Gradual, autocatalytic and punctuational models of hominid brain evolution: A cautionary tale

Abstract

The tempo and pattern of macroevolutionary change have bearing on current controversies concerning the processes of macroevolutionary change. In this paper we reexamine the evidence for increase in cranial capacity in light of traditional arguments and interpretations, paying special attention to methodological problems inherent in data transformations and manipulations. Despite a large volume of descriptive material published on the subject, there has been relatively little attention paid to testing competing hypotheses of processes of macroevolutionary change (punctuational, gradual, autocatalytic); the descriptions which have emerged often reflect unstated and, perhaps, unrealized a priori assumptions made by researchers. Log-log transformations of cranial capacity versus time are misleading and inappropriate. A uniform pattern of change in hominid cranial capacity is less obvious than generally assumed.