The biochemical roots of the RNA world: from zymonucleic acid to ribozymes.

The history of the ideas that led to the RNA World hypothesis is reviewed. As the understanding of the properties of RNA molecules progressed, the evolutionary interpretation of their genetic properties and widespread distribution in intracellular environments, as well as the catalytic properties of nucleotide coenzymes and the participation of RNA monomers in metabolic pathways, led to several independent proposals of protein-free primordial life forms. Current ideas on the RNA World are part of a long and storied scientific perspective in which these different hypotheses were developed. However, the lack of continuity between them may be explained in part by the absence of an evolutionary framework that characterized the early development of molecular biology, as well as by the demise of certain areas of research like coenzyme chemistry.