Kiara, diamant écorché par le sang. Vol. 3

Hazel Diaz

Description

"This is a serious, excellent piece of science writing ... Bratman's prose captures the core idea and gives a faithful rendering for a non-specialist audience" - Eric Smith, PhD. Coauthor of The Origin and Nature of Life: The Emergence of the Fourth Geosphere.

The most widely discussed theory of the origin of life, "RNA-first," depends on the accidental formation of self-catalyzing RNA molecules. Metabolism-first is an alternate theory that does not invoke lucky accidents. Instead, it grounds life's origins in a thermodynamically favored process, the resolution of an energy disequilibrium.

In undersea hydrothermal vents, upwelling magma is brought in contact with the ocean. Electrons in magma stand at a higher chemical energy level than those in seawater. (More technically, the oxidation potential of magma is higher than that of seawater.) Ordinary laws of chemistry favor a resolution of this differential, but in the absence of living organisms, the chemical processes that do so are slow and inefficient.

When an energy disequilibrium resolves itself by moving energy through a system, it can drive the system to spontaneously reorganize itself in such a way that energy begins to move more efficiently. According to metabolism-first, this is exactly what happened in ancient hydrothermal vents. Spontaneous organization in the organic chemistry of hydrothermal vents progressively enhanced the efficiency of energy flow. The resulting efficient system for resolving electron differentials is the form of matter we call "life."

The pathway along which energy moves through living things is called metabolism, and the chemical cycles that constitute core metabolism have changed remarkably little since life began. According to the metabolism-first theory, the constituents of RNA and then RNA itself emerged out of these processes, chemically favored because they catalyzed their own formation. From this perspective, life is not a lucky accident but a logical consequence of early Earth conditions. Thermodynamic processes drove the biosphere into being.

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