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One of the four pillars of the anthropological protocol is the estimation of sex. The protocol generally consists of linear metric analysis or visually assessing individual skeletal traits on the skull and pelvis based on an ordinal scale of 1–5, ranging from very masculine to very feminine. The morphologic traits are then some how averaged by the investigator to estimate sex. Some skulls may be misclassified because of apparent morphologic features that appear more or less robust due to size differences among individuals. The question of misclassification may be further exemplified in light of comparisons across populations that may differ not only in cranial robusticity but also in stature and general physique. The purpose of this study is to further examine the effect of size and sex on craniofacial shape among American populations to better understand the allometric foundation of skeletal traits currently used for sex estimation. Three-dimensional coordinates of 16 standard craniofacial landmarks were collected using a Microscribe-3DX digitizer. Data were collected for 118 American White and Black males and females from the W.M. Bass Donated Collection and the Forensic Data Bank. The MANCOVA procedure tested shape differences as a function of sex and size. Sex had a significant influence on shape for both American Whites ( F = 2.90; d.f. = 19, 39; p > F = 0.0024) and Blacks ( F = 2.81; d.f. = 19, 37; p > F = 0.0035), whereas size did not have a significant influence on shape in either Whites ( F = 1.69; d.f. = 19, 39; p > F = 0.08) or Blacks ( F = 1.09; d.f. = 19, 37; p > F = 0.40). Therefore, for each sex, individuals of various sizes were statistically the same shape. In other words, while significant differences were present between the size of males and females (males on average were larger), there was no size effect beyond that accounted for by sex differences in size. Moreover, the consistency between American groups is interesting as it suggests that population differences in sexual dimorphism may result more from human variation in size than allometric variation in craniofacial morphology. [ABSTRACT FROM AUTHOR]

This study tests for differences in articular and diaphyseal size and shape of the distal femur and proximal tibia between normal weight and obese individuals, and discusses the effects of obesity on the patterns of sexual dimorphism and secular change in the skeletal morphology of the knee. Measurements of the femur and tibia were recorded for 143 American White adult males and females born in the 20th century. The sample was divided into normal and obese weight categories based on the body mass index. Results show differences between normal weight and obese individuals in the size and shape of the femoral shaft and the medial side of the knee joint, none of which affect the pattern of sexual dimorphism. While changes in skeletal morphology associated with obesity may be observed in recent secular changes, its role is still unclear because of the relatively recent increase in obesity prevalence. [ABSTRACT FROM AUTHOR]

This study examines spheno-occipital synchondrosis fusion in the modern American population and presents age ranges for forensic use. The sample includes 162 modern individuals aged 5-25 years. The basilar synchondrosis was scored as open, closing, or closed via direct inspection of the ectocranial site of the suture. Transition analysis was used to determine the average ages at which an individual transitions from unfused to fusing and from fusing to fused. The maximum likelihood estimates from the transition analysis indicate that females are most likely to transition from open to closing at 11.4 years and males at 16.5 years. Females transition from closing to closed at 13.7 years and males at 17.4 years. The probability distributions associated with these maximum likelihood estimates were used to derive age ranges for age estimation purposes. These results reflect sexual dimorphism in basilar synchondrosis fusion and agree approximately with average age at pubertal onset. [ABSTRACT FROM AUTHOR]

Anterior zygomatic projection (ZP) is historically referenced as a useful trait in ancestry estimation, particularly when differentiating between Native Americans and U.S. Whites and Blacks. However, methods of assessing ZP vary, are susceptible to multiple interpretations, and have not been quantitatively validated. This study uses 228 3D surface scans of U.S. Whites, U.S. Blacks, and Native Americans to quantitatively test the ZP methods published by Rhine in 1990 (Skeletal attribution of race: methods for forensic anthropology, Albuquerque, NM, Maxwell Museum of Anthropology, 1990) and Bass in 1995 (Human osteology: a laboratory and field manual, Columbia, MO: Missouri Archaeological Society, 1995). Two ZP angles and two distances, representing method interpretations, were collected and analyzed via ANOVA and discriminant function analyses. Although significant ancestry differences were found across all variables, only the Bass inferior zygomatic distance successfully differentiated the pooled Native American group from pooled U.S. Whites/Blacks (73.7% correct). Arctic Native Americans, displaying the most projecting zygomas, are driving group differences. Significant overlap in measurement distributions were observed between groups in all variables, indicating limited forensic utility., (© 2019 American Academy of Forensic Sciences.)

Current techniques used by forensic anthropologists for the identification of unknown human skeletal remains have largely been created using U.S. Black and White samples. When applied to Hispanics, these techniques perform poorly and can lead to misclassifications; consequently, there is an imperative need for population-specific standards for Hispanics. This research examines the classification accuracies obtained by the original Walker (Am J Phys Anthropol, 136, 2008) and Klales et al. (Am J Phys Anthropol, 149, 2012) methods for nonmetric sex estimation and provides recalibrated regression equations specifically for Hispanics. Ordinal data were collected for five skull and three pelvic traits from a sample of 54 modern Hispanic individuals. Recalibration of the Klales et al. equation improved accuracy (90.3% vs. 94.1%), while recalibration of the Walker method equation decreased accuracy (81.5% vs. 74.1%), but greatly improved sex bias (22.2% vs. −7.4%), thereby making the recalibrated equations more appropriate for use with Hispanics. [ABSTRACT FROM AUTHOR]

Ancestry estimation methods using macromorphoscopic (MMS) traits commonly focus exclusively on cranial morphology. The objective of this study was to demonstrate the value of postcranial MMS traits, highlighting a combined cranial/postcranial trait approach to ancestry estimation using quadratic discriminant function and a variety of machine learning classification models including artificial neural networks (aNN), random forest models, and support vector machine. Eight cranial and eleven postcranial MMS traits were collected from the Terry and Bass Skeletal Collections (American Black = 81; American White = 173). Our classification models using cranial and postcranial traits correctly classified 88-92% of the sample, improving classification accuracies by nearly fifteen percent over models relying exclusively on cranial data. These same results demonstrate the importance of a multivariate statistical framework incorporating cranial and postcranial data and the nearly unlimited potential of machine learning models to improve the accuracy of ancestry estimates over traditional methods of analysis. To facilitate implementation in casework, one of the more robust models (aNN) is incorporated into a web-based application, ComboMaMD Analytical, to facilitate cranial and postcranial MMS traits analysis for ancestry estimation., (© 2019 American Academy of Forensic Sciences.)

Population-specific reference data are necessary for sex estimation in forensic anthropological practice. Currently, there are no population-specific data for Hispanics equivalent to data available for American Blacks and Whites. Individuals of Mexican origin represent the largest group of Hispanics in the United States (Spradley and Jantz. 2011. J Forensic Sci;56:289). This paper presents new population-specific sex estimation criteria for postcranial measurements for Mexican Hispanics. Metric data come from positively identified border-crossing fatalities at the Pima County Office of the Medical Examiner and documented cemetery collections curated at Universidad Nacional Autónoma de México and Universidad Autónoma de Yucatán. Stepwise variable selection procedures and discriminant function analyses were utilized to generate classification functions for postcrania. Sectioning points were also created for select measurements. Both the cross-validated classification rates and sectioning points achieved accuracy rates as high as 95% and 92%, respectively. These new criteria will improve sex estimation for US Mexico border crossers and Hispanics in the US. [ABSTRACT FROM AUTHOR]

When forensic anthropologists estimate the sex of Hispanic skeletal remains using nonpopulation specific metric methods, initial observations cause males to frequently misclassify as female. To help improve these methods, this research uses postcranial measurements from United States- Mexico border migrant fatalities at the Pima County Office of the Medical Examiner in Tucson, Arizona, as well as Hispanic individuals from the Forensic Anthropology Data Bank. Using a total of 114 males and 28 females, sectioning points and discriminant functions provide classification rates as high as 89.43% for Hispanic individuals. A test sample assessed the reliability of these techniques resulting in accuracy up to 99.65%. The clavicle maximum length measurement provides the best univariate estimate of sex, while the radius provides the best multivariate estimated of sex. The results of this research highlight the need for population specific data in the creation of a biological profile, especially when working with individuals considered Hispanic. [ABSTRACT FROM AUTHOR]

Examination of the adult os coxae and sacrum is one of the most common methods of sex estimation from bone. Medical imaging, such as computed tomography (CT), provides the opportunity for three-dimensional (3D) imaging of the skeleton from clinical scans of known individuals in situ. In this study, a randomly selected subset of abdominopelvic CT-derived models were used to evaluate simple, repeatable metric methods of sex estimation based on a combination of obstetric measurements and the traditionally nonmetric Phenice-derived traits. A four-variable discriminant function for sex estimation was developed based on statistical analyses. Overall, the cross-validated accuracy of this method was 100%, with inter-observer error showing an average of only 2.2%. Comparative analysis was run on the data set using FORDISC 3.0. This study shows that current sex determination standards from the pelvis should be updated to include more in vivo data to increase the accuracy of identification. [ABSTRACT FROM AUTHOR]

Forensic science is a fundamental transitional justice issue as it is imperative for providing physical evidence of crimes committed and a framework for interpreting evidence and prosecuting violations to International Humanitarian Law (IHL). The evaluation of evidence presented in IHL trials and the outcomes various rulings by such courts have in regard to the accuracy or validity of methods applied in future investigations is necessary to ensure scientific quality. Accounting for biological and statistical variation in the methods applied across populations and the ways in which such evidence is used in varying judicial systems is important because of the increasing amount of international forensic casework being done globally. Population variation or the perceived effect of such variation on the accuracy and reliability of methods is important as it may alter trial outcomes, and debates about the scientific basis for human variation are now making their way into international courtrooms. Anthropological data on population size (i.e., the minimum number of individuals in a grave), demographic structure (i.e., the age and sex distribution of victims), individual methods applied for identification, and general methods of excavation and trauma analysis have provided key evidence in cases of IHL. More generally, the question of population variation and the applicability of demographic methods for estimating individual and population variables is important for American and International casework in the face of regional population variation, immigrant populations, ethnic diversity, and secular changes. The reliability of various skeletal aging methods has been questioned in trials prosecuted by the International Criminal Tribunal for the Former Yugoslavia (ICTY) in The Prosecutor of the Tribunal against Radislav Krstiċ (Case No. IT-98-33, Trial Judgment) and again in the currently ongoing trial of The Prosecutor of the Tribunal against Zdravko Tolimir, Radivolje Miletiċ, Milan Gvero, Vinko Pandureviċ, Ljubisa Beara, Vujadin Popoviċ, Drago Nikoliċ, Milorad Trbiċ, Ljubomir Borovcanin (IT-05-88-PT, Second Amended Indictment). Following the trial of General Krstiċ, a collaborative research project was developed between the Forensic Anthropology Center at The University of Tennessee (UT) and the United Nations, International Criminal Tribunal for the Former Yugoslavia, Office of the Prosecutor (ICTY). The purpose of that collaboration was to investigate methods used for the demographic analysis of forensic evidence and where appropriate to recalibrate methods for individual estimation of age, sex, and stature for specific use in the regions of the former Yugoslavia. The question of “local standards” and challenges to the reliability of current anthropological methods for biological profiling in international trials of IHL, as well as the performance of such methods to meet the evidentiary standards used by international tribunals is investigated. Anthropological methods for estimating demographic parameters are reviewed. An overview of the ICTY-UT collaboration for research aimed at addressing specific legal issues is discussed and sample reliability for Balkan aging research is tested. The methods currently used throughout the Balkans are discussed and estimated demographic parameters obtained through medico-legal death investigations are compared with identified cases. Based on this investigation, recommendations for improving international protocols for evidence collection, presentation, and research are outlined. [ABSTRACT FROM AUTHOR]

Femur subtrochanteric size and shape can be used to differentiate between adult Native Americans and American Blacks and Whites, but little is known about when shape differences are established during growth and development. Ontological changes in subtrochanteric shape were examined using 74 Native American and 61 American Black/White subadult femora. At birth, the proximal femur diaphysis is relatively circular in both groups. Between birth and 5 years, the diaphysis becomes more mediolaterally broad, especially in Native Americans, due to differential growth between the mediolateral and anteroposterior planes. This change may be due to biomechanical stresses associated with developing a mature gait pattern. After the age of 5, growth occurs more equally in the two planes and shape does not change significantly. The adult shape of the proximal femur is established by c. 5 years of age and can be used to discriminate between Native American and American Black/White femora in older subadults. [ABSTRACT FROM AUTHOR]

Clavicles from 1289 individuals from cohorts spanning the 20th century were scored with two scoring systems. Transition analysis and Bayesian statistics were used to obtain robust age ranges that are less sensitive to the effects of age mimicry and developmental outliers than age ranges obtained using a percentile approach. Observer error tests showed that a simple three-phase scoring system proved the least subjective, while retaining accuracy levels. Additionally, significant sexual dimorphism was detected in the onset of fusion, with women commencing fusion at least a year earlier than men (women transition to fusion at approximately 15 years of age and men at 16 years). Significant secular trends were apparent in the onset of skeletal maturation, with modern Americans transitioning to fusion approximately 4 years earlier than early 20th century Americans and 3.5 years earlier than Korean War era Americans. These results underscore the importance of using modern standards to estimate age in modern individuals.