The use of transition analysis in skeletal age estimation

Assessing the existence of the male-female health-survival paradox in the past: Dental caries in medieval London

OBJECTIVES

This study seeks to identify signals of the male-female health-survival paradox in medieval London.

MATERIALS AND METHODS

This study uses skeletal data on age, sex, dental caries (n = 592) and antemortem tooth loss (n = 819) from adult individuals from medieval London cemeteries (c. 1200-1540 CE). The association between age and dental caries was assessed using binary logistic regression. The associations among age, time period (pre- vs. post-Black Death), oral biomarker (dental caries or antemortem tooth loss), and sex were tested using hierarchical log-linear analysis.

RESULTS

The analyses reveal significantly higher odds of dental caries with increasing adult ages, more older adults after the Black Death, different age distributions of dental caries between the sexes, and a greater decrease in the prevalence of dental caries for females after the Black Death. These results appear not to be an artifact of trends in AMTL. However, this study does not yield evidence suggesting that females experienced both a survival advantage and a decline in oral health at late adult ages after the Black Death relative to males.

CONCLUSIONS

These results do not provide evidence of the existence of a male-female health-survival paradox, but they do corroborate existing evidence of improvements in health in general in the aftermath of the Black Death. The decreased prevalence of dental caries after the Black Death may reflect dietary improvements or the effects of selective mortality during the epidemic.

Age estimation from iliac auricular surface using Bayesian inference and principal component analysis: a CT-based study in an Indian population

Age estimation constitutes one of the pillars of human identification. The auricular surface of the ilium presents as a durable and robust structure within the human skeletal framework, capable of enabling accurate age estimation in older adults. Amongst different documented auricular age estimation methods, the Buckberry-Chamberlain method offers greater objectivity through its component-based approach. The present study aimed to test the applicability of the Buckberry-Chamberlain method in an Indian population through a CT-based examination of the auricular surface. CT scans of 435 participants undergoing CT examinations following the advice of their treating physicians were scrutinized for different age-related auricular changes. Three of the five morphological features described by Buckberry-Chamberlain could be appreciated on CT scans, and thus further statistical analysis was restricted to these features. Transition analysis coupled with Bayesian inference was undertaken individually for each feature to enable age estimation from individual features, while circumventing age mimicry. A Bayesian analysis of individual features yielded highest accuracy percentages (98.64%) and error rates (12.99 years) with macroporosity. Transverse organization and apical changes yielded accuracy percentages of 91.67% and 94.84%, respectively, with inaccuracy computations of 10.18 years and 11.74 years, respectively. Summary age models, i.e. multivariate age estimation models, derived by taking this differential accuracy and inaccuracy into consideration yielded a reduced inaccuracy value of 8.52 years. While Bayesian analysis undertaken within the present study enables age estimation from individual morphological features, summary age models appropriately weigh all appreciable features to yield more accurate and reliable estimates of age.

Considerations for age estimation accuracy: Method-derived outcomes and practitioner interpretations

Recent research observed 92% accuracy for age-at-death estimations by U.S. forensic anthropologists. The present study compares this case report level accuracy to method level accuracy for the most commonly used methods in U.S. casework, drawing from the Forensic Anthropology Database for Assessing Methods Accuracy (FADAMA). Method application rate (i.e., how often a method is used in casework) was analyzed for n = 641 cases and identified 15 methods with an application rate >45 cases, and the present study focused further analyses on these 15 methods. Of the 15, only four yielded accuracies greater than or equal to the 92% documented for case-report level accuracy. The other 11 methods produced accuracy rates ranging from 54% to 91%, with six of these below 70% This disconnect between highly accurate age estimations at the case report level compared to the poor performance at method level suggests that practitioner interpretation and synthesis of the methods' outcomes is a critical step for increasing the accuracy rates of the age estimations as reported on the final case report. This inference was further supported by the study's results which indicated that practitioner interpretations of frequently used method combinations improve accuracy and age range width of age estimation. The study also performed a Fisher's Exact test to assess whether case report-level accuracy differed with the number of aging methods used in a case, and found no significant differences.

Estimating adult age categories in commingled skeletons with Transition Analysis 3

OBJECTIVES

We estimate adult age frequencies from Unar 1 and Unar 2, two late Umm an-Nar (2400-2100 BCE) tombs in the modern-day Emirate of Ras al-Khaimah, United Arab Emirates. These collective tombs each contained hundreds of skeletons in commingled, fragmented, and variably cremated states. Previous studies placed the vast majority of this mortuary community in a generalized "adult" category, as have most analyses of similar tombs from this period. We sought to test how adult age estimation methods compare in identifying young, middle, and old-age individuals in commingled assemblages.

MATERIALS AND METHODS

We employed Transition Analysis 3 (TA3) and traditional age estimation methods to generate adult age frequencies for each tomb. We compared these frequencies between tomb contexts as well as by method.

RESULTS

Unar 1 and Unar 2 had similar adult age frequencies within each method, but TA3 age frequencies included significantly more middle and older adult individuals than those generated by traditional methods.

DISCUSSION

These results support findings of earlier iterations of transition analysis in regard to sensitivity in old adult age estimation, compared with traditional methods. Our findings indicate a potential use of TA3 in reconstructing age frequencies and mortality profiles in commingled skeletal assemblages. Increasing our understanding of everyday life in the distant past necessitates better understandings of adult age, and here, we illustrate how age estimation method choice significantly changes bioarchaeological interpretations of aging in Bronze Age Arabia.

RESEARCH HIGHLIGHTS

Adult age estimation using TA3 revealed significantly more middle and older adults than traditional methods in two commingled tombs. Similar mean maximum likelihood point estimates by side and across skeletal elements were found between tombs.

The Black Death in Hereford, England: A demographic analysis of the Cathedral 14th-century plague mass graves and associated parish cemetery

OBJECTIVES

This study explores the paleoepidemiology of the Black Death (1348-52 AD) mass graves from Hereford, England, via osteological analysis. Hereford plague mortality is evaluated in the local context of the medieval city and examined alongside other Black Death burials.

METHODS

The Hereford Cathedral site includes mass graves relating to the Black Death and a 12th-16th century parish cemetery. In total, 177 adult skeletons were analyzed macroscopically: 73 from the mass graves and 104 from the parish cemetery. Skeletal age-at-death was assessed using transition analysis, and sex and stress markers were analyzed.

RESULTS

The age-at-death distributions for the mass graves and parish cemetery were significantly different (p = 0.0496). Within the mass graves, young adults (15-24 years) were substantially over-represented, and mortality peaked at 25-34 years. From 35 years of age onwards, there was little variation in the mortality profiles for the mass graves and parish cemetery. Males and females had similar representation across burial types. Linear enamel hypoplasia was more prevalent within the mass graves (p = 0.0340) whereas cribra orbitalia and tibial periostitis were underrepresented.

CONCLUSIONS

Mortality within the Hereford mass graves peaked at a slightly older age than is seen within plague burials from London, but the overall profiles are similar. This demonstrates that young adults were disproportionately at risk of dying from plague compared with other age groups. Our findings regarding stress markers may indicate that enamel hypoplasia is more strongly associated with vulnerability to plague than cribra orbitalia or tibial periostitis.

An evaluation of the three-component pubic symphyseal human age estimation method: a CT-based exploration in an Indian population

Age estimation constitutes an important facet of human identification within forensic, bioarchaeological, repatriation, and humanitarian contexts. Within the human skeletal framework, the pubic symphysis comprises one of the more commonly utilized structures for age estimation. The present investigation was aimed at establishing the applicability of the McKern-Stewart pubic symphyseal age estimation method in males and females of an Indian population, an aspect previously unreported. Three hundred and eighty clinical CT scans of the pubic symphysis were collected and scored in accordance with the McKern-Stewart method. An overall accuracy of 68.90% was obtained on applying the method to males, demonstrating a limited applicability of the method in its primal form. Subsequently, Bayesian analysis was undertaken to enable accurate age estimation from individual components in both sexes. Bayesian parameters obtained with females suggest that McKern-Stewart's components fail to accommodate for age-related changes within the female pubic bone. Improved accuracy percentages and reduced inaccuracy values were obtained with Bayesian analysis in males. With females, the error computations were high. Weighted summary age models were utilized for multivariate age estimation, and furnished inaccuracy values of 11.51 years (males) and 17.92 years (females). Error computations obtained with descriptive analysis, Bayesian analysis, and principal component analysis demonstrate the limited applicability of McKern-Stewart's components in generating accurate age profiles for Indian males and females. The onset and progression of age-related changes within the male and female pubic bone may be of interest to biological anthropologists and anatomists involved in exploring the underlying basis for aging.

Mixed cumulative probit: a multivariate generalization of transition analysis that accommodates variation in the shape, spread and structure of data

Biological data are frequently nonlinear, heteroscedastic and conditionally dependent, and often researchers deal with missing data. To account for characteristics common in biological data in one algorithm, we developed the mixed cumulative probit (MCP), a novel latent trait model that is a formal generalization of the cumulative probit model usually used in transition analysis. Specifically, the MCP accommodates heteroscedasticity, mixtures of ordinal and continuous variables, missing values, conditional dependence and alternative specifications of the mean response and noise response. Cross-validation selects the best model parameters (mean response and the noise response for simple models, as well as conditional dependence for multivariate models), and the Kullback-Leibler divergence evaluates information gain during posterior inference to quantify mis-specified models (conditionally dependent versus conditionally independent). Two continuous and four ordinal skeletal and dental variables collected from 1296 individuals (aged birth to 22 years) from the Subadult Virtual Anthropology Database are used to introduce and demonstrate the algorithm. In addition to describing the features of the MCP, we provide material to help fit novel datasets using the MCP. The flexible, general formulation with model selection provides a process to robustly identify the modelling assumptions that are best suited for the data at hand.

The computational age-at-death estimation from 3D surface models of the adult pubic symphysis using data mining methods

Age-at-death estimation of adult skeletal remains is a key part of biological profile estimation, yet it remains problematic for several reasons. One of them may be the subjective nature of the evaluation of age-related changes, or the fact that the human eye is unable to detect all the relevant surface changes. We have several aims: (1) to validate already existing computer models for age estimation; (2) to propose our own expert system based on computational approaches to eliminate the factor of subjectivity and to use the full potential of surface changes on an articulation area; and (3) to determine what age range the pubic symphysis is useful for age estimation. A sample of 483 3D representations of the pubic symphyseal surfaces from the ossa coxae of adult individuals coming from four European (two from Portugal, one from Switzerland and Greece) and one Asian (Thailand) identified skeletal collections was used. A validation of published algorithms showed very high error in our dataset-the Mean Absolute Error (MAE) ranged from 16.2 and 25.1 years. Two completely new approaches were proposed in this paper: SASS (Simple Automated Symphyseal Surface-based) and AANNESS (Advanced Automated Neural Network-grounded Extended Symphyseal Surface-based), whose MAE values are 11.7 and 10.6 years, respectively. Lastly, it was demonstrated that our models could estimate the age-at-death using the pubic symphysis over the entire adult age range. The proposed models offer objective age estimates with low estimation error (compared to traditional visual methods) and are able to estimate age using the pubic symphysis across the entire adult age range.

Interpreting error in the estimation of skeletal growth profiles from past populations: An example demonstrating skeletal growth in historic African American communities

OBJECTIVES

The study of growth in the past is a critical component of bioarcheological analyses. However, our understanding of growth in the past is subject to a number of methodological challenges. This study aims to model the skeletal growth of past populations by considering the challenges associated with the data collection process and the challenges associated with the age estimation procedures.

MATERIALS AND METHODS

We use skeletal remains from two historic African American cemeteries in the American South to model femoral diaphyseal length-for-age. We estimate the age of each individual using dental development techniques and present growth curves as both a product of the maximum likelihood (MLE) age estimate and the estimated posterior age distribution. Growth was compared against a reference sample from the University of Colorado Child Research Council Study.

RESULTS

The results of our analyses showed that femoral diaphyseal length in two historic African American communities is small-for-estimated age as compared to a modern reference sample. However, the magnitude and characterization of this difference is variable when taking into account the broader posterior age distribution.

DISCUSSION

Both samples may be small-for-age due to physiological stress associated with racism, inequality, and the compounding effects of early urbanization. However, the interpretation of growth in the past is muddled when considering the relationship between the study sample and the reference sample, when accounting for uncertainty in the age estimation procedure, and the error-inducing steps taken during the data collection process. Future interpretation of skeletal growth in the past must include a full account of the possible sources of error in order to present an accurate representation of growth.

The accuracy of age estimation using transition analysis in the Hamann-Todd collection

OBJECTIVES

Reconstructing demography of past populations using skeletal data is challenging when analyzing adults because the process of biological aging does not always reflect the individual's chronological age. A proposed solution to address the limitations of traditional age estimation methods is transition analysis (TA), a multifactorial method of age estimation. However, despite its methodological refinement, TA has varying degrees of accuracy when applied to different known-age skeletal samples. This study assesses TA's accuracy by comparing age estimates to known age at death in the Hamann-Todd Collection.

MATERIALS AND METHODS

We contrasted the maximum likelihood age estimates generated by the ADBOU program to the known ages of 221 individuals. The absolute error was calculated for the entire sample, and compared between sex and ancestry.

RESULTS

The mean absolute error in the sample is 11.6 (SD = 10.3) years, with white individuals' errors (14.1 years) being significantly higher than black individuals' (9.1 years; p < 0.001). No significant differences were found between sexes (p = 0.621). A weak to moderate positive correlation was found between known age and absolute error for white males (R = 0.607; p < 0.001), white females (R = 0.509; p < 0.001), and black males (R = 0.371; p = 0.006). The accuracy of TA age estimates varied when each anatomical region was analyzed independently, but the combination of all three anatomical regions yielded the most accurate age estimates.

DISCUSSION

These findings further support that TA accuracy depends on the prior distribution used and, in the Hamann-Todd Collection, the accuracy for white individuals is more influenced by this limitation than when black individuals are analyzed.

A comparison of subadult skeletal and dental development based on living and deceased samples

OBJECTIVES

A fundamental assumption in biological anthropology is that living individuals will present with different growth than non-survivors of the same population. The aim is to address the question of whether growth and development data of non-survivors are reflective of the biological consequences of selective mortality and/or stress.

MATERIALS AND METHODS

The study compares dental development and skeletal growth collected from radiographic images of contemporary samples of living and deceased individuals from the United States (birth to 20 years) and South Africa (birth to 12 years). Further evaluation of deceased individuals is used to explore differential patterns among manners of death (MOD).

RESULTS

Results do not show any significant differences in skeletal growth or dental development between living and deceased individuals. However, in the South African deceased sample the youngest individuals exhibited substantially smaller diaphyseal lengths than the living sample, but by 2 years of age the differences were negligible. In the US sample, neither significant nor substantial differences were found in dental development or diaphyseal length according to MOD and age (>2 years of age), though some long bones in individuals <2 years of age did show significant differences. No significant differences were noted in diaphyseal length according to MOD and age in the SA sample.

DISCUSSION

The current findings refute the idea that contemporary deceased and living individuals would present with differential growth and development patterns through all of ontogeny as well as the assumptions linking short stature, poor environments, and MOD.