Evolution before genes - theoretical analysis of autocatalytic molecular networks and its implications for metabolism-first theories of the origin of life

Resumen

A basic property of life is its capacity to experience Darwinian evolution. But how could such a complex system as a living entity appear in the first place? Natural selection is known to be a very efficient self-organizing principle outside the realm of biology too. We argue that evolution preceded life, and we must understand the origin of evolvable chemical systems, as their gradual increase of complexity lead to the appearance of life. There are two camps in the origin of life that put forward different chemical systems as possible candidates. The genetics-first supporters envision an RNA world where RNA strands capable of template replication also possessed catalytic activity and were most likely enclosed in compartments; the metabolism-first camp advocates suggest that self-reproducing and evolving proto-metabolic networks predated full-fledge cell-like entities. The Gordian knot of the situation is the following: it is equally improbable that RNA-like self-replicating polymers appeared without a self-organizing force such as natural selection, as molecular networks without genetic control could have undergone Darwinian evolution. In my dissertation I focus on the second issue. Although metabolism-first theories of the origin of life have been intensively discussed in the literature for decades, no rigorous analysis of their putative evolutionary capacity has been carried out so far. At the most, researchers have been satisfied with demonstrating the existence of multiple attractors in pre-template systems. We took the next step: we put reaction networks in a population dynamical context and analyzed their behaviour directly. The two most prominent models ¿ the GARD and the autocatalytic set models ¿ were examined in detail. The aim of my dissertation is to evaluate the evolutionary capacity of autocatalytic reaction networks.