Sex estimation in the cranium and mandible: a multislice computed tomography (MSCT) study using anthropometric and geometric morphometry methods.

INTRODUCTION: The purpose of this study was to analyze the respective contribution of the skull and mandible to sex estimation in an entire cranium using metric and geometric morphometric methods and multislice computed tomography (MSCT) analysis. MATERIALS: The study sample comprised 120 individuals aged 23 to 84 years and divided into three groups (whole sample and over or under 40 years of age). METHODS: Forty-eight osteometric landmarks were positioned using Osirix®, 34 for the cranium and 14 for the mandible. The data were analyzed using univariate analyses and logistic regression using backward stepwise selection with cross-validation of the classification results. Generalized procrustes analysis (GPA) was used, and Goodall's F test and Mahalanobis D2 matrices allowed an assessment of statistical significance. RESULTS: The classification accuracy of cranium models ranged from 87% to 88.3%, and from 68% to 81.4% for the mandibular models. With geometric morphometry, accuracy was of 94-100% for the cranium and 84.2% for the mandible. DISCUSSION: We conclude that the mandible had a higher accuracy rate for individuals over 40 years than individuals under 40 years of age, although the accuracy of geometric morphometry did not differ significantly between the age groups. The cranium, however, presented greater predictability for all the parameters assessed.

Improving the extraction of ancient Yersinia pestis genomes from the dental pulp.

Ancient DNA preserved in the dental pulp offers the opportunity to characterize the genome of some of the deadliest pathogens in human history. However, while DNA capture technologies help, focus sequencing efforts, and therefore, reduce experimental costs, the recovery of ancient pathogen DNA remains challenging. Here, we tracked the kinetics of ancient Yersinia pestis DNA release in solution during a pre-digestion of the dental pulp. We found that most of the ancient Y. pestis DNA is released within 60 min at 37°C in our experimental conditions. We recommend a simple pre-digestion as an economical procedure to obtain extracts enriched in ancient pathogen DNA, as longer digestion times release other types of templates, including host DNA. Combining this procedure with DNA capture, we characterized the genome sequences of 12 ancient Y. pestis bacteria from France dating to the second pandemic outbreaks of the 17th and 18th centuries Common Era.

Sexual dimorphism of the mandibular conformational changes in aging human adults: A multislice computed tomographic study by geometric morphometrics.

The aging process has an impact on mandibular bone morphology and can therefore affect shape sexual dimorphism. Understanding the effect of senescence on mandibular shape changes is particularly important to correctly estimate the sex of an individual and predict age-related conformational modifications. The purpose of this study was to assess age-related changes in mandibular shape and sexual dimorphism. The study sample comprised 160 Multi Slice Computed Tomography examinations of individuals aged 40 to 79 years. Geometric morphometric analysis of fourteen osteometric landmarks was used to examine sexual dimorphism and patterns of mandibular shape variation with age. Results showed that mandibular sexual dimorphism of shape remained significant with aging. Conformational changes occurred between 50 and 70 years and were different for male and female individuals. Females presented earlier and more marked age-related shape changes than males. These observations suggest that mandibular senescence is a sexually dimorphic process since its onset, rate, and the areas subjected to conformational changes differ from male to female individuals. Senescence-related changes present substantial variability, and further investigation is required to determine precisely the age that marks their onset.