Intra-population dental morphological variability among the Prehispanic Maya

The present paper proposes a new approach to the estimation of intra-site variability of dental morphological traits when they are dichotomized into presence vs absence. It rests on the assumption that (1) higher intra-site variability is the expression of intense population dynamics and gene flow; and (2) maximum variability is reached when each trait is expressed in the population with a frequency of 50%. The approach simulates the calculation of frequency of heterozygotes in Mendelian traits (2xiyi), where xi and yi are the frequency of presence and absence of the trait. For every population, the final value corresponds to the average of (2xiyi) calculated from all the scored traits. Two separate analyses were performed using 50 and 40 traits recorded in 11 Prehispanic Maya skeletal collections from the Yucatán Peninsula. Resulting average values were related to the sites' positions within the region's social, political and economic sphere of influence. Dental collections that were obtained from important city centers or by grouping many sites from a single region present the highest values of internal variability, followed by sites known to have played an important role in trade activities or in other socio-political contexts. At the other end, dental collections that represent smaller communities or more isolated, kin-related groups are set at the lower ranks of internal variability. One-way ANOVA tests for both 50 and 40 variables show that sample means present significant differences between the extreme ends of the ranked set of samples.