Spontaneous emergence of self-replication in chemical reaction systems

Explaining origins of life requires us to explain how self-replication arises. Specifically, how can self-replicating entities develop spontaneously from chemical reaction systems in which no reaction is self-replicating? Previous models either supply a framework for minimal living systems or only consider catalyzed reactions, and thus fail to provide a comprehensive theory. We establish a general model for chemical reaction systems that properly accounts for energetics, kinetics and conservation laws. We find that (1) some systems are collectively-catalytic (e.g., the citric acid cycle), while others self-replicate as a whole (e.g., the formose reaction); (2) side reactions do not always inhibit such systems; (3) many alternative chemical universes often contain one or more such systems; (4) in some self-replicating systems, the entropy of certain parts spontaneously decreases; (5) complex self-replicating molecules emerge spontaneously from simple reaction systems through a sequence of transitions. Together these results start to explain origins of prebiotic evolution.