The Atapuerca Sites and Their Contribution to the Knowledge of Human Evolution in Europe

Since the late 1980s, paleoanthropology has witnessed a paradigm shift in interpretation of the evolution of the genusHomo.1 The anagenetic evolutionary model, which postulate an unbroken lineal temporal succession of the reproductive continuity of Homo habilis, Homo erectus, and Homo sapiens, representing three evolutionary grades, is gradually being replaced by the cladogenetic model of speciation, which recognizes several speciation events throughout the evolution of the genus Homo. These events (cladogenesis) might have been favored by successive dispersals of hominins out of Africa and migratory movements between Africa and Eurasia during the Pleistocene, as well as events of reproductive isolation due to climatic and ecological changes. The anagenetic model divides the fossil record, or the morphological space of the genus Homo, into three evolutionary grades. As the morphospace is filled with new findings, it is becoming increasingly difficult to agree on the exact boundaries between species. The difficulties of this model are exemplified by the frequent use of terms such as “advanced,” “primitive,” “early archaic,” “archaic,” and “late archaic” to modify Homo sapiens. These terms and other similar ones2,3 have no taxonomical validity, but suggest a need to describe morphological diversity. The cladogenetic model also has difficulties. Cladistics requires the establishment of character polarities (the phylogeny of the characters), the selection of independent traits, and the identification of homoplasies. These difficulties have opened several debates concerning the recognition of one or more species in a given hypodigm. One of the most prominent examples concerns the possible partition of a large portion of the Early Pleistocene fossil record into two species, Homo erectus, Dubois 1892, and Homo ergaster, Groves and Mazak 1975. Homo ergaster would be restricted to Africa (if we consider the hominins found in the Dmanisi site, Republic of Georgia, to belong to a different species4), while Homo erectus may have representatives in Asia and Africa.1 The distinctions are based on the absence of some specific traits in the African fossils that are present in the Asian ones, to which the species name erectus applies. These include a midline keel on the vault, strong reduction of the postglenoid process, an angular torus at the posterior-inferior corner of the parietal bone, overall thickening of the braincase, and reduced superstructures in the temporal-occipital region. Moreover, Homo erectus ss exhibits a styloid process, as well as differences in the size and shape of the supraorbital torus.5–7 The debate about the partitioning of the fossil record is beyond the scope of this paper but, from this point on, we assign the specimens José Marı́a Bermúdez de Castro is Research Professor at the Consejo Superior de Investigaciones Cientı́ficas (CSIC), Spain and co-director of the Atapuerca Research Project. E-mail: [email protected] Eudald Carbonell is Professor at the University Rovira i Virgili of Tarragona, Spain and co-director of the Atapuerca Research Project. Marı́a Martinón-Torres, Susana Sarmiento and Marina Lozano are researchers with the Atapuerca team, having a primary interest in dental anthropology. Antonio Rosas is Research Fellow at the CSIC, Spain and member of the Atapuerca Research Team. Jan van der Made is Research Fellow at the CSIC, Spain and member of the Atapuerca Research Team.