Life-History Inference in the Early Hominins Australopithecus and Paranthropus

Data are presented on adult body mass for 230 of 249 primate species, based on a review of the literature and previously unpublished data. The issues involved in collecting data on adult body mass are discussed, including the definition of adults, the effects of habitat and pregnancy, the strategy for pooling data on single species from multiple studies, and use of an appropriate number of significant figures. An analysis of variability in body mass indicates that the coefficient of variation for body mass increases with increasing species mean mass. Evaluation of several previous body mass reviews reveals a number of shortcomings with data that have been used often in comparative studies.

Reconstructing the diets of extinct hominins is essential to understanding the paleobiology and evolutionary history of our lineage. Dental microwear, the study of microscopic tooth-wear resulting from use, provides direct evidence of what an individual ate in the past. Unfortunately, established methods of studying microwear are plagued with low repeatability and high observer error. Here we apply an objective, repeatable approach for studying three-dimensional microwear surface texture to extinct South African hominins. Scanning confocal microscopy together with scale-sensitive fractal analysis are used to characterize the complexity and anisotropy of microwear. Results for living primates show that this approach can distinguish among diets characterized by different fracture properties. When applied to hominins, microwear texture analysis indicates that Australopithecus africanus microwear is more anisotropic, but also more variable in anisotropy than Paranthropus robustus. This latter species has more complex microwear textures, but is also more variable in complexity than A. africanus. This suggests that A. africanus ate more tough foods and P. robustus consumed more hard and brittle items, but that both had variable and overlapping diets.