Networks and Hierarchies: Approaching Complexity in Evolutionary Theory

Abstract

This expansion of the hierarchy theory of evolution provides a new perspective in which biological phenomena are conceptualized. In this work, we (1) attempt to revise the ontology of levels of biological organization and clarify the relationship between the economic and genealogical hierarchies; (2) explore the implications of network theory for evolutionary dynamics in a hierarchical context; and (3) elucidate evolutionary causality by disentangling abiotic drivers from proximal evolutionary processes (the origin and sorting of variation) and their integration across hierarchies. We suggest that a pervasive pattern of stability in living systems across scale results from the architecture of nature’s economy itself—biological systems consisting of hierarchically nested, complex networks are extremely robust to extrinsic perturbations. We further argue that instances of evolution are episodic and rapid; they are transient between equilibrial states that ensue when network stability is compromised by sufficiently strong disturbances affecting biological entities at multiple levels of organization. We also claim that environmental abiotic factors are ultimately responsible for these perturbations that, when filtered through the economic hierarchy, shape the patterns of diversity and disparity of life as we know it.