Reflexive Catalysis, a Possible Mechanism of Molecular Duplication in Prebiological Evolution

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Abstract
Oparin's account of the origin of life assumed the possibility of natural selection among unorganized colloid droplets. This is not consistent with modern views of natural selection, which would require self-duplicating, mutable systems. On the other hand, the common conception of of nucleoprotein genes as the simplest self-duplicating mutable units may be mistaken. Any molecule that catalyzed the synthesis of one of its precursors, in a system where these precursors eventually formed more of the same molecule, would be reproducing itself in the sense required by natural selection. The term reflexive catalysis is suggested for this process to distinguish it from autocatalysis. Molecular reproduction by reflexive catalysis would generally have a low specificity or "high mutability." It might at any time result in new molecules capable of catalyzing steps in their own respective syntheses. Competition would result in selective propagation of the more efficient reflexive catalysts, and the accelerated consumption of starting materials would gradually extinguish inefficient or uncatalyzed competing reactions. This can be demonstrated in a mathematical model and appears to be subject to test in relatively simple, though long term, laboratory experiments. The concept of reflexive catalysis applies not only to reactions in solution. It can, for instance, be extended to include such physical effects as the stabilization of a colloid droplet by a molecule being synthesized in that droplet. Thus provided with natural selection on a molecular level, Oparin's description of the origin and early evolution of protoplasm becomes reasonable.

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