Sex assessment from carpals bones: discriminant function analysis in a contemporary Mexican sample

Sex assessment is one of the first essential steps in human identification, in both medico-legal cases and bio-archaeological contexts. Fragmentary human remains compromised by different types of burial or physical insults may frustrate the use of the traditional sex estimation methods, such as the analysis of the skull and pelvis. Currently, the application of discriminant functions to sex unidentified skeletal remains is steadily increasing. However, several studies have demonstrated that, due to variation in size and patterns of sexual dimorphism, discriminant functions are population-specific. In this study, in order to improve sex assessment from skeletal remains and to establish population-specific discriminant functions, the diagnostic values of the carpal bones were considered. A sample of 136 individuals (78 males, 58 females) of known sex and age was analyzed. They belong to a contemporary identified collection from the Laboratory of Physical Anthropology, Faculty of Medicine, UNAM (Universidad Nacional Autónoma de México, Mexico City). The age of the individuals ranged between 25 and 85 years. Between four and nine measurements of each carpal bone were taken. Independent t-tests confirm that all carpals are sexually dimorphic. Univariate measurements produce accuracy levels that range from 61.8% to 90.8%. Classification accuracies ranged between 81.3% and 92.3% in the multivariate stepwise discriminant analysis. In addition, intra- and inter-observer error tests were performed. These indicated that replication of measurements was satisfactory for the same observer over time and between observers. These results suggest that carpal bones can be used for assessing sex in both forensic and bio-archaeological identification procedures and that bone dimensions are population specific.     

Discriminant function analysis for sex assessment in pelvic girdle bones: sample from the contemporary Mexican population

Sex assessment of skeletal remains plays an important role in forensic anthropology. The pelvic bones are the most studied part of the postcranial skeleton for the assessment of sex. It is evident that a population-specific approach improves rates of accuracy within the group. The present study proposes a discriminant function method for the sex assessment of skeletal remains from a contemporary Mexican population. A total of 146 adult human pelvic bones (61 females and 85 males) from the skeletal series pertaining to the National Autonomous University of Mexico were evaluated. Twenty-four direct metrical parameters of coxal and sacral bones were measured and subsequently, sides and sex differences were evaluated, applying a stepwise discriminant function analysis. Coxal and sacra functions achieved accuracies of 99% and 87%, respectively. These analyses follow a population-specific approach; nevertheless, we consider that our results are applicable to any other Hispanic samples for purposes of forensic human identification.     

Metric determination of sex from the humerus in a Guatemalan forensic sample

The absence of population-specific standards for sex, age and stature estimation for rural Guatemala is problematic for the forensic analysis of skeletal remains recovered from clandestine graves attributed to the recent armed conflict in that country. In order to increase the reliability of the forensic analyses being undertaken in Guatemala, standards for metric determination of sex were developed. Data was collected on several bones; the results for the humerus are presented here. A sample of 118 complete humeri (68 male and 50 female) was studied; maximum length, maximum diameter of the head, circumference at midshaft, maximum diameter at midshaft, minimum diameter at midshaft and epicondylar breadth were measured and subjected to discriminant function analysis. The classification accuracies for the univariate functions range from 76.8% for the maximum diameter at midshaft to 95.5% for the maximum diameter of the head. The classification accuracy for the stepwise procedure was 98.2%.     

The acetabulum: sex assessment of prehistoric New Zealand Polynesian innominates

With increasing urban development in New Zealand, prehistoric Polynesian skeletal remains are frequently being recovered. Since such material must often be reinterred quickly, it has become important that the sex of individuals be determined from the remains in a relatively short time. For this purpose, discriminant function analysis was utilised for sex determination of prehistoric adult New Zealand Polynesian innominates (21 male and 35 female). Maximum diameter of the acetabulum was measured and subjected to SPSS direct discriminant function analysis. Accuracy of sex determination ranged from 85.2% to 86.2%. Reduction in error over random assignment by sex ranged from 70% to 72%. The two discriminant functions derived will provide a useful tool for the assessment of human remains in the forensic and archaeological context because they incorporate a single measurement which can be taken on incomplete bones.     

Articular surfaces of the pectoral girdle: sex assessment of prehistoric New Zealand Polynesian skeletal remains

Prehistoric Polynesian skeletal remains are frequently being recovered in New Zealand due to the increasing pace of urbanisation. Since such material must often be reinterred quickly, it is important that the sex of individuals be determined from the remains in a relatively short time. For this purpose, discriminant function analysis was utilised for sex determination of prehistoric adult New Zealand Polynesian clavicles (31 male and 31 female) and scapulae (33 male and 38 female). Diameters of the acromial and sternal ends of the clavicle and the height and breadth of the scapular glenoid cavity were measured and subjected to Statistical Package for the Social Sciences (SPSS) direct discriminant function analysis. For the single discriminant function derived, accuracy of sex determination was 97.7% and reduction in error over random assignment by sex was 95%. This discriminant function will be a useful tool in the assessment of human remains in the forensic and archaeological context because it incorporates measurements which can be taken on incomplete bones.     

Development of discriminant functions to estimate sex in upper limb bones for mixed ancestry South Africans

South Africa has one of the highest murder rates in the world, which is associated with an increasing number of unidentified individuals. Forensic anthropologists can assist in these cases to reduce the number of potential victims the remains may belong to. Sex estimation potentially decreases the number of possible victims by half. The mixed ancestry population in South Africa is the second largest group of people; however, there remains a paucity of data and population-specific methods for sex estimation in this group. The aim of this study was to assess the potential for metrices obtained around the nutrient foramen and the maximum length of upper limb long bones to estimate sex in mixed ancestry South Africans using discriminant function analysis. A total of 328 humeri, radii and ulnae from individuals of mixed ancestry were analysed. Sex was correctly classified with an average classification accuracy of 84.3% in the humeri, 88.3% for radii and 83.5% for the ulnae. Total length was the single best predictor of sex; the combination of total length with dimensions related to the nutrient foramen produced high classification accuracies in the current study. Overall, sexual dimorphism was observed in mixed ancestry South Africans upper limb long bones. The findings of this study further emphasise the need for population-specific standards of sexing in an attempt to improve current methods of forensic identification of descendants.     

Sexual Dimorphism in the 7th Cervical and 12th Thoracic Vertebrae from a Mediterranean Population

Sex determination is an important task in physical anthropology and forensic medicine. The study sample comprised 121 individuals of known sex, age, and cause of death from San Jose cemetery in Granada (Spain). Eight dimensions were analyzed, and discriminant function analysis was performed for each vertebra to obtain discriminating functions and study the percentage of correct assignations of these functions. The percentage accuracy was approximately 80% for both vertebrae, but varied according to the sex, being higher for the 7th cervical in males and higher for the 12th thoracic in females. As reported in other populations, the greatest dimorphism values were found for the length of the inferior surface of the vertebral body and the width and length of the vertebral foramen of the 7th cervical vertebra and for the length of the inferior surface of the vertebral body of the 12th thoracic vertebra.     

The reliability of forensic osteology--a case in point. Case study

The medico-legal investigation of skeletons is a trans-disciplinary effort by forensic scientists as well as physical anthropologists. The advent of DNA extraction and amplification from bones and teeth has led to the assumption that morphological assessment of skeletal remains might soon become obsolete. But despite the introduction and success of molecular biology, the analysis of skeletal biology will remain an integral part of the identification process. This is due to the fact, that the skeletal record allows relatively fast and accurate inferences about the identity of the victim. Moreover, a standard biological profile may be established to effectively narrow the police investigator's search parameters. The following study demonstrates how skeletal biology may collaborate in the forensic investigation and support DNA fingerprinting evidence.In this case, the information gained from standard morphological methods about the unknown person's sex, age and heritage immediately led the police to suspect, that the remains were that of a young man from Vietnam, who had been missing for 2.5 years. The investigation then quickly shifted to prove the victim's identity via DNA extraction and mtDNA sequence analysis and biostatistical calculations involving questions of kinship [4].     

Sex Determination Using the Second Cervical Vertebra—A Test of the Method*

Abstract: Sex is one of the critical questions addressed when unidentified skeletal remains are discovered in forensic or archeological contexts. Continuous testing and re‐evaluation of existing techniques is essential to improve accuracy and precision. The Wescott (J Forensic Sci 2000; 45 (2):462–6) method of sex determination from dimensions of the second cervical vertebra was blind‐tested on 153 adult individuals from the Spitalfields documented collection of human skeletal remains held at the Natural History Museum, London. Significant sex differences were determined for all dimensions measured (independent two‐sample t‐test, p < 0.05–0.001). The discriminant functions developed by Wescott were shown to have an overall accuracy of classification of 76.99%. Using stepwise discriminant analysis, a discriminant function based on the Spitalfields data correctly classified sex in 83.3% of individuals and was able to classify males and females with equal accuracy. Additional discriminant functions are presented for use in instances where preservation of the second cervical vertebra is poor.     

Testing the validity of population-specific sex estimation equations: An evaluation based on talus and patella measurements

Sex estimation is essential for forensic scientists to identify human skeletal remains. However, the most sexually dimorphic elements like pelvis or skull are not always assessable. Osteometric analyses have proven useful in sex estimation, but also to be population specific. The main purpose of this study was to test the validity of contemporary Greek and Spanish discriminant functions for the talus and the patella, respectively, on a Swiss skeletal sample and to quantify the utility of the measurements as a novel approach in osteometric sex assessment.Four talus and three patella measurements on dry bone were obtained from 234 individuals of the modern cemetery SIMON Identified Skeletal Collection. The previously derived discriminant functions were applied, accuracies determined, the utility of the different measurements was assessed and new multivariable equations constructed.Accuracies varied between 67% and 86% for talus and 63% and 84% for patella, similar to those reported by the original studies. Multivariable equations should be preferred over equations based on single measurements and combining the most significant measurements rather than using several variables obtained the best possible accuracy. The new discriminant functions did not provide a substantial improvement to the original ones. The overall utility of talus and patella is limited, allowing sex estimation with sufficient certainty only in a small proportion of individuals.Discriminant functions developed in contemporary Greek or Spanish populations are in principle applicable also to Swiss contemporary populations. We recommend that at present existent studies of this type should be validated and tested rather than developing new formulas.     

Morphometrics of the hyoid bone for human sex determination from digital photographs

The identification of unknown remains is very important. When unknown remains are found, anthropologists first determine their sex and age. The sex of most skeletons is determined by their shape. In the hyoid bone, the shape is sex related, so it can be used forensically to determine the sex. This study focused on sex-based morphometry of the hyoid bone in Koreans using digital photographs. Hyoid bones from 52 males and 33 females were examined. For each subject, we took 34 measurements from photographs using a computer program, and the data were analyzed statistically using SPSS 11.0. Twenty-one of 34 measurements had significant sex differences (p<0.05). The discriminant functions based on three measurements (X(1)-X(3)) were as follows: The accuracy of discriminant functions is 88.2% in both groups, so these can be used to distinguish males from females in a statistically significant manner.     

Sexual Dimorphism of the Arm Bones in a Modern Greek Population

Abstract: Several studies have shown that sex determination methods based on measurements of the skeleton are population specific. Metric traits of the long bones of the arm have been reported as reliable indicators of sex. This study was designed to determine whether the three long bones of the arm can be used for sex determination on a skeletal population from Greece. The material used consists of the arm bones of 204 adult individuals (111 males and 93 females) coming from the Modern Human Skeletal Collection of the University of Athens. The age range is 19–96 years for males and 20–99 years for females. The maximum lengths and epiphyseal widths were measured in the long bones of the arm (humerus, radius, and ulna). The discriminant analysis of the metrical data of each long bone gave very high discrimination accuracies. The rate of correct sex discrimination based on different long bones ranges from 90.30% (ulna) to 95.70% (humerus). In addition, intra‐ and inter‐observer error tests were performed. These indicated that replication of measurements was satisfactory for the same observer over time and between observers. The results of this study show that metric characteristics of the arm bones can be used for the determination of sex in skeletal remains from Greece and that bone dimensions are population specific.     

Accuracy and reliability in sex determination from skulls: a comparison of Fordisc® 3.0 and the discriminant function analysis

Identification in forensic anthropology and the definition of a biological profile in bioarchaeology are essential to each of those fields and use the same methodologies. Sex, age, stature and ancestry can be conclusive or dispensable, depending on the field. The Fordisc(?) 3.0 computer program was developed to aid in the identification of the sex, stature and ancestry of skeletal remains by exploiting the Forensic Data Bank (FDB) and computing discriminant function analyses (DFAs). Although widely used, this tool has been recently criticised, principally when used to determine ancestry. Two sub-samples of individuals of known sex were drawn from French (n=50) and Thai (n=91) osteological collections and used to assess the reliability of sex determination using Fordisc(?) 3.0 with 12 cranial measurements. Comparisons were made using the whole FDB as well as using select groups, taking into account the posterior and typicality probabilities. The results of Fordisc(?) 3.0 vary between 52.2% and 77.8% depending on the options and groups selected. Tests of published discriminant functions and the computation of specific DFA were performed in order to discuss the applicability of this software and, overall, to question the pertinence of the use of DFA and linear distances in sex determination, in light of the huge cranial morphological variability.     

New identification criteria for the Chilean population: Estimation of sex and stature

In the analysis of human skeletal or otherwise unidentifiable remains the assessment of sex is an initial vital element when rendering a biological profile. As such other aspects of the biological profile are sex-specific (e.g. stature and age) and cannot be successfully determined without this preliminary assessment. In addition, the estimation of stature is an essential parameter of the biological profile, which is often used to confirm or exclude presumptive identifications.The purpose of this study is to present newly developed local identification criteria for the estimation of sex from the postcrania and stature for Chileans. Linear discriminant functions were derived for the humerus and femur. Sexing accuracies of 87%, 86%, and 82% were achieved. Furthermore, new univariate predictive stature equations are presented using a Bayesian approach for the humerus, femur and tibia.     

The talus: sex assessment of prehistoric New Zealand Polynesian skeletal remains

Prehistoric Polynesian skeletal remains are frequently being recovered in New Zealand due to the increasing pace of urbanisation. Since such material must often be reinterred quickly, it is important that the sex of individuals be determined from the remains in a relatively short time. For this purpose, discriminant function analysis was utilised for sex determination of prehistoric adult New Zealand Polynesian tali (24 males and 27 females). Five measurements were taken and subjected to Statistical Package for the Social Sciences (SPSS) discriminant function analysis. For the discriminant functions derived, accuracy of sex determination ranged from 85.1 to 93.3%. Reduction in error over random assignment by sex ranged from 70 to 87%.     

The calcaneus: sex assessment of prehistoric New Zealand Polynesian skeletal remains

The increasing pace of urbanisation has meant that prehistoric Polynesian skeletal remains are frequently being recovered in New Zealand. Since such material must often be reinterred quickly, it is important that the sex of individuals be determined from the remains in a relatively short time. For this purpose, discriminant function analysis was utilised for sex determination of prehistoric adult New Zealand Polynesian calcanei (26 male and 22 female). Five measurements were taken and subjected to Statistical Package for the Social Sciences (SPSS) discriminant function analysis. For the discriminant functions derived, accuracy of sex determination ranged from 88.4 to 93.5%. Reduction in error over random assignment by sex ranged from 77 to 87%.     

Discriminating sex in South African blacks using patella dimensions

For many years, sex determination has been carried out on skeletal remains to identify individuals in forensic cases and to assess populations in archaeological cases. Since it has been shown that not all bones are found in a forensic case, discriminant function equations should be derived for all bones of the body to assist in sex determination. Numerous studies have shown the usefulness of bones of the lower extremity (e.g. femur, tibia) in sex determination using discriminant function analysis, but the use of patella measurements has not been extensively investigated for this purpose. It is therefore the aim of this study to derive discriminant function equations for sex determination from measurements of the patella of South African blacks as represented in the Raymond A. Dart Collection of Human Skeletons. A total sample of 120 (60 male, 60 female) patellae were measured using six measurements. The Statistical Product and Service Solutions (SPSS) program was used to derive the equations. Stepwise and direct analyses were performed with the highest rate of classification of 85% thereby making the patella useful for sex determination. Thus, the proposed equations derived from this study should be used with caution and only on the South African black population group.     

The femoral head: sex assessment of prehistoric New Zealand Polynesian skeletal remains

Prehistoric Polynesian skeletal remains are frequently being recovered in New Zealand due to the increasing pace of urbanisation. Since such material must often be reinterred quickly, it is important that the sex of individuals be determined from the remains in a relatively short time. For this purpose, discriminant function analysis was utilised for sex determination of prehistoric adult New Zealand Polynesian femora (47 male and 44 female). Three measurements of the femoral head were taken and subjected to Statistical Package for the Social Sciences (SPSS) discriminant function analysis. For the discriminant functions derived, accuracy of sex determination ranged from 80.9% to 82.4%. Reduction in error over random assignment by sex ranged from 62% to 65%.     

Identification of sex depending on radiological examination of foot and patella

Forensic anthropology involves the building of an antemortem profile of an individual from skeletal remains. This includes sex, race determination, and age and stature estimation. Because most bones that are conventionally used for sex determination are often recovered either in a fragmented or incomplete state, it has become necessary to use denser bones that are often recovered intact, eg, the patella, calcaneus, and talus. The present work was performed to investigate the possibility of estimation of sex from some radiologic measurements among a known cross-section of Egyptian population. In this study lateral and anteroposterior radiographs of the right foot and knee were made on 160 living unfractured and nonpathologic individuals comprising 80 males and 80 females aged 25 to 65 years referred to the Radiology Department of Assiut University Hospital. Two measurements on right patella (maximum height and maximum width) and 2 measurements of metatarsal bones (length and midshaft diameter), were used to determine sex by univariate and multivariate discriminant analysis. Eighty radiographs of foot and patella of individuals not used in the original sample were randomly selected to test the accuracy of this method. The study revealed that significant sex differences were demonstrated based on these measurements taken on metatarsal bones more than on patella. One function associating 2 parameters (length and midshaft) of the third metatarsal bone obtained the highest value of correct sex determination with rate of 100% accuracy. The multivariate function associating length of the first, third, and fifth metatarsal bones and midshaft of first, second, and fifth metatarsal gave 100% accuracy. Test of multivariate function on the independent sample revealed a correct classification of 87.5%.     

Metric characterization of the human coxal bone on a recent Italian sample and multivariate discriminant analysis to determine sex

The ability of human pelvic bones to sexually differentiate has been of great interest in forensic anthropology for quite some time as it allows for the determination of skeletal sex by combining metric and morphological data. However, the criteria for determining the sex of a skeleton must be calibrated according to the variability of the population to which it belongs. The aim of this work is the metric characterization of the human coxal bone on a recent sample (of known sex) from the region of Apulia, in southern Italy, in order to establish its efficacy in sex determination by way of multivariate discriminant analysis. Seventeen standard anthropological measurements used in sex determination were taken from 168 coxal bones (78 males and 90 females) all belonging to 86 adult skeletons (40 males and 46 females). The bones used were taken from subjects who had died in the 1960s and 1970s in Apulia. The results obtained define the variability in size and proportion of the sample analyzed with respect to the variations of other skeletal populations. Nine discriminant functions, utilizing between 4 and 11 variables, have been shown to be useful in determining the sex of coxal bones, whether they be complete, partial, or fragmented. All of the functions selected resulted in an attribution error equal to zero, and differ only in the number of variables utilized and by the degree of separation between the groups. The results of this study confirm the validity and utility of diagnostic techniques based on discriminant functions as reported in the literature for other population groups. The combination of metric characteristics from various regions of the coxal bone is, therefore, a valid aid in the correct attribution of skeletal sex even when the combination of variables is numerically limited, but sufficient in sex determination from partial coxal bones.