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Working independently, the Russian scientist Aleksander I. Oparin (1894-1980) and the English scientist John Burdon S. Haldane (1892 - 1964) proposed in the 1920, similar assumptions about how life would have originated on Earth.
Although there are slight differences between the hypotheses of these scientists, they basically proposed that the first living things emerged from organic molecules that would have formed in the primitive atmosphere and then in the oceans from inorganic substances.
John Burdon S. Haldane and Aleksander I. Oparin
Let us, in simplified terms, present a synthesis of these ideas: the conditions of the earth before the appearance of the first living beings were very different from today. Volcanic eruptions were very frequent, releasing large amounts of gases and particles into the atmosphere.
These gases and particles were retained by the force of gravity and began to compose the primitive atmosphere.
Although there is no consensus on the composition of the early atmosphere, it was initially proposed that it was probably formed by methane (CH4), ammonia (NH3), hydrogen gas (H2) and water vapor (H2O). There was no oxygen gas (O2) or he was present in very low concentration; so we talk about reducing environment, ie non oxidizing. At this time, the earth was undergoing a cooling process, which allowed the accumulation of water in the depressions of its coast, forming the primitive seas.
At electrical discharges and the radiation was intense and they would have provided energy for some molecules present in the atmosphere to come together, giving rise to larger and more complex molecules: the first organic molecules. It is important to remember that in the atmosphere of that time, unlike what happens today, there was no ozone shield (O3) against radiation, especially ultraviolet, which thus hit the earth with great intensity.
The organic molecules formed were dragged through the rainwater and began to accumulate in the early, warm, shallow seas. This process, repeated over many years, would have turned the early seas into veritable “Nutritious soups”, rich in organic matter. These organic molecules could have aggregated, forming coacervated, name derived from Latin coacervare, which means forming groups. In this case, the sense of coacervates is the set of organic molecules assembled in groups surrounded by water molecules.
These coacervates were not living beings, but a primitive organization of organic substances in a semi-isolated system from the environment, being able to exchange substances with the external environment and with the possibility of numerous chemical reactions within.
It is not known how the first cell emerged, but it can be assumed that if it was possible for an organized system like the coacervates to emerge, equivalent systems might have arisen, surrounded by a membrane formed by lipids and proteins and containing within it the nucleic acid molecule. With the presence of nucleic acid, these forms would have acquired the ability to reproduce and regulate internal reactions.
By this time the first living beings would have appeared, although they were very primitive, capable of reproducing themselves, giving rise to other beings similar to them.