Homo habilis

Unfortunately, very little shoulder material is known for H. habilis (Table 7.1). The most complete specimen is the OH 48 clavicle, which Napier (1965) describes as basically human-like except for the cross-sectional shape of the medial end. Based on the orientation of the long axis of this cross-section, he concludes that the clavicle would have been rotated slightly around its longitudinal axis and the shoulder positioned higher than in modern humans to sit on a thorax with a steep inlet. Oxnard (1969) reports a significantly higher degree of torsion in the OH 48 clavicle than in modern humans, and concurs that it would have been twisted cranially and the shoulder positioned more superiorly, which he interprets as reflecting some ability for upper limb suspension. Day (1978) however argues that the missing ends of the specimen make any measure of torsion unreliable, and emphasizes the basically human appearance of the fossil, a perspective echoed by Ohman (1986). The only other shoulder remains attributed to H. habilis are the lateral portion of a clavicle and a small piece of the scapular spine from the KNM-ER 3735 partial skeleton. Leakey et al. (1989) interpret the thickness of the latter as well as the large size of other forelimb features of KNM-ER 3735 as evidence of substantial climbing ability in H. habilis. Based on this very limited sample, therefore, it is possible that early Homo continued to possess a somewhat primitive shoulder configuration like that of earlier hominins.

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