Homo antecessor lower molars at a glance

Since the recovery of about a hundred human fossil remains from the TD6 level of the Gran Dolina cave (Burgos, Spain) in 1994, the paradigm on human evolution in Europe has considerably changed. These fossils were dated to the Early Pleistocene and attributed to a new species, Homo antecessor. Furthermore, the increasing number of human fossil remains found in Africa and Eurasia has allowed new phylogenetic interpretations for Homo antecessor hominins as well as alternative hypotheses about the settlement of Europe. To date, the Gran Dolina-TD6 human remains are the oldest and most representative human fossils from Europe. The unique combination of primitive and derived cranial and postcranial traits provides important data to understand the first settlement of this continent. The trigonid crest pattern has an extraordinary utility for taxonomic and phylogenetic studies. The main aim of this study is to characterize the pattern of trigonid crest expression at the internal and external surfaces of the lower permanent (n = 11) and deciduous (n = 3) molars from Homo antecessor by means of micro-computed tomography (microCT). In order to explore the evolutionary meaning of this feature, Homo antecessor specimens will be compared against the outer enamel surface (OES) and enamel dentine junction (EDJ) of modern humans and other Pleistocene Homo in Eurasia. The results of our analysis show that Homo antecessor present continuous mid-trigonid crests, although in lower frequencies than in other Middle and Upper Pleistocene hominins from Eurasia. This finding suggests that this feature cannot be considered a Neanderthal apomorphy as it is not exclusive to this species. In addition, our study also explores the evolutionary status of this species and its relationship with the Middle Pleistocene populations of Europe. Overall, evidence points to a less linear settlement of Europe and the possibility of Homo antecessor representing one of the successive hominin waves into Europe, possibly from Western Eurasia.