Sex estimation from modern American humeri and femora, accounting for sample variance structure: SEX ESTIMATION FROM HUMERAL & FEMORAL DIMENSIONS

No Bones About It: Sex Is Binary

Anthropologists have led the way in formulating techniques that reveal skeletal differences between males and females. Understanding of physical differences in the pelvis related to childbirth, hormonal impacts on bones, and extensive comparative studies have provided anthropologists with an array of traits and measurements that help them estimate sex using just bones. Forensic anthropologists and bioarcheologists are improving their ability to differentiate males and females by increasing research on a variety of postcranial bones and through the use of molecular data, especially new methods called proteomics, to identify sex in prepubescent juveniles. As remains from more cultures and time periods are studied, sex identification will continue to improve, because skeletal sex differences are in large part biologically determined. Yet, anthropologists have also been at the forefront of arguing that sex lies on a spectrum. Anthropologists who view sex as on a spectrum may deter sex identification progress; from their perspective, an individual of an undetermined sex may just be a nonbinary individual. Anthropologists who consider sex is on a spectrum are coming to this conclusion in part because they are looking for anatomical ideals, mistaking pathology for variation, and confusing independent variables with dependent variables. Nonetheless, anthropologists need to continue to improve sex identification techniques to reconstruct the past accurately, which may reveal less strict sex roles than previously presumed and help with the identification of crime victims. Forensic anthropologists should also increase their efforts to identify whether individuals have undergone medical procedures intended to change one's gender due to the current rise in transitioning individuals.

Assigned sex estimation with the clavicle and scapula: A study in a Portuguese reference sample

The estimation of biological sex is a critical step in the assessment of the biological profile of an anonymous skeletonized individual. In certain recovery circumstances, the most dimorphic skeletal areas, such as the pelvis, are absent or fragmented; in that case, other bones of the skeleton, including the clavicle and scapula, can be used to predict sex. The purpose of this research is to generate new models for the estimation of sex with clavicular and scapular measurements using a study-sample of 129 individuals with clavicle (65 males and 64 females) and 112 individuals with scapula (50 males and 62 females) from the Lisbon Identified Skeletal Collection (Portugal). A decision tree classifier (C4.5) and logistic regression (LR) were employed to create univariable and multivariable sex prediction models. Accuracy under cross-validation of the classification models is high (up to 93.8%), with minimal bias (<5%), particularly in the multivariable models. The proposed LR models facilitate the probabilistic estimation of biological sex, accounting for the significant overlap in the expression of sexual dimorphism.

The effect of reference sample composition and size on dental age interval estimates

OBJECTIVES

Validation studies in juvenile dental age estimation primarily focus on point estimates while interval performance for reference samples of different ancestry group compositions has received minimal attention. We tested the effect of reference sample size and composition by sex and ancestry group on age interval estimates.

MATERIALS AND METHODS

The dataset consisted of Moorrees et al. dental scores from panoramic radiographs of 3334 London children of Bangladeshi and European ancestry and 2-23 years of age. Model stability was assessed using standard error of mean age-at-transition for univariate cumulative probit and sample size, group mixing (sex or ancestry), and staging system as factors. Age estimation performance was tested using molar reference samples of four sizes, stratified by year of age, sex, and ancestry. Age estimates were performed using Bayesian multivariate cumulative probit with 5-fold cross-validation.

RESULTS

Standard error increased with decreasing sample size but showed no effect from mixing by sex or ancestry. Estimating ages using a reference and target sample of different sex reduced success rate significantly. The same test by ancestry groups had a lesser effect. Small sample size (n < 20/year of age) negatively affected most performance metrics.

DISCUSSION

We found that reference sample size, followed by sex, primarily drove age estimation performance. Combining reference samples by ancestry produced equivalent or better estimates of age by all metrics than using a single-demographic reference of smaller size. We further proposed that population specificity is an alternative hypothesis of intergroup difference that has been erroneously treated as a null.

Machine learning and discriminant function analysis in the formulation of generic models for sex prediction using patella measurements

Sex prediction from bone measurements that display sexual dimorphism is one of the most important aspects of forensic anthropology. Some bones like the skull and pelvis display distinct morphological traits that are based on shape. These morphological traits which are sexually dimorphic across different population groups have been shown to provide an acceptably high degree of accuracy in the prediction of sex. A sample of 100 patella of Mixed Ancestry South Africans (MASA) was collected from the Dart collection. Six parameters: maximum height (maxh), maximum breadth (maxw), maximum thickness (maxt), the height of articular facet (haf), lateral articular facet breadth (lafb), and medial articular facet breath (mafb) were used in this study. Stepwise and direct discriminant function analyses were performed for measurements that exhibited significant differences between male and female mean measurements, and the "leave-one-out" approach was used for validation. Moreover, we have used eight classical machine learning techniques along with feature ranking techniques to identify the best feature combinations for sex prediction. A stacking machine learning technique was trained and validated to classify the sex of the subject. Here, we have used the top performing three ML classifiers as base learners and the predictions of these models were used as inputs to different machine learning classifiers as meta learners to make the final decision. The measurements of the patella of South Africans are sexually dimorphic and this observation is consistent with previous studies on the patella of different countries. The range of average accuracies obtained for pooled multivariate discriminant function equations is 81.9-84.2%, while the stacking ML technique provides 90.8% accuracy which compares well with those presented for previous studies in other parts of the world. In conclusion, the models proposed in this study from measurements of the patella of different population groups in South Africa are useful resent with reasonably high average accuracies.

Forensic Anthropology and Archaeology in Denmark

In this paper, we provide a brief overview of the status of forensic anthropology and forensic archeology in Denmark, as well as related information about education, research, and skeletal collections. Forensic anthropologists mainly deal with the examination of unidentified skeletal remains. Some special tasks include cranial trauma analysis of the recently deceased, advanced 3D visualization from CT scanning of homicide cases, and stature estimation of perpetrators using surveillance videos. Forensic anthropologists are employed at one of Denmark’s three departments of forensic medicine (in Copenhagen, Odense, and Aarhus) and have access to advanced imaging equipment (e.g., CT and MR scanning, surface scanners, and 3D printers) for use in both their requisitioned work and their research. Extensive research is conducted on different topics, such as the health and diseases of past populations, age estimation, and human morphology. Research is based on skeletal material from the archeological collections housed in Copenhagen and Odense or on CT data from the recently deceased. There is no full degree in forensic anthropology in Denmark, but elective courses and lectures are offered to students at different levels and to people from different professional backgrounds.

Forensic archaeology is a relatively new field of expertise in Denmark, and relevant cases are rare, with only one or two cases per year. No forensic archeologists are officially employed in any of the departments of forensic medicine. Until recently, the Special Crime Unit of the police handled crime scene investigations involving excavations, but with the option of enlisting the help of outside specialists, such as archaeologists, anthropologists, and pathologists. An official excavation work group was established in 2015 under the lead of the Special Crime Unit of the police with the aim of refining the methods and procedures used in relevant criminal investigations. The group is represented by five police officers from the Special Crime Scene Unit, a police officer from the National Police Dog Training center, the two archaeologists from Moesgaard Museum, a forensic anthropologist from the Department of Forensic Medicine (University of Copenhagen), and a forensic pathologist from the Department of Forensic Medicine (University of Aarhus).

Paleodemography: From archaeology and skeletal age estimation to life in the past

Much of paleodemography, an interdisciplinary field with strong ties to archaeology, among other disciplines, is oriented toward clarifying the life experiences of past people and why they changed over time. We focus on how human skeletons contribute to our understanding of preindustrial demographic regimes, including when changes took place that led to the world as we know it today. Problems with existing paleodemographic practices are highlighted, as are promising directions for future work. The latter requires both better age estimates and innovative methods to handle data appropriately. Age-at-death estimates for adult skeletons are a particular problem, especially for adults over 50 years that undoubtedly are mistakenly underrepresented in published studies of archaeological skeletons. Better age estimates for the entirety of the lifespan are essential to generate realistic distributions of age at death. There are currently encouraging signs that after about a half-century of intensive, and sometimes contentious, research, paleodemography is poised to contribute much to understandings of evolutionary processes, the structure of past populations, and human-disease interaction, among other topics.

A paleodemographic assessment of mortality and fertility rates during the second demographic transition in rural central Indiana

OBJECTIVES

Since its inception, skeletally based paleodemographic research has emphasized the utility of biocultural models for interpreting the dynamic relationship between the sociocultural and ecological forces accompanying demographic transitions and shaping populations' health and well-being. While the demographic transition associated with the Neolithic Revolution has been a common focus in bioarcheology, the present study analyzes human skeletal remains from a large 19th century cemetery in central Indiana to examine population dynamics during the second demographic transition, a period generally characterized by decreasing fertility rates and improvements in life expectancy. This study demonstrates the potential to methodologically identify regional variations in the timing and interactions between broad-scale socioeconomic changes and technological advancements that characterized the time period through observed changes in survivorship and fertility based on age-at-death distributions.

MATERIALS AND METHODS

This study uses three temporally distinct samples (AD 1827-1869; 1870-1889; 1890-1935) from the Bethel Cemetery (n = 503). Kaplan-Meier survival analyses with a log- rank tests are utilized to evaluate survivorship and mortality over time. Next, Cox proportional hazard analyses are employed to examine the interaction between sex and time as covariates. Finally, the D0-14/D ratio is applied to estimate fertility for each of the three temporally bounded cohorts.

RESULTS

The Kaplan-Meier survival analyses and Cox proportional hazard modeling revealed statistically significant differences in survivorship between the three time periods. Age-specific mortality rates are reduced among adult female and male age classes in this rural community over the course of the 19th and early 20th centuries, resulting in the increasing life expectancies associated with the second demographic transition. While mortality in early adulthood was common during the first time period and decreases thereafter, sex was not identified as a meaningful covariate. The proportion of juveniles in the three temporal samples indicate that fertility rates were higher than national averages for the better part of the 19th century and subsequently declined around the turn of 20th century for this community.

CONCLUSIONS

The results indicate temporal differences between the three periods, demonstrating increased survivorship and decreased mortality and fertility over time. These findings corroborate two key features of the second demographic transition characterized by the move from high rates of both fertility and mortality to reduced rates and a general easing of demographic pressures. The observed trends likely reflect improvements in health, coinciding the industrial advance and economic development within and around Indianapolis. While the socioeconomic factors characterizing the Industrial Revolution drove demographic shifts that parallel an equally important epidemiological transition, potential regional differences are discussed to highlight variability in the timing of demographic transitions. The paleodemographic methods utilized in this study demonstrate improved accuracy and efficacy, which ultimately advances researchers' potential to disentangle population-specific socioeconomic factors that may contribute to asymmetrical experiences of health and mortality.

Estimation of sex based on postcranial elements in European American and Latin American populations

This study assesses the use of postcranial elements for sex estimation taking population variability into account. European American and Latin American populations are independently analyzed. Nine measurements from postcranial elements were collected from 72 European American individuals, and 59 Latin American individuals. Statistical analyses were performed using the Statistical Package for Social Science (SPSS) version 15. Statistical analyses were conducted to corroborate that there were no intra- or interobserver errors. In both populations, significant differences were found on all measured traits between males and females, except Scapular Breadth in Latin Americans. According to Discriminant Function Analysis (DFA) in the European American population the Ulna Minimum Breadth of the Olecranon (UMBO) correctly classified 91.3% of individuals. When this parameter was combined with the Diameter of Humeral Head (HHD), the two correctly classified 98% of individuals. In Latin Americans, the UMBO correctly classified 82.4% of the individuals. When combined with HHD, the measurements correctly classified 79.4% individuals. UMBO is the most useful trait to correctly assign the sex of the remains in both populations. Including the HHD improved accuracy rates in the European American sample. These results are in agreement with previous studies, which named the humerus as one of the potentially useful bones to consider for sex estimation based on its accuracy. Thus, these two anatomical regions could be used alone or in combination with other methodologies for sex estimation, which is particularly important in situations of fragmentary remains and incomplete skeletons.

Estimation of sex based on patella measurements in a contemporary Chinese population using multidetector computed tomography: An automatic measurement method

Sex estimation is an important part of creating a biological profile, and ultimately assisting in creating a presumptive identification of unidentified skeletal remains. However, manual methods of anthropometric are time-consuming and prone to observer variability. The present study is an attempt to estimation of sex from automatic measurement of patella by multidetector computed tomography (MDCT) in a contemporary Chinese population. Four measurements for every patella, including maximum height (MAXH), maximum breadth (MAXB), maximum thickness (MAXT) and patellar volume (PV), were automatically provided by the software from CT image of 300 Chinese. The sample is composed of 156 males and 144 females with an average age of 41.44 and 45.68 years, respectively. The statistical analyses showed that all variables were sexually dimorphic. Receiver operating characteristic (ROC) analysis was performed to estimate sex from patella. The univariate analysis of each patellar parameter yielded a sex classification accuracy rate of 73.1% to 85.7%. The classification accuracy rates of sex estimation using the combination of the patellar parameters are 81.9% to 91.6%. This paper provides indications that the patella is important bone for sex estimation and it may be used as an alternative in forensic cases when the skull and pelvis are unavailable.

Determining gender by taking measurements from magnetic resonance images of the patella

BACKGROUND

A key step in making a positive identification in forensic medicine is the establishment of a biological profile, which involves determining factors such as gender, age, ancestry, and stature. The goal of this study was to determine if gender could be established by taking various measurements of the patella taken from magnetic resonance imaging (MRI) images and analyzing the variations by gender.

METHODS

The sample group consisted of 220 patients (110 male and 110 female) whose patella were measured using MRI images of their left knee. Reasons for exclusion were any previous surgery, patella bipartite variation, any fracture in the patella due to trauma or findings of mass or infection. Three measurements - transverse length (TP), craniocaudal length (CC) and anteroposterior length (APP) - were taken off T2-weighted axial and sagittal MRI scans. The program SPSS (Version 21.0) was used to make a descriptive analysis, independent t-test and discriminative analysis.

RESULTS

It was found possible to determine gender with an accuracy rate of 91% for females and 87% for males. Since measurements were made individually the accuracy for gender estimation is lower than that seen in other methods.

CONCLUSION

The findings are important in that they show that it is possible to determine gender with a high degree of accuracy using just a few measurements taken from the patella.

Dimensions around the nutrient foramina of the tibia and fibula in the estimation of sex

Sex estimation from skeletal remains is one of the key components in establishing a biological profile and consequent identification of an individual in a forensic and medico-legal practice. The use of dimensions around the nutrient foramen in instances where long bones may be fragmented and damaged is of benefit due to the fact that the nutrient foramen is easily identifiable and may be preserved on the shaft of long bones. This study is an investigation of the usefulness of various measurements around the nutrient foramen of the tibia and fibula of South Africans in an attempt to develop osteometric standards for sex estimation. The sample included 206 tibiae and 204 fibulae of South African Africans (SAA) and South African whites (SAW) procured from the Raymond A. Dart Collection of Human Skeletons based at the University of the Witwatersrand. Sex was correctly classified for the tibia with an accuracy ranging between 79-82% in SAA and 84-88% in SAW, with the circumference at the level of the nutrient foramen as the single best predictor of sex in both populations. An accuracy ranging from 69 to 74% in SAA and 70-77% in SAW was observed for the combined measurements on the fibula. The current study confirms the usefulness of measurements around the nutrient foramen of the tibia in the assignment of sex. However functions of the fibula generally performed poorly and should be used with caution.