Technical Note: Geometric morphometrics and sexual dimorphism of the greater sciatic notch in adults from two skeletal collections: The accuracy and reliability of sex classification (original) (raw)
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Technical Note: Geometric Morphometrics and Sexual, 2013
The greater sciatic notch (GSN) is one of the most important and frequently used characteristics for determining the sex of skeletons, but objective assessment of this characteristic is not without its difficulties. We tested the robustness of GSN sex classification on the basis of geometric morphometrics (GM) and support vector machines (SVM), using two different population samples. Using photographs, the shape of the GSN in 229 samples from two assemblages (documented collections of a Euroamerican population from the Maxwell Museum, University of New Mexico, and a Hispanic population from Universidad Nacional Aut onoma de M exico, Mexico City) was segmented automatically and evaluated using six curve representations. The optimal dimensionality for each representation was determined by finding the best sex classification. The classification accuracy of the six curve representations in our study was similar but the highest and concurrently homologous cross-validated accuracy of 92% was achieved for a pooled sample using Fourier coefficient and Legendre polynomial methods. The success rate of our classification was influenced by the number of semilandmarks or coefficients and was only slightly affected by GSN marginal point positions. The intrapopulation variability of the female GSN shape was significantly lower compared with the male variability, possibly as a consequence of the intense selection pressure associated with reproduction. Males were misclassified more often than females. Our results show that by using a suitable GSN curve representation, a GM approach, and SVM analysis, it is possible to obtain a robust separation between the sexes that is stable for a multipopulation sample. Am J Phys Anthropol 152:558-565,
American Journal of Physical Anthropology
The greater sciatic notch (GSN) is one of the most important and frequently used characteristics for determining the sex of skeletons, but objective assessment of this characteristic is not without its difficulties. We tested the robustness of GSN sex classification on the basis of geometric morphometrics (GM) and support vector machines (SVM), using two different population samples. Using photographs, the shape of the GSN in 229 samples from two assemblages (documented collections of a Euroamerican population from the Maxwell Museum, University of New Mexico, and a Hispanic population from Universidad Nacional Autónoma de México, Mexico City) was segmented automatically and evaluated using six curve representations. The optimal dimensionality for each representation was determined by finding the best sex classification. The classification accuracy of the six curve representations in our study was similar but the highest and concurrently homologous cross-validated accuracy of 92% wa...
International Journal of Osteoarchaeology, 2017
Sex estimation in non-adult skeletons is crucial in bioarchaeology and forensic anthropology. It was not extensively considered in the past, mainly because it was stated that the dimorphic osteological features were difficult to identify before adulthood. Over the past few years, this statement was disproved, and the study of numerous dimorphic non-adult skeletal traits was approached. This paper presents a new methodology that evaluates the auricular surface of the non-adult ilia. Several morphological and continuous variables were recorded for 34 individuals (21 females and 13 males) aged between 7 and 18 from the Coimbra Identified Skeletons Collection (University of Coimbra, Portugal). The results show low intra and inter-observer errors for all the variables, which renders the methodology replicable. Two ratios related to the shape of the anterior area of the auricular surface offer the most dimorphic data (proportions of cases correctly assigned: 0.82 and 0.88; sexual allocation probabilities: 0.85 for both variables). A discriminant function and a logistic regression were developed, which correctly classified the 82.35 and the 88.23% of the individuals, respectively. Moreover, two qualitative variables, referred to as the overall morphology and the apex morphology, also show statistically significant differences between males and females (proportions of correct assignation: 0.82 and 0.76; sexual allocation probabilities: 0.79 and 0.76). These variables can be incorporated in a multifactorial approach together with other indicators already available in the specialised literature in order to help improve the accuracy of the results obtained. This methodological procedure has to be applied with other identified samples, including younger individuals, so as to test whether the trends presented in this context are maintained and are useful in populations from a different geographical provenience.
American Journal of Physical Anthropology, 2007
This study aims to integrate the craniofacial morphological variation of southern South American populations with the results of mtDNA haplogroup variation, to discuss the South America peopling. Because the causes of morphological differentiation of Fueguian populations are still a controversial subject, the comparison with neutral variation could contribute to elucidate them. Samples of human remains from South America regions were used to analyze the evolutionary relationships. Several craniofacial traits observed in frontal and lateral view were analyzed by means of geometric morphometrics techniques, and the evolutionary relationships based on morphological and molecular data were established in base to ordination analyses. The results from the facial skeleton agree with those obtained from mtDNA haplogroup frequencies, with La Pampa/Chaco samples detached from the Patagonian samples. Hence, the same mechanism that accounts for the pattern of frequency of haplogroups could explain the variation found in facial skeleton among the samples. It is suggested that such geographic pattern of craniofacial and molecular diversity may reflect the effect of genetic drift that occurred in the small founding populations isolated by distance or geographic barriers. Conversely, the results obtained using the traits from the lateral view slightly differ from the molecular results, showing differences between southernmost Patagonian and the other samples. Therefore, mechanisms other than genetic drift (e.g., natural selection) could have acted to shape the pattern observed in some craniofacial structures present in the lateral view, characterized by the fact that the southernmost Patagonian samples display the most robust and dolichocephalic crania. Am J Phys Anthropol, 2007. © 2007 Wiley-Liss, Inc.
International Journal of Osteoarchaeology, 2021
This paper aims to systematically investigate the value of combining traits from different anatomical regions in osteological sexing by contrasting the utility of single traits and established scores with those of ensembles of traits from single or multiple anatomical regions, allowing metric and morphological traits to be combined. The utility was defined as the fraction of the population for whom we could reach a posterior probability above 95% of being male or female. A total of 675 adult individuals from the sixth to eighth century AD cemetery of Mannheim Bösfeld, Germany, were assessed, and 27 postcranial metric traits and 41 morphological traits from the pelvis, mandible, and cranium were used. In addition, 13 metric and 3 morphological scores were considered. Linear discriminant analysis (LDA) was used to construct rules and cross validation to determine accuracy and utility. These parameters were determined for single traits and scores, trait groups defined by anatomical regions and/or previously considered in the literature, and ensembles of traits defined by selecting several promising traits from different anatomical regions. Accuracy of single traits ranged from 0.76 to 0.94, with scores even reaching 0.97, but utility remained around 0.2-0.4 for metric traits and up to 0.6 for morphological traits. Only scores and ensembles combining traits from different anatomical regions reached a utility above 0.7; that is, sex could be estimated in more than 70% of the individuals with a posterior probability above 95%. When selecting a limited number of traits for systematic sexing in a human skeletal series, it is advisable to select traits from different anatomical regions to obtain a reasonably reliable result in as many individuals as possible. Large scale investigations covering all relevant anatomical regions and involving a wide range of populations are required for more precise recommendations.
A Geometric Morphometric Approach to Sex Estimation of the Greater Sciatic Notch
MSc Dissertation, University of Exeter, 2020
Sex estimation is one of the first analyses carried out on unidentified skeletal remains, and new methods for accurate and reliable sex estimation are constantly being created and tested to determine the sex of unknown individuals. This project was undertaken in order to assess the reliability of morphological scales in comparison to geomorphic morphometric (GMM) techniques for sex estimation of the greater sciatic notch. The study analyses the pelvises of a medieval (11th-15th century AD) skeletal population from Exeter, England to assess the morphology of the greater sciatic notch and its potential for the application of geomorphic morphometric techniques. Currently, sex estimation of the greater sciatic notch is often undertaken using Walker’s standardised ordinal scale, which is based on a modern American population, to assign a specimen as either masculine, feminine or indeterminate. The reliability of this scale on archaeological samples will be assessed to determine the differences in accuracy when applying an ordinal scale versus GMM analyses to the greater sciatic notch. Thus, it is necessary to also determine the viability and reliability of assigning sex in such a way. The results of this study indicate that, by using GMM in conjunction with coding, there are statistically significant differences in male and female greater sciatic notch shape. This study found it was possible to write and execute commands to predict the sex of an individual of unknown sex based solely on their sciatic notch, in tandem with the data gathered from other previously sexed specimens within the same sample.
Human Evolution, 1993
Evolution of Hominid Femur and Tibia: a morphometric approach to the evolutionary research in anthropology Some theoretical and methodological morphometrical approaches in evolutionary anthropology and paleoanthropology are reviewed in this study. It is shown which are the contemporary possibilities of sophisticated biometrical and biostatistical methods and the role of the morphometrical approach. A new approach, experimental morphometrics, is presented, reflecting recent trends in evolutionary morphology as well as sophisticated biostatistical methods. The approach emphasizes the complex interrelated approach to the data processing and a double nature of morphometric data, i.e. biological and biostatistical one. The practical use of experimental morphometry is given for the two examples of analyses of the evolution of the hominoid and hominid femur and tibia. The hypothesis on a two stage restructuring of morphology of the hominid femur and tibia is supported by experimental results. Two different steps during this restructuring could be recognized: 1) Structural remodelling typical for the origin of hominids and australopithecine evolution, and 2) proportional remodelling of lower limb long bones which is connected with the Australopithecus/Homo transition (i.e. mainly Homo habilis stage). The results confirm the increasing trend of bipedal adaptations on the early hominid lower limb skeleton. Analysis of mieroevolutionary trends on the Homo sapiens femur and tibia indicates at least three different morphological patterns, Paleolithic, Neolithic and Recent, with numerous specific features in morphology and proportions. Neanderthal morphology is very derived. Upper Paleolithic/Mesolithic/Neolithic transition has a key character for the understanding of post-Paleolithic morphology. A very high sexual dimorphism of the femur and tibia has been demonstrated for Upper Paleolithic and Neolithic populations.