ABSTRACT
To date, an enlarged occipital/marginal sinus system (O/M) occurs in 100% of scorable cranial remains of both “ robust” australopithecines (N = 7) and the Hadar material attributed to Australopithecus afarensis (N = 6). This trait is not fixed in any other group of fossil hominids and is reduced to 6% in extant Homo sapiens (Falk, 1986a). A functional analysis of an enlarged O/ M system in early hominids led to the conclusion that “A. afarensis was directly ancestral to, or shared a common ancestor with, ‘robust’ australopithecines” (Falk and Conroy, 1983), a view put forward earlier by Olson (1981, 1985) for entirely different reasons. The recent discovery of KNM-WT 17000, a “ robust” australopithecine dated to 2.5 Myr (Walker et al., 1986), is consistent with this view; and it now appears that, despite the earlier belief that “ robust” australopithecines descended from Australopithecus africanus rather than A. afarensis (Johanson and White, 1979), many paleontologists believe that the population of “ robust” australopithecines represented by KNM-WT 17000 descended from earlier Hadar hominids.
