A reassessment of four cranial features used to define a new Middle Pleistocene hominid species from Spain, Homo antecessor
Nevgloski, Alexander J.
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In 1994 a Spanish research team, consisting primarily of Jose Bermudez de Castro, Juan Luis Arsuaga and Eudald Carbonell, discovered human fossil remains associated with fauna and lithics near Burgos, Spain. The level containing the hominids was originally dated to 500 kya, but was later re-dated to approximately 800,000 years old. More controversial than the dating was the analysis and interpretation of the fossil material. In their original description, Bermudez de Castro and colleagues listed twenty-nine features that define these particular hominids (especially the morphology of hominid 3, or ATD6-69). In 1999, Arsuaga and coworkers discussed hominid 3 in more detail, noting the coronal orientation of the infraorbital plate, a sagittal orientation of the lateral nasal wall, an arched or horizontal orientation of the zygomaticoalveolar crest, an inferior-posterior orientation of the infraorbital bone (which causes a depression known as the canine fossa), and the complete fusion of the lateral and spinal crests of the nasal aperture. These authors contend that this morphology is reminiscent of modem humans. Based on the combination of modem and primitive features in these fossils, Bermudez de Castro and other members of the Spanish team found it necessary to name a new species, Homo antecessor. The present study is designed as a descriptive and comparative analysis of four of the features used to define Homo antecessor. Detailed analyses of the canine fossa, nasal crests, malar tubercle and mylohyoid groove were conducted on Middle Pleistocene hominid fossils. This was accomplished using casts and relevant literature. These four features were also analyzed on a large modem human sample from skeletal material housed at the University of the Pacific Dental School in San Francisco, the Cleveland Museum of Natural History in Cleveland, and the physical anthropology lab at Northern Illinois University in Dekalb, Illinois. These data were then compared with the morphological and interpretive analysis submitted by Arsuaga and co-workers. The results of this analysis are not consistent with the results obtained by Arsuaga and colleagues. The canine fossa exhibited by ATD6-69 is not homologous with that exhibited by modem humans, nor do the nasal crests unite Homo antecessor with modem humans while simultaneously excluding Neandertals. Likewise, the claims of uniqueness for the malar tubercle and mylohyoid groove have not been substantiated in this study either. Thus, based on the analysis of these four features, the naming of a new species is not warranted, making Homo antecessor an invalid species.