RNA world hypothesis

The thought that RNA was the first form of life.

This hypothesis is supported by RNA's ability to participate in the storage, transmission, and duplication of genetic information, similarly to DNA, coupled with it's ability to to act as an enzyme, catalyzing certain reactions.

At first glance, the RNA world hypothesis seems implausible given that in today's world large RNA molecules are especially fragile, subject to hydrolysis? that degrades these long biopolymers into their constituent monomeric nucleotides. However, in today's world enzymes capable of catalyzing this hydrolysis called RNAses ("ar-en-ases") are ubiquitous, contributing to this fragility. In a pre-biotic world absent any protein, including RNAses, a given RNA molecule might have "lived" longer then than it can today.

The RNA world hypothesis, if true, has important implications for the very definition of life. We may be too ready to define life in terms of DNA and proteins. After all, in today's world, DNA and proteins seem to be the dominant macromolecules in the living cell, with RNA serving, for the most part, as a mere messenger between them. But the RNA world hypothesis places RNA at center-stage when life originated, and therefore requires that we define life primarily in terms of RNA, and only secondarily in terms of DNA and proteins. If the RNA world hypothesis is true, life can be defined as the set of strategies that RNA polynucleotides have used and continue to use to perpetuate themselves.