Jana Velemínská

Three-dimensional geometric morphometric analysis of cranio-facial sexual dimorphism in a Central European sample of known sex

This article presents an approach for estimating the sexual dimorphism of adult crania using three-dimensional geometric morphometric methods. The study sample consisted of 139 crania of known sex (73 males and 66 females) belonging to persons who lived during the first half of the 20th century in Bohemia. The three-dimensional co-ordinates of 82 ecto-cranial landmarks and 39 semi-landmarks covering the midsagittal curve of the cranial vault were digitised using a MicroScribe G2X contact digitiser. The purposes of the investigation were to define the regions of the cranium where sexual dimorphism is most pronounced and to investigate the effectiveness of this method for determining sex from the shape of the cranium. The results demonstrate that it is better to analyse apportionable parts of the cranium rather than the cranium as a whole. Significant sexual differences (significance was determined using multivariate analysis of variance) were noted in the shape of the midsagittal curve of the vault, upper face, the region of the nose, orbits, and palate. No differences were recorded either in the shape of the cranium as a whole or in the regions of the base and the neurocranium. The greatest accuracy in determining sex was found in the region of the upper face (100% of study subjects correctly classified) and the midsagittal curve of the vault (99% of study subjects correctly classified).

Skull shape asymmetry and the socioeconomic structure of an early medieval central european society

The socioeconomic structure of an early medieval society from the Mikulčice settlement (Czech Republic) was studied on the basis of an evaluation of the fluctuating and directional asymmetry (DA) of skulls. Two distinct inhabited regions, castle and sub-castle, were compared. Fluctuating asymmetry (FA) was used as a bioindicator of environmental stress, which is thought to have been different in the Mikulčice castle and sub-castle regions. DA is consistent with biomechanical loading, and it was expected to reflect different subsistence patterns. The material consisted of 129 crania from what was presumed to be a higher socioeconomic class (Mikulčice castle) and 71 crania from middle and lower socioeconomic classes (Mikulčice sub-castle). As a comparative sample, 138 crania from modern, lower socioeconomic classes (Pachner Collection) were used. The three-dimensional coordinates of 68 landmarks were digitized and analyzed using geometric morphometrics. In terms of DA, the highest values were recorded in the sub-castle sample and confirmed their lower socioeconomic position, with a grittier and lower protein diet compared with the castle sample. In terms of FA, distinctive differences between the sexes were found. In males, no differences were observed between castle and sub-castle, and the lowest FA values were recorded. In females, significantly higher values of FA were found, surprisingly in the castle sample, comparable with the more stressed Pachner Collection. We suspect that the FA reflects a more varied population of castle females as a consequence of patrilocality, although environmental stress remains a possibility.

Surface facial modelling and allometry in relation to sexual dimorphism

Sexual dimorphism is responsible for a substantial part of human facial variability, the study of which is essential for many scientific fields ranging from evolution to special biomedical topics. Our aim was to analyse the relationship between size variability and shape facial variability of sexual traits in the young adult Central European population and to construct average surface models of adult males and females. The method of geometric morphometrics allowed not only the identification of dimorphic traits, but also the evaluation of static allometry and the visualisation of sexual facial differences. Facial variability in the studied sample was characterised by a strong relationship between facial size and shape of sexual dimorphic traits. Large size of face was associated with facial elongation and vice versa. Regarding shape sexual dimorphic traits, a wide, vaulted and high forehead in combination with a narrow and gracile lower face were typical for females. Variability in shape dimorphic traits was smaller in females compared to males. For female classification, shape sexual dimorphic traits are more important, while for males the stronger association is with face size. Males generally had a closer inter-orbital distance and a deeper position of the eyes in relation to the facial plane, a larger and wider straight nose and nostrils, and more massive lower face. Using pseudo-colour maps to provide a detailed schematic representation of the geometrical differences between the sexes, we attempted to clarify the reasons underlying the development of such differences.

Variability in palatal shape and size in patients with bilateral complete cleft lip and palate assessed using dense surface model construction and 3D geometric morphometrics

Bilateral complete cleft lip and palate (BCLP) is the most severe of the common orofacial clefts and is associated with the greatest deformity during development. The aim of this study was to use geometric morphometrics to evaluate palatal shape and size variability in patients with BCLP in comparison to nonclefted Czech boys. The variability of palatal size and shape in BCLP patients was greater when compared with the nonclefted population. Though palate variability in BCLP was wide, nonclefted palatal shapes were generally different (a high, wide and vaulted palate) and fell almost outside the range of BCLP variability. The palatal size and shape of BCLP patients (range from 12.1 to 16.5 years) was not correlated with age. A comparison of the mean shapes of the clefted and nonclefted groups showed that the BCLP palate is flatter and narrower. The most notable size difference was found in the area between the maxilla and premaxilla. This phenomenon is associated with the persisting separation of the premaxilla from the rest of the palate. The shape of the palatal configuration of the premaxilla and adjacent area was concave in the nonclefted group and convex in BCLP patients.

Comparison of methods to determine sex by evaluating the greater sciatic notch: Visual, angular and geometric morphometrics

Sex estimation is the first step for biological profile reconstruction of an unknown skeleton (archaeological or contemporary) and consequently for positive identification of skeletal remains recovered from forensic settings. Several tools have been developed using different osseous structures. With the intention to provide an objective method comparison, we reported the analysis of three different methods (visual, metric and geometric morphometrics) for sex assessment of the greater sciatic notch. One hundred and thirty pelvic bones (45.4% females and 54.6% males) from the National Autonomous University of Mexico Skeletal Collection pertaining to the contemporary Mexican population were analyzed. We used the ROC-analysis to test between desired false positive thresholds (1-specificity) and expected true positive rates (sensitivity) in order to predict the best approach to sex assessment. The comparison of the area under the ROC-curves shows significant differences among visual and metric methods. At the same time, the analysis suggested that higher morphological variation among the sexes is independent of the methodological approach. The results indicate that the metric (angle), with a high percent of indeterminate cases (34.6%), and visual, with 26.2% of the cases allocated as intermediate cases, were poorly accurate; we cannot recommend these techniques for sexing an unknown specimen. On the other hand, the geometric morphometrics approach improves sex estimation in 82.3% of correctly classified individuals with more than 95% of posterior probability. In addition to the method comparison, the major sexual variation of the greater sciatic notch was determined to be located on its posterior border.

Three-Dimensional Morphology of the Palate in Subjects With Unilateral Complete Cleft Lip and Palate at the Stage of Permanent Dentition

Objective Three-dimensional analysis of palate size and shape in patients with complete unilateral cleft lip and palate (UCLP) at the stage of permanent dentition. Subjects Thirty randomly selected dental casts of boys approximately 15 years old with complete UCLP and 28 dental casts of normal boys of the same age. Interventions All patients underwent lip repair according to Tennison with primary periosteoplasty (mean age 8.5 months) and palate repair by pushback and pharyngeal flap surgery (mean age 4.9 years). Main Outcome Measures Data on the palate height in 210 defined locations. Results The palate in patients with UCLP was narrower throughout its whole extent, more anteriorly than posteriorly. From the canines posteriorly, it was also lower, and the difference as compared with controls increased in a posterior direction up to the level of second premolars (up to 30%) and then slightly diminished (to 21% between the first molars). The reduction of area of transverse sections reached 45% between premolars and 39% between first molars. The palate in the anterior portion was highest on the cleft side and in a posterior direction the maximum height of the palate shifted toward the midline and even beyond that line toward the noncleft side. Palatal height did not depend on dentoalveolar arch width. Conclusion The smaller width and height of the palate confirm the substantially reduced space for the tongue in patients with UCLP. The reduction is only slightly larger than in previously examined patients with isolated cleft palate. Palatal vault is asymmetrical, highest anteriorly on the cleft side and posteriorly on the noncleft side.

Technical Note: Geometric Morphometrics and Sexual Dimorphism of the Greater Sciatic Notch in Adults From Two Skeletal Collections: The Accuracy and Reliability of Sex Classification

The greater sciatic notch (GSN) is one of the most important and frequently used characteristics for determining the sex of skeletons, but objective assessment of this characteristic is not without its difficulties. We tested the robustness of GSN sex classification on the basis of geometric morphometrics (GM) and support vector machines (SVM), using two different population samples. Using photographs, the shape of the GSN in 229 samples from two assemblages (documented collections of a Euroamerican population from the Maxwell Museum, University of New Mexico, and a Hispanic population from Universidad Nacional Autónoma de México, Mexico City) was segmented automatically and evaluated using six curve representations. The optimal dimensionality for each representation was determined by finding the best sex classification. The classification accuracy of the six curve representations in our study was similar but the highest and concurrently homologous cross-validated accuracy of 92% was achieved for a pooled sample using Fourier coefficient and Legendre polynomial methods. The success rate of our classification was influenced by the number of semilandmarks or coefficients and was only slightly affected by GSN marginal point positions. The intrapopulation variability of the female GSN shape was significantly lower compared with the male variability, possibly as a consequence of the intense selection pressure associated with reproduction. Males were misclassified more often than females. Our results show that by using a suitable GSN curve representation, a GM approach, and SVM analysis, it is possible to obtain a robust separation between the sexes that is stable for a multipopulation sample.

Changes in the sexual dimorphism of the human mandible during the last 1200 years in Central Europe.

According to many investigations, changes in mandibular morphology can occur synchronously with changes in the environment, and sexual dimorphism of the mandible can be influenced by the environment. Sexual dimorphism during the last 1200 years was evaluated using geometric morphometric analysis of virtual cranial models. The method of geometric morphometrics allows differences in size and shape to be assessed separately. We analyzed groups of adult individuals dating to Early Middle Ages, High Middle Ages, Early Modern Ages and from a modern Czech population (21st century). Significant sexual dimorphism in mandibular size was found in all populations. A trend in the sexual dimorphism of size was seen, with differences between the sexes increasing gradually over time. Size changes in female mandibles were a better reflection of environmental conditions and climate than size changes in male mandibles. Regarding changes in the sexual dimorphism of shape, significant dimorphism was found in all four samples. However, the pattern of mandibular shape dimorphism was different and varied considerably between samples. There was only one stable shape trait showing sexual dimorphism across all four samples in our study: the gonion lies more laterally in male than in female mandibles and male mandibles are relatively wider than female mandibles. Sexual dimorphism of shape is not influenced by the climate; instead sexual selection might play a role. This research supports earlier studies that have found that the degree and pattern of sexual dimorphism is population-specific and the factors regulating sexual dimorphism today may not be the same as those in the past.

Development of facial sexual dimorphism in children aged between 12 and 15 years: a three‐dimensional longitudinal study

OBJECTIVES To evaluate sexual dimorphism of facial form and shape and to describe differences between the average female and male face from 12 to 15 years. SETTING AND SAMPLE POPULATION Overall 120 facial scans from healthy Caucasian children (17 boys, 13 girls) were longitudinally evaluated over a 4-year period between the ages of 12 and 15 years. MATERIALS AND METHODS Facial surface scans were obtained using a three-dimensional optical scanner Vectra-3D. Variation in facial shape and form was evaluated using geometric morphometric and statistical methods (DCA, PCA and permutation test). Average faces were superimposed, and the changes were evaluated using colour-coded maps. RESULTS There were no significant sex differences (p > 0.05) in shape in any age category and no differences in form in the 12- and 13-year-olds, as the female faces were within the area of male variability. From the age of 14, a slight separation occurred, which was statistically confirmed. The differences were mainly associated with size. Generally boys had more prominent eyebrow ridges, more deeply set eyes, a flatter cheek area, and a more prominent nose and chin area. CONCLUSION The development of facial sexual dimorphism during pubertal growth is connected with ontogenetic allometry.

Sexual dimorphism of facial appearance in ageing human adults: A cross-sectional study

In the forensic sciences, knowledge of facial ageing is very important in searching for both dead and living individuals. Ageing estimations typically model the biological profile, which can be compared to missing persons. The main goals of this current study were to construct ageing trajectories for adult human faces of both sexes and evaluate sexual dimorphism in relation to static allometry. Our study was based on the analysis of three-dimensional facial surface models of 194 individuals 20-80 years of age. The evaluation consisted of a dense correspondence analysis of facial scans and multivariate statistics. It was shown that both age and sex have a significant influence on facial form and shape. Male features included a longer face, with more protruded foreheads, eyebrow ridges and nose, including the region under the upper lip and mandible region, but more retruded cheeks compared to females. Ageing in both sexes shared common traits, such as more pronounced roundness of the face (rectangular in males), decreased facial convexity, increased visibility of skin folds and wrinkles connected with the loss of skin elasticity, and soft tissue stretching, especially in the orbital area and lower face; however, male faces exhibited more intense ageing changes. The above-mentioned sexual dimorphic traits tended to diminish in the elderly age category, though overall sexual dimorphism was heightened with age. The static allometric relationships between size and form or shape were similar in both sexes, except that the larger faces of elderly males displayed more intensive ageing changes.