Teeth: the «black box»

Teeth represent the best source of information to address different questions regarding growth, development and hominins’ lifestyle, including cultural and behavioural aspects. Moreover, teeth are very useful tools in paleodemographic, paleopathological, and paleoenvironmental studies. They are safe DNA containers and exhibit a suite of key features that can be used to characterize paleodemes. In summary, we can consider that teeth are a true “black box” to ascertain and document the events that happened during our ancestors’ and our own life, as well as to establish reliable relationships between past and present populations. The recent recovering of nuclear DNA sequences from two specimens from the Atapuerca-Sima de los Huesos (SH) Middle Pleistocene site has confirmed the close relationship between these hominins and the Neandertals . All previous morphological studies of the about 6,500 human remains recovered so far in SH reached a similar conclusion. In particular, pioneering morphological and metrical studies of the teeth showed a close phylogenetic relationship between the SH hominins and the Neandertals. Additional studies using larger samples and different methodological approaches confirmed previous results. Although we are aware that a substantial part of the dental morphology and dimensions are conditioned by environmental factors, it is also true that teeth are the skeletal part carrying the strongest taxonomical signal. Some of the dental derived features we identify in the fossils are highly reliable to characterize paleodemes. Here we illustrate the derived morphology of the permanent lower first premolars of the SH hominins. Among other features, the P3s of these paleodemes are characterized by the presence of a small and swollen lingual cusp. It is usually separated by a fine cleft from the distal marginal ridge. The lower half of the buccal face shows a remarkable swelling, which is slightly more pronounced on the mesial side. This derived form has a more symmetrical occlusal outline than in earlier teeth. There are no signs of a buccal cingulum. We show the morphological similarities of these teeth with those of the lower first premolars of other paleodemes, which have been hypothetically included in the Neandertal genealogy.