Whereas 'natural evolution' is a well-studied biological theory, the notion of 'chemical evolution' remains ambiguous. At least two major meanings of 'chemical evolution' can be found. As used by cosmologists, planetologists or geochemists among others, chemical evolution - call it chemical evolution1 - refers to the changes in chemical composition of stellar or inter-stellar systems due to the spontaneous occurrence of thermodynamically and kinematically favored chemical reactions. On the other hand, following Melvin Calvin (1955), chemical evolution - call it chemical evolution2 - refers to a prebiotic process similar to the biological process of 'natural evolution' and articulated on three major mechanisms: a mechanism of molecular amplification, a mechanism of chemical variation and a mechanism of chemical selection. Whereas for Calvin chemical evolution2 essentially aimed at explaining the appearance of generic organic polymers, like random DNA strands on the prebiotic Earth, I argue that chemical evolution2 can explain the appearance of some of these very specific organic polymers, in particular those that have interesting catalytic properties of uttermost relevance for living systems, and that it is in this respect that chemical evolution2 is of uttermost significance. Furthermore, I propose that recent work on the in vitro synthesis of catalytic RNAs, also called ribozymes, can help shed new light on the very mechanisms of chemical evolution2.
