An official website of the United States government
Abstract ObjectivesLinear enamel hypoplasia (LEH) is a common skeletal marker of physiological stress (e.g., malnutrition or illness) that is studied within and across populations, without reference to familial risk. We examine LEH prevalence in a population with known genealogical relationships to determine the potential influence of genetic heritability and shared environment. MethodsLEH data of 239 individuals from a single population were recorded from the Ohio State University Menegaz‐Bock collection dental casts. All individuals were of known age, sex, and genealogy. Narrow‐sense heritability estimates were obtained for LEH presence and count data from all unworn, fully erupted teeth (excluding third molars) using SOLAR (v.8.1.1). Age, sex, and age–sex interaction were included as covariates. Models were re‐run with a household effect variable. ResultsLEH persists across generations in this study population with moderate, significant heritability estimates for presence in four teeth, and count in four teeth (three teeth were significant for both). When a household effect variable was added, no residual heritability remained for LEH count on any tooth. There was no significant household effect for three of the four teeth that had significant heritability estimates for LEH presence. Age was a significant covariate. Further analyses with birth year data revealed a secular trend toward less LEH. ConclusionsThis study provides evidence for familial risk of LEH (genetic and environmental) that has consequences for the broad use of this skeletal marker of stress. These results have repercussions for archaeological assemblages, or population health studies, where genetic relatives and household groups might be heavily represented.
more »
« less
Quantitative genetic analyses of postcanine morphological crown variation
Abstract ObjectivesThis 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 MethodsAfrican American dental casts from the Menegaz‐Bock collection were recorded for the Arizona State University Dental Anthropology System. Estimates of narrow‐sense 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. ResultsHeritability 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. ConclusionsIn 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.
more »
« less
- Award ID(s):
- 1750089
- PAR ID:
- 10462605
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- American Journal of Physical Anthropology
- Volume:
- 168
- Issue:
- 3
- ISSN:
- 0002-9483
- Format(s):
- Medium: X Size: p. 606-631
- Size(s):
- p. 606-631
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract ObjectivesMost research in human dental age estimation has focused on point estimates of age, and most research on dental development theories has focused on morphology or eruption. Correlations between developing teeth using ordinal staging have received less attention. The effect of demographic variables on these correlations is unknown. I tested the effect of reference sample demographic variables on the residual correlation matrix using the lens of cooperative genetic interaction (CGI). Materials and MethodsThe sample consisted of Moorrees et al.,Journal of Dental Research, 1963, 42, 1490–1502, scores of left mandibular permanent teeth from panoramic radiographs of 880 London children 3–22.99 years of age stratified by year of age, sex, and Bangladeshi or European ancestry. A multivariate cumulative probit model was fit to each sex/ancestry group (n = 220), each sex or ancestry (n = 440), and all individuals (n = 880). Residual correlation matrices from nine reference sample configurations were compared using Bartlett's tests of between‐sample difference matrices against the identity matrix, hierarchical cluster analysis, and dendrogram cophenetic correlations. ResultsBartlett's test results were inconclusive. Cluster analysis showed clustering by tooth class, position within class, and developmental timing. Clustering patterns and dendrogram correlations showed similarity by sex but not ancestry. DiscussionExpectations of CGI were supported for developmental staging. This supports using CGI as a model for explaining patterns of variation within the dentition. Sex was found to produce consistent patterns of dental correlations, whereas ancestry did not. Clustering by timing of development supports phenotypic plasticity in the dentition and suggests shared environment over genetic ancestry to explain population differences.more » « less
-
IntroductionPapionins are a well-studied and morphologically diverse clade of cercopithecid monkeys. Understanding how craniodental morphology varies in this clade has implications for interpreting taxonomic variation in the fossil record and for our understanding of primate evolution. MethodsWe quantified the phenotypic relationship between facial length and dental proportions in N=314 cercopithecid individuals across 10 species (six papionins, two cercopithecins, and two colobines) using dental ratios MMC (molar module component, ratio of the lengths of the third and first molars) and PMM (premolar-molar module, ratio of the lengths of the second molar and the fourth premolar) and two metrics of facial length: palatal length and prosthion – glabella. ResultsFacial length and molar dental proportions are significantly correlated interspecifically across cercopithecids (PGLS, p<0.01), where species with longer faces have relatively longer maxillary and mandibular third molars. These traits are generally not correlated intraspecifically in the cercopithecids sampled, with some exceptions. DiscussionOur data demonstrate that prognathic faces evolved convergently at least twice in papionins, with parsimony supporting that Papio/Theropithecus shared a prognathic ancestor after the divergence of Lophocebus. Additionally, this study lends support to the hypothesis that facial reduction and third molar reduction in human evolution were coordinated and may have been the result of pleiotropy alongside changes in diet.more » « less
-
As herbivorous, diphyodont mammals with relatively low-crowned molars, primates experience changes in dental function during their lifetimes as teeth become progressively worn. Maintaining tooth function with wear is thought to pose a particular challenge for folivorous primates whose diets emphasize molar shearing actions. Recent studies using dental topographic methods suggest that certain primate folivores have molar morphology that maintains or increases functional shearing surfaces with tooth wear (‘dental sculpting’). Evidence for this phenomenon has been found in folivorous but not frugivorous New World monkeys, supporting the hypothesis that dental sculpting is an adaptive trait linked to diet. This analysis extends these methods to two sympatric Old World monkeys from Sabah, Malaysia, possessing distinct diets and dental morphologies: the folivorous colobine Trachypithecus cristatus (n=25) and the more frugivorous cercopithecine Macaca fascicularis (n=22). For each species, 3D shear crest lengths and four dental topographic variables (relief index, slope, angularity, and Dirichlet Normal Energy [DNE]) were measured from variably worn lower second molars. Preliminary results indicate that for any given degree of wear, Trachypithecus has longer shear crest lengths and higher relief, slope, angularity, and DNE than Macaca. The two species exhibit different patterns and degrees of change in topography and shearing crest lengths across the wear series. However, these changes do not always match expectations based on their respective diets. Correlations between 3D shear crest lengths and other dental topographic measurements suggests that the type of metric used to assess shearing potential may affect whether or not dental sculpting is detected.more » « less
-
ABSTRACT Increased fluctuating asymmetry, or random differences between right and left sides, has been associated with developmental stress or developmental instability. This study examines fluctuating asymmetry (FA) of mesio‐distal and bucco‐lingual dimensions of deciduous maxillary molars (m1, m2), and permanent maxillary premolars and molars (P3, P4, M1, M2) of 466 rhesus macaques (Macaca mulatta) born between 1950 and 2018 from Cayo Santiago (CS), Puerto Rico. All included individuals were of known age, sex, birth year, and matriline. We assess whether a secular trend occurs in FA over a 68‐year period, sex differences in FA, and whether environmental or management factors in the colony history resulted in decreased FA. Regression of FA on birth year tested for a secular trend in FA. A mixed‐model two‐way analysis of variance was used to test for the influence of food supplementation, tetanus vaccination and hurricane experience during dental development on FA. Differences across matrilines in response to the management or environmental factors were tested by ANOVA. There was no significant secular trend in FA. There was limited reduction of FA with implementation of the high protein diet, and limited support for the decreased FA associated with the implementation of tetanus vaccination. There is also limited difference in dental FA associated with exposure to a hurricane during dental development. Matrilineal differences in FA were observed for several teeth. The free‐ranging environment of Cayo Santiago is a complex environment, with many factors influencing the development of young rhesus macaques. While the introduction of a high protein diet or the implementation of a tetanus vaccination program may have improved individual health overall, there are likely other factors that may cause developmental stress and result in dental FA.more » « less
