Size and shape of a human foot bone from Klasies River main site, South Africa

INTRODUCTION Rightmire et al.’s (2006) recent study of three late Pleistocene human metatarsal bones from Klasies River main site, situated on the southern coast of South Africa provides valuable insights into Middle Stone Age (MSA) occupation of these archaeologically informative deposits. Although there is still some debate on the age of the site (Parkington 1990; Wolpoff 1989), the general consensus is that the early Klasies River humans date between 80 000 and 100 000 years ago. One of these bones, a left first metatarsal (KRM 6113B), was recovered during the 1967–1968 excavations, originally thought to be from a non-human hominin, later regarded as indistinguishable from modern humans (Rightmire & Deacon 1991). Rightmire et al. (2006) describe this specimen as broadly comparable in size to that of Late Stone Age (LSA) San males drawn from Cape burials. The univariate comparison of the dimensions of the Klasies River Mouth (KRM) first metatarsal reveal that the length, proximal and distal dimensions are slightly smaller than average black South Africans. Mid-shaft diameters are comparable to those of black females. All dimensions are close to the averages for early Holocene males from the western and southern Cape (Zipfel 2004; Rightmire et al. 2006). The appearance of the KRM specimen is therefore unremarkable and based upon size is suggested to be male. This is also supported by the stature estimates of Rightmire et al. (2006) based on the formula by Byers et al. (1989), who found significant correlations between metatarsal lengths and stature. Despite Rightmire et al.’s well justified hypothesis that the KRM first metatarsal probably belonged to a male based on size, the important question of shape remains unresolved. Shape-associated sexual dimorphism, or in some cases ‘dimorphisms’ have been reported in foot bones (e.g. Kidd 1995; Kidd & Oxnard 1997; Ferrari et al. 2004; Zipfel 2004) in which the intercorrelation between variables reveals more information than individual dimensions or indices on their own. Numerous studies have addressed sex estimation from the hands and feet with varying results (e.g. Robling & Uberlaker 1997; Case & Ross 2007) which require clear identification of the population being considered. Determining the sex of an isolated specimen such as a metatarsal from an extinct group of humans thus poses a challenge. As late Pleistocene human postcranial remains are extremely scarce, further investigation of such remains are justified. The analysis presented here subjects the KRM first metatarsal and comparative human samples to selected morphometric analyses, in an attempt to test the hypothesis regarding shape associated sexual dimorphism as a means to estimate sex in the KRM individual.