Interpreting the Dental Peculiarities of the ‘Robust’ Australopithecines

Abstract

It is now widely recognised that during the early Pleistocene there were at least two distinct hominid lineages (Tobias, 1973; Leakey and Walker, 1976; White, Johanson and Kimbel, 1981; Wood, 1981). Whatever the nomenclatural devices used, there is also widespread agreement that one lineage contains, or leads to, the group we know informally as the ‘robust’ australopithecines. Most workers also accept that the specialisations which demarcate that lineage are most developed within the hypodigm of Australopithecus (Paranthropus) boisei. The first attempt to define the functional adaptations underlying the evolution of ‘robust’ australopithecines (what Tattersall and Eldredge (1977) call the evolutionary ’scenario’) was made three decades or more ago (Robinson, 1954) and since then nearly all such attempts have identified characteristic features of the teeth, jaws and cranium and stressed their likely association with particular dietary and feeding regimes (Robinson, 1963; Jolly, 1970; Du Brul, 1977; Walker, 1981). Before one can proceed to postulate hypothetical scenarios, however, it is most important to examine whether the basis for identifying the morphological sets, or phena, is a sound one. Even though the case for the distinctiveness of the ‘robust’ australopithecines is widely accepted, there is much less agreement about the taxonomic and functional implications of the features cited. In particular, there is discussion about whether the apparently distinctive morphological features are not simply the scale effects of a larger body size, rather than evidence of more profound functional modifications. In this paper I will discuss the general problem of how such assessments are made, and examine two examples which relate to dental morphology. The first is the relationship between canine and molar size and between canine/molar size and body size, and the second is the link, if any, between overall size and the relative cusp size of mandibular molar teeth.