Incisor size and wear in Australopithecus africanus and Paranthropus robustus

Comparisons based upon recent body size estimates indicate that the maxillary central incisors of Paranthropus robustus are relatively smaller than those of Australopithecus africanus. The MD diameters of A. africanus incisors are similar to expected values for a large-bodied catarrhine. The P. robustus crowns are noticeably smaller, being comparable to those of modern humans among extant catarrhines. This suggests that P. robustus may have ingested foods that required less extensive incisal preparation than the foods consumed by A. africanus. I¹ bevelling patterns suggest that a horizontal incisal wear surface was probably maintained in both taxa through posterior tipping of these teeth. This indicates that the incisal surfaces of differently worn crowns may be legitimately compared in microwear analyses. The ratio of microwear pits to scratches, scratch orientations and wear feature dimensions do not differ significantly between the two early hominid taxa. Indeed, the differences among the labial, incisal and lingual surfaces within each species are commonly more noticeable than the differences between the two species. Microwear feature densities in A. africanus, however, are significantly higher for all three I¹ surfaces. Comparisons with extant primates suggest that A. africanus incisors may have been employed to process a greater variety of foods, including larger, more abrasive items than were encountered by P. robustus.