Dimension variability of the M2 human molar teeth: comparisons between prehistoric and medieval samples

Abstract

Teeth are a valuable source of information for studies regarding past human populations in archaeological and forensic contexts. In dental anthropology, the linear measurements of tooth crowns are used for assessing morphological variability and sexual dimorphism in both modern and past human populations. The aim of this research is to evaluate the M2 molar crown variability in archaeological human populations from Prehistory (Chalcolithic and Bronze Age, ~ 5000-1150 BCE) and Middle Ages (13th-17th centuries) discovered in sites from North-Eastern Romania. The objectives of this study emphasize on the diachronic comparison of the M2 molar crown variables between prehistoric and medieval samples (1), and the assessment of sexual dimorphism expression (2). The two crown measurements, mesio-distal (MD) and bucco-lingual (BL) diameters, were performed using ImageJ software on occlusal digital images acquired stereo-microscopically. The crown index (CI), crown area (CA) and the sexual dimorphism index (SDI), along with the two linear measurements, were subjected to univariate and multivariate statistical analysis. Our results show that the variation coefficient (CV) differs for the MD variable in the female upper M2 molars, being higher in the medieval sample than the prehistoric one; also, a higher variability is remarked for the mandibular molar in the medieval sample than in prehistoric one. In females, the MD and CA variables for mandibular M2 molars and the BL and CA for maxillary molars showed significant statistical differences between the medieval and prehistoric mandibular teeth, with higher values for the exemplar from Middle Ages. Similar result was obtained in males, for the CA variable in the upper M2 molars. In our study, the sexual dimorphism manifested at the M2 crown molar was highlighted in the prehistoric sample, though less in the medieval one.