Comparative analysis of the trigonid crests patterns in Homo antecessor molars at the enamel and dentine surfaces

As the Atapuerca fossil samples are the most representative remains to understand the evolution of the genus Homo in Europe during the Early and Middle Pleistocene, the study of their dentition is becoming increasingly important. Based on these findings, recent studies have helped to refine the evolutionary hypotheses about the settlement of Europe proposing a less linear settlement of the continent with several migrations and/or interbreeding of these groups. Here, we deal with the affinities between the Early and the Middle Pleistocene populations of Europe by studying the dental morphology of these groups with microtomography (microCT). The aim with this report is to present for the first time the trigonid crest pattern exhibited by the Early Pleistocene hominins from Gran Dolina-TD6 assigned to Homo antecessor species. For this purpose, and knowing that the molar trigonid crest pattern bears a significant taxonomic and phylogenetic value, we also present a comparative study of this trait at the outer enamel surface (OES) and enamel dentine junction (EDJ) of H. antecessor, Sima de los Huesos (SH), Homo neanderthalensis and Homo sapiens. Further morphological comparisons among them will help to provide new and valuable information to investigate the evolutionary scenario of the first European settlement. Our study ratifies the similarities between SH and H. neanderthalensis in the expression of a continuous mid-trigonid crests at the enamel and dentine surfaces. However, this feature cannot be considered a Neanderthal apomorphy since it can be also found in lower frequencies in the Gran Dolina hominins. Thus, H. antecessor would be phenetically closer to H. sapiens who would have preserved a primitive pattern.