An alternative interpretation of the Australopithecus scapula

In PNAS, Young et al. (1) conclude that the scapula of the last common ancestor (LCA) of chimpanzees and humans was African ape-like, supporting what they call the “African ape” model. This model was favored over the “ape convergence” model, in which the ancestral condition was more primitive and some morphological similarities shared among modern apes would reflect convergent evolution. The authors suggest that less ape-like morphology in Australopithecus afarensis reflects an adaptive trade-off between arboreality and tool use (1).