Stability in chemistry and biology: Life as a kinetic state of matter*

Despite the considerable advances in our understanding of biological processes, the physicochemical relationship between living and nonliving systems remains uncertain and a continuing source of controversy. In this review, we describe a kinetic model based on the concept of dynamic kinetic stability that attempts to incorporate living systems within a conventional physicochemical framework. Its essence: all replicating systems, both animate and inanimate, represent elements of a replicator space. However, in contrast to the world of nonreplicating systems (all inanimate), where selection is fundamentally thermodynamic, selection within replicator space is effectively kinetic. As a consequence, the nature of stability within the two spaces is of a distinctly different kind, which, in turn, leads to different physicochemical patterns of aggregation. Our kinetic approach suggests: (a) that all living systems may be thought of as manifesting a kinetic state of matter (as apposed to the traditional thermodynamic states associated with inanimate systems), and (b) that key Darwinian concepts, such as fitness and natural selection, are particular expressions of more fundamental physicochemical concepts, such as kinetic stability and kinetic selection. The approach appears to provide an improved basis for understanding the physicochemical process of complexification by which life on earth emerged, as well as a means of relating life’s defining characteristics—its extraordinary complexity, its far-from-equilibrium character, and its purposeful (teleonomic) nature—to the nature of that process of complexification.