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.