These results suggest that the high heritabilities previously published may reflect overestimates inherent in previous study designs; as such the standard estimate of 0.55 used in biodistance analyses may not be appropriate. For the Gullah, isolation and endogamy coupled with elevated levels of physiological and economic stress may suppress narrow-sense heritability estimates. Pleiotropy analyses suggest a more highly integrated dentition in humans than in other mammals.

Additive genetic variation contributes to dental morphological variation, although the estimates are uniformly lower than those observed for odontometrics. Patterns of genetic correlation affirm most standard practices in dental biodistance. Patterns of negative pleiotropy involving lingual and labial crown features suggest a genetic architecture and developmental complex that differentially constrain morphological variation of distinct surfaces of the same tooth crown. These patterns warrant greater consideration and cross-population validation.

Objectives: This article presents estimates of narrow-sense heritability and bivariate genetic correlation for 14 tooth crown morphological variants scored on permanent premolars, first molars, and second molars. The objective is to inform data collection and analytical practices in dental biodistance and to provide insights on the development of molar crowns as integrated structures.Materials and Methods: African American dental casts from the Menegaz-Bock collection were recorded for the Arizona State University Dental Anthropology System. Estimates of narrowsense heritability and genetic correlation were generated using SOLAR v.8.1.1, which included assessment of age, sex, and birth year as covariates. Both continuous scale and dichotomized estimates are provided.Results: Heritability estimates were nonsignificant for the majority of variables; however, for variables yielding significant estimates, values were moderate to high in magnitude and comparable to previous studies. Comparing left and right-side heritability estimates suggests directional asymmetry in the expression of environmental variance, something not seen in anterior tooth traits. Genetic correlations were moderate among antimeres and metameres and low for different traits scored on the same tooth crown. Although several negative correlations were noted, few reached statistical significance. Results affirm some of the current data cleaning and analytical practices in dental biodistance, but others are called into question. These include the pooling of males and females and combining left and right-side data into a single dataset.Conclusions: In comparison to anterior tooth crown traits, postcanine heritabilities were more often non-significant; however, those traits with significant heritability also tended to produce higher estimates. Genetic correlations were unremarkable, in part, because they were underpowered. However, M1 results may provide insight into the complex relationship between genes, environment, and development in determining ultimate crown form. K E Y W O R D Sbiodistance, dental morphology, heritability, pleiotropy, quantitative genetics

Recent attempts to study cranial modification have suggested that the practice was a part of embodiment and socialization among the Maya. Comparison of colonial and modern Maya childbirth and socialization practices supports these arguments. We suggest that the next question to be asked is: “Why was the head specifically targeted for modification among the Maya?” This paper argues that one of the motivations behind cranial modification among the Maya was to protect newborns from injury. We present evidence from colonial documents and ethnographic studies on midwifery showing that animating essences resided in the head and that newborns were particularly at risk for soul loss and injury from evil winds. Further we present data on metaphoric polysemy between the human body and houses to argue that newborn humans were much like newly constructed houses in their susceptibility and that both required ritual ensoulment. The construction of the house roof parallels cranial modification. This likely has parallels in Classic Maya times, with some temple dedications and the construction of vaulted roofs with capstones, and suggests that the need to guard against soul loss has pre-Columbian roots.