Origins of Life: Chemistry and Evolution

Our understanding of the origins of life will be enhanced if models and their predictions are clearly understood and explicitly articulated. Here we outline two distinct models that are currently used to explain the origins of life. In one model, which has been pursued for a half century, inherent chemical reactivities of prebiotic chemical species produced RNA, which then invented evolution. This direct synthesis model enables the prediction that if the conditions of the ancient earth are sufficiently constrained, chemists will discover the synthetic pathways that produced RNA. In a fundamentally different model, which is more recent and less mature, RNA in concert with other biopolymers arose from prolonged, selection-based changes that occurred during chemical evolution, which transitioned smoothly into biological evolution. This evolutionary model predicts common chemistry of linkage and amazing structures, assemblies and co-assemblies, as represented by double stranded DNA, tRNA, cellulose, collagen, globular proteins, ATP synthase, and the ribosome. This evolutionary model predicts profound integration of biological subsystems as represented by ATP, which is central to and inextricable from biopolymer structure and biosynthesis and metabolic systems. In the evolutionary model, inherent chemical reactivities of biological building blocks are not necessarily relevant to the origins of life and do not predict biosynthesis. The two models of the origins of life are fundamentally different from one another and guide design of very different experimental approaches to test their underlying assumptions. It is currently undetermined which model, or a hybrid of them, is closer to reality

Evolution of Complex Chemical Mixtures Reveals Combinatorial Compression and Population Synchronicity

Some of the most interesting open questions about the origins of life and molecular sciences center on chemical evolution and the spontaneous generation of complex and functional chemical species. The processes that generated the spectacular biopolymers that underlay biology demonstrate an untapped, by modern science, creative potential. We have established a robust, facile, and generally applicable platform for observing and analyzing chemical evolution using complex mixtures. While previous studies have characterized the formation of proto-polymers via chemical reactions, we systematically studied the process itself. We report empirical outcomes that were not foreseen or predicted. We have constructed an experimental platform to study the evolution of chemical systems that: (i) undergoes continuous recursive change with transitions to new chemical spaces while not converging throughout the course of the experiment, (ii) demonstrates chemical selection, during which combinatorial explosion is avoided, (iii) maintains synchronicity of molecular sub-populations, and (iv) harvests environmental energy that is stored in chemical energy. We have established some general guidelines for conducting chemical evolution. Our results suggest that chemical evolution can be adapted to produce a broad array of molecules with novel structures and functions