New hominin dental remains from the Drimolen Main Quarry, South Africa (1999–2008)

Abstract

Objectives: Twenty-four dental specimens from the Drimolen Main Quarry (DMQ) are described. This increases the number of DMQ Paranthropus robustus specimens from 48 to 63 and DMQ Homo specimens from 8 to 12. This allows reassessment of the proposed differences between the DMQ P. robustus assemblage and that of Swartkrans. Analysis conducted assesses intraspecific and inter-locality variation.Materials and Methods: We examined the P. robustus and early Homo assemblages from South Africa. Morphology was observed using a hand lens and a binocular microscope. Mesiodistal and buccolingual measurements were taken using plastictipped calipers. Summary statistics were generated and patterns of variability in P. robustus were assessed through box plots and Mann-Whitney U tests.Results: Comparison between the expanded DMQ and Swartkrans P. robustus assemblages demonstrates overlap in size. Ten dental variables show statistically significant differences.Discussion: The expanded P. robustus sample allowed us to re-examine previous analyses of differences in tooth size between the samples. While analyses presented here show a high degree of overlap in the MD and BL dimensions of the two assemblages, significant differences were found in the mean values of these variables in the postcanine maxillary teeth-consistent with previous analyses. Two current hypotheses may explain this pattern: 1) dental size increase through the P. robustus lineage or 2) different sample composition between the two sites. Small sample sizes for all permanent dental classes in the DMQ assemblage represents a limitation on this analysis and interpretations thereof. Any addition to the DMQ or the Swartkrans samples may alter these results.

A lineage perspective on hominin taxonomy and evolution

“…Recently discovered craniodental fossils from the site of Drimolen Main Quarry (DMQ), South Africa, have added considerably to the P. robustus sample 46,85,86 allowing for the reassessment of hypotheses concerning variability within the P. robustus hypodigm (Figure 2).…”

“…Recently discovered craniodental fossils from the site of Drimolen Main Quarry (DMQ), South Africa, have added considerably to the P. robustus sample 46,85,86 allowing for the reassessment of hypotheses concerning variability within the P. robustus hypodigm (Figure 2). Previously, the morphological differences between the DMQ robust australopiths and those found at Swartkrans Member 1 Hanging Remnant (SWM1HR) and Kromdraai B Members 4 to 7 (KBM4–7) were interpreted as sexual dimorphism, with the best preserved specimen at DMQ (DNH 7) being female and those from SWM1HR and KBM4‐7 being male 87–91 .…”

“…Referred specimens : These include all specimens (DNH 7, 8, 51, 53, 54, 56‐58, 79, 86, 89, 96, 106, 108, 121, 122, 126, 128, 133, 136, 146, 147, 152, and 155) from DMQ that can both be confidently allocated to P. robustus 46,85–87,90,95 and that can be considered with any confidence to be derived from the in situ deposits of the lowermost flowstone bound unit (FBU1) of the site's central talus cone that dates to between ~2.04 and 1.95 Ma 85 …”