The Atapuerca dental remains. New evidence (1987-1991 excavations) and interpretations

Abstract

Abstract The metrical features and some morphological traits of 133 permanent teeth from the site Sima de los Huesos (Sierra de Atapuerca, Burgos, Spain) are analysed and compared with those of other hominid samples. Since the sample sizes were greater for the lower than for the upper teeth, the main conclusions are fundamentally based on the analysis of the mandibular dentition. As an extreme case of the mosaic evolutionary pattern which characterizes hominid dental evolution, the Atapuerca lower dentition shows a strong imbalance between the size of the anterior (I1-P3) and posterior (P4-M3) teeth in relation to modern humans, and even with regard to other middle Pleistocene hominids and the Neandertals. On the average, the dimensions of the Atapuerca mandibular posterior teeth are similar to those of modern humans. Probably very much related to this, the hypoconulid was frequently absent in the lower molars. These observations imply that the selective pressures which operated to maintain a certain size of the posterior dentition during the middle Pleistocene were less restrictive than is assumed by previous evolutionary models. The dimensions of the Atapuerca lower and upper anterior teeth are also small in relation to the middle Pleistocene specimens and Krapina, but they are comparable to those of the late Pleistocene Neandertals, and there is certain expansion of the buccolingual dimensions of the upper lateral incisors with regard to early Homo . The anterior/posterior size pattern of variability observed in Atapuerca is discussed in terms of the different selective pressures which presumably operated over the anterior and posterior segments of the dentition. The multivariate tooth shape analysis indicates a relatively close relationship between Atapuerca and the Neandertals, though some significant differences between them were observed. The limited European middle Pleistocene dental fossil record does not permit a rigorous study of the relationships between Atapuerca and other European middle Pleistocene populations. However, the present evidence suggests that Atapuerca had an unique and probably derived pattern regarding dental dimensions. Furthermore, a great shape dissimilarity has been observed between Atapuerca and Zhoukoudian, which is mainly due to the anterior/posterior tooth size differences between both samples.