Notable: Scapula morphology in humans and African apes

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Notable paper: Green, David J., Ted A. Spiewak, Brielle Seitelman and Philipp Gunz. 2016. Scapular shape of extant hominoids and the African ape/modern human last common ancestor. Journal of Human Evolution 94:1–12. doi:10.1016/j.jhevol.2016.01.001

Synopsis: Green and colleagues examined the shape of the outline of the scapula in African apes, orangutans, gibbons and humans, to try to understand how it was transformed among the evolution of these species. They find that humans and gorillas overlap substantially in this aspect of scapula morphology, and suggest that the ancestor of the African apes and humans may have been relatively gorilla-like in their shoulder, with chimpanzees as a derived form different from this ancestor.

Interesting because: Australopithecus afarensis has been argued to be gorilla-like in scapular morphology, particularly with reference to Green and Alemseged’s work on the Dikika juvenile skeleton, but also to some extent Lucy’s scapula. By contrast, the KSD-VP 1/1 skeleton attributed to Au. afarensis does not have a particularly gorilla-like scapula, it is rather more humanlike in its anatomical configuration. Is this variation within Au. afarensis? Which of these actually reflects the ancestral configuration? Is it possible that somebody is wrong about one of these skeletons?