Third Molar Agenesis in Post-Medieval Chichester

Third molar agenesis is a dental anomaly that occurs in approximately 25% of people worldwide and results in the complete absence of one or more of the third molars in the dentition. A rise in the prevalence of congenitally absent third molars has been noted in modern populations, and it has been proposed as the final evolutionary step in the dental reduction of the human dentition. Whilst much research has been conducted in modern cohorts, relatively little has been published on third molar agenesis in archaeological assemblages. A post-medieval assemblage from Chichester was visually and radiographically analysed to determine the prevalence of this anomaly. Third molars were measured to determine if there was an association between agenesis and size reduction. Prevalence of agenesis was found to be relatively high at 42.7% and 2 of 8 measurements were found to produce significant differences. Consequently, it can be said that high rates of third molar agenesis are not solely a modern phenomenon, as many prevalence rates in recent populations are lower. However, if we are to assess the significance of size differences in third molars of those with agenesis and those without, and to detect patterns within and between these groups, assemblages with larger sample sizes are needed. In order to better understand the trajectory and evolution of this anomaly, more archaeological assemblages must be examined.

Odontometric parameters in human mandibular molars for sex estimation in a forensic context

When encountering human skeletal remains in forensic contexts, one important step in the identification process is the estimation of sex, because it reduces the number of individuals to approximately one half. The pelvis and skull are considered the most efficient elements for this estimation; however, when unavailable, teeth may be used alternatively. This study aims to evaluate the usefulness of specific odontometric parameters from the mandibular first molar – mesiolingual-distobuccal distance (MLDB) and mesiobuccal-distolingual distance (MBDL) - on sex estimation, in a sample composed from 135 mandibles selected from the Coimbra Identified Skeletal Collection (University of Coimbra). Since canines seem to be the most accurate teeth for sexual diagnosis, comparison of molars parameters and canines was performed, through measurement of their mesiodistal dimensions (MD). Statistical analysis showed sexual dimorphism in human first molars and determination of cut-off points assigned individuals to the male or female group. In the first molar, 60.7% and 65.2% of individuals were correctly classified by using MLDB and MBDL, respectively. Highest sexual diagnosis accuracy was achieved with Canine MD, reaching 74.6%. Our results indicate that although mandibular molar dimensions are useful for sex estimation, the canine should be prioritized when using the dentition to perform this task.

The Impact of dental wear on the analysis of morphological affinities based on dental non-metric traits

Dental wear is described as a limitation to dental morphological studies, as it obscures important crown trait features, resulting in significant differences on trait frequencies, an essential component for estimating biodistances. However, the actual impact of dental wear on biological distances still requires further characterization. We explore the impact of dental wear on morphological affinities for Brazilian pre-colonial series in the context of worldwide reference series. Twenty crown traits were scored using the Arizona State University Dental Anthropological System, and dental wear was quantified as an ordinal scale between 1 (no wear) and 8 (crown eroded). Seven crown trait frequencies are significantly associated with dental wear (p<0.05), demonstrating its impact on their analysis. To explore this impact on biodistances, data was divided by wear categories (all teeth, low-wear, moderate/severe wear) and morphological affinities among series was compared through Euclidean distances, Mean Measure of Divergence, and Principal Component Analysis. Results show the impact of wear is only meaningful when a sample contains many wear-biased traits with only moderate/severe wear. We conclude despite the impact of wear on individual trait frequencies, its impact on morphological affinities can be mitigated by including other variables or when comparisons focus only on large-scale biological differences.

Patterns of Antemortem Tooth Loss in Late Prehistoric West-central Tennessee

The later prehistoric subsistence-settlement pattern in the Kentucky Lake Reservoir (KLR) of northern west-central Tennessee is of interest as human occupation inexplicably terminates by AD 1450 as part of a larger regional depopulation. Antemortem tooth loss (ATL) collectively and by tooth type was identified in four site samples from the KLR. These are a Late Woodland (AD 600-900) sample (Hobbs) and three Middle Mississippian period (AD 1100- 1400) hierarchically organized and presumptively maize agriculturalist samples (Link/Slayden, Gray Farm , Thompson Village). ATL prevalence in the Hobbs sample is consistent with a native crop and seasonal foraging economy. The ATL in the Link sample is more congruent with the pre-maize Late Woodland sample than the essentially contemporaneous Gray Farm site sample. Thompson Village, a later-dated satellite community of the Gray Farm polity, exhibits significantly fewer ATL than the Gray Farm sample. This may flag climate-influenced agricultural shortfall of dietary carbohydrates later in the occupation sequence. Additionally, males in the Gray Farm site sample have significantly more ATL than males in the other two Mississippian samples. The patterns suggest regional, possibly shortfall mitigated, differences in maize intensification with a polity-specific male-focused maize consumption in the Gray Site.

Growth rates of accessory human enamel: a histological case study of a modern-day incisor from Northern England

This study investigates enamel growth of a modern-day human upper first incisor (S197) possessing an accessory cusp. Growth rates collected from the accessory enamel are compared to data collected from the primary cusp and healthy incisors from the same population. Upper first incisors (n=12) and S197 were analysed using histological methods. Daily secretion rates (DSRs) were calculated for inner, mid, and outer regions of cuspal and lateral sites. Additional DSRs were calculated for equivalent regions of S197’s accessory cusp. S197’s primary cusp DSRs were significantly faster than the accessory cusp for all lateral regions, but significantly slower in the inner and mid cuspal regions. S197’s primary cusp DSRs were also significantly faster than the healthy incisor sample for all lateral regions, but significantly slower in the inner and mid cuspal regions. The DSRs of the healthy sample were significantly faster than those of S197’s accessory cusp for all lateral regions, but significantly slower in the inner cuspal region. This case study displays that human teeth possessing accessory cusps can present varying DSRs to healthy teeth of the same population, and that accessory enamel growth may not follow the same pattern of increasing DSRs along the length of enamel prisms.

A Morphofunctional Hypothesis for Selection on EDAR V370A and Associated Elements of Sinodonty

The phenomenon of sinodonty refers to a suite of dental characters shared between East Asian and Native American populations, and most prominently to the presence of shoveled incisors. Although this syndrome is a conspicuous aspect of dental differentiation among extant human populations, elements of which have been recent subject of detailed genetic analysis, adaptive consequences of shoveled incisors and related features remains unclear. Here, I hypothesize that many of the associated differences in dentition (along with reduction in mandibular length and increases in salivary gland branching) arose in parallel with the opportunistic consumption of wild rice and millet in central and northern China, respectively, and with their subsequent domestication in the Upper Paleolithic. More efficient mastication and digestion of plant grains (and of other starchy foods obtained via broad-spectrum foraging) would potentially have been enabled by these traits, yielding greater rates of nutritional intake as wild crops were progressively domesticated. This functional hypothesis, although not mutually exclusive relative to other proposed selective factors, matches the estimated timeline in China for both origin and time to fixation of the associated allele (EDAR V370A), and is consistent with chronic energetic gain and fitness benefits independent of any assumptions for concurrent climatic conditions.

Permanent molar trait expression in the Late Neolithic cave burials of the Meuse Basin, Belgium

At least 250 cave burials along the Meuse river basin of Belgium yield prehistoric remains, and most date from the Late Neolithic period. Several have been radiocarbon dated, including the early/late Neolithic deposits of Hastière Caverne M and Hastière Trou Garçon C and the final/late Neolithic caves of Sclaigneaux and Bois Madame. An additional collective burial, Maurenne Caverne de la Cave is radiocarbon dated to the Middle Neolithic and final/late Neolithic periods, circa 4,635 to 3,830 BP, encompassing the range of dates for the other collective burials. Most individuals are represented by fragmentary gnathic remains with in situ dental elements. Arizona State University Dental Anthropology System (ASUDAS) scores of permanent molars are employed to examine whether differences within and between the caves exist, and whether chronology and ecogeography can account for the variation in traits. The final/late Neolithic cave of Sclaigneaux, the most geographically distinct cave burial, and Hastière Caverne M, possibly the earliest site, emerge as the most distinctive. The final/late Neolithic sites of Sclaigneaux and Bois Madame exhibit the greatest variability of trait expression. These results bear on the mobility and continuity of human groups in Belgium during the terminus of the Neolithic prior to the Bronze Age.

The impact of hybridization on upper first molar shape in robust capuchins (Sapajus nigritus x S. libidinosus)

To better understand the impact of hybridization on development and morphology, I analyze an understudied phenotype in hybrid morphology research: tooth shape. I apply a 2D geometric morphometric approach to compare variation in first upper molar cusp tip positions and crown outline shape among 31 crested capuchins (Sapajus nigritus), 37 bearded capuchins (S. libidinosus), and 44 hybrids (S. nigritus x S. libidinosus). A principal components analysis shows that group membership accounts for a significantly greater proportion of variance along the first major axis of M1 shape variation than does allometry. While most hybrids have S. nigritus-like M1s, several possess a transgressive M1 shape not observed in either parental species. Procrustes distances are greater in hybrids compared to the parental capuchins, and two-block partial least squares analyses show that hybrids exhibit weaker integration between cusp tip positions and crown outline shape. These results demonstrate that hybridization generates novel M1 shapes and support the hypothesis that destabilized development results in elevated phenotypic variance in hybrids. Further studies of dental shape in hybrid primates will generate important data for on-going efforts to detect potential hybrids in the hominin fossil record and to understand the evolutionary outcomes of anthropogenic hybridization.