1School of Archaeology and Anthropology, Australian National University, 2Evolutionary Studies Institute and Centre for Excellence in PalaeoSciences, University of the Witwatersrand, 3Department of Anatomy, Midwestern University, 4College of Veterinary Medicine, North Carolina State University, 5Department of Evolutionary Anthropology, Duke University, 6Anthropological Institute and Museum, University of Zuerich, 7Department of Anthropology, University of Wisconsin-Madison
April 16, 2016 9:00, Imperial Ballroom A
The recently announced species, Homo naledi (Rising Star Cave, Cradle of Humankind, South Africa), combines an australopith-like cranial capacity with dental characteristics more akin to early Homo. Its postcranium is similarly mosaic; although the hand, foot, and lower limb share many derived characteristics, the H. naledi shoulder girdle and upper limb is strikingly primitive. Here, we describe the H. naledi upper extremity (exclusive of the hand) in greater detail and place it in comparative context with extant hominoids, Australopithecus, and key specimens attributed to early Homo.
Homo naledi is characterised by a short clavicle and humerus with extremely low torsion. This suggests that the scapula – with a markedly cranially-oriented glenoid – was situated superiorly and laterally about the thorax. This configuration is similar to that of Australopithecus and distinct from the modern human shoulder girdle, which is positioned low and dorsally about the thorax. Early African Homo erectus is derived in scapular morphology, but also maintains primitive clavicle and humeral features.
The evolution of the hominin shoulder girdle appears to have occurred in concert with a behavioural shift from an upper limb involved predominantly in locomotion to one adapted for manipulation. Throwing adaptations may have also influenced more recent transitions, especially with regards to features that characterize the modern human shoulder girdle. However, the overall picture evinced by the H. naledi upper limb is one that is markedly primitive, retaining morphology conducive to climbing, and lacking many of the derived features purported to characterize other members of Homo.
This work was generously supported by grants from the National Science Foundation, the Wenner-Gren Foundation, and the Leakey Foundation.