Introduction: the principle of common precursors

Higher organisms consist of a plurality of different cells. They can reproduce only by an orderly reproduction of all their individual component cells. Therefore, we hold that unicellular organisms are logically and phylogenetically prior to multicellular organisms.

Unicellular organisms are known to exist. They consist of a plurality of different components: a cell envelope, a genetic machinery, a machinery for chemiosmosis, a set of enzymes, and a host of metabolites. The organisms reproduce by reproducing all these components. Therefore, it is reasonable to hold that a subset of these components is logically and phylogenetically prior to unicellular organisms and that it is in fact the primordial form of life.

The cell envelope is an important component of cellular organisms. It is the physical basis for organismic individuation. Therefore, some have conjectured that a lipid vesicle (endowed with light-driven chemiosmosis) self-organized and self-reproduced in a primordial broth of lipids and later came to “invent” a genetic machinery and a metabolism (Morowitz 1992).

The genetic machinery is another important component. Nucleic acids are the physical basis for inheritable information. Therefore, others have conjectured that an RNA-like molecule (endowed with the capability of a replicase) self-organized and self-replicated in a broth of activated nucleotides and later came to “invent” a cell envelope and a metabolism (“RNA world”) (James and Ellington 1995).

In contrast to these two proposals, which focus on complex machineries, a third proposal focuses on the underlying process of the cell, the metabolism that is more fundamental than any of the cell machineries (Wächtershäuser 1988a, 1990, 1992, 1994, 1997).