On Prebiotic Ecology, Supramolecular Selection and Autopoiesis
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On Prebiotic Ecology, Supramolecular Selection and Autopoiesis Rafal Wieczorek
Published online: 7 November 2012 # Springer Science+Business Media Dordrecht 2012
Keywords Origin of life . Autopoiesis . Prebiotic ecology . RNA world critique . Lipid world The existence of many “worlds” in origin-of-life literature; such as the “lipid world” (Segré et al. 2001), the“iron-sulfur world” (Wächtershäuser 1992), the “aromatic world” (Ehrenfreund et al. 2006) and others, leads to the impression that there are many competing hypothesis for the origin of life. However, if one postulates that a concrete theory for the origin of life should provide a plausible pathway from the stage of prebiotic soup to the stage of life in a series of logical steps, then none of the above mentioned “worlds” comply with this requirement. Most simply 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 the RNA-world theory goes something like this: On an early Earth there was a prebiotic soup stage in which, in some aqueous environment, there was an abundance of various organic molecules, 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 RNA molecule. Once such a molecule was present it made many copies of itself. Due to nonperfect replication, some of the molecules were different and thus behaved differently in the environment (for example they were better replicators), thus paving the way for hereditary features, environmental selection and therefore evolution. Some of these RNAs (namely ribozymes) possessed catalytic activities. RNA molecules which were encapsulated inside lipid vesicles were advantaged over those that were not, principally thanks to protection from the outside environment. Later on those that were able to catalyse synthesis of their own lipid vesicles prevailed over those that could not. At this stage the macromolecular conglomerate started resembling modern cells and the RNA in these “cells” performed both genetic and enzymatic functions. At some point, the RNA protocell “invented” DNA for R. Wieczorek (*) FLinT Center, Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark e-mail: [email protected]
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R. Wieczorek
storing genetic information and proteins to perform catalysis with greater efficiency. At this point we arrive at form of life that is ancestral to all modern life on Earth—LUCA. This scenario could, in principle, happen again (given the right conditions) or be recapitulated in a laboratory experiment. Because of contingent factors we would not expect to recreate in such an experiment exactly the historical LUCA, but something comparable to it: a LUCA-like entity; something that would be equally, unequivocally alive. In this asp
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