Estimation of ancestry for an undocumented mandibular sample using dental morphology.

ABSTRACT: Dental morphology is a useful resource in archaeology, anthropology and paleontology, due to its genetic determination. Teeth are a material of high durability and stability. This work aims to study the dental morphology and test the Portuguese and European biological affinities of an undocumented mandibular sample, through comparison with global and Iberian samples. The dental traits in 163 mandibles (kept at the Museum of Natural History of the University of Oporto, Portugal) were scored using a standardized methodology (ASUDAS: Arizona State University Dental Anthropology System) and compared to other world-wide and Iberian samples through Principal Components (PCA) and Mean Measure of Divergence analyses. The undertaken quantitative and statistical tests demonstrated the unknown sample to be closer to the Coimbra Portuguese sample in all three comparisons. This suggests this undocumented mandibular sample is possibly of Portuguese 19th/20th century origin.

Dental nonmetric trait intraobserver precision: three observations of a large sample.

ABSTRACT: The utility of nonmetric dental traits in population phenetic studies is well documented. However, consistency in scoring trait expression is a concern due to the subjectivity in scoring quasicontinuous variables with graded scales. The aims of this study are to 1) analyze intraobserver results from an independent scorer and 2) interpret the least precise results. Six hundred individuals (300 of each sex) were scored for 48 dental nonmetric traits using ASUDAS, in one preliminary (100 individuals) and two full observations. Intraobserver precision between scoring sessions yielded adequate results (85% to 100%), with two notable exceptions (UI2 tuberculum dentale and LC distal accessory ridge) and three somewhat problematic cases (UM2 hypocone, UM1 Carabelli's trait, and LM1 anterior fovea). Kendall's τ-b rank correlation coefficients are usually moderate to strong (> 0.3). The results are similar to previously published studies of observer error. Error rates are likely caused by inexperience in observable surface selection and trait/grade definition. ASUDAS requires restraint from scoring teeth that are too worn or modified by caries or chipping. A careful study of trait and grade definitions is strongly encouraged. The key element in achieving high precision rates is experience. Intraobserver (and, if needed, interobserver) error should always be calculated. Overall, ASUDAS is a reliable and useful method, especially if the author's recommendations are followed.

The mandibular molar pit-tubercle (MMPT) dental nonmetric trait: Comprehensive analysis of a large sample.

Dental nonmetric traits are quasicontinous variables, mostly of genetic origin. Thus, sets of such traits allow biological distance estimation between samples. Mandibular molar pit-tubercle (MMPT) is a buccal trait defined by Weets (2009) in Irish samples. This study aims to analyze (a) trait frequencies, (b) grade definitions, (c) intraobserver error, (d) sexual dimorphism, (e) asymmetry, and (f) trait associations for MMPT in a Portuguese sample. The first (LM1), second (LM2) and third (LM3) lower molars of 600 identified individuals from the Coimbra collections were scored for MMPT in three scoring sessions. Intraobserver error, bilateral asymmetry and trait correlations were tested using Kendall's τ-b, while sexual dimorphism was verified using Pearson's χ2. Frequencies (LM1: 2.1%; LM2: 3.5%; LM3: 30.3%) were similar to previous reports. However, a new free apex cusp form (grade 3+) was detected. Considering three scoring sessions, intraobserver precision was above 85%, and correlation coefficients between observations were positive and moderate to very strong (0.291<τ-b<0.835). Intrasample variation was low, since only LM3 showed sexual dimorphism (female: 30.2%; males: 16.2%; χ2=15.512; p<0.001; df=1; n=556) and large asymmetry (27.1%). There were no strong (τ-b>0.3) intertrait associations involving MMPT. MMPT shows low trait presence, sexual dimorphism and asymmetry in stable teeth (LM1 and LM2). Intraobserver precision is high, so scoring should be reliable, although a plaque and better threshold grade definition is needed. After further research on non-European samples, MMPT can be useful in biodistance research.