A sub-continent of caries: prevalence and severity in early Holocene through recent Africans

The most recognizable pathological condition of the human oral cavity is, arguably, dental caries. Beyond a direct impact on oral health, caries presence (or absence) provides important data for bioarchaeologists—to help reconstruct the diet of past populations and individuals. This study explores such data in 44 samples (n=2,119 individuals, 33,444 teeth) dating between 10,000 BP and recent times across the African sub-continent. It is, to date, the most extensive investigation of its kind in this part of the world, entailing descriptions and quantitative comparisons of caries by period, environment, sub-sistence strategy and sex. Mann-Whitney U tests and factorial ANOVA results provide expected and some unexpected findings, including: 1) a diachronic increase in caries prevalence across the sub-continent, likely related to diet change from widespread population movement; 2) savanna peoples exhibit more caries than those from other environmental regions; 3) subsistence strategy plays a major role in caries occurrence; and 4) males and females do not evidence significant differences in caries frequencies, but variation does exist in several regional groups. These findings reveal that global trends described by previous researchers often apply, though not always—so it is prudent to consider regions independently

A probable genetic origin for pitting enamel hypoplasia on the molars of Paranthropus robustus

We report the frequencies of linear enamel hypoplasia (LEH) and, specifically, pitting enamel hypoplasia (PEH) defects in the teeth of Paranthropus robustus, for comparison with four other South African hominin species and three extant nonhuman primate species. Unlike LEH, the lesser known PEH is characterized by multiple circular depression defects across a tooth crown and is often difficult to interpret in terms of developmental timing and etiology. Teeth in all samples were examined macroscopically with type, position and number of defects recorded. Frequencies of teeth with LEH vary among hominin species, but the differences in PEH are considerable. That is, P. robustus has much higher rates of pitting defects, with 47% of deciduous teeth and 14% of permanent teeth affected, relative to 6.7% and 4.3%, respectively, for all other hominin teeth combined; none of the extant primate samples evidences comparable rates. The defects on P. robustus molars are unlike those in other species, with entire crowns often covered in small circular depressions. The PEH is most consistent with modern human examples of amelogenesis imperfecta. Additionally, the defects are: 1) not found on anterior teeth, 2) uniform in shape and size, and 3) similar in appearance/severity on all molars. Therefore, this form of PEH may have been a side effect of selection on another trait that shares the same coding gene(s), i.e., these defects have a genetic origin. We discuss a possible scenario that may explain how this form of PEH evolved to become so common in the Paranthropus genu

Who were they really? model-free and model-bound dental nonmetric analyses to affirm documented population affiliations of seven South African "Bantu" samples.

OBJECTIVES: For bioarchaeological biodistance analyses it is common to "assume" that skeletal samples are representative of the populations to which they are attributed. Here, alternatively, samples with "known" attribution in the Raymond A. Dart Collection are assessed regarding their suitability for use in such analyses. Prior curation issues may call their ascribed identities into question. MATERIALS AND METHODS: These 20th century samples ostensibly derive from South African Ndebele, Sotho, Swazi, Tswana, Venda, Xosa, and Zulu populations. First, the mean measure of divergence (MMD) is used to obtain among-sample dental phenetic distances for comparison with documented population relationships. Second, the Mantel test evaluates fit of the isolation-by-distance model between MMD and geographic distances, i.e., among the historic homelands. Third, R-matrices and minimum and estimated Fst from MMD distances give an indication of genetic micro-differentiation. RESULTS: Output from these model-free and model-bound analyses suggest that five and perhaps six samples are representative of their attributed populations-presenting differences along population lines and evidence of more ancient ancestry. DISCUSSION: Other than the Swazi and perhaps Nedebele, the among-sample variation: 1) mirrors documented population history, 2) reveals a moderately positive correlation between phenetic and geographic distances, and 3) although evidencing much homogeneity, provides measures of genetic distance in support of the phenetic distances. Therefore, with the two noted exceptions-perhaps from collection issues, swamping of past genetic structure, or both, most samples appear suitable for bioarchaeological analyses. On this basis, results are offered to supplement published findings concerning the biological relationships of these peoples. Am J Phys Anthropol, 2015. © 2015 Wiley Periodicals, Inc

Double Teeth and Coexistent Anomalies: Examples From Continental Africa

OBJECTIVES: Whether gemination or fusion, double teeth are rare worldwide, including Africa based on few published data. New cases from the continent are tallied, and anomalies potentially associated with double teeth are identified. These findings should interest a range of dental researchers. METHODS: The presence of double teeth was recorded in 97 modern and premodern North and sub-Saharan African samples (5631 inds.). They and coexistent anomalies are described relative to published examples. Prevalence was estimated as possible, using a Poisson model for 95% confidence intervals (CI). RESULTS: Three maxillary double teeth were identified: a primary left lateral incisor in a Nubian child (1938-1756 BC), permanent left central incisor in an adult Egyptian (3650-3500 BC), and permanent right central incisor in a modern (19th century) adult from Guinea. Each co-occurs, respectively, with a talon cusp, peg lateral incisor and, in the latter individual, second premolar crown variation with rotation, and third molar dens evaginatus. Double tooth prevalence is 0.048% (CI 0.001%-0.270%), with regional variation, in premodern, and 0.000% in modern North Africans. It is 0.000% for premodern and 0.048% for modern sub-Saharan Africans (0.008%-1.714%). CONCLUSIONS: The double incisors are comparable to other global examples, indicative of common developmental processes during odontogenesis. Prevalence is lower than published modern rates, to suggest some exceptionality in Africans as reported earlier for other dental variants. Finally, though circumstantial, double teeth and accompanying anomalies may share an etiology. Continuing research overall, and in Africa specifically, will promote an improved understanding of double teeth formation and expression

Hyperdontia across sub-Saharan Africa: Prevalence, patterning, and implications

Objective: Hyperdontia data in modern and premodern sub-Saharan Africans are presented by region—West, Central, East, and South, and sex. Beyond describing the anomaly, comparisons are made with other world populations and future work is promoted. These findings may be useful to both dental clinicians and anthropologists. Methods: Hyperdontia presence and patterning were recorded in 51 samples of skeletal dentitions and hardstone casts (n = 1916). Its infrequency prompted regional pooling after grouping by time. Only adults were included to record later forming fourth molars reportedly common in Africans. Quantitative analyses, including 95% confidence intervals, were conducted to characterize spatiotemporally sub-Saharan peoples. Results: Forty-four of 1429 modern individuals (3.08%) exhibit hyperdontia (CI 2.24–4.13%). Regional variation is significant, particularly West-Central vs. East-South, between 6.8% and 1.5%. Four of 487 premodern individuals, 0.82%, have hyperdontia (0.22–2.10%), with minimal regional differences. Males are most affected, as reported by other researchers. Other similarities with non-African research are evident regarding isomere, antimere, and form, with one key exception—a proclivity for the posterior over anterior maxilla. Conclusions: 3.08% is toward the upper end of published world ranges, including an oft-cited 0.1–3.6 + %. However, the regional variation argues against a single prevalence to describe collectively the subcontinental inhabitants. This variation parallels past west to east and south migrations like other biocultural indicators. Thus, beyond a health concern to clinicians or interesting anomaly to anthropologists, hyperdontia may be useful in other studies. There are no equivalent premodern ranges for comparison. Similarity in patterning overall to previous findings suggests a shared, potentially ancient genetic component in expression

Agenesis of the permanent teeth in sub-Saharan Africans: Prevalence, patterns, interpretations

Objective: Dental agenesis data in modern and premodern sub-Saharan Africans are presented by region, West, Central, East, and South, and by sex. Beyond characterizing the anomaly, comparisons are made with other populations and future work is encouraged. The findings should be of use to dental clinicians and anthropologists. Methods: Agenesis of the UI2, LI1, UP2, LP2, UM3, and LM3 was recorded in 52 discrete samples of mainly skeletal dentitions (n = 2162) from across the subcontinent. After dividing into temporal categories, regional pooling was effected for adequate sample sizes across the vast geographic area. Only adults were included to record M3 status. Analyses included 95% confidence intervals and chi-square comparisons by region and sex. Results: Of 1668 modern individuals 2.3% have UI2-LP2 agenesis (CI 1.6–3.1%). Regional and sex differences are non-significant, though females are most affected. For M3s it is 7.0% (5.7–8.4%), with the Central region sample differing significantly from the East and South. Females again have greater prevalence, with the difference in the West significant. UI2-LP2 agenesis affects 0.6% of 494 premodern individuals (0.1–1.8%), while M3 agenesis is 8.5% (6.1–11.5%). None of these differences are significant. Conclusions: Rates are toward the low end of global ranges, including 0.0–12.6% for UI2-LP2 from case reports, and 5.3–56.0% for M3 agenesis. With exceptions, generally insignificant inter-region differences imply that rates reasonably represent sub-Saharan peoples overall. Results will be of interest to anthropologists, but those related to risk factors, patterning, and prevalence may assist clinicians in tailoring treatment, while informing patients how this anomaly differs by population ancestry

Root grooves on two adjacent anterior teeth of Australopithecus africanus

Tooth root grooves and other ante-mortem dental tissue loss, not associated with caries found on or near the cementoenamel junction (CEJ), are commonly termed non-carious cervical lesions. Three main processes are implicated in forming these lesions: abrasion, dental erosion, and abfraction. As yet, these lesions have not been described in non-Homo hominins. In this study, South African fossil hominin collections were examined for evidence of any type of non-carious cervical lesion. Only one individual shows ante-mortem root grooves consistent with non-carious cervical lesions. Two teeth, a mandibular right permanent lateral incisor (STW 270) and canine (STW 213), belonging to the same Australopithecus africanus individual, show clear ante-mortem grooves on the labial root surface. These lesions start below the CEJ, extend over a third of the way toward the apex, and taper to a point towards the lingual side. The characteristics of these grooves suggest the predominant aetiology was erosive wear. In addition, they are extremely similar to clinical examples of dental erosion. These are the oldest hominin examples of non-carious cervical lesions and the first described in a genus other than Homo. Further, the lesions suggest that this individual regularly processed and consumed acidic food items. © 2018 Elsevier Inc

Relative tooth size, Bayesian inference, and Homo naledi

Objectives: Size-corrected tooth crown measurements were used to estimate phenetic affinities among Homo naledi (~335–236 ka) and 11 other Plio-Pleistocene and recent species. To assess further their efficacy, and identify dental evolutionary trends, the data were then quantitatively coded for phylogenetic analyses. Results from both methods contribute additional characterization of H. naledi relative to other hominins. Materials and Methods: After division by their geometric mean, scaled mesiodistal and buccolingual dimensions were used in tooth size apportionment analysis to compare H. naledi with Australopithecus africanus, A. afarensis, Paranthropus robustus, P. boisei, H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, H. sapiens, and Pan troglodytes. These data produce equivalently scaled samples unaffected by interspecific size differences. The data were then gap-weighted for Bayesian inference. Results: Congruence in interspecific relationships is evident between methods, and with many inferred from earlier systematic studies. However, the present results place H. naledi as a sister taxon to H. habilis, based on a symplesiomorphic pattern of relative tooth size. In the preferred Bayesian phylogram, H. naledi is nested within a clade comprising all Homo species, but it shares some characteristics with australopiths and, particularly, early Homo. Discussion: Phylogenetic analyses of relative tooth size yield information about evolutionary dental trends not previously reported in H. naledi and the other hominins. Moreover, with an appropriate model these data recovered plausible evolutionary relationships. Together, the findings support recent study suggesting H. naledi originated long before the geological date of the Dinaledi Chamber, from which the specimens under study were recovered

Recording and interpreting enamel hypoplasia in samples from archaeological and palaeoanthropological contexts

Enamel hypoplasia is often split into several macroscopic categories, including pit, localised, linear and planeform defects. All types have been considered a sign of ‘non-specific stress’ during dental development in archaeological, as well as palaeoanthropological and other samples. there is growing evidence suggesting many defects may not be caused by illness or malnutrition during childhood, instead relating to trauma to the developing tooth, genetic conditions or specific environmental factors, i.e., may not be associated with ‘stress’ to the individual. In this study all types of macroscopic enamel hypoplasia were recorded, including pitting, linear, plane and localised type defects, in two extant great ape species and three fossil hominin species. The aim is to compare the characteristics and prevalence of different types of enamel hypoplasia among species and discuss potential differences in aetiology. The results show that samples have diverse prevalence’s of different kinds of defects, and pitting, linear and localised defects likely have different aetiologies. Additionally, dental characteristics (e.g., tooth morphology, developmental timing/speed and enamel structure) heavily influence the likelihood of specific types of enamel hypoplasia forming. In sum, studies that include only one type of enamel hypoplasia, or focus on one tooth type, to generate a ‘stress’ rating for a sample may miss relevant information when comparing groups. Instead, it may be beneficial to record different types of defects separately, for all teeth, and then consider how genetic, environmental and tooth property factors may influence sample differences

The transition from hunting–gathering to agriculture in Nubia: dental evidence for and against selection, population continuity and discontinuity

Some researchers posit population continuity between Late Palaeolithic hunter–gatherers of the late Pleistocene and Holocene agriculturalists from Lower (northern) Nubia, in northeast Africa. Substantial craniodental differences in these time-successive groups are suggested to result from in situ evolution. Specifically, these populations are considered a model example for subsistence-related selection worldwide in the transition to agriculture. Others question continuity, with findings indicating that the largely homogeneous Holocene populations differ significantly from late Pleistocene Lower Nubians. If the latter are representative of the local populace, post-Pleistocene discontinuity is implied. So who was ancestral to the Holocene agriculturalists? Dental morphological analyses of 18 samples (1075 individuals), including one dated to the 12th millennium BCE from Al Khiday, near the Upper Nubian border, may provide an answer. It is the first Late Palaeolithic sample (n = 55) recovered within the region in approximately 50 years. Using the Arizona State University Dental Anthropology System to record traits and multivariate statistics to estimate biological affinities, Al Khiday is comparable to several Holocene samples, yet also highly divergent from contemporaneous Lower Nubians. Thus, population continuity is indicated after all, but with late Pleistocene Upper—rather than Lower Nubians as originally suggested—assuming dental traits are adequate proxies for ancient DN