Figure 12. Occlusal view of H. naledi mandibular teeth compared to those of other hominins.
Teeth from the canine to the third molar are shown, if present, in the orientation in which they are found within the mandible. All individuals are aligned vertically by the distal margin of the first molar. Mandibles from the Lesedi Chamber, U.W. 102 c-589 and LES1 are shown next to DH1 and U.W. 101–377 (Berger et al., 2015). The mandibles illustrated from H. erectus have relatively little occlusal wear, so their morphology can be seen more clearly than that of worn mandibles. The immature U.W. 101–377 (H. naledi) is comparable in developmental age and wear to O.H. 7 (H. habilis), as well as to D2735 and KNM-WT 15000 (H. erectus). When compared to H. habilis, H. erectus, and australopiths, H. naledi is notable for its relatively small first molars, its relatively small canines, and its lack of supernumerary cusps and crenulation on the molars. The complexity of molar cusp and groove patterns is especially evident in the chronologically early H. erectus specimens from Africa and Georgia shown here. For example, the unworn M2 of the immature U.W. 101–377 mandible of H. naledi has a relatively simple crown anatomy with very little wrinkling or crenulation. By comparison, the M2 of D2735, D211, and KNM-WT 15000, all with minimal occlusal wear, show extensive crenulation and supernumerary cusps. Canine size and molar crown complexity vary substantially among modern human populations, but the southern African individual illustrated on the right is not atypical for its population, and has greater molar crown complexity and larger canine dimensions than any of the H. naledi mandibular dentitions. The morphology of the third premolar varies extensively among these hominin species and within H. erectus. The H. naledi P3 anatomy can be seen clearly in the immature U.W. 101–377 individual. It is characterized by roughly equally prominent lingual and buccal cusps and an expanded talonid. In H. naledi, this tooth is broadly similar in morphology and size to the P4. This configuration of the P3 is not present in the other species, with only KNM-WT 15000 exhibiting some expansion of the lingual cusp in what remains an asymmetrical and rounded P3. A.L. 400–1, O.H. 7 and KNM-WT 15000 are represented by casts; The left dentition of U.W. 102 c-589 and O.H. 7 have been mirrored to compare to right mandibles. Images have been scaled by measured first molar dimensions.