19 RNA: The Shape of Things to Come

Abstract

This enormous book and the literature behind it establish a new conventional wisdom. Today it is common to assert that an RNA world once existed and flowed into the present biosphere. Introductory texts and review articles softly (or staunchly [Watson et al. 1987]) proclaim that RNA comprises the collection of genetic and catalytic molecules that began the biosphere and then gracefully stepped into the background as a richer life unfolded. In this volume are papers that define the position RNA might have held. Having read many such papers, we note that by the scientific rules of evidence, the concept of an RNA world may stand only as an attractive idea, an idea that never can be tested adequately. One problem is that known RNA catalysts are few, and thus we have no way to assess the catalytic breadth of RNA by normal observation and experimentation. Methods now exist to inspect the catalytic and binding properties of small RNA molecules without recourse to the identification of RNAs in the present biosphere. In this paper, we illustrate the chemical and likely catalytic potential of RNA by reference to work done by us using these new methods. The plausibility and limitations of an early RNA world are addressed by the work. We have come to an astonishing and unexpected conclusion. RNA apparently has a huge distribution of sizes and shapes, and a collection of RNA molecules, even a collection of rather short RNA molecules, could have been used for an enormous variety of...