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.

Perinatal Disorders and Small Birthweight Are Significantly Associated With Small Vertebral Neural Canal Size in a Contemporary Pediatric Autopsy Sample.

STUDY DESIGN: A retrospective, nonblinded, single-center observational study. OBJECTIVE: The purpose of this study is to examine associations between small vertebral neural canal (VNC) measurements with verified experiences of early-life stress (ELS) (premature birth, disorders or conditions arising in the perinatal period, and congenital disorders) in a pediatric autopsy sample, paired with other skeletal indicators of stress, and known demographic/health information. SUMMARY OF BACKGROUND DATA: Most studies linking small VNC size to ELS are for human remains from archeological sites without known demographic information or health history, making it difficult to assess what kind of stress might affect VNC growth. METHODS: This is a single-center retrospective study in a pediatric autopsy sample of 623 individuals (aged 0.5 to 20.9 yr) with known sex, age, and manner of death (MOD), who died between 2011 and 2019. Data were collected from postmortem computed tomography scans, autopsy, and field investigator reports. Data include VNC anteroposterior and transverse (TR) diameters of the 12th thoracic (T12) and fifth lumbar (L5) vertebrae, bone mineral density, and Harris lines. RESULTS: Small birthweight males have significantly smaller VNC than those with an average birthweight. The natural MOD is associated with smaller VNC. Perinatal disorders and growth stunting are associated with smaller T12 anteroposterior, T12-TR, and L5-TR diameters. Congenital disorders and Harris lines are not associated with small VNC. CONCLUSIONS: Reduced VNC size is a reliable indicator of severe ELS, but not all ELS leads to reduced VNC. Females appear less susceptible to perinatal environmental stress than males. Reduced VNC may also be indicative of heightened risk of disease and death in those who died of natural MOD. LEVEL OF EVIDENCE: Level 2.

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.

Agreement and error rates associated with standardized data collection protocols for skeletal and dental data on 3D virtual subadult crania.

Observer error and agreement rates for craniometrics, odontometrics, and cranial and dental morphological traits have been inconsistently evaluated on three-dimensional cranial reconstructions and almost never assessed on subadult individuals. This study uses a computed tomography (CT) scan sample of 12 subadults aged between birth and 20 years from the Subadult Virtual Anthropology Database (SVAD) to evaluate intra- and inter-observer error and agreement rates associated to these four types of data on virtual crania. Forty-eight cranial landmarks, 33 standard inter-landmark distances (ILDs), 13 cranial macromorphoscopic traits, four permanent and four deciduous dental landmarks and measurements per tooth, and 21 permanent and 12 deciduous dental morphological traits were collected on each individual. Results matched or improved on published standards for dry bones, teeth, or dental casts. Technical Error of Measurement (TEM) associated with metric data ranged from 0.00 mm to 0.99 mm and relative TEM ranged from 0% to 5.76%. Cohen's kappa coefficient values for agreement on morphological traits scores were above K = 0.5 for 90% of the traits. Type III cranial landmarks showed higher error rates than Type I and II cranial landmarks. Agreement on dental morphology scores seemed influenced by observer experience and rater agreement improved when using di- or tri-chotomized grades. Skeletal maturity did not significantly affect error rates, meaning most craniofacial and dental metrics and morphological traits can be reliably obtained from virtual subadult crania.

New insights on hip bone sexual dimorphism in adolescents and adults using deformation-based geometric morphometrics.

Morphological variation of the human pelvis, and particularly the hip bone, mainly results from both female-specific selective pressure related to the give birth of large-headed newborns, and constraints in both sexes for efficient bipedal locomotion, abdominal stability, and adaptation to climate. Hip bone morphology has thus been extensively investigated using several approaches, although the nuances of inter-individual and sex-related variation are still underappreciated, and the effect of sex on ontogenetic patterns is debated. Here, we employ a landmark-free, deformation-based morphometric approach to explore variation in modern human hip bone shape and size from middle adolescence to adulthood. Virtual surface models of the hip bone were obtained from 147 modern human individuals (70 females and 77 males) including adolescents, and young and mature adults. The 3D meshes were registered by rotation, translation, and uniform scaling prior to analysis in Deformetrica. The orientation and amplitude of deviations of individual specimens relative to a global mean were assessed using Principal Component Analysis, while colour maps and vectors were employed for visualisation purposes. Deformation-based morphometrics is a time-efficient and objective method free of observer-dependent biases that allows accurate shape characterisation of general and more subtle morphological variation. Here, we captured nuanced hip bone morphology revealing ontogenetic trends and sex-based variation in arcuate line curvature, greater sciatic notch shape, pubic body and rami length, acetabular expansion, and height-to-width proportions of the ilium. The observed ontogenetic trends showed a higher degree of bone modelling of the lesser pelvis of adolescent females, while male variation was mainly confined to the greater pelvis.

How low can we go? A skeletal maturity threshold for probabilistic visual sex estimation from immature human os coxae.

OBJECTIVES: The appearance of sexually dimorphic traits varies depending on the type of bone, age, environmental and genetic factors and is closely linked to skeletal maturation sequence. Subadult sex estimation currently shows inconsistent accuracy and methods do not incorporate indicators of maturation. The goal of this study is to apply the Santos et al. (2019) adult sex estimation method on virtually reconstructed subadult os coxae and account for pelvic maturation. MATERIAL AND METHODS: The right os coxae of 194 female and male individuals aged 11-30 years from Marseille, France were virtually reconstructed from computed tomography (CT) scans. Santos et al.'s (2019) 11 traits were scored as female, male, or indeterminate. Maturation of 10 pelvic epiphyseal sites was scored using a four-stage system (0-3) to obtain a composite maturity score from 1 to 30. RESULTS: Three maturity groups were identified based on composite maturity scores ranging from 0 to 30. Individuals with a composite maturity score of 15 or higher showed 98 % sex estimation accuracy and a 6 % indeterminate rate. Scores of 2 for the ischiatic tuberosity or 1 for the anterior superior iliac spine can be used as proxies for a composite maturity score of 15 and application on incomplete bones. DISCUSSION: Sexual dimorphism was observed in the epiphyseal maturation sequence and the development of sexually dimorphic pelvic traits. The Santos et al. (2019) method is applicable on immature individuals who meet a maturation threshold with comparable accuracy to adults, without relying on known or estimated age.

The importance of processing procedures and threshold values in CT scan segmentation of skeletal elements: An example using the immature os coxa.

As the accessibility and utility of virtual databases of skeletal collections continues to grow, the impact that scan processing procedures has on the accuracy of data obtained from virtual databases remains relatively unknown. This study quantifies the intra- and inter-observer error generated from varying computed tomography (CT) scan processing protocols, including re-segmentation, incrementally varying thresholding value, and data collectors' selection of the threshold value on a set of virtual subadult pelves. Four observers segmented the subadult ossa coxarum from postmortem CT scans of the fully-fleshed bodies of eleven individuals of varying ages. Segmentation protocol was set, with the exception of each observer selecting their own thresholding value for each scan. The resulting smoothed pelvic surfaces were then compared using deviation analyses. Root mean square error (RMSE), average distance deviation, and maximum deviation distances demonstrated that thresholding values of ∼50 HU (Hounsfield units) are easily tolerated, the surfaces generated are robust to error, and threshold value selection does not systematically vary with user experience. The importance of consistent methodology during segmentation protocol is highlighted here, especially with regards to consistency in both selected thresholding value as well as smoothing protocol, as these variables can affect subsequent measurements of the resultant surfaces.

Sub-adult aging method selection (SAMS): A decisional tool for selecting and evaluating sub-adult age estimation methods based on standardized methodological parameters.

OBJECTIVES: A decisional tool was developed to select sub-adult age estimation methods referenced in a centralized database. Through a freely accessible webpage interface, this tool allows users to evaluate how much the sampling and statistical protocols of these referenced methods comply with methodological recommendations published for building and applying methods in forensic anthropology. MATERIALS AND METHODS: 261 publications on sub-adult age estimation were collected. Three search parameters describing the anatomical element(s) and the indicators used to obtain age estimates are chosen by the user to filter the database and present the publications that best correspond to the user's selection. A simple algorithm was created to score age estimation methods according to their relevance and validity. "Relevance" and "Validity" parameters indicate how much a publication complies with user queries and published methodological recommendations, respectively; "Score" is a combination of "Relevance" and "Validity". The closer these parameters are to 1, the better the method complies with the user's choice and standardized protocols. RESULTS: The publications resulting from the user's query appear as search results alphabetically. They are characterized by their "Relevance", "Validity" and "Score" values and descriptors relating to their methodology, sampling and statistical protocols. The reference of the publications and an URL to access them online are also provided. CONCLUSIONS: SAMS is a decisional tool based on a centralized database for selecting, accessing and evaluating sub-adult age estimation methods based on published methodological recommendations. Protocol validity can be easily and fully accessed to provide the necessary information for method evaluation. The database will be gradually updated and implemented as new sub-adult age estimation methods are made available online.

Integrating Growth Variability of the Ilium, Fifth Lumbar Vertebra, and Clavicle with Multivariate Adaptive Regression Splines Models for Subadult Age Estimation.

Subadult age estimation should rely on sampling and statistical protocols capturing development variability for more accurate age estimates. In this perspective, measurements were taken on the fifth lumbar vertebrae and/or clavicles of 534 French males and females aged 0-19 years and the ilia of 244 males and females aged 0-12 years. These variables were fitted in nonparametric multivariate adaptive regression splines (MARS) models with 95% prediction intervals (PIs) of age. The models were tested on two independent samples from Marseille and the Luis Lopes reference collection from Lisbon. Models using ilium width and module, maximum clavicle length, and lateral vertebral body heights were more than 92% accurate. Precision was lower for postpubertal individuals. Integrating punctual nonlinearities of the relationship between age and the variables and dynamic prediction intervals incorporated the normal increase in interindividual growth variability (heteroscedasticity of variance) with age for more biologically accurate predictions.

A critical review of sub-adult age estimation in biological anthropology: Do methods comply with published recommendations?

The diversity of approaches and the high number of publications on sub-adult age estimation is a testament to the relevance of this particular area of forensic anthropological research. However, a downside of this diversity is the many methodological, sampling and statistical discrepancies between publications, which can lead to difficulties in method definition, application and comparison. Several authors have published recommendations highlighting standardized methodological parameters that should be respected and clearly appear in the original publications for anthropological methods to be valid. This study aims to objectively evaluate a corpus of 269 publications on dental and skeletal postnatal sub-adult age estimation using these recommendations translated into descriptors. These descriptors cover five sampling and five statistical parameters that can be considered valid or invalid according to published methodological recommendations. Parameter and descriptor distributions are shown in frequency tables and graphs, illustrating the general invalidity of the sampling and/or statistical protocols. Provided our corpus of methods is an accurate representation of available publications, the extrapolation of these results leads to conclude that most sub-adult age estimates are at worst invalid, at best questionable, and almost certainly method-dependent. In view of this study, rigorous and standardized sampling and statistical approaches should be preferred when applying and building sub-adult age estimation methods.

A New Approach of Juvenile Age Estimation using Measurements of the Ilium and Multivariate Adaptive Regression Splines (MARS) Models for Better Age Prediction.

Juvenile age estimation methods used in forensic anthropology generally lack methodological consistency and/or statistical validity. Considering this, a standard approach using nonparametric Multivariate Adaptive Regression Splines (MARS) models were tested to predict age from iliac biometric variables of male and female juveniles from Marseilles, France, aged 0-12 years. Models using unidimensional (length and width) and bidimensional iliac data (module and surface) were constructed on a training sample of 176 individuals and validated on an independent test sample of 68 individuals. Results show that MARS prediction models using iliac width, module and area give overall better and statistically valid age estimates. These models integrate punctual nonlinearities of the relationship between age and osteometric variables. By constructing valid prediction intervals whose size increases with age, MARS models take into account the normal increase of individual variability. MARS models can qualify as a practical and standardized approach for juvenile age estimation.