The most significant sexual differences in the human skull are located in the upper third of the face (the frontal bone), which is a useful research object, mainly in combination with virtual anthropology methods. However, the influence of biological relatedness on sexual dimorphism and frontal bone variability remains unknown. This study was directed at sexual difference description and sex classification using the form and shape of the external surface of the frontal bones from a genealogically documented Central European osteological sample (nineteenth to twentieth centuries). The study sample consisted of 47 cranial CT images of the adult members of several branches of one family group over 4 generations. Three-dimensional virtual models of the frontal bones were analyzed using geometric morphometrics and multidimensional statistics. Almost the entire external frontal surface was significantly different between males and females, especially in form. Significant differences were also found between this related sample and an unrelated one. Sex estimation of the biologically related individuals was performed using the classification models developed on a sample of unrelated individuals from the recent Czech population (Čechová et al. in Int J Legal Med 133: 1285 1294, 2019), with a result of 74.46% and 63.83% in form and shape, respectively. Failure of this classifier was caused by the existence of typical traits found in the biologically related sample different from the usual manifestation of sexual dimorphism. This can be explained as due to the increased degree of similarity and the reduction of variability in biologically related individuals. The results show the importance of testing previously published methods on genealogical data.

• Keywords
• Forensic anthropology, Genealogical documented sample, Geometric morphometrics, Kinship,
• MeSH
• Frontal Bone * diagnostic imaging   anatomy & histology   MeSH
• Adult MeSH
• Humans MeSH
• Tomography, X-Ray Computed MeSH
• Sex Characteristics MeSH
• Forensic Anthropology * methods   MeSH
• Sex Determination by Skeleton * methods   MeSH
• Imaging, Three-Dimensional * MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH

Biomechanical load and hormonal levels tended to change just like the soft and skeletal tissue of the elderly with age. Although aging in both sexes shared common traits, it was assumed that there would be a reduction of sexual dimorphism in aged individuals. The main goals of this study were (1) to evaluate age-related differences in cranial sexual dimorphism during senescence, (2) to determine age-related differences in female and male skulls separately, and (3) to compare skull senescence in Czech and French adult samples as discussed by Musilová et al. (Forensic Sci Int 269:70-77, 2016). The cranial surface was analyzed using coherent point drift-dense correspondence analysis. The study sample consisted of 245 CT scans of heads from recent Czech (83 males and 59 females) and French (52 males and 51 females) individuals. Virtual scans in the age range from 18 to 92 years were analyzed using geometric morphometrics. The cranial form was significantly greater in males in all age categories. After size normalization, sexual dimorphism of the frontal, occipital, and zygomatic regions tended to diminish in the elderly. Its development during aging was caused by morphological changes in both female and male skulls but secular changes must also be taken into account. The most notable aging changes were the widening of the neurocranium and the retrusion of the face, including the forehead, especially after the age of 60 in both sexes. Sexual dimorphism was similar between the Czech and French samples but its age-related differences were partially different because of the population specificity. Cranial senescence was found to degrade the accuracy of sex classification (92-94%) in the range of 2-3%.

• Keywords
• Age-related changes, Aging, Cranium, Geometric morphometrics, Sexual dimorphism,
• MeSH
• Adult MeSH
• Skull anatomy & histology   diagnostic imaging   MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Tomography, X-Ray Computed MeSH
• Sex Characteristics * MeSH
• Bone Remodeling physiology   MeSH
• Aged MeSH
• Aging physiology   MeSH
• Sex Determination by Skeleton * MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic MeSH
• France MeSH

Frontal sinus analysis has potential utility for detecting biologically related individuals. However, the methodological approach to its evaluation, as well as its informative value, have been questioned. The aim of this work is to introduce a new approach to evaluating the frontal sinus using the 'external supraorbital line' (ESOL) and to determine whether there are sex differences within families in frontal sinus measurements and whether frontal sinus similarity reflects known genetic relationships in both measurements and morphology. We examined the skeletal remains of 41 adult individuals (25 males, 16 females), all members of one family over four generations (19th to 20th centuries), including individuals with very close consanguinity. CT images of skulls were acquired, and both the dimensions and morphology of the frontal sinuses were analyzed using their portions above the ESOL. No significant sex differences were found within families based on frontal sinus dimensions. Significant relationships were found between biological distance and the maximum height and morphology of the frontal sinuses. The greatest degree of similarity was found among closely related individuals. Additionally, in several cases, there was a greater degree of similarity between first cousins or grandparents and their grandchildren than among siblings or parents and their children. Total surface, volume and width are not significant indicators of relatedness. Known genetic relationships are also supported by individual morphological features. Variability within families with very close consanguineous relationships was lower than within families with common degrees of consanguinity, although differences are significant only for some variables.

• Keywords
• dimensions, frontal sinus anatomy, genealogical documented sample, inbreeding, morphology,
• MeSH
• Adult MeSH
• Skull anatomy & histology   diagnostic imaging   MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Tomography, X-Ray Computed MeSH
• Sex Characteristics * MeSH
• Consanguinity MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Frontal Sinus anatomy & histology   diagnostic imaging   MeSH
• Body Remains * MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Sex estimation is a task of utmost importance in forensic anthropology and bioarcheology. Along with the pelvic bone, the skull is the most important source of sexual dimorphism. On the human skull, the upper third of the face (i.e., the frontal bone) is one of the most significant sexually dimorphic structures useful in anthropological research, especially when studied by methods of virtual anthropology. This study was focused on sex estimation using the form and shape of the external surface of the frontal bone with or without the inclusion of its sinuses. The study sample consisted of 103 cranial CT images from a contemporary Czech population. Three-dimensional virtual models of the frontal bones and sinuses were analyzed using geometric morphometrics and multidimensional statistics: coherent point drift-dense correspondence analysis (CPD-DCA), principal component analysis (PCA), and support vector machine (SVM). The whole external frontal surface was significantly different between males and females both in form and shape. The greatest total success rate of sex estimation based on form was 93.2%, which decreased to 86.41% after crossvalidation, and this model identified females and males with the same accuracy. The best estimation based on shape reached a success rate of 91.26%, with slightly greater accuracy for females. After crossvalidation, however, the success rate decreased to 83.49%. The differences between sexes were significant also in the volume and surface of the frontal sinuses, but the sex estimation had only 64.07% accuracy after crossvalidation. Simultaneous use of the shape of the frontal surface and the frontal sinuses improved the total success rate to 98.05%, which decreased to 84.46% after crossvalidation.

• Keywords
• Forensic anthropology, Frontal bone, Frontal sinuses, Geometric morphometrics, Sex estimation, Sexual dimorphism,
• MeSH
• Frontal Bone anatomy & histology   diagnostic imaging   MeSH
• Skull anatomy & histology   diagnostic imaging   MeSH
• Humans MeSH
• Sex Characteristics MeSH
• Forensic Anthropology methods   MeSH
• Sex Determination by Skeleton methods   MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Czech Republic MeSH