Authors: Raul A. Félix de Sousa
Comments: 39 pages. KEYWORDS: origin of life, geochemical cycles, biogenic elements, oxygen, palaeoatmosphere, homochirality
A model for biopoesis is proposed where a complex, dynamic ecosphere, characterised by steep
redox potentials, precedes and conditions the gradual formation of organismal life. A flow of
electrons across the Archean hydrosphere, proceeding from the reducing constituents of the
lithosphere and pumped by the photolytic production of oxygen in the Earth's atmosphere is the
central feature of this protobiological environment. The available range of electrochemical
potentials allows for the geochemical cycling of biogenic elements. In the case of carbon,
carboxylation and decarboxylation reactions are essential steps, as in today's organisms.
Geochemical evidence for high levels of carbon dioxide in the Earth's early atmosphere and
the biological relevance of carboxylations are the basis for a hypercarbonic conception of
the primitive metabolic pathways. Conversion of prochiral chemical species into chiral molecules,
inherent to hypercarbonic transformations, suggests a mechanistic method for the generation
of homochirality through propagation. The solubility of oxygen in lipid materials points to
an aerobic course for the evolution of cellularity.