Hominoid Scapular Morphology Suggests a Generalized Last Common Ancestor
Despite locomotor differences, African apes have been considered simple size vicars, and a recent analysis of hominid scapular morphology has suggested an African ape-like human ancestor. However, fossil evidence suggests that humans did not evolve from a chimpanzee-like ancestor. To compare hominoid scapulae, we conducted four discriminant function analyses (DFAs) that included a broad sample of anthropoids. To limit size issues, we used five scapular angles that reflect overall shape. All DFAs yielded highest loadings for spine orientation, glenoid-vertebral border position, spine-axillary border angle, and inferior angle. At least 74% of cases were correctly assigned. In the initial DFA, apart from one gorilla grouped as a chimpanzee, African apes and humans were distinct from one another. We then conducted three DFAs in which gorillas, chimpanzees, and humans were each initially unclassified, and then assigned to the distribution post hoc. When this procedure was followed, only one gorilla was identified as a chimpanzee, whereas 16 of 29 were categorized as Lagothrix. All 29 chimpanzees were grouped as Ateles. No human was categorized as an African ape, whereas 15 of 28 were classified as Alouatta. Chimpanzees were similar to Ateles in having a more cranially oriented glenoid, more highly angled spine, and narrower scapula than do gorillas, which are more similar to the predominantly clambering Lagothrix. Group centroids also placed gorillas closer to humans, suggesting that both likely lie closer than chimpanzees to a generalized ancestor for extant hominoids, consistent with a more generalized common ancestor as exhibited by Ardipithecus ramidus.
American Journal of Physical Anthropology
Selby, Michael S. and Lovejoy, C. Owen, "Hominoid Scapular Morphology Suggests a Generalized Last Common Ancestor" (2017). PCOM Scholarly Papers. 1807.
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