The theory of increasing autonomy in evolution: a proposal for understanding macroevolutionary innovations

Attempts to explain the origin of macroevolutionary innovations have been only partially successful. Here it is proposed that the patterns of major evolutionary transitions have to be understood first, before it is possible to further analyse the forces behind the process. The hypothesis is that major evolutionary innovations are characterized by an increase in organismal autonomy, in the sense of emancipation from the environment. After a brief overview of the literature on this subject, increasing autonomy is defined as the evolutionary shift in the individual system–environment relationship, such that the direct influences of the environment are gradually reduced and a stabilization of self-referential, intrinsic functions within the system is generated. This is described as relative autonomy because numerous interconnections with the environment and dependencies upon it are retained. Features of increasing autonomy are spatial separations, an increase in homeostatic functions and in body size, internalizations and an increase in physiological and behavioral flexibility. It is described how these features are present in different combinations in the major evolutionary transitions of metazoans and, consequently, how they should be taken into consideration when evolutionary innovations are studied. The hypothesis contributes to a reconsideration of the relationship between organisms and their environment.