Brief communication: Dental microwear and diet of Homo naledi

Objectives: A recent study of dental chipping suggested that Homo naledi teeth were exposed to "acute trauma" on a regular basis during life, presumably from the consumption of grit-laden foods. This follows debate concerning the etiology of dental chips in South African hominin teeth that dates back more than half a century. Some have argued that antemortem chips result from consumption of hard foods, such as nuts and seeds or bone, whereas others have claimed that exogenous grit on roots and tubers are responsible. Here we examine the dental microwear textures of H. naledi, both to reconstruct aspects of diet of these hominins and to assess the possibility that hard foods (gritty or otherwise) are the culprits for the unusually high antemortem chip incidence reported.

Methods: We made high-resolution replicas of original molars and found that ten individuals preserve antemortem wear. These were scanned by white-light scanning confocal profilometry and analyzed using scale-sensitive fractal analysis. Resulting data were compared with those published for other fossil hominins and extant non-human primates.

Results: Our results indicate that H. naledi had complex microwear textures dominated by large, deep pits. The only known fossil hominin with higher average texture complexity is Paranthropus robustus, and the closest extant primates in a comparative baseline series appear to be the hard-object feeder, Cercocebus atys, and the eurytopic generalist, Papio ursinus.

Conclusions: This study suggests that H. naledi likely consumed hard and abrasive foods, such as nuts or tubers, at least on occasion, and that these might well be responsible for the pattern of chipping observed on their teeth.