Autocatalytic sets and boundaries.

Autopoietic systems, chemotons, and autogens are models that aim to explain (the emergence of) life as a functionally closed and self-sustaining system. An essential element in these models is the notion of a boundary containing, maintaining, and being generated by an internal reaction network. The more general concept of collectively autocatalytic sets, formalized as RAF theory, does not explicitly include this notion of a boundary. Here, we argue that (1) the notion of a boundary can also be incorporated in the formal RAF framework, (2) this provides a mechanism for the emergence of higher-level autocatalytic sets, (3) this satisfies a necessary condition for the evolvability of autocatalytic sets, and (4) this enables the RAF framework to formally represent and analyze (at least in part) the other models. We suggest that RAF theory might thus provide a basis for a unifying formal framework for the further development and study of such models. Graphical abstractThe emergence of an autocatalytic (super)set of autocatalytic (sub)sets.