, ammonia, methane and water vapor. Miller first heated the flask to circulate water vapor in the tube. Then he discharged two electrodes to generate electric sparks, simulating lightning in the primitive sky, to stimulate chemical reactions of different gases in the sealed device, and the lower part of the spherical space was connected The condenser tube allows the reaction product and water vapor to cool down to form a liquid, which then flows back to the flask at the bottom, simulating the process of rainfall. After a week of constant experimentation and cycling. When Miller analyzed its chemical composition, he found that it contained a variety of new organic compounds including 5 amino acids and different organic acids, and also formed hydrogen cyanide, which can synthesize adenine, which is composed of The basic unit of nucleotide.

Miller's experiment tried to prove to people that the first step in the origin of life, the formation of organic small molecule substances from inorganic small molecule substances, was completely possible under the conditions of the primitive earth. In the second stage, biological macromolecular substances are generated from organic small molecule substances. This process occurred in the primitive ocean, that is, amino acids, nucleotides and other organic small molecule substances, after long-term accumulation and interaction, under appropriate conditions (such as the adsorption of clay), formed through condensation or polymerization. Primitive protein molecules and nucleic acid molecules. The third stage is to form a multi-molecular system from biological macromolecules. How is this process formed? Former Soviet scholar Obalin proposed the agglomerate hypothesis. He showed through experiments that when proteins, polypeptides, nucleic acids, and polysaccharides are placed in a suitable solution, they can automatically condense and aggregate into dispersed Spherical droplets, these droplets are agglomerates. Obalin and others believe that aggregates can show life phenomena such as synthesis, decomposition, growth, and reproduction. For example, agglomerates have membrane-like boundaries, and their internal chemical characteristics are significantly different from the external solution environment. The aggregates can absorb certain molecules from the external solution as reactants, and can also undergo specific biochemical reactions under the catalysis of enzymes, and the reaction products can also be released from the aggregates. In addition, some scholars have also proposed other hypotheses such as microspheres and lipid spheres to explain the process of organic polymer materials forming multi-molecular systems. The fourth stage, a schematic diagram of the simple metabolism of aggregates. The fourth stage, the organic multi-molecular system evolved into primitive life. This stage was formed in the primitive ocean and is the most complex and decisive stage in the origin of life. ?