Some Aspects of the Evolution of Early Hominid Sexual Dimorphism [and Comments and Reply]

This paper reviews the patterns of sexual dimorphism in the living higher primates and suggests criteria for sex determination in the australopithecines. Using the bimodal distribution for australopithecine canine breadths, sex determination for individual specimens is attempted. The pattern of sexual dimorphism in the australopithecines differs from that in other higher primates: posterior-tooth dimorphism, mandibular-corpus dimorphism, and probably, therefore, body-size dimorphism are at the extreme of the higher-primate range, while canine dimorphism is considerably less than in most living primates, although greater than in living humans. It is suggested that the primary cause of the difference between hominid and pongid trends in the evolution of sexual dimorphism is the increasing importance of tools as a supplement and replacement for the canines in hominid evolution.