Phenetic Affinities of Plio-Pleistocene Homo Fossils from South Africa: Molar Cusp Proportions

As aptly observed by Aiello et al. (2000), any attempt to reconstruct human evolutionary history depends upon reliable hypotheses pertaining to the species groups that are represented in the hominin fossil record. There has been a notable lack of consensus regarding the species of Homo that are represented in the Plio-Pleistocene karst cave deposits of South Africa (Howell, 1978; Clarke, 1977a, b, 1985a, b, 1994; Chamberlain, 1987; Rightmire, 1990; Wood, 1991; Tobias, 1991; Kimbel and Rak, 1993; Grine et al., 1993, 1996; Ahern, 1998; Kuman and Clarke, 2000; Grine, 2001, 2005; Curnoe, 2001, 2002, 2008; Prat, 2002; Dunsworth and Walker, 2002; Schwartz and Tattersall, 2003; Curnoe and Tobias, 2006; Smith and Grine, 2008). To some degree, this is because these discussions have been restricted to a few incomplete mandibles and crania from the sites of Sterkfontein and Swartkrans. However, there are larger collections of teeth from these and other sites that have been attributed to this genus and which might shed light on this issue. We here attempt to assess the phenetic affi nities of some of these dental remains by comparison with penecontemporaneous East African fossils that have been referred to H. rudolfensis, H. habilis and H. erectus (=H. ergaster). Overall crown size and shape may sometimes serve to distinguish the molar teeth Homo from those of Australopithecus and Paranthropus, but it is not clear that these attributes are necessarily useful in differentiating among species of Homo. At the same time, however, the utility of molar cusp sizes and proportions in species-level distinctions has been explored by a number of workers (Corruccini, 1977; Lavelle, 1978; Hills et al., 1983; Hartman, 1989; Uchida, 1991, 1992, 1998a, b; Wood and Xu, 1991; Macho and Moggi-Cecchi, 1992; Matsumura et al., 1992; Smith, 1999; Bailey, 2004). Such data have been shown to be of some use in taxonomic evaluations of the hominin fossils from East Africa (Wood et al., 1983; Wood and Uytterschaut, 1987; Wood and Engleman, 1988; Suwa, 1988, 1990; Suwa et al., 1994, 1996).