Abiogenesis

Abiogenesis (from the Greek a-bio-genesis, “non-biological origins”), or informally the origin of life, is the natural process by which life originates from non-living matter, such as simple organic compounds.

The transition from non-living system to living organism was not a single event but rather a gradual process of increasing system complexity. Abiogenesis is studied by combining knowledge from molecular biology, paleontology, astrobiology, and biochemistry to determine how the increasing organization of abiotic chemical reactions in nonliving systems led to the origin of life both on Earth and elsewhere in the universe, some time after its inception to the present day.

From the scientific point of view, the research on abiogenesis follow different ways: the most important are geology and biochemistry. In the first case we use the data obtained from the traces of microorganisms in terrestrial rocks of which it is possible to know the age with sufficient approximation, from the examination of meteorites and the findings of lunar exploration. These traces consist of organic compounds in which have particular importance some hydrocarbons (phytane, pristane) from living organisms containing chlorophyll.

Lunar exploration and scientific laboratories installed on the planets of the solar system should allow us to compare these data with those provided by rocks containing the same basic elements, but coming from places where life has not been generated or is still at an elementary level. The more specifically biochemical researches aim to reproduce in laboratory experiments transformations similar to those caused by solar energy, cosmic rays and radioactivity on compounds (methane, ammonia, hydrogen and water) that constituted the Earth’s atmosphere at the time when life is believed to have originated.

These researches, begun by A. I. Oparin and continued by S. L. Miller, M. Calvin and many other researchers, led to the formation of a compound, the dicyanamide, able to cause the polycondensation of amino acids to proteins. It was then assumed the formation of a primordial “broth” rich in organic substances of protein type, which would be gradually assembled to form the coacervates, which in turn would have given rise to the first forms of life.

The experiments all started from the assumption that the primordial atmosphere was similar to that of Jupiter, that is highly reducing as it is rich in methane, ammonia, hydrogen and water vapor. Subjecting these inorganic compounds to electrical discharges, which wanted to simulate ultraviolet radiation and atmospheric lightning, it was obtained the synthesis of some amino acids. The starting hypothesis of a primordial reducing atmosphere has never found, however, great supporters among geologists, who believe that the primitive atmosphere was rich in carbon dioxide and molecular nitrogen, similar to the current one but without oxygen, and therefore tendentially neutral.

In addition, in light of knowledge about the dynamics of the lithosphere, endogenous and exogenous phenomena that act on it, and the action of light rays, it seems unlikely that they could form large accumulations of organic substances: minerals subtract organic matter to water that accumulates in the oceans, as well as the action of ultraviolet rays destroy biological molecules, not favoring the synthesis. Consequently to justify the appearance of the first organic molecules it is necessary to assume other chains of events.

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