Dental topography and the diet of Homo naledi

Abstract

Though late Middle Pleistocene in age, Homo naledi is characterized by a mosaic of Australopithecus-like (e.g., curved fingers, small brains) and Homo-like (e.g., elongated lower limbs) traits, which may suggest it occupied a unique ecological niche. Ecological reconstructions inform on niche occupation, and are particularly successful when using dental material. Tooth shape (via dental topography) and size were quantified for four groups of South African Plio-Pleistocene hominins (specimens of Australopithecus africanus, Paranthropus robustus, H. naledi, and Homo sp.) on relatively unworn Ms to investigate possible ecological differentiation in H. naledi relative to taxa with similar known geographical ranges. H. naledi has smaller, but higher-crowned and more wear resistant teeth than Australopithecus and Paranthropus. These results are found in both lightly and moderately worn teeth. There are no differences in tooth sharpness or complexity. Combined with the high level of dental chipping in H. naledi, this suggests that, relative to Australopithecus and Paranthropus, H. naledi consumed foods with similar fracture mechanics properties but more abrasive particles (e.g., dust, grit), which could be due to a dietary and/or environmental shift(s). The same factors that differentiate H. naledi from Australopithecus and Paranthropus may also differentiate it from Homo sp., which geologically predates it, in the same way. Compared to the great apes, all hominins have sharper teeth, indicating they consumed foods requiring higher shear forces during mastication. Despite some anatomical similarities, H. naledi likely occupied a distinct ecological niche from the South African hominins that predate it.

Dust affects chewing efficiency and tooth wear in forest dwelling Western chimpanzees (Pan troglodytesverus)

“…Again, in the light of our findings this would make a dust‐loaded diet unlikely but rather suggests that this microwear signature was the result of small sized seeds. However, we cannot fully exclude the possibility that grit (sensu stricto—coarse sand with a grain size of 0.5–2 mm) caused these chips and was also involved in texture formation as suggested by Towle, Irish, and De Groote () and Berthaume, Delezene, and Kupczik (). Both fossil hominin examples show that more field observations and feeding experiments under controlled conditions are needed to better understand texture formation.…”

Mandibular molar root and pulp cavity morphology in Homo naledi and other Plio-Pleistocene hominins

“…It has recently been suggested that the Middle Pleistocene Cave of Hearths mandible, which has been assigned to H. sapiens rhodesiensis (Tobias, 1971), could belong to H. naledi (Berger et al, 2017). However, this is unlikely given that the Cave of Hearths mandible differs from the latter in several dental morphological features including occlusal topography of the M2 (Berthaume et al, 2018), overall premolar and molar crown morphology (L.K.D., pers. obs.)…”

Technical note: Comparing dental topography software using platyrrhine molars

“…ArcGIS (Esri, Redlands, CA) is a GIS software package that can measure or provide input measures for OR, m , and a (e.g., Dennis et al, ; M'Kirera & Ungar, ; Ungar et al, ; Ungar & M'Kirera, ; Ungar & Williamson, ; Zuccotti et al, ). MorphoTester (Winchester, ), calculates OPCR, DNE, and OR (see Berthaume, ; Berthaume, Delezene & Kupczik, ; Berthaume & Schroer, ; Polivka, ; Prufrock, Boyer & Silcox, ). Finally, molaR, an R package capable of calculating OPCR, DNE, m , and OR (Pampush et al, ) has been employed in a number of dental topography studies (e.g., Harper, Parras & Rougier, in press; Pampush et al, , ; Peredo, Peredo & Pyenson, ; Renaud & Ledevin, ; Renaud et al, ).…”