1Department of Anthropology / Applied Forensic Sciences, Mercyhurst University, 2Evolutionary Studies Institute and Centre for Excellence in PaleoSciences, University of Witwatersrand, 3Department of Anthropology, University of Arkansas, 4Department of Anthropology, University of Wisconsin, 5Evolutionary Anthropology, Duke University, 6Department of Anthropology, Tulane University
April 16, 2016 11:00, Imperial Ballroom A
The discovery of 1550 Homo naledi fossil specimens from the Dinaledi Chamber of the South African Rising Star cave system provides a rare opportunity to study intra-specific body size variation and sexual dimorphism in a geographically and temporally constrained sample of hominin fossils. Using linear measurements and equations derived from a variety of modern human reference samples, we estimated body mass and evaluated sexual size dimorphism from 20 adult postcranial specimens. Because the sample may represent any single individual multiple times, a subsample of eight non-antimeric proximal femora was also analyzed. Stature was estimated from a mostly complete adult humerus (U.W.101-283) and tibia (U.W.101-484). H. naledi canine (n = 6) and molar (n = 9) size dimorphism was evaluated using coefficients of variation and were compared to modern humans and extant apes using bootstrap analyses.
Results indicate that body mass estimates for the 20 specimens range from 35 to 56 kg. H. naledi had an average body size most consistent with early Homo species (~147 cm and 45 kg). H. naledi males weighed approximately 20 percent more than females, which is consistent with other reports of sexual size dimorphism in Homo. Canine and molar size dimorphism is minimal and more similar to modern humans than extant apes. Endocranial volumes (465 – 560 cm3) and encephalization quotients (~2.5), however, are most similar to Australopithecus. H. naledi’s relatively small brain paired with Homo-like body size and levels of sexual dimorphism may have important implications for behavioral and ecological interpretations of fossil hominins.