ABSTRACT
This chapter explores to speculate about the selective forces which brought the australopithecine group into existence, caused adaptive radiation within the group, and resulted in the origin of man. Adaptive radiation cannot be discussed fruitfully if it is not clear what categories are involved in the group concerned; indeed whether adaptive radiation has actually occurred must first be decided by taxonomic analysis. Some adaptive radiation in early Australopithecine history, particularly if it involved difference of diet, should consequently occasion no surprise. It might be felt that looking for the origin of the change in locomotor specialization is wrong; that behavioral changes might have led to erect posture. On the other hand it seems logical to suppose that tool-using, tool-making, and increased brainsize are virtually inevitable consequences of erect posture and that they will have followed the origin of the latter fairly rapidly in terms of the geological time scale.
