Crown formation times in Homo antecessor molars (Gran Dolina-TD6, Sierra de Atapuerca, Spain)

Introduction Human remains from Atapuerca-Gran Dolina TD6 level represent at least 11 individuals that are dated to approximately 0.9 million years. These fossils were recovered in different seasons since 1994 and were the base to name a new human species, Homo antecessor. There are several publications regarding the morphological features of this hominin, including teeth. However, information available about Homo antecessor dental development is scarce, and those studies did not employed histological variables. Here, we studied the crown formation times of of Homo antecessor lower molars. Our results are compared with molar crown formation times in other hominin species and great apes obtained from the literature. Material and methods We studied seven Homo antecessor molars that are assigned to three individuals: two lower molars (one M1 and one M3) and five upper molars (three M1, one M2 and one M3). Environmental scanning electron microscope (ESEM) was used to estimate the imbricational enamel formation time and microtomography (microCT) was used to estimate the appositional enamel formation time. Results Crown formation times of Homo antecessor molars fit within the variability of other hominin species. Discussion and conclusions Molar crown formation times are relatively stable throghout hominid evolution at least from the last common ancestor with chimpanzees, regardless dental morphological differences. Thus, differences in the eruption times might be mostly based on differences in the root extension rates.