Scapular Breadth Does Not Discriminate Suspension from Clambering in Hominoids: A Response to Spear and Williams

Spear and Williams ( 2018 ) are incorrect in stating that we (Selby & Lovejoy, 2017 ) argued that “a mediolaterally narrow scapula is unrelated to suspensory locomotion and therefore…early crown hominoids could not have been suspensory.” We clearly stated that scapular breadth is related to suspension, but is not a primary determinant of suspension. We posited instead that scapular narrowing was a fundamental change in the bauplan of primates that abandoned strict above branch quadrupedality in favor of more diverse arboreal locomotor postures, especially above and below branch palmigrade clambering. And, of course, early crown hominoids could have been suspensory; the point of import is, however, that they were most likely not . As we have argued elsewhere, the morphology of the wrist, elbow, foot, hip, and thigh, as well as the limb proportions of Ardipithecus , all point to a generalized clambering locomotor pattern in the last common ancestor (LCA) of extant African apes and humans (Lovejoy, Simpson, White, Asfaw, & Suwa,2009; Lovejoy, Suwa, Simpson, Matternes, & White, 2009 ; White, Lovejoy, Asfaw, Carlson, & Suwa, 2015 ).