The variation in molar tooth size in humans and our closest relatives (hominins) has strongly influenced our view of human evolution. The reduction in overall size and disproportionate decrease in third molar size have been noted for over a century, and have been attributed to reduced selection for large dentitions owing to changes in diet or the acquisition of cooking. The systematic pattern of size variation along the tooth row has been described as a 'morphogenetic gradient' in mammal, and more specifically hominin, teeth since Butler and Dahlberg. However, the underlying controls of tooth size have not been well understood, with hypotheses ranging from morphogenetic fields to the clone theory. In this study we address the following question: are there rules that govern how hominin tooth size evolves? Here we propose that the inhibitory cascade, an activator-inhibitor mechanism that affects relative tooth size in mammals, produces the default pattern of tooth sizes for all lower primary postcanine teeth (deciduous premolars and permanent molars) in hominins. This configuration is also equivalent to a morphogenetic gradient, finally pointing to a mechanism that can generate this gradient. The pattern of tooth size remains constant with absolute size in australopiths (including Ardipithecus, Australopithecus and Paranthropus). However, in species of Homo, including modern humans, there is a tight link between tooth proportions and absolute size such that a single developmental parameter can explain both the relative and absolute sizes of primary postcanine teeth. On the basis of the relationship of inhibitory cascade patterning with size, we can use the size at one tooth position to predict the sizes of the remaining four primary postcanine teeth in the row for hominins. Our study provides a development-based expectation to examine the evolution of the unique proportions of human teeth.

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.

Deciduous crown morphology performed well in identifying related sibling pairs. However, there was considerable variation in the extent to which different families exhibited similarly low levels of phenotypic divergence.

ObjectivesThis study generates a series of narrow‐sense heritability estimates for crown morphology of the deciduous and permanent dentition with two overarching aims. The first is to test the hypothesis that deciduous teeth provide a more faithful reflection of genetic information than their permanent successors. The second is to use quantitative genetic methods to evaluate assumptions underlying common data collection and analysis practices in biodistance research.Materials and MethodsDental morphology data were collected from longitudinal dental casts representing Australian twins and families using Arizona State Dental Anthropology System standards. Polygenic models and estimates of narrow‐sense heritability were generated using SOLAR v.8.1.1. Each model considered age, sex, and age/sex interaction as covariates.ResultsHeritability estimates significantly differed from zero for the majority of morphological crown characters. Most estimates fell within the 0.4–0.8 range typically observed for crown morphology. Mean heritability was stable across the dental complex, but for paired homologues, permanent traits often yielded higher estimates than their deciduous counterparts. Results indicate directional asymmetry in environmental influence for crown morphology and inform biodistance “best practices” related to data collection and treatment.ConclusionsOverall, results for this sample support the use of crown morphology as a proxy for genetic variation in evolutionary research. This includes the deciduous dentition, which justifies the expansion of efforts to incorporate subadults into reconstructions of past microevolutionary processes. Results do not indicate that deciduous phenotypes more closely approximate underlying genotype, at least for deciduous/permanent homologues.

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

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Theoretical developments in sociocultural anthropology have transformed the study of kinship. Here, we review these theoretical developments, consider their influence on bioarchaeological kinship research, and propose an alternative framework for studying relatedness in antiquity. We find that broader, more flexible conceptions of relatedness have grown increasingly prevalent in 21st-century bioarchaeology, but kinship research largely continues to emphasize methodological improvement and identification of biological kin in archaeological contexts. By approaching kinship as a multiscalar dimension of social identity, bioarchaeologists can leverage complex conceptions of relatedness with diverse types of data to gain nuanced perspectives on family-based social organization in the past.