On Prebiotic Ecology, Supramolecular Selection and Autopoiesis

Abstract

Keywords Originoflife.Autopoiesis.Prebioticecology.RNAworldcritique.LipidworldThe existence of many “worlds” in origin-of-life literature; such as the “lipid world” (Segre etal.2001),the“iron-sulfur world ”(Wachtershauser1992),the“aromaticworld”(Ehrenfreundetal. 2006) and others, leads to the impression that there are many competing hypothesis for theorigin of life. However, if one postulates that a concrete theory for the origin of life shouldprovide a plausible pathway from the stage of prebiotic soup to the stage of life in a series oflogical steps, then none of the above mentioned “worlds” comply with this requirement. Mostsimply provide us with new or alternative ways of making components of the prebiotic soup,whether monomeric or polymeric.There is only one origin-of-life theory which complies with the above stated requirement:the so called “RNA world” theory (Gilbert 1986). A brief, modern recapitulation of theRNA-world theory goes something like this: On an early Earth there was a prebiotic soupstage in which, in some aqueous environment, there was an abundance of various organicmolecules, including nucleotide components. The complex interactions of these molecules,at some point, allowed for the emergence of RNA chains and later on a self-replicating RNAmolecule. Once such a molecule was present it made many copies of itself. Due to non-perfect replication, some of the molecules were different and thus behaved differently in theenvironment (for example they were better replicators), thus paving the way for hereditaryfeatures, environmental selection and therefore evolution. Some of these RNAs (namelyribozymes) possessed catalytic activities. RNA molecules which were encapsulated insidelipid vesicles were advantaged over those that were not, principally thanks to protectionfrom the outside environment. Later on those that were able to catalyse synthesis of theirown lipid vesicles prevailed over those that could not. At this stage the macromolecularconglomerate started resembling modern cells and the RNA in these “cells” performed bothgenetic and enzymatic functions. At some point, the RNA protocell “invented” DNA for