Studying human fossil teeth has multiple applications. One of these is evaluating the growth times and patterns of dental pieces and possible correlation with biological variables of human development and maturation, opening a window onto how the hominins on our evolutionary tree developed.

The Dental Anthropology Group at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH) and the Human Evolution Laboratory at the Universidad de Burgos (UBU) have led a paper published recently in the American Journal of Biological Anthropology on the dental development pattern of the populations from the Atapuerca sites (Burgos): Homo antecessor, from Gran Dolina (860,000 years old), and the hominins from Sima de los Huesos (430,000 years old), which indicates that the relative development of their molars was faster than in modern humans.

This investigation of relative dental development is complementary to the work carried out on the enamel formation times in these fossil populations from Atapuerca, already published in Scientific Reports. In the latter study, it was shown that enamel growth in H. antecessor and the Sima de los Huesos teeth was some 27% faster than in modern humans.

Hominins from Atapuerca would reached adulthood at the age of 14-15 years old

“Bearing in mind that there is a relative correlation between dental development and skeletal maturation, the combination of the two studies allows us to establish the hypothesis that the Atapuerca hominins reached adulthood at the age of 14-15”, explains Mario Modesto-Mata, joint lead author of this paper with Rebeca García-González.

Statistical study

A statistical approach based on Bayes' Theorem on conditional probability, never previously used for populations earlier than the Neandertals, was employed. The teeth were classified into eight categories according to their state of mineralization, which was determined using computerized axial tomography images obtained at the CENIEH Microscopy Laboratory.

These categories could then be compared statistically with a relatively broad sample of dental development sequences from modern humans. These modern sequences are from the Universidad de Burgos and the University of Bordeaux. The latter includes a sample of persons from sub-Saharan Africa.

“Not only did we find differences when we compared these two populations with modern humans, but we were also able to identify differences between H. antecessor and the Sima de los Huesos fossils. For instance, the Sima de los Huesos hominins have more advanced second molar development with respect to the first molar than does H. antecessor”, adds Modesto-Mata.