Oparin sometimes is called "Charles Darwin" of the 20th century. Although he began by reviewing the various panspermia theories, including those of Hermann von Helmholtz and William Thomson Kelvin,he was primarily interested in how life initially began. As early as 1922, he asserted the following tenets:
1. There is no fundamental difference between a living organism and lifeless matter. The complex combination of manifestations and properties so characteristic of life must have arisen in the process of the evolution of matter.
2. Taking into account the recent discovery of methane in the Celestial body atmospheres of Jupiter and the other giant planets, Oparin postulated that the infant Earth had possessed a strongly reducing atmosphere, containing methane, ammonia, hydrogen, and water vapor. In his opinion, these were the raw materials for the evolution of life.
3. At first there were the simple solutions of organic substances, the behavior of which was governed by the properties of their component atoms and the arrangement of those atoms in the molecular structure. But gradually, as the result of growth and increased complexity of the molecules, new properties have come into being and a new colloidal-chemical order was imposed on the more simple organic chemical relations. These newer properties were determined by the spatial arrangement and mutual relationship of the molecules.
4. In this process biological orderliness already comes into prominence. Competition, speed of cell growth, survival of the fittest struggle for existence and, finally the natural selection determined such a form of material organization which is characteristic of living things of the present time.
Oparin outlined a way in which basic organic chemicals might form into microscopic localized systems possible precursors of the Cell from which primitive living things could develop. He cited the work done by de Jong on coacervates and other experimental studies, including his own, into organic chemicals which, in solution, may spontaneously form droplets and layers. Oparin suggested that different types of coacervates might have formed in the Earth's primordial ocean and been subject to a selection process leading eventually to life.
While Oparin himself was unable to do extensive experiments to investigate any of these ideas, scientists were later able to. In 1953 Stanley Miller performed what is perhaps the first experiment to investigate whether chemical self-organization would have been possible on the early earth. Miller-Urey experiment showed that from a mixture of several simple components of a reducing atmosphere, with the input only of heat to provide reflux and electrical energy (sparks, to simulate lightning), a variety of familiar organic compounds such as amino acids were synthesised within a fairly short period of time. The compounds that formed were somewhat more complex than the molecules that were present at the beginning of the experiment.
As the molecular structure of DNA and RNA became understood, due to the work of James D. Watson and Francis Crick, the opinion became more widespread among molecular geneticists, that it would take very little time before life could be artificially created: even if it needed to be limited to very simple life forms. They agreed to Oparin's theory.
The Origin of Life on the Earth(1957)
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