Sex Estimation Methods Research Articles

A Semi-Automatic Method on a Small Italian Sample for Estimating Sex Based on the Shape of the Crown of the Maxillary Posterior Teeth

Teeth are known to be reliable substrates for human identification and are endowed with significant sexual dimorphism not only in the size but also in the shape of the crowns. In the preliminary phase of our study (already published in 2021), a novel sex estimation method based on dental morphometric geometric (GMA) analysis combined with the artificial neural network (ANN) was developed and validated on a single dental element (first upper premolar) with an accuracy rate of 80%. This study aims to experiment and validate the combination of GMA-ANN on the upper first and second left premolars and the upper left first molar to obtain a reliable classification model based on the sexual dimorphic traits of multiple maxillary teeth of Caucasian Italian adults (115 males and 115 females). A general procrustes superimposition (GPS) and principal component analysis (PCA) were performed to study the shape variance between the sexes and to reduce the data variations. The "set-aside" approach was used to validate the accuracy of the proposed ANN. As the main findings, the proposed method correctly classified 94% of females and 68% of males from the test sample and the overall accuracy gained was 82%, higher than the odontometric methods that similarly consider multiple teeth. The shape variation between male and female premolars represents the best dimorphic feature compared with the first upper molar. Future research could overcome some limitations by considering a larger sample of subjects and experimenting with the use of computer vision for automatic landmark positioning and should verify the present evidence in samples with different ancestry.

Sex, gender, and sexuality in paleopathology: Select current developments and pathways forward

ObjectiveOverall, paleopathology trails behind related fields in exploring sex, gender, and sexuality in past societies. Here, we interrogatively synthesize scholarship on topics not included in similar reviews, focusing on sex estimation methods, and considering the social determinants of health; trauma; reproduction and family; and childhood – to highlight novel, social epidemiology- and social theory-informed frameworks and interpretive devices. ConclusionsMany paleopathological interpretations focus on sex-gender differences relative to health, with increasing use of intersectionality. Others consistently project present-day ideologies about sex, gender, and sexuality (e.g., binary sex-gender systems) into paleopathological interpretations (i.e., presentism). SignificancePaleopathologists have an ethical imperative to generate scholarship that contributes to social justice initiatives focused on dismantling structural inequalities, especially relative to sex, gender, and sexuality (e.g., homophobia), such as through denaturalizing presentist binary systems. They also have a responsibility towards greater inclusivity relative to researcher identity and diversification of method and theory. LimitationsIn addition to material limitations complicating reconstructions of sex, gender, and sexuality relative to health and disease in the past, this review wasn’t comprehensive. The review was also limited by the relative paucity of paleopathological work on these topics.Suggestions for Future Research: The outlook for paleopathological research on sex, gender, and sexuality is, however, positive; paleopathology is well situated to tackle these aspects of social identity. Future work should consider critical, self-reflective movement away from presentism; more robust contextualization; and further engagement with social theory and social epidemiology theory and approaches, including the Developmental Origins of Health and Disease (DOHaD), social determinants of health, and intersectionality.

Accuracy comparison of tooth volume and mesiodistal diameter measurements for sex dimorphism based on cone-beam computed tomography: a study for the northern Chinese population.

Sex estimation based on teeth could help to narrow the scope for individual identification. According to the different teeth morphology among both genders, we plan to establish a sex estimation method for the northern Chinese population through mesiodistal diameter and teeth volume measurements and compare the accuracy of the two methods. In this study, measurements were taken from cone-beam computed tomography images collected from 142 males and 140 females aged 21-59years. The mesiodistal diameter and volume of the left canines and the first molars in both upper and lower jaws were measured and analyzed for suitable coefficients. We selected 80% samples as the training set to set up the logistic regression formulas and 20% as the test set to obtain accuracy. The accuracy of sex estimation by mesiodistal diameter can reach 87.50%, and the volume is up to 78.57%. The measurement of mesiodistal diameter is less time-consuming. This work established and tested a method to estimate sex for the northern Chinese population. Results showed that sex estimation based on the mesiodistal diameter of teeth has higher accuracy than the method based on teeth volume.

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.

Using 3D images of Korean's mastoid process to estimate sex: A metric study

• We validated a forensic anthropological sex estimation for the mastoid process in Koreans by 3DCT. • The volume of the mastoid process in males was greater than that in females. • Using mastoid process volumes in a metric method increased the accuracy of sex estimation by 20%. • Our metric methods for sex estimation are more applicable to skulls found in the Korea population. • This method helps to increase accuracy and reliability of sex estimation using Korean skulls. This study reports an approach for forensic anthropological sex estimation by examining the mastoid process in Koreans using three-dimensionally reconstructed computed tomography images of skulls. The purpose was to validate this metric sex estimation method using only the mastoid process in a Korean population compared to a non-metric sex estimation method derived from a previously used non-Korean method. In this study, 661 images were gathered and 100 of these were randomly set aside for use in the non-metric method. We then applied our metric analysis to the remaining 561 images. Our findings showed that the volume of the mastoid process in males was greater than that in females. As a result, using the mastoid process volume in a metric method increased the accuracy of sex estimation by 20% compared to that using the non-metric method. Our metric methods for sex estimation are more applicable to skulls found in Korea than to those from non-Korean populations, and the metric methods for sex estimation are more useful than non-metric methods. In future studies, it is necessary to derive new equations from measurements of the glabella, mental eminence, supraorbital margin, and nuchal crest for Korean skulls; this method contributes to increased accuracy and reliability of sex estimation using Korean skulls.

Employing deep learning for sex estimation of adult individuals using 2D images of the humerus

Biological profile estimation, of which sex estimation is a fundamental first stage, is a really important task in forensic human identification. Although there are a large number of methods that address this problem from different bone structures, mainly using the pelvis and the skull, it has been shown that the humerus presents significant sexual dimorphisms that can be used to estimate sex in their absence. However, these methods are often too subjective or costly, and the development of new methods that avoid these problems is one of the priorities in forensic anthropology research. In this respect, the use of artificial intelligence may allow to automate and reduce the subjectivity of biological profile estimation methods. In fact, artificial intelligence has been successfully applied in sex estimation tasks, but most of the previous work focuses on the analysis of the pelvis and the skull. More importantly, the humerus, which can be useful in some situations due to its resistance, has never been used in the development of an automatic sex estimation method. Therefore, this paper addresses the use of machine learning techniques to the task of image classification, focusing on the use of images of the distal epiphysis of the humerus to classify whether it belongs to a male or female individual. To address this, we have used a set of humerus photographs of 417 adult individuals of Mediterranean origin to validate and compare different approaches, using both deep learning and traditional feature extraction techniques. Our best model obtains an accuracy of 91.03% in test, correctly estimating the sex of 92.68% of the males and 89.19% of the females. These results are superior to the ones obtained by the state of the art and by a human expert, who has achieved an accuracy of 83.33% using a state-of-the-art method on the same data. In addition, the visualization of activation maps allows us to confirm not only that the neural network observes the sexual dimorphisms that have been proposed by the forensic anthropology literature, but also that it has been capable of finding a new region of interest.

Evaluating costal cartilage for sex and age estimation from PA chest radiographs of North Indian population: a retrospective study

BackgroundThis study is conducted to estimate age and sex from chest radiographs. The aim of this study was to determine (I) whether costal cartilage calcification pattern help in estimating sex in North Indian sample and (ii) whether there is any relation between age and costal cartilage calcification.ResultsThe statistical probability of estimating peripheral pattern in male was 99.3%, and for females, it was 100% for central type of calcification. The minimum age where lower costal calcification was present was 22-year-old female and 21 years old male. The degree of calcification and age showed positive correlation; similarly, the value of spearman’s rho showed significant result (for whole sample rs = 0.911, p < 0.01 (for male subjects, it was rs = 0.921, p < 0.01; for females, it was rs = 0.905, p < 0.01)).ConclusionsThe degree of calcification is useful in estimating age groups and becomes more determined with advancing age. Prediction of sex by using radiological method gives the advantages of simplicity, inexpensiveness, speed, and high accuracy. This method for age and sex estimation will play a useful role in screening test and in cases where the thoracic part of the body is found like dismembered body, putrefied dead remains, and unidentified bodies.

Cranial and Odontological Methods for Sex Estimation-A Scoping Review.

The estimation of sex from osteological and dental records has long been an interdisciplinary field of dentistry, forensic medicine and anthropology alike, as it concerns all the above mentioned specialties. The aim of this article is to review the current literature regarding methods used for sex estimation based on the skull and the teeth, covering articles published between January 2015 and July 2022. New methods and new approaches to old methods are constantly emerging in this field, therefore resulting in the need to summarize the large amount of data available. Morphometric, morphologic and biochemical analysis were reviewed in living populations, autopsy cases and archaeological records. The cranial and odontological sex estimation methods are highly population-specific and there is a great need for these methods to be applied to and verified on more populations. Except for DNA analysis, which has a prediction accuracy of 100%, there is no other single method that can achieve such accuracy in predicting sex from cranial or odontological records.

R Code: Meta-analysis of sex estimation method

R Code: Meta-analysis of sex estimation method

A Geometric Morphometric Study on Sexual Dimorphism in Viscerocranium.

Simple SummarySex estimation is a crucial step in the identification of unknown bone remains. The accuracy of sex estimation methods depends on the level of sexual dimorphism manifested by the human bones. Therefore, the evaluation of sex differences of particular bones of the skeleton is an important preceding stage. We have used geometric morphometric techniques to investigate the sexual dimorphism in the size and shape of the facial part of the skull and its subregions. Our results show that the facial skeleton in males and females differs more in size than in shape, so its overall size is a more useful sex indicator than its shape. The same result is observed for all facial subregions studied here. However, the best discrimination between the male and female skulls is achieved when both size and shape are considered together.The level of sexual dimorphism manifested by human bones is an important factor for development of effective sex estimation methods. The aim of the study was to investigate the sexual dimorphism in the size and shape of the viscerocranium using geometric morphometric techniques. It also aimed to explore the sex differences in distinct viscerocranial regions and to establish the most dimorphic region with regard to size and shape. Computed tomography images of 156 males and 184 females were used in the study. Three-dimensional coordinates of 31 landmarks were acquired. Five landmark configurations were constructed from the viscerocranium and its orbital, nasal, maxillary, and zygomatic region. Generalized Procrustes superimposition, principal component analysis, and discriminant analysis were applied to each configuration. The significance of the sex differences in size and shape was assessed and significant differences were found in all configurations. The highest accuracy was obtained from both shape and size of the whole viscerocranium. Based on size only, the highest accuracy was achieved by the nasal region. The accuracy based on shape was generally low for all configurations, but the highest result was attained by the orbital region. Hence, size is a better sex discriminator than shape.

Evaluating Morphological Methods for Sex Estimation on Isolated Human Skeletal Materials: Comparisons of Accuracies between German and South African Skeletal Collections

Objectives: The focus of this research is to evaluate the sex estimation methods on isolated human materials by applying morphological methods published in various forensic and anthropological literature on different skeletal series. Materials and Methods: 165 individuals from the 19th to 20th century Inden skeletal series, 252 individuals from the 13th to 14th century Lübeck skeletal series of German ancestry housed at the Department of Historical Anthropology and Human Ecology, the University of Göttingen, Germany, and 161 individuals from the 19th and 20th century of South African African ancestry housed within the Raymond A. Dart collection of modern human skeletons at the University of Witwatersrand, South Africa, with crania, mandibles, and pelves, were assessed. The evaluation criteria are burial information on the Inden series, genetic sex on both the Inden and the Lübeck series, and previous demography on cadavers from the South African African series. Results and Discussion: The sex estimation with cranial traits perform better in Inden and South Africa samples and worse in Lübeck sample. The mandible accuracies for pooled sexes are not exemplary, but the individual traits perform better for males in the Inden, Lübeck, and South Africa samples, except for gonion and angle, which performs better in females. The pelvic traits perform better in the Inden and South Africa samples compared to the Lübeck sample. The statistical tests show that there is a huge difference in the accuracy rates and the performance between both population groups from Germany itself, considering that Inden and Lübeck samples share the same ancestry. The accuracy rates improve with the exclusion of ambiguous individuals.

Sexual dimorphism in shape and size of the neurocranium.

Sex identification is a primary step in forensic analysis of skeletal remains. The accuracy of sex estimation methods greatly depends on the sexual dimorphism manifested by the target anatomical region. The study aims to evaluate the sexual dimorphism in shape and size of the neurocranium and to compare the potential of shape and size of different cranial regions to classify correctly the male and female crania. The study was carried out on computed tomography images of 373 Bulgarian adults (161 males and 212 females). Three-dimensional coordinates of 32 landmarks were acquired. The landmarks were arranged in 4 configurations: neurocranium, frontal bone, parietotemporal region, and occipital bone. For each configuration, the presence of significant sex differences in shape and size was tested. Principal component analysis (PCA) was applied to explore the shape variation. The classification power of size and shape was tested using discriminant analysis and k-means clustering. The neurocranium shows significant sex differences in shape and size. The parietotemporal region is the most dimorphic neurocranial part in size and the frontal bone is the most differing one in shape. The size of the parietotemporal region and frontal bone classifies correctly more than 80% of the crania. The discrimination ability based on shape is rather low as the highest values of about 70% are obtained for the frontal and occipital bone. The PCA plots show large overlapping of the male and female crania. It can be inferred that the sex-specific size differences in the neurocranium are more important than the shape differences.

Development of new odontometric method of sex estimation through lower canines in Portuguese and Mozambican populations

Development of new odontometric method of sex estimation through lower canines in Portuguese and Mozambican populations

EVALUATION OF ANTEGONIAL ANGLE, ANTEGONIAL DEPTH AND GONIAL ANGLE IN SEX PREDICTION IN THE TURKISH PEDIATRIC POPULATION OF THE EASTERN MEDITERRANEAN REGION

AIM: In this study, it was examined whether antegonial angle (AGA), antegonial depth (AGD), and gonial angle (GA) are associated with sex in a Turkish pediatric sample to be able to determine a reliable method for sex estimation in children. METHODS: The study was retrospectively carried out on panoramic radiographs previously taken for children’s dental treatments for different reasons. An oral and maxillofacial radiologist measured AGA, AGD, and GA on the right and left sides on panoramic radiographs, and their mean values were calculated. RESULTS: The mean age of 197 children was 11.5±1.28 years. The results revealed that AGA and AGD significantly differed between the children by sex. However, it was not the case for GA by sex. CONCLUSION: Overall, it was concluded that AGA and AGD can be used to estimate sex in the Turkish pediatric population from the Eastern Mediterranean region; nevertheless, GA is not reliable.

The Estimation of Sex of Human Skeletal Remains in the Portuguese Identified Collections: History and Prospects

The estimation of biological sex is of paramount significance for the identification of anonymous skeletal remains in contemporary medico-legal contexts or bioarcheological studies of past societies. Sex estimation techniques are usually affected by population-specific sexual dimorphism. As such, the need for distinctive standards for each population has long been acknowledged. This paper aims to document and critically address sex estimation methods that have been created, or tested, in Portuguese identified skeletal collections in a historically situated dimension. Moreover, the ever-changing landscape of forensic anthropology calls for a deep reflection about a plethora of issues regarding sex estimation in human remains, including the usage of medical imaging methods and innovative statistical approaches, the biological and social resignification of sex and gender, the problems arising from secular change, and the ethics involving the use of human skeletal collections within the discipline.

Repeatability of a morphoscopic sex estimation technique for the mental eminence on micro-focus X-ray computed tomography models

• Scoring the mental eminence trait on virtual 3D models is challenging. • A personal affinity for assessing virtual 3D models of bone may play a role. • Scores 1 and 5 were easier to score on virtual 3D models than intermediate expressions. • A more detailed definition of the mental eminence trait could be useful. Walker's sex estimation method is based on five morphoscopic features of the human skull. This study aimed at testing the repeatability of one of the five traits, the mental eminence, visually on three-dimensional (3D) models, compared to the traditional, tactile scoring approach on bone. The sample comprised 105 mandibles from the Pretoria Bone Collection and their respective virtual 3D models, obtained from micro-focus X-ray computed tomography (micro-XCT) scans. Four observers independently scored the bones first, followed by the virtual 3D modality. Intra- and interobserver errors (interOE and intraOE) were performed with Fleiss’ and Cohen's Kappa, respectively. We calculated the intermodality agreement per observer with Wilcoxon Signed-Rank tests. The intraOE was moderate on bone (κ=0.448) and substantial on 3D (κ=0.799), while the Fleiss’ Kappa test for the interOE resulted in slight agreement both on bone (κ=0.163) and 3D (κ=0.169) irrespective of level of experience. All Wilcoxon Signed-Rank test P -values were significant. The application of the morphoscopic sex estimation for the mental eminence to micro-XCTs could be a matter of personal affinity as the level of experience did not play a role in the results. The expression of the mental eminence trait being population-specific, the individual's population affinity should be considered when sex is estimated in South African skeletons. It remains unclear whether the slight agreement between observers is due to the unreliability of the trait for sex estimation or whether the modalities are not easily interchangeable.

Reconstruction of full femora from partial bone fragments for anthropological analyses using statistical shape modeling

ObjectivesDue to taphonomic processes such as burial, fire, or animal activity, bones are often found incomplete, which can pose problematic for establishing the biological profile of the deceased using anthropological methods. The aim of this study is to test the feasibility of using statistical shape modeling (SSM) to reconstruct full femora from simulated partial femora and determine the accuracy of the reconstruction. Moreover, we assess the accuracy of sex estimation and the degree of stature error added based on the reconstructed femur using different anthropological methods. MethodsA total of 42 (28 female, 14 female) 3D models of left femora extracted from computed tomography (CT) scans were used. We performed a leave-one-out cross-validation (LOOCV) where 41 bones were used to build the SSM and one bone was used for testing. This bone was cut in 1 cm steps proximally, distally and from both ends up to 10 cm, reconstructed using SSM, and tested using the methods established by Stewart and Purkait (2005), Trotter and Gleser (1952), as well as a method based on SSM.with landmarks being automatically identified. ResultsThe error induced by reconstructing the femur to the length measurements was low, which translated into useful stature estimations (single sided cuts up to 10 cm: 0.4–1.1%, double sided<2% for cuts shorter than 6 cm). Using Purkaits method for sex estimation on reconstructed bones looked promising as well (single sided: 90.5% when compared to applying Purkaits method on the original bone, double sided 78.6% (10 cm cut) to 97.6% (1–3 cm cuts)) Using SSM for sex classification looked promising as well (single sided cut: 81–85.7%, double sided cut: 59.5–85.3%) ConclusionSSM can be used to reconstruct fragmented femora. These reconstructions can be used for sex and stature estimations, at the cost of lower accuracy. Using SSM might give investigators an additional tool to gain information about the biological profile of a deceased in cases where the fragmentation of a femur does not allow for using other anthropological methods.

Exploring sexual dimorphism of human occipital and temporal bones through geometric morphometrics in an identified Western‐European sample

AbstractSex estimation is a paramount step of bioprofiling in both forensic anthropology and osteoarchaeology. When the pelvis is not optimally preserved, anthropologists commonly rely on the cranium to accurately estimate sex. Over the last decades, the geometric morphometric (GM) approach has been used to determine sexual dimorphism of the crania, in size and shape, overcoming some difficulties of traditional visual and metric methods. This article aims to investigate sexual dimorphism of the occipital and temporal region through GM analysis in a metapopulation of 50 Western‐European identified individuals. Statistical analyses were performed to compare centroid size and shape data between sexes through the examination of distinct functional modules. Regression and Procrustes ANOVA were used to examine allometric and asymmetrical implications. Discriminant functions, combining size and shape data, were established. Significant dimorphism in size was found, with males having larger crania, confirming the major influence size has on cranial morphology. Allometric relationships were found to be statistically significant in both right and left temporal bones while shape differences between sexes were only significant on the right temporal bone. The visualization of the mean consensus demonstrated that males displayed a larger mastoid process associated with a reduced mastoid triangle and less projected occipital condyles. This exploratory study confirms that GM analysis represents an effective way to quantitatively capture shape of dimorphic structures, even on complex rounded ones such as the mastoid region. Further examination in a larger sample would be valuable to design objective visualization tools that can improve morphoscopic sex estimation methods.

Qafzeh 9 Early Modern Human from Southwest Asia: age at death and sex estimation re-assessed.

Qafzeh 9 is an almost complete skeleton commonly employed as representative of the population of the eponymous site. However, its biological profile is still largely based on the age at death and sex estimation methods in use at the time of its discovery. Moreover, post-mortem damage to the skeleton has made difficult the observation of some morphoscopic features, particularly pelvic ones currently used in sex estimation. Here, we apply recent methods and paleoimaging to re-evaluate the biological profile of Qafzeh 9, taking into account post-mortem damage. The results suggest a young age at death, indicating that Qafzeh 9 died before reaching complete dental and bone maturity; they also support a male sex assignment.

Cognitive bias and the order of examination in forensic anthropological non-metric methods: a pilot study

ABSTRACT Research has established that contextual information has the potential to influence the decisions of examiners in various forensic domains, including forensic anthropology. Studies have demonstrated that the non-metric sex estimation methods are susceptible to issues of cognitive bias, however the different types of stimuli that can influence the decision-making process remain understudied. As forensic anthropologists will examine multiple skeletal elements to estimate the sex of skeletal remains, a pilot study was designed to assess the potential of cognitive bias resulting from the order of examination. Two groups performed a non-metric sex estimation of the innominates and the skull with methods from Standards on one individual complete skeleton. Group A examined the skull first followed by the innominates, while Group B examined the innominates first followed by the skull. Results reveal a significant difference between the two groups in the sex estimation of the innominates and the complete skeleton (p = 0.020 and p = 0.022, respectively). This research demonstrates that order of examination for sex estimation may act as context and potentially influence the subsequent analyses. Additional research is necessary to broaden the understanding of decision-making and aid in the establishment of standard operating procedures designed to mitigate the potential effects of cognitive bias.