Geochemical Continuity and Catalyst/Cofactor Replacement in the Emergence and Evolution of Life.

The origin of life is mostly divided into "genetics first" and "metabolism first" hypotheses. The former is based on spark-tube tests and organic species from meteorites and comets, and proposes a heterotrophic origin of life also consistent with the "RNA World" concept. The "metabolism first" hypothesis posits that life began autotrophically on minerals and/or hydrothermal vents. The lack of direct evidence means it is not possible to lend solid support to either hypothesis but the "metabolism first" option can be explored if a continuous geochemical, catalytically dynamic process is assumed. Using this approach, it is speculated that purine and pyrimidine synthesis originated on a mineral surface, which was later replaced by ATP. The same applies to redox processes where metal-bound hydrides could have been replaced by NAD.