Population variation in skeletal sexual dimorphism

Prioritizing a high posterior probability threshold leading to low error rate over high classification accuracy: the validity of MorphoPASSE software for cranial morphological sex estimation in a contemporary population

An increasing number of software tools can be used in forensic anthropology to estimate a biological profile, but further studies in other populations are required for more robust validation. The present study aimed to evaluate the validity of MorphoPASSE software for sex estimation from sexually dimorphic cranial traits recorded on 3D CT models (n = 180) from three populations samples (Czech, French, and Egyptian). Two independent observers performed scoring of 4 cranial traits (2 of them bilateral) in each population sample of 30 males and 30 females. The accuracy of sex estimation using traditional posterior probability threshold (pp = 0.5) ranged from 85.6% to 88.3% and overall classification error from 14.4% to 11.7% for both observers, and corresponds to the previously published values of the method. The MorphoPASSE method is also affected by the subjectivity of the observers, as both observers show agreement in sex assignment in 83.9% of cases, regardless of the accuracy of the estimates. Applying a higher posterior probability threshold (pp 0.95) provided classification accuracy of 97.9% and 93.3% of individuals (for observer A and B respectively), minimizing the risk of error to 2.1% and 6.7%, respectively. However, sex estimation can only be applied to 54% and 66% of individuals, respectively. Our results demonstrate the validity of the MorphoPASSE software for cranial sex estimation outside the reference population. However, the achieved classification success is accompanied by a high risk of errors, the reduction of which is only possible by increasing the posterior probability threshold.

Anatomical variation is the norm: A novel curriculum framework

Anatomical variation is an inherent part of every health curriculum, due in large to the negative clinical consequences that can ensue if anatomical variation is not thoroughly understood. However, current literature fails to describe any structured whole-of-course pedagogy for the teaching of anatomical variation in higher education. This study therefore aimed to (i) propose a whole-of-course curriculum framework to guide academic development and implementation of anatomical variation resources and assessment; and (ii) assess the depth of anatomical variation knowledge in a multiyear undergraduate health-science cohort (n = 152) at the Queensland University of Technology. Current anatomical variation pedagogy, and subsequently the need for the curriculum framework, were explored using a scoping review protocol. As part of this study, anatomical variation was novelly defined as macroscopic differences in morphology (shape and size), topography (location), developmental timing, or frequency (number) of an anatomical structure between individuals that form during embryological or subadult development and result in no substantive, observable interruption to physiological function. The framework incorporated three themes of anatomical variation learning outcomes: description of anatomical variation, theories of the professional implications of variation, and investigation of variant formation. These themes were strongly aligned with the concepts recommended for teaching identified through the scoping review. Significant deficits in anatomical variation student knowledge were identified, with the third-year cohort recording a mean total score of only 54.6%. A strong recommendation to implement the anatomical variation curriculum framework in all medical and health-science curricula is made to intentionally develop student understanding of anatomical variation and improve future clinical practice.

Sex estimation research trends in forensic anthropology between 2000 and 2022 in five prominent journals

In forensic anthropology, osteological sex estimation methods are continuously reevaluated and updated to improve classification accuracies. Therefore, to gain a comprehensive understanding of recent trends in sex estimation research in forensic anthropology, a content analysis of articles published between 2000 and 2022 in Forensic Science International, the Journal of Forensic Sciences, the International Journal of Legal Medicine, the American Journal of Biological Anthropology, and Forensic Anthropology, was performed. The main goals of this content analysis were to (1) examine trends in metric versus morphological research, (2) examine which areas of the skeleton have been explored, (3) examine which skeletal collections and population affinities have been most frequently utilized, and (4) determine which statistical methods were commonly implemented. A total of 440 articles were coded utilizing MAXQDA and the resulting codes were exported for analysis. Statistical analyses were conducted utilizing the Cochran-Armitage and Jonckheere-Terpstra tests for trends, as well as Fisher-Freeman-Halton tests. The results demonstrate that sex estimation research published in these journals has prioritized metric over morphological methods. Further, the most utilized skeletal regions continue to be the skull and pelvis, while the most popular classification statistics continue to be discriminant function analysis and logistic regression. This study also demonstrates that a substantial portion of research has been conducted utilizing U.S. and Europe-based collections and limited populations. Based on these results, future sex estimation research must continue exploring the use of long bones and other postcranial elements, testing newer methods of analysis, as well as developing population-inclusive methods.

Forensic evaluation of craniometric characteristics of the Kazakhstan population

Background

The human skull is the part of the skeleton most frequently used in population studies, as it was more exposed to genetic factors and less exposed to environmental factors. The skull is an important component in human forensic identification.

Materials and methods

The craniometric characteristics of 186 male and 114 female skulls found on the territory of Kazakhstan were studied. Dimensions were measured using standard anthropometric methods and instruments. The results of measurements of 25 craniometric parameters are presented. Methods of descriptive and parametric statistics were used.

Results

Statistical analysis showed significant regional dimorphism, confirming theindividuality of the Kazakhstan population. Statistically significant deviations werefound in 6 male craniometric characteristics and 4 female craniometric characteristics(p<0.05). The most dimorphous variables for regional identification in Kazakhstanmales were the higher skull base and frontal chord width , full face height , condylarand bigonial width , and low mandibular body reference values (p<0.05). For females,significant statistical discrepancies were seen in the transverse diameter and skullbase width, mastoid and occipital aperture width (p<0.05).

Conclusion

The recorded variations and changes in the morphology of the humanskull of the population of Kazakhstan indicate the need to develop and updateosteometric standards used in practice for specific populations. All this will significantlyimprove the accuracy of forensic identification and more fully study the biologicalpatterns of population formation, as well as evaluate the comparative effectiveness ofindividual features in the reconstruction of the population history of various populationgroups.

Estimation of ancestry from cranial measurements based on MDCT data acquired in a Japanese and Western Australian population

The estimation of ancestry is important not only towards establishing identity but also as a required precursor to facilitating the accurate estimation of other attributes such as sex, age at death, and stature. The present study aims to analyze morphological variation in the crania of Japanese and Western Australian individuals and test predictive models based on machine learning for their potential forensic application. The Japanese and Western Australian samples comprise computed tomography (CT) scans of 230 (111 female; 119 male) and 225 adult individuals (112 female; 113 male), respectively. A total of 18 measurements were calculated, and machine learning methods (random forest modeling, RFM; support vector machine, SVM) were used to classify ancestry. The two-way unisex model achieved an overall accuracy of 93.2% for RFM and 97.1% for SVM, respectively. The four-way sex and ancestry model demonstrated an overall classification accuracy of 84.0% for RFM and 93.0% for SVM. The sex-specific models were most accurate in the female samples (♀ 95.1% for RFM and 100% for SVM; ♂91.4% for RFM and 97.4% for SVM). Our findings suggest that cranial measurements acquired in CT images can be used to accurately classify Japanese and Western Australian individuals into their respective population. This is the first study to assess the feasibility of ancestry estimation using three-dimensional CT images of the skull.

Sex-biased gene regulation varies across human populations as a result of adaptive evolution

OBJECTIVES

Studies of human sexual dimorphism and gender disparities in health focus on ostensibly universal molecular sex differences, such as sex chromosomes and circulating hormone levels, while ignoring the extraordinary diversity in biology, behavior, and culture acquired by different human populations over their unique evolutionary histories.

MATERIALS AND METHODS

Using RNA-Seq data and whole genome sequences from 1000G and HGDP, we investigate variation in sex-biased gene expression across 11 human populations and test whether population-level variation in sex-biased expression may have resulted from adaptive evolution in regions containing sex-specific regulatory variants.

RESULTS

We find that sex-biased gene expression in humans is highly variable, mostly population-specific, and demonstrates between population reversals. Expression quantitative trait locus mapping reveals sex-specific regulatory regions with evidence of recent positive natural selection, suggesting that variation in sex-biased expression may have evolved as an adaptive response to ancestral environments experienced by human populations.

DISCUSSION

These results indicate that sex-biased gene expression is more flexible than previously thought and is not generally shared among human populations. Instead, molecular phenotypes associated with sex depend on complex interactions between population-specific molecular evolution and physiological responses to contemporary socioecologies.

Comparing Walker's (2008) skull trait sex estimation standard to proteomic sex estimation for a group of South Asian individuals

This research assesses the potential for misidentification of sex in individuals of South Asian ancestry using the Walker (2008) morphological skull sex estimation standard [1]. Chromosomal sex was assessed using proteomic analysis targeting sex chromosome-specific amylogenic peptides. Results showed that the Walker method produced incorrect classification for 36.7 % of individuals. Overwhelmingly, those incorrectly assigned were chromosomally male. Misidentification was due to males within the group having lower trait scores (i.e., more gracile traits) than the standard would predict. There was also a high level of overlap in trait scores between male and females indicating reduced expression of sexual dimorphism. The use of established multivariate statistical techniques improved accuracy of sex estimation in some cases, but larger osteological data sets from South Asian individuals are required to develop population-specific standards. We suggest that peptide analysis may provide a useful tool for the forensic anthropologist when assessing sex in populations without population specific osteological standards.

Age estimation from mandibles in Malay: A 2D geometric morphometric analysis

Objectives

In this study, the sizes and forms of mandibles in various age groups of the Malay population were measured and compared.

Methods

Geometric morphometric (GM) analysis of mandibles from 400 dental panoramic tomography (DPT) specimens was conducted. The MorphoJ program was used to perform generalized Procrustes analysis (GPA), Procrustes ANOVA, principal component analysis (PCA), discriminant function analysis (DFA), and canonical variate analysis (CVA). In the tpsDig2 program, the 27 landmarks were applied to the DPT radiographs. Variations in mandibular size and form were categorized into four age groups: group 1 (15-24 years), group 2 (25-34 years), group 3 (35-44 years), and group 4 (45-54 years).

Results

The diversity in mandibular shape among the first eight principal components was 81%. Procrustes ANOVA revealed significant shape differences (P < 0.001) among age groups. Mahalanobis distances indicated substantial differences among all age groups; group 1 and group 4 scored highest, at 2.114. The ranges for the cross-validation and discriminant function tests were 90-72% and 81-49%, respectively.

Conclusion

GM analysis through radiography is a simple, non-invasive, and non-destructive method of estimating age by using the mandible. GM analysis is unique because it can visualize the changes in mandible shape among age groups. This method should aid in age identification in forensic odontology investigations.

A study of the influence of genetic variance and sex on the density and thickness of the calvarial bone in collaborative cross mice

BACKGROUND

Bone microarchitecture is affected by multiple genes, each having a small effect on the external appearance. It is thus challenging to characterize the genes and their specific effect on bone thickness and porosity. The purpose of this study was to assess the heritability and the genetic variation effect, as well as the sex effect on the calvarial bone thickness (Ca.Th) and calvarial porosity (%PoV) using the Collaborative Cross (CC) mouse population.

METHODS

In the study we examined the parietal bones of 56 mice from 9 lines of CC mice. Morphometric parameters were evaluated using microcomputed tomography (μCT) and included Ca.Th and %PoV. We then evaluated heritability, genetic versus environmental variance and the sex effect for these parameters.

RESULTS

Our morphometric analysis showed that Ca.Th and %PoV are both significantly different among the CC lines with a broad sense heritability of 0.78 and 0.90, respectively. The sex effect within the lines was significant in line IL111 and showed higher values of Ca.Th and %PoV in females compared to males. In line IL19 there was a borderline sex effect in Ca.Th in which males showed higher values than females.

CONCLUSIONS

These results stress the complexity of sex and genotype interactions controlling Ca.Th and %PoV, as the skeletal sexual dimorphism was dependent on the genetic background. This study also shows that the CC population is a powerful tool for establishing the genetic effect on these traits.

Comparison of Morphological Sex Assessment and Genetic Sex Determination on Adult and Sub-Adult 17th-19th Century Skeletal Remains

The first step in the analysis of human skeletal remains is the establishment of the biological profile of an individual. This includes sex assessment, which depends highly on the age of the individual and on the completeness and preservation state of the remains. Macroscopic methods only provide the assessment of sex, while for sex determination, molecular methods need to be included. However, poor preservation of the remains can make molecular methods impossible and only assessment can be performed. Presented research compares DNA-determined and morphologically assessed sex of adult and non-adult individuals buried in a modern-age cemetery (17th to late 19th century) in Ljubljana, Slovenia. The aim of the study was to assess the accuracy of commonly used macroscopic methods for sex assessment on a Slovenian post-medieval population. Results demonstrate that for adults, macroscopic methods employed are highly reliable and pelvic morphology, even the sciatic notch alone, is more reliable than skull. In non-adults, macroscopic methods are not as reliable as in adults, which agrees with previous research. This study shows how morphological and molecular methods can go hand in hand when building a biological profile of an individual. On their own, each methodology presented some individuals with undetermined sex, while together, sex of all the individuals was provided. Results confirm suitability of sex assessment based on skull and especially pelvic morphology in Slovenian post-medieval adults, while in the non-adult population molecular methods are advised.

Comparative study of sex estimates in adult skulls using direct measurement and tomographic image reconstruction

Sex estimation is an important procedure in forensic anthropology for human identification. The development of new technologies, such as three-dimensional computed tomography (CT), has provided excellent alternatives for this purpose. This study examined and compared a morphological method for sex estimation using two different approaches - direct measurement of physical structures and tomographic analysis using 3D images. A total of 111 skulls from the Museum of Human Anatomy at the University of São Paulo (MAH-USP) were used, (60 males and 51 females). All specimens were scanned by Philips Brilliance 64 CT scanner equipment and their corresponding images were reconstructed in three-dimensional (3D) models. The morphological characteristics of the skulls were analyzed by an observer who was blinded to the sex of the specimens. Five cranial structures were analyzed: external occipital crest, mastoid process, supraorbital margin, glabella, and mental eminence. The structures were scored 1 to 5 according to Buikstra and Ubelaker and validated by Walker. The success rates of the sex estimates obtained through direct measurement of the dry skulls ranged from 67.4% to 70.4% as compared to 60.2% to 68.1% for CT reconstruction. When analyzed separately, the maximum accuracy of the method was 68.33% in males and 88.24% in females in the physical analysis of structures. The glabella and mastoid process were the most effective structures to estimate sex through both techniques, respectively. Our results show that 3D CT images can be accurately used in the morphological analysis for sex estimation, representing a viable alternative in forensic anthropology.

Human femur morphology and histology variation with ancestry and behaviour in an ancient sample from Vietnam

BACKGROUND

There is a genetic component to the minimum effective strain (MES)-a threshold which determines when bone will adapt to function-which suggests ancestry should play a role in bone (re)modelling. Further elucidating this is difficult in living human populations because of the high global genetic admixture. We examined femora from an anthropological skeletal assemblage (Mán Bạc, Vietnam) representing distinct ancestral groups. We tested whether femur morphological and histological markers of modelling and remodelling differed between ancestries despite their similar lifestyles.

METHODS

Static histomorphometry data collected from subperiosteal cortical bone of the femoral midshaft, and gross morphometric measures of femur robusticity, were studied in 17 individuals from the Mán Bạc collection dated to 1906-1523 cal. BC. This assemblage represents agricultural migrants with affinity to East Asian groups, who integrated with the local hunter-gatherers with affinity to Australo-Papuan groups during the mid-Holocene. Femur robusticity and histology data were compared between groups of 'Migrant' (n = 8), 'Admixed' (n = 4), and 'Local' (n = 5).

RESULTS

Local individuals had more robust femoral diaphyses with greater secondary osteon densities, and relatively large secondary osteon and Haversian canal parameters than the migrants. The Migrant group showed gracile femoral shafts with the least dense bone made up of small secondary osteons and Haversian canals. The Admixed individuals fell between the Migrant and Local categories in terms of their femoral data. However, we also found that measures of how densely bone is remodelled per unit area were in a tight range across all three ancestries.

CONCLUSIONS

Bone modelling and remodelling markers varied with ancestral histories in our sample. This suggests that there is an ancestry related predisposition to bone optimising its metabolic expenditure likely in relation to the MES. Our results stress the need to incorporate population genetic history into hierarchical bone analyses. Understanding ancestry effects on bone morphology has implications for interpreting biomechanical loading history in past and modern human populations.

Sex estimation using measurements of the proximal femur in a historical population from Poland

Sex estimation is one of the most important components in assessing the biological profile of an individual. In an archaeological context, the pelvis, which is the most dimorphic part of the skeleton, is often poorly preserved, which can cause an inability to use morphological sex estimation methods. Therefore, alternative methods are required in such cases. Because the utility of the metric methods based on the femur measurement has been confirmed, and the bone is usually available for examination due to its good preservation, developing methods using the landmarks of the femur could have important implications in sex estimation.   This study aimed to derive a discriminant function equation for a Polish archaeological population based on measurements of the proximal end of the femur.   The study sample included individuals from a medieval cemetery in Milicz (n = 62) and an early modern necropolis at Czysty Square in Wrocław, Poland (n = 162). The analysis included seven measurements collected from the right and left proximal femora. To estimate the reproducibility of the measurements, intra-and interobserver errors and reliability coefficients were calculated. Subsequently, univariate and stepwise discriminant analyses were performed, and the sex sectioning points and equations were proposed.   No differences were observed between measurements of the right and left femora. The results indicated a high utility and reproducibility of the FHD measurement (regardless whether left or right femur was measured). The discriminant equations for sex estimation reached an accuracy of 83.0–92.3%, which implies the utility of the function on Polish historical populations when the other methods for sex estimation cannot be used. 

The lateral collateral ligament complex of the elbow in a Thai population: an anatomical study of 56 cadaveric specimens

The purpose of this study was to investigate the anatomical features of the lateral collateral complex (LCC) of the elbow in a Thai population. We dissected 56 cadaveric elbows and described the LCC three-dimensionally in sagittal and coronal planes. We found that the characteristics differed from previous reports in other ethnic populations. In the sagittal plane, the centre of the origin of the LCC was located 3 mm anteriorly and 4 mm inferiorly to the apex of the lateral humerus epicondyle, and in the coronal plane it was 4 mm deep. The vertical distance between the origin of the lateral ulnar collateral ligament (LUCL) and the lateral epicondyle and the distance from the LUCL insertion to the border of the ulnar bone differed significantly between sexes. These data may be useful for surgeons during reconstruction of injures to the LCC of the elbow.Level of evidence: V.

Sexual Dimorphism of Cranial Morphological Traits in an Italian Sample: A Population-Specific Logistic Regression Model for Predicting Sex

Simple Summary

Despite the fact that sex estimation methods from crania are very popular in forensic anthropology, few validation studies have verified their accuracy and reliability in different populations. Different from craniometrics, for which validation studies have remarkably increased lately, the methods based on cranial morphology still need to be thoroughly investigated, even if a large consensus exists on the effects of population variability on sexual cranial dimorphism. When dealing with forensic contexts, appropriately-validated methods should be applied for building accurate biological profiles. Since the possible sexual dimorphism variation of cranial morphological traits needs to be evaluated properly in various populations, in this study, we analyzed the accuracy of existing regression models for predicting sex from cranial morphological traits in an Italian contemporary/modern population. In addition, we propose new logistic regression models that are more accurate and specific for our sample. The results also update the reference standards for populations of this geographical area and provide an additional important warning on sexual dimorphism to anthropologists working in forensic contexts.

Abstract

Although not without subjectivity, the cranial trait scoring method is an easy visual method routinely used by forensic anthropologists in sex estimation. The revision presented by Walker in 2008 has introduced predictive models with good accuracies in the original populations. However, such models may lead to unsatisfactory performances when applied to populations that are different from the original. Therefore, this study aimed to test the sex predictive equations reported by Walker on a contemporary Italian population (177 individuals) in order to evaluate the reliability of the method and to identify potential sexual dimorphic differences between American and Italian individuals. In order to provide new reference data to be used by forensic experts dealing with human remains of modern/contemporary individuals from this geographical area, we designed logistic regression models specific to our population, whose accuracy was evaluated on a validation sample from the same population. In particular, we fitted logistic regression models for all possible combinations of the five cranial morphological traits (i.e., nuchal crest, mastoid process, orbital margin, glabella, and mental eminence). This approach provided a comprehensive set of population-specific equations that can be used in forensic contexts where crania might be retrieved with severe taphonomic damages, thus limiting the application of the method only to a few morphological features. The results proved once again that the effects of secular changes and biogeographic ancestry on sexual dimorphism of cranial morphological traits are remarkable, as highlighted by the low accuracy (from 56% to 78%) of the six Walker’s equations when applied to our female sample. Among our fitted models, the one including the glabella and mastoid process was the most accurate since these features are more sexually dimorphic in our population. Finally, our models proved to have high predictive performances in both training and validation samples, with accuracy percentages up to 91.7% for Italian females, which represents a significant success in minimizing the potential misclassifications in real forensic scenarios.

Sex estimation using radius in a Thai population

The estimation of sex is an essential component of forensic osteological analyses, and the potential of an incomplete radius for sex determination of human remains is investigated. The present study was conducted on 200 left-right pairs of radial bone from a northern Thai population (100 males and 100 females). The most dimorphic single parameter was maximum head diameter (MDH) with accuracies 92.0% for the right side and 90.5% for the left side. At the distal part of radius, the distal end width of the radius (RDEW) was the best sex indicator, in which the sex classification accuracies were 91.5% and 89.0%, for the right and left sides, respectively. Stepwise discriminant function analysis was performed for all measurements and specified separately to the proximal and distal radius. The circumference of the radial neck, head-tuberosity length, MDH, and RDEW were selected for the stepwise procedure as these parameters produced the best correct classification results for both sides. The use of proximal radius for sex estimation was examined, with accuracies of 95.0% and 93.0% for the right and left sides, respectively. The sex classification functions for distal radius provided the accuracies of 92.5% and 89.5%, for the right and left sides, respectively. In summary, the fragments of radius indicated a high ability to estimate sex in the Northern Thai population.

Defining the popliteal fossa by bony landmarks and mapping of the courses of the neurovascular structures for application in popliteal fossa surgery

Surgical access to the posterior knee poses a high-risk for neurovascular damage. The study aimed to define the popliteal fossa by reliable bony landmarks and comprehensively mapping the neurovascular structures for application in posterior knee surgery. Forty-five (20 male, 25 female) embalmed adult cadaveric knees were included. The position of the small saphenous vein (SSV), medial cutaneous sural nerve (MCSN) and lateral cutaneous sural nerv (LCSN), tibial nerve (TN) and common fibular nerve (CFN) nerves, and popliteal vein (PV) and popliteal artery (PA) were determined in relation to either medial (MFE) or lateral (LFE) femoral epicondyles, medial (MTC) and lateral (LTC) tibial condyles and the midpoint between the MFE and MTC and LFEF and LTC. The distance between the MFE and the PA, PV, TN, MCSN, and SSV was 38.4±12.1 mm, 38.4±12.9 mm, 39.4±10.2 mm, 39.2±14.0 mm and 37.6±12.5 mm respectively for males and 34.6±4.9 mm, 32.8±5.6 mm and 38.0±8.1 mm 38.8±10.1 mm and 37.9±8.2 mm respectively for females. The distance between LFE and the CFN and LCSN was 13.4±8.2 mm and 24.9±7.3 mm respectively for males and 8.4±9.1 mm and 18.4±10.4 mm respectively in females. This study defined the popliteal fossa by reliable bony landmarks and provided a comprehensive map of the neurovascular structures and will help to avoid injuries to the important neurovascular structures.

Sexual differences in human cranial morphology: Is one sex more variable or one region more dimorphic?

The quantification of cranial sexual dimorphism (CSD) among modern humans is relevant in evolutionary studies of morphological variation and in a forensic context. Despite the abundance of quantitative studies of CSD, few have specifically examined intra-sex variability. Here we quantify CSD in a geographically homogeneous sample of adult crania, which includes Italian individuals from the 19th and 20th centuries. Cranial morphology is described with 92 3D landmarks analyzed using Procrustean geometric morphometrics (PGMM). Size and shape variables are used to compare morphological variance between sexes in the whole cranium and four individual regions. The same variables, plus Procrustes form, are used to quantify average sex differences and explore classification accuracy. Our results indicate that: (a) as predicted by Wainer's rule, males present overall more variance in size and shape, albeit this is statistically significant only for total cranial size; (b) differences between sexes are dominated by size and to a lesser extent by Procrustes form; (c) shape only accounts for a minor proportion of variance; (d) the cranial base shows almost no dimorphism for shape; and (e) facial Procrustes form is the most accurate predictor of skeletal sex. Overall, this study suggests developmental factors underlying differences in CSD among cranial regions; stresses the need for population-specific models that describe craniofacial variation as the basis for models that facilitate the estimation of sex in unidentified skeletal remains; and provides one of the first confirmations of "Wainer's rule" in relation to sexual dimorphism in mammals specific to the human cranium.

Influence of climatic stress on nonmetric sexually dimorphic features of the skull and pelvis

OBJECTIVES

Human sexual dimorphism is frequently assessed through skull and pelvic size and shape. Researchers suggest that climatic variation and the associated stress may be significant factors in sexual dimorphism's etiology. However, little research has specifically investigated climatic effects on nonmetric skeletal indicators of sex. To further appreciate the plasticity of human biology, a comparative study of standard skull and pelvic nonmetric sex indicators is presented.

METHODS

A Native Alaskan archeological sample (n = 104) and a component of the Terry collection (n = 99) represent populations originating from different climatic environments in recent history. These sex-balanced groups are compared through Tukey-Kramer's method and Greene's t-test to determine any variation in degree of sexual dimorphism within and between samples.

RESULTS

The results reinforce the complex and multifaceted relationship between climate and sexual dimorphism. The Terry sample demonstrated a greater degree of sexual dimorphism with statistically significant differences in robusticity of the mastoid process and nuchal crest compared with the Native Alaskans. A more "male" morphotype and reduced dimorphism are appreciated in the pelves of Native Alaskans than the Terry sample.

CONCLUSIONS

This research highlights a reduction in sexual dimorphism in populations under greater climatic stress and contributes to the production of more accurate skeletal assessments in future investigations. Discussion of confounding factors suggest more research is necessary to untangle climate and human morphology's complex relationship. This study contributes to a greater appreciation of human biological plasticity, ecogeographic variation, and the evolution of modern human diversity.

Sex assessment with the radius in Portuguese skeletal populations (late 19th - early to mid 20th centuries)

The assessment of sex is of immense relevance in the analysis of human skeletal remains, as other parameters of the biological profile are usually sex-specific (e.g., age at death or stature). The radius can be used to estimate sex when more dimorphic bones are not available or in the case of incomplete and fragmentary remains. Ten radius measurements collected in a sample of 364 individuals (166 females and 198 males) from the Coimbra Identified Skeletal Collection (late 19th - early 20th centuries) were employed to generate univariable and multivariable models for sex estimation. All models were evaluated with a 10-fold cross-validation method and an independent holdout sample from the Luís Lopes Collection (late 19th - mid 20th centuries) encompassing 50 individuals (25 females and 25 males). Univariable models show an accuracy ranging from 77.7% to 89.8% (cross-validation), and from 70% to 86% (test sample), while accuracy in the multivariable models varies from 88.7% to 93.4% (cross-validation), and 84.0% to 90.0% (test sample). Results suggest that measurements of the radius are useful to develop standard guidelines for sex estimation of anonymous skeletal remains.

Test of the auricular surface sex estimation method in fetuses and non-adults under 5 years old from the Lisbon and Granada Reference Collections

Non-adult sex estimation is an active field of forensic inquiry as morphological variations between males and females are subtle, but observable, even from intrauterine development. The objectives of this study are threefold: to test the validity of the auricular surface method for sex estimation (Int J Osteoarchaeol 27:898-911, 2017) in fetuses and children under the age of 5 years old; to evaluate if health conditions, reported as the cause of death, influence its accuracy; and to detect possible secular trends in sexual dimorphism. One-hundred and ninety-seven skeletal individuals from the Lisbon and Granada Identified Collections were studied. Individuals were divided according to the hormonal peaks (< 0, 0-2, < 2, and 2.1-5 years old), cause, and year of death (before and after 1960). As in previous studies, two ratios (FI/CF and DE/AD) and two qualitative variables (OM and MRS) showed the highest frequencies of correct estimation (0.81-0.86). The correct sex allocations increased when the discriminant function (0.85) and logistic regression (0.86) were applied. Males of the age groups < 0 and 2.1-5 years were all correctly sexed by both formulae, and the same was observed for the female probabilities of adequate allocation. The cause and year of death were identified as variables without statistical significance. It is proposed that this method can be incorporated with confidence into the multifactorial laboratory protocols for non-adult sex estimation from skeletal remains.

A novel method of male sex identification of human ancient skeletal remains

Sex identification of ancient individuals is important to understand aspects of the culture, demographic structure, religious practices, disease association, and the history of the ancient civilizations. Sex identification is performed using anthropometric measurements and molecular genetics techniques, including quantification of the X and Y chromosomes. These approaches are not always reliable in subadult, or fragmented, incomplete skeletons or when the DNA is highly degraded. Most of the methods include the identification of the male and female sexes, but the absence of a specific marker for the males does not mean that the sample obtained was from a female. This study aims (1) to identify new male-specific regions that allow male identification; (2) to contrast the effectiveness of these markers against AMELX/AMELY and anthropometric measurement procedures; and (3) to test the efficacy of these markers in archaeological samples. For the first two aims, we used known sex samples, and for the third aim, we used samples from different archaeological sites. A novel molecular technique to identify male-specific regions by amplification of TTTY7, TSPY3, TTTY2, and TTTY22 genes of the human Y chromosome was developed. The results showed amplification of the specific DNA regions of Y chromosome in male individuals, with no amplification being observed in any of the female samples, confirming their specificity for male individuals. This approach complements the current procedures, such as the AMELX/AMELY test and anthropometric principle.

Anthropometry of the human calcaneus and orientation of the articular facet for the cuboid bone as a basis for anatomically correct positioning of osteosynthetic screws in fracture treatment

PURPOSE

Fractures of the calcaneus are reported most commonly in the tarsal region. Their incidence is highest among active people in productive age. As such, optimal treatment can have vast implications for patients. The study aimed to compare calcaneal proportions of the Czech population in the last centuries to present day, for a precise choice and positioning of the osteosynthetic material, and its safe implantation in the anterior part of the calcaneus. Furthermore, we describe the frequency of the calcaneocuboid joint involvement in calcaneal fractures.

METHODS

We obtained 69 macerated (dry) human calcanei from anatomical collections along with multiplanar reconstructions obtained from 43 serial CT scans from patients with injuries other than calcaneal fractures. Specimens were measured using a modified set of Bidmos et al. criteria (2006). Two groups (CT scans of macerated specimens and patients' CT scans) were statistically evaluated and compared with the help of an experienced statistician. Furthermore, scans of 80 surgically treated patients were retrospectively assessed for calcaneocuboid joint involvement.

RESULTS

The median tilt of the calcaneocuboid joint in the transverse plane was 67° in the anatomical specimens and 72° in the multiplanar reconstructed CT scans taken from patients with intact tarsal regions. These results suggest that the length of screws should be ideally in the range between 21.3 and 25mm. In 47.3% of the patients presenting with a fractured calcaneus, the calcaneocuboid joint was involved. There was a statistically significant difference in most of the variables observed between the two groups.

CONCLUSION

As the calcaneocuboid joint involvement appears to be present in up to 50% of cases, adequate care should be taken. To maximize the biomechanical properties of the construct and to minimize the risks, our findings suggest the screws should be at an inner tilt of 68-74° from the lateral calcaneal wall and be of 23.5-26.2mm length. However, due to differences between the two groups and the small sample size, further investigation is needed.

Preliminary study on sexual dimorphism of metric traits of cranium and mandible in a modern Italian skeletal population and review of population literature

This study aims to assess the sexual dimorphism of skull in a modern skeletal collection through a direct anthropometric methodology by using a logistic regression analysis as statistical approach in order to provide specific regression formulae for the Italian population. Thirtyfour measurements (24 from cranium, 10 from mandible; 33 linear distances, one angle) were taken on 80 individuals (40 males, 40 females). A stepwise discriminant function analysis selected the combination of variables which best discriminated between sexes, and a cross-validation assessed the accuracy rate of the original sample. Most distances resulted longer in males than in females, but differences were statistically significant only for 12 and 6 out of respectively 24 cranium and 10 mandibular distances. Five combined cranium features returned a prediction accuracy of 88.6% (y = -81.01 + 0.14* Maximum cranial length + 0.16* Basion-bregma height -0.05* Cranial base length +0.20* Bizygomatic breadth +0.31* Nasal height; adjusted R2 = 47.0%). Nine mandibular features were required to reach 74.7% accuracy (y = -93.08 + 0.19* Bigonial width +0.14* Bicondylar breadth +0.11* Mandibular length +0.18* Height of the mandibular body at mental foramen +0.21* Chin height -0.09* Mandibular angle -0.06* Minimum ramus breadth -0.05* Maximum ramus height -0.01* Maximum ramus breadth; adjusted R2 = 23.92%). Current results and existing literature suggested that only few cranial measurements can be used for diagnosis of sex: the same variables showed similar accuracy in different ethnic contexts. In conclusion, some aspects of sexual dimorphism of skull seem to be independent from ancestry.

Morphometric research and sex estimation of lumbar vertebrae in a contemporary Spanish population

In the identification and reconstruction of the biological profile of skeletal remains in physical and forensic anthropology, sex estimation is a fundamental step, and is essential to achieve methods that allow the highest allocation accuracy. This study proposes a method to estimate the sex of skeletal remains using lumbar vertebrae. A total of 33 linear measurements for each lumbar vertebra were taken in 94 identified, contemporary, and adult skeletal remains (46 male and 48 female) from the cemetery of San José in Granada. The sexual dimorphism of each variable was analyzed, an intra- and interobserver error analysis was developed to assess the variables with best concordance, and the discriminant equations were obtained through a binary logistic regression analysis. All lumbar vertebrae show statistically significant sexual dimorphism with higher values in males than in females. Equations with an allocation accuracy of between 80% and 94.5% were obtained, showing that the lumbar vertebrae are a useful alternative for sex estimation when other skeletal elements are not well-preserved or available. The differences of biogeographic history between populations could translate into morphometric differences, which means that it is not advisable to use discriminant equations in a universal way. In spite of the high allocation accuracy of the equations developed, they should be applied in adults from populations similar to the present study to obtain reliable results of sexual estimation, until its validation in other populations.

Sexual dimorphism of maxillary sinuses in children and adolescents - A retrospective CT study

BACKGROUND

In the postnatal period, some sexual dimorphism is observed from the moment of birth, but it is most pronounced from puberty. The aim of the study based on CT images was to assess possible sexual dimorphism of the maxillary sinus in children aged 0-18.

METHODS

The retrospective analysis of CT images of the head (assessed as normal by radiologists) of 170 patients aged 0-18 (85 females and 85 males) was performed. The maxillary sinuses of every patient were bilaterally measured in three planes. Three diameters were obtained: maximum transverse (horizontal) diameter (the maxillary sinus width, MSW); maximum vertical diameter (the maxillary sinus height, MSH) and maximum antero-posterior diameter (maxillary sinus length, MSL). The automatic CT image segmentation algorithm was used (Syngo Via for Oncology, Siemens) to establish maxilla retrospective analysis of CT images of the head (assessed as normal by radiologists) of 170 patients aged 0-18 (85 females and 85 males) was performed. The maxillary sinuses of every patient were bilaterally measured in three planes. Three diameters were obtained: maximum transverse (horizontal) diameter (the maxillary sinus width, MSW); maximum vertical diameter (the maxillary sinus height, MSH) and maximum antero-posterior diameter (maxillary sinus length, MSL). The automatic CT image segmentation algorithm was used (Syngo Via for Oncology, Siemens) to establish maxillary sinus volume (MSV). The coefficient of variation used in the study allowed the biological variation between sexes to be observed.

RESULTS AND CONCLUSIONS

The sexual dimorphism of maxillary sinus parameters is variable and depends on the phase of ontogenesis. All investigated parameters of maxillary sinuses are larger in males at 2-3 years (except for the length, which is larger in females by the end of three years, between six and nine years and after 15 years). The sexual dimorphism is less evident during the first year of age, and the most evident between 15 and 16 years. During the first two years, females are dominant with all parameters being larger than in males. The maxillary sinus length is developmentally the most stable parameter of maxillary sinuses, because throughout the investigated ontogenesis, the sexual differences are very similar. The most evident sexual dimorphism is observed in the volume of the maxillary sinus.

Volumetric assessment of the dental crown for sex estimation by means of cone-beam computed tomography

Sex estimation has a vital role in the solution of forensic cases when the identification of a large number of victims is needed. Considering the sexual dimorphism of the human teeth, the objective of this study was to estimate human sex by means of cone beam computed tomography (CBCT)-based volumetric assessment of the dental crown. A total of 78 CBCT images of the upper central incisors, upper and lower canines, and lower lateral incisors were equally selected from a Brazilian population aged between 8 and 36 years old. The dental crowns were subjected to image-based volumetric assessment by manual segmentation using the 3D slicer software, and the outcomes were compared by the Mann-Whitney test, unpaired t-test, Pearson correlation test, conditional backward stepwise logistic regression and intraclass correlation coefficient (α=0.05). The volumetric accuracy of the upper central incisor, upper canine and lower canine for sex estimation were 64.1%, 74.4% and 79.5%, respectively. The combined analysis of the upper and lower canines allowed an average accuracy of 83.7%. In conclusion, the combined volumetric analysis of the crown of the upper and lower canines can be applied for sex estimation in the studied population.

CADOES: An interactive machine-learning approach for sex estimation with the pelvis

The pelvis is consistently regarded as the most sexually dimorphic region of the human skeleton, and methods for sex estimation with the pelvic bones are usually very accurate. In this investigation, population-specific osteometric models for the assessment of sex with the pelvis were designed using a dataset provided by J.A. Serra (1938) that included 256 individuals (131 females and 125 males) from the Coimbra Identified Skeletal Collection and 38 metric variables. The models for sex estimation were operationalized through an online application and decision support system, CADOES. Different classification algorithms generated high accuracy models, ranging from 85% to 92%, with only three variables; and from 85.33% to 97.33%, with all 38 variables. CADOES conveys a probabilistic prediction of skeletal sex, as well as a suite of attributes with educational applicability in the fields of human skeletal anatomy and statistics. This study upholds the value of the pelvis for the estimation of skeletal sex and provides models for that can be applied with high accuracy and low bias.

Evaluating macroscopic sex estimation methods using genetically sexed archaeological material: The medieval skeletal collection from St John's Divinity School, Cambridge

OBJECTIVES

In tests on known individuals macroscopic sex estimation has between 70% and 98% accuracy. However, materials used to create and test these methods are overwhelming modern. As sexual dimorphism is dependent on multiple factors, it is unclear whether macroscopic methods have similar success on earlier materials, which differ in lifestyle and nutrition. This research aims to assess the accuracy of commonly used traits by comparing macroscopic sex estimates to genetic sex in medieval English material.

MATERIALS AND METHODS

Sixty-six individuals from the 13th to 16th century Hospital of St John the Evangelist, Cambridge, were assessed. Genetic sex was determined using a shotgun approach. Eighteen skeletal traits were examined, and macroscopic sex estimates were derived from the os coxae, skull, and os coxae and skull combined. Each trait was tested for accuracy to explore sex estimates errors.

RESULTS

The combined estimate (97.7%) outperformed the os coxae only estimate (95.7%), which outperformed the skull only estimate (90.4%). Accuracy rates for individual traits varied: Phenice traits were most accurate, whereas supraorbital margins, frontal bossing, and gonial flaring were least accurate. The preauricular sulcus and arc compose showed a bias in accuracy between sexes.

DISCUSSION

Macroscopic sex estimates are accurate when applied to medieval material from Cambridge. However, low trait accuracy rates may relate to differences in dimorphism between the method derivative sample and the St John's collection. Given the sex bias, the preauricular sulcus, frontal bossing, and arc compose should be reconsidered as appropriate traits for sex estimation for this group.

Virtual reconstruction of the Upper Palaeolithic skull from Zlatý Kůň, Czech Republic: Sex assessment and morphological affinity

The incomplete cranium discovered at the Zlatý kůň site in the Bohemian Karst is a rare piece of skeletal evidence of human presence in Central Europe during the Late Glacial period. The relative position of cranial fragments was restored and missing parts of the cranium were virtually reconstructed using mirroring and the Thin-plate splines algorithm. The reconstruction allowed us to collect principal cranial measurements, revise a previous unfounded sex assignment and explore the specimen's morphological affinity. Visual assessment could not reliably provide a sexual diagnosis, as such methods have been developed on modern populations. Using a population-specific approach developed on cranial measurements collected from the literature on reliably sexed European Upper Palaeolithic specimens, linear discriminant analysis confirmed previous assignment to the female sex. However, caution is necessary with regard to the fact that it was assessed from the skull. The Zlatý kůň specimen clearly falls within the range of Upper Palaeolithic craniometric variation. Despite the shift in cranial variation that accompanied the Last Glacial Maximum (LGM), the Zlatý kůň skull exhibits a morphological affinity with the pre-LGM population. Several interpretations are proposed with regard to the complex population processes that occurred after the LGM in Europe.