Evaluating methods in Dental Anthropology to study biological affinities in Medieval Iberian Populations

Dental anthropologists have used dental morphology and measurements to infer biological relatedness among species, populations, and sometimes even family members, for nearly a century. The rapid development of new technologies in the last 15 years has resulted in sophisticated methods. These new methods have allowed us to observe teeth and dental structures which we could not study without destroying other human remains or that we could not access because they were kept at museums overseas. While many researchers have embraced the new methods, few studies have examined what they bring to dental anthropology, whether they improve on traditional methods, and when it is best to use them. I compared four methods to estimate biological relatedness in terms of the information they yield, their reliability, and the ease of application: metric variables, nonmetric dental traits included in the Arizona State University system, and 2-Dimensional and 3-Dimensional geometric morphometrics. To make this comparison, I used three archaeological medieval samples from different cultural contexts (one Christian and two Muslim) in the Iberian Peninsula. I aimed to infer whether there are biological differences among the samples and if so, which samples are biologically closer to one another. I chose these samples because traditionally, historians have thought that the Muslim entry to the Iberian Peninsula occurred in very low numbers and that the vast majority of Muslims that lived in the Iberian Peninsula during the Middle Ages were local people converted to Islam, so I tested if this was observed when comparing samples with different cultural backgrounds. Of the four methods, 2-Dimensional geometric morphometrics and nonmetric dental traits found the most significant differences between populations. These significant differences were between the Christian and the Muslim samples, although one of the Muslim samples, whose cultural background was Christian, was geographically closer to the Christian sample. The fact that there are significant differences between the Muslim and the Christian samples suggests that the Islamic arrival to the Iberian Peninsula was made in larger numbers than it was thought, even if there was an admixture with the local population. I also found that 3-Dimensional geometric morphometrics was difficult to apply, more time-consuming, and provided results that were not consistent with the results obtained with the other methods. The results of 3-Dimensional geometric morphometrics could have improved if used in the enamel-dentine junction of CT-scans of the teeth, but that requires a great deal of money, time, and skills. Researchers aiming to study the biological relatedness of archaeological samples should choose their methods taking into account the samples used, their degree of expertise, and their availability of resources if they want to avoid results that do not necessarily reflect such relatedness