Evolution of the human shoulder: some possible pathways

Osteometric data, apparently reflecting functional parameters of the shoulder in the Anthropoidea, have been examined by a combination of multivariate techniques in an attempt to define minimum pathways possibly followed in the evolution of the human shoulder. Principal components analysis has been used to gauge size-related shape effects. The combination of D² and canonical analysis has suggested that the shoulder in man is unlikely to have evolved (a) from one similar to that of any extant monkey whether arboreal or terrestrial, (b) from one similar to that of any terrestrial ape (like present-day Pan and Gorilla), or (c) from one similar to that of a highly specialised ricochetal armswinging ape (such as present day Hylobates and Symphalangus). The analyses suggest positively that the minimum evolutionary pathway may well have been from the shoulder of a totally arboreal ape, presumably genetically related to Pan and Gorilla, but functionally similar to that evolved in parallel in the highly arboreal orang-utan, Pongo. Information from fragmentary fossils (the scapula from Sterkfontein and the clavicle from Olduvai) supports these conclusions.