General principles of biological hierarchical systems

This contribution sets the stage for the following selection of articles addressing general aspects of the hierarchy theory of evolution. It does so by reviewing basic principles of hierarchical systems in general and biological nested hierarchies in particular. More specifically, the article provides formal definitions of a hierarchy, levels of organization, and considers the nature of emergence that arises as a consequence of a hierarchical architecture. The overall dynamics of the hierarchical systems is best described by the synergy between intra-level interactions (best approached using the network theory) and the inter-level relationships (interpreted as emergent constraints). These basic properties of hierarchical systems are then used to represent the overarching model of the structure of the organic world, consisting of two interacting systems: the economic (ecological) hierarchy of interactors and the genealogical hierarchy of replicators. This model is at the heart of the hierarchy theory of evolution, providing a novel ontological framework for inferring causality of a great diversity of evolutionary phenomena.