ABSTRACT
Tobias (1967) also saw the “ robust” australopithecines as evolving from a relatively unspecialized ancestral form. He regarded both A. africanus and A. boisei as being derived from such an australopithecine ancestor; the former representing “ a more conservative residual line” and the latter a “ megadontic” form with “ specialized dentition.” The latter was believed to have undergone “ moderate reduction in cheek-tooth size . . . shortening of the face and reduction of the jaws” to become A. robustus (Tobias, 1967:243) (Fig. 17. 1B). In subsequent papers, Tobias was more specific about the identity of the unspecialized australopithecine ancestor, for he came to regard A. africanus as fulfilling the criteria of a common ancestral form (Tobias, 1973, 1978, 1980). The sequence A. boisei to A. robustus is also given less emphasis in subsequent phylogenetic trees (Tobias, 1978) (Fig. 17.1C).
