Jaroslav Bruzek

A new approach to sexual diagnosis in past populations. Practical adjustments from Van Vark's procedure

Determination of sex is a key aspect in the study of past populations. Bias in skeletal sexing is well known, however, and depends upon the completeness of the skeletal remains and the representativeness of reference samples. In order to correct these difficulties, the authors propose practical adjustments to Van Varks well-known procedure. Two fundamental aspects are considered to reduce the bias of sex allocation. First, we propose to increase the effectiveness of sexing during the first step (primary diagnosis only from the pelvic bone). Second, to improve the final step (secondary diagnosis from the extra-pelvic skeleton), we consider posterior probabilities as essential. These two practical adjustments are successfully tested in a sample of known sex and lead to a classification with 94.5% accuracy. These results significantly improve sex determination in archaeological samples and therefore contribute to a better understanding of past populations.

Methodology and Reliability of Sex Determination From the Skeleton

Once a body is completely decomposed, it is necessary to determine sex from the skeleton. The hip bone is the most reliable indicator for sex determination because the pattern of sexual dimorphism is common to the whole human race. Two reliable visual methods are suggested to assess sex from the hip bone. However, the authors recommend the use of a method based on discriminant function analysis including a probabilistic approach that the authors recently developed with a large sample of known-sex individuals. The population specificity of sexual dimorphism of the other parts of the skeleton is also discussed. The authors particularly insist on the inherent limits of discriminant functions on extrapelvic measurements.

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.

Dental Age Assessment in Children: A Comparison of Four Methods in a Recent French Population

The aim of this study was to analyze the accuracy and the reliability of four methods of dental age estimation (Demirjian, Willems I, Willems II, and Chaillet standards) in a French population. Orthopantomograms of 743 children aged between 4 and 15 years were used. The Demirjian standards gave a consistent overestimation of dental age compared with chronological age (+0.45 and +0.46 years for girls and boys, respectively). We found that three modified methods were more accurate for both sexes than Demirjians method: the Willems I method appeared to be more suitable when the sex and ethnicity are both known (−0.09 and +0.14 years for girls and boys, respectively); the Willems II method was more accurate for children of unknown sex (mean difference = 0.00 years), and the Chaillet method was found to be more accurate than the Demirjian method, but less accurate than the Willems I method (−0.59 and −0.18 years for girls and boys, respectively).

Statistical sex determination from craniometrics: Comparison of linear discriminant analysis, logistic regression, and support vector machines

Accuracy of identification tools in forensic anthropology primarily rely upon the variations inherent in the data upon which they are built. Sex determination methods based on craniometrics are widely used and known to be specific to several factors (e.g. sample distribution, population, age, secular trends, measurement technique, etc.). The goal of this study is to discuss the potential variations linked to the statistical treatment of the data. Traditional craniometrics of four samples extracted from documented osteological collections (from Portugal, France, the U.S.A., and Thailand) were used to test three different classification methods: linear discriminant analysis (LDA), logistic regression (LR), and support vector machines (SVM). The Portuguese sample was set as a training model on which the other samples were applied in order to assess the validity and reliability of the different models. The tests were performed using different parameters: some included the selection of the best predictors; some included a strict decision threshold (sex assessed only if the related posterior probability was high, including the notion of indeterminate result); and some used an unbalanced sex-ratio. Results indicated that LR tends to perform slightly better than the other techniques and offers a better selection of predictors. Also, the use of a decision threshold (i.e. p>0.95) is essential to ensure an acceptable reliability of sex determination methods based on craniometrics. Although the Portuguese, French, and American samples share a similar sexual dimorphism, application of Western models on the Thai sample (that displayed a lower degree of dimorphism) was unsuccessful.

Comparison of methods to determine sex by evaluating the greater sciatic notch: Visual, angular and geometric morphometrics

Sex estimation is the first step for biological profile reconstruction of an unknown skeleton (archaeological or contemporary) and consequently for positive identification of skeletal remains recovered from forensic settings. Several tools have been developed using different osseous structures. With the intention to provide an objective method comparison, we reported the analysis of three different methods (visual, metric and geometric morphometrics) for sex assessment of the greater sciatic notch. One hundred and thirty pelvic bones (45.4% females and 54.6% males) from the National Autonomous University of Mexico Skeletal Collection pertaining to the contemporary Mexican population were analyzed. We used the ROC-analysis to test between desired false positive thresholds (1-specificity) and expected true positive rates (sensitivity) in order to predict the best approach to sex assessment. The comparison of the area under the ROC-curves shows significant differences among visual and metric methods. At the same time, the analysis suggested that higher morphological variation among the sexes is independent of the methodological approach. The results indicate that the metric (angle), with a high percent of indeterminate cases (34.6%), and visual, with 26.2% of the cases allocated as intermediate cases, were poorly accurate; we cannot recommend these techniques for sexing an unknown specimen. On the other hand, the geometric morphometrics approach improves sex estimation in 82.3% of correctly classified individuals with more than 95% of posterior probability. In addition to the method comparison, the major sexual variation of the greater sciatic notch was determined to be located on its posterior border.

Dental health and lifestyle in four early mediaeval juvenile populations: comparisons between urban and rural individuals, and between coastal and inland settlements.

Dental stress markers such as enamel hypoplasia and caries are suitable indicators of population health and lifestyle, although they must be recorded and interpreted carefully. To date, they have been predominantly studied in adult samples, whereas juvenile remains are also affected by these lesions. In this study, dental enamel hypoplasia and caries were both evaluated on 613 non-adult individuals from four early mediaeval Moravian and Frankish skeletal series, who had experienced contrasting environments and lifestyles. The aim of this study is to assess the relationship between these biological traits and living conditions, and how this is manifested in the juvenile dental remains. Significant differences between populations were found in stress markers, dental lesions and the way these were manifested. Exposure to stressful conditions varies between urban and rural populations and is related to age groups. Although the children under investigation seem to have had different diets, it is difficult to distinguish the biological contribution (different enamel susceptibility) from the lifestyle contribution (different food, environment) in the formation of caries. Moreover, such studies must be interpreted carefully due to the possibility of intra- and inter-observer errors and the subjectivity of the scoring techniques. Nevertheless, this study also demonstrates that results of an investigation of juvenile skeletal remains can be as informative as a study of adults and that juvenile skeletons can be included in large bioarchaeological population studies.

The antiquity of cranial surgery in Europe and in the Mediterranean basin

Through personal observations and a literature study we have made a synthesis of the most ancient healed trephinations in Europe and in the Mediterranean basin. Cases of small dimensions that were carried out with simple techniques are found in the Mesolithic populations from North Africa, Ukraine and Portugal. The first Neolithic examples of trephinations are extensive and have been realised with more sophisticated techniques. This suggests that the development of agriculture was accompanied by the command of new procedures in the field of surgery.

Modeling neolithic dispersal in Central Europe: Demographic implications

On the basis of new examination of ancient DNA and craniometric analyses, Neolithic dispersal in Central Europe has been recently explained as reflecting colonization or at least a major influx of near eastern farmers. Given the fact that Neolithic dispersal in Central Europe was very rapid and extended into a large area, colonization would have to be associated with high population growth and fertility rates of an expanding Neolithic population. We built three demographic models to test whether the growth and fertility rates of Neolithic farmers were high enough to allow them to colonize Central Europe without admixture with foragers. The principle of the models is based on stochastic population projections. Our results demonstrate that colonization is an unlikely explanation for the Neolithic dispersal in Central Europe, as the majority of fertility and growth rate estimates obtained in all three models are higher than levels expected in the early Neolithic population. On the basis of our models, we derived that colonization would be possible only if (1) more than 37% of women survived to mean age at childbearing, (2) Neolithic expansion in Central Europe lasted more than 150 years, and (3) the population of farmers grew in the entire settled area. These settings, however, represent very favorable demographic conditions that seem unlikely given current archaeological and demographic evidence. Therefore, our results support the view that Neolithic dispersal in Central Europe involved admixture of expanding farmers with local foragers. We estimate that the admixture contribution from foragers may have been between 55% and 72%.

Burials and Graphs: Relational Approach to Mortuary Analysis

This article demonstrates the analytical potential of graph theory for understanding mortuary practices in past societies. We take advantage of social network analysis software PAJEK to model relationships among burials. The case study of the Early Bronze Age cemetery Rebešovice (Czech Republic) is used to explore the potential of the network approach to explain the contrast between the center and the periphery of the cemetery. Two hypotheses are proposed to explain this contrast: Chronological and social. The first hypothesis explains the difference between the center and the periphery as an effect of social standing, while the latter as an effect of time. The data set includes archaeological and biological data from 72 burials. We calculate simple matching distance matrices as a measure of dissimilarity among the burials based on socially and chronologically significant variables and Euclidean matrix as a measure of spatial proximity among pairs of graves. We project the results into geographic space and compare the patterns with the expectations derived from the two research hypotheses. The evaluation of results allows us to reject both hypotheses and formulate a new model of spatial organization based on a few contemporary subsections of the cemetery used by different corporate groups. Finally, the potential of computer-aided modeling of matrices and graphs is discussed in context of other analytical techniques used for the investigation of intracemetery mortuary variability.