G. E. Kennedy

On the autapomorphic traits of Homo erectus

Abstract An investigation was carried out on 12 character states often said to be autapomorphic of the neurocranium of H. erectus . The African pongids were used as the outgroup. The majority of these traits were qualitative (i.e., present or absent) and could thus be treated using the classic Hennigian method. Of these, none was autapomorphic in H. erectus . However, the occipital torus was apomorphic for H. erectus and anatomically modern H. sapiens ; the neandertals and the “ante-neandertals” appear to demonstrate an autapomorphic pattern in their occipital torus. The remainder of the traits were quantitative; a Students t with a level of significance of 0·05 was used as the point of discrimination between primitive and derived character states, although problems with this technique were noted. Of these metric character states, none was autapomorphic in H. erectus . However, one included metric trait, increased cranial vault thickness, was found to show significant statistical discrimination of H. erectus from the outgroups, the australopithecines and anatomically modern Homo sapiens . However, thickened cranial vault bone was also found in the neandertals and in most other non-modern hominids although it was generally less in these groups relative to H. erectus . The presence of thickened vault bone in these groups prevents the trait from being a H. erectus autapomorph. It was hypothesized here that cranial thickness in hominoids occurs in two ways. Increased superior vault thickness is derived for H. erectus and most other non-modern hominids. Thickness of the inferior cranium, on the other hand, reflects retained pneumatodiploic bone and is symplesiomorphic, being shared by the outgroups, the australopithecines and H. erectus . Inferior vault expansion has decreased (relative to H. erectus , the australopithecines and the outgroups) in the neandertals and most other non-modern hominids. Several hypotheses concerning the relationship of H. erectus to other hominids were tested. Among the conclusions are that on the basis of the included traits H. erectus , as presently defined and using the methodology of phylogenetic systematics, cannot be considered a valid species. It was argued, however, that the challenge to the taxon H. erectus rests less with the biological reality of such a group than with the present taxonomic configuration of middle and early upper Pleistocene hominids. It was also suggested that the neandertals, who appear to have a number of autapomorphs, should not be included within the modern species, Homo sapiens .

Some aspects of femoral morphology in Homo erectus

The available femora of lower and middle Pleistocene hominines were examined osteometrically and radiographically. This fossil sample was compared with samples of Romano-British and Bushmen femora. The results showed distinctive internal and external morphological patterns in the Homo erectus group. This pattern consisted, in part, of very thick cortical bone, narrow AP shaft diameters and a low point of minimum shaft breadth. Where preserved, the trabeculae of the medial femoral neck showed a distinctive diffuse pattern. The Trinil femora showed a basically sapient pattern although they demonstrated thickened cortical bone in the distal shaft. The restricted distribution of this thickened cortex suggests that it may not be homologous with the generally thickened cortex seen in Homo erectus . Several hypotheses are proposed to explain the thickened cortex in Homo erectus .

Bone thickness in Homo erectus

Although the presence in Homo erectus of thickened tabular bone in the cranium and thickened cortical bone in the post cranium has been noted by a number of researchers, few hypotheses have been proposed to explain that presence. Using as controls femora from several Homo sapiens groups (Romano-British, Murray Valley Australians and Bushmen), it can be shown that the cortical bone in the Homo erectus femur is thickened to a statistically significant level. It can further be shown that the “additional” bone in the fossil femora is located at the endosteal rather than at the subperiosteal surface. Two hypotheses are proposed to explain this thickened cortical bone in Homo erectus ; these hypotheses are not necessarily mutually exclusive.

Aspartic Acid Racemization and Radiocarbon Dating of an Early Milling Stone Horizon Burial in California

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