SEX-DIFFERENCES IN THE SCIATIC NOTCH OF GREAT APES AND MODERN HUMANS

The sciatic notch has been widely used as a sexing criterion in modern humans. In order to better understand the sex differences of this fea ture in modern humans and great apes, four measurements of the sciatic notch were taken on samples of modern humans and great apes of known sex. Univariate (ANOVA) analysis and discriminant function analysis we re performed on the extant taxa to determine: (1) the discriminating p ower of each variable in these samples of known group membership; and (2) which of these extant taxa shows the best discrimination between t he sexes for the sciatic notch. Of the four extant taxa, the sciatic n otch of Homo sapiens is the most sexually dimorphic, followed by Goril la gorilla, and more weakly by Pongo pygmaeus, while Pan troglodytes i s the least dimorphic of these taxa. Since the presence of a well defi ned sciatic notch is a hominid trait resulting from the dorsal extensi on of the posterior ilium, the close approximation of the sacrum to th e acetabulum, the shortened ischium, and the accentuation of the ischi al spine as part of the bipedal adaptation, it seems likely that the c onfiguration of the sciatic notch in hominids was initially related to bipedalism, not reproduction. The development of sex differences in t he sciatic notch of modern humans is more likely to have occurred afte r the transition to bipedality. (C) 1996 Wiley-Liss, Inc.