Evolving a Field: Can Evolutionary Theory Provide What the Study of Human Evolution Requires?

The extended evolutionary synthesis (EES) is a school of thought that maintains that genetic determination and natural selection are over-emphasized in the study of evolution at the expense of non-genetic inheritance and processes of evolution beyond selection. Its proponents call for the de-emphasis of genetics and the adoption of a broader model of inheritance that includes cultural and epigenetic transgenerational effects and strong adaptive phenotypic plasticity. Presenting itself as a radical alternative to what it claims is a rigid and ossified theoretical orthodoxy, the EES has lately gained considerable traction among scholars of human evolution, and a distinct sub-branch of the EES unique to the biological anthropological study of human evolution has emerged (the EES in human evolution). To date, however, no direct comparison between the EES in human evolution and other contemporary evolutionary approaches has been attempted to evaluate whether the EES in human evolution affords researchers an edge in articulating good questions and structuring research programs to answer them. After reviewing the landscape of evolutionary theory, we evaluate whether the EES in human evolution is capable of delivering the processually pluralistic vision of evolution it has long promised and whether it brings something that the decades-long ongoing synthesis (OS) of evolutionary theory since the modern synthesis does not. We then conduct a head-to-head comparison to evaluate the relative explanatory efficacy of the EES and our preferred OS theoretical framework on several issues of human morphological evolution. We demonstrate that evolutionary perspectives as drawn from the OS have a much more clarifying effect on the investigation of human evolution than their EES-based competitor. Far from being a radical extension of evolutionary thought, the EES in human evolution offers little more than another idiom in which to tell adaptationist stories and triumphalist narratives of the ascent of humanity. Theory from the OS opens up new horizons of possible investigation of human evolution in a uniquely processually pluralistic and rigorous framework.