||The occurrence and aetiology of congenitally absent third molars is widely researched in modern human populations. Previous research on third molar agenesis has, however, seldom been conducted on medieval populations, and archaeological research on other time periods has focussed on either agenesis patterns, prevalence within a population, or relations to dental wear. Osteoarchaeology can contribute to understanding third molar agenesis in a way that exceeds temporal and geographical boundaries, and therefore it can contribute to unravelling different aetiological contributors of third molar agenesis. This research is about third molar agenesis in the Late Medieval Dutch skeletal collections of Klaaskinderkerke (rural) and Alkmaar (urban) in order to gain insight into congenitally absent third molars during the Dutch Late Medieval period. To enhance knowledge about third molar agenesis, this study conducts prevalence and metric analyses of the jaws in relation to third molar agenesis patterns. The main question is ‘Do sex, size and robustness of the mandible and the maxilla, and the place in the jaw (mandible versus maxilla), relate to the agenesis, impaction, or presence of the third molar in a Late Medieval Dutch sample?’
To answer the research questions, 19 mandibular and 9 maxillary measurements are used to quantify size and robustness. Radiological examination is used to differentiate between third molar agenesis and impaction. Statistical analyses explore the relationships between category and metric variables and third molar agenesis. The results show that impaction of the third molar was not present in the two late medieval sites. The frequency of third molar agenesis is insignificantly higher for females (36.8%) than for males (29.4%). Congenitally absent third molars are insignificantly more often observed in the mandibles than in the maxillae (29.7% versus 25.0%). Congenitally absent third molars were observed significantly more frequently in the Alkmaar collection (46.5%) than in the Klaaskinderkerke (25.5%) sample. These differences may be related to differences in environment, genetic variation, or ways of living. The socioeconomic background is similar for both sites, and should not be a contributing factor. The statistical results indicate that third molar agenesis is to some extent related to size and robustness of the jaws, but only a few measurements correlate with agenesis. All correlating measurements differ between males and females, except for Body Height. The contribution of the current study to understanding the development of third molar agenesis is that it provides osteoarchaeological data on a (sex specific) relationship between size and robustness of the jaws and third molar agenesis in the Dutch Middle Ages.