Spheno-occipital synchondrosis fusion in modern Americans

This study examines spheno-occipital synchondrosis fusion in the modern American population and presents age ranges for forensic use. The sample includes 162 modern individuals aged 5-25 years. The basilar synchondrosis was scored as open, closing, or closed via direct inspection of the ectocranial site of the suture. Transition analysis was used to determine the average ages at which an individual transitions from unfused to fusing and from fusing to fused. The maximum likelihood estimates from the transition analysis indicate that females are most likely to transition from open to closing at 11.4 years and males at 16.5 years. Females transition from closing to closed at 13.7 years and males at 17.4 years. The probability distributions associated with these maximum likelihood estimates were used to derive age ranges for age estimation purposes. These results reflect sexual dimorphism in basilar synchondrosis fusion and agree approximately with average age at pubertal onset.     

Auricular Surface Aging: Comparing Two Methods that Assess Morphological Change in the Ilium with Bayesian Analyses

Modern standards in forensic anthropology require rigorous testing and evaluation of methods used for aging skeletal remains. Age estimation has been criticized for bias, inaccuracy, and population specificity; issues which are minimized by the application of Bayesian methodology. Using Bayesian statistics, we compare the Lovejoy et al. (Am J Phys Anthropol, 68, 1985, 15) (original) and Buckberry and Chamberlain (Am J Phys Anthropol, 119, 2002, 231) (revised) auricular surface aging methods. Transition analysis parameters derived from American males (n = 372), in combination with a Thai male (N = 37) informative prior, statistically model age in Portuguese males (n = 221). Cumulative binomial tests assess the accuracy of the generated age ranges. Overall, the application of transition analysis and Bayesian statistics significantly improved age estimation with both methods (also outperforming Suchey‐Brooks pubic symphysis aging). Moreover, the accuracy of the original method was low without statistical modeling, whereas the revised method can be applied accurately without further statistical analysis. Additionally, reference tables for aging Portuguese males are provided.     

Introducing Computed Tomography Standards for Age Estimation of Modern Australian Subadults Using Postnatal Ossification Timings of Select Cranial and Cervical Sites,

Contemporary, population‐specific ossification timings of the cranium are lacking in current literature due to challenges in obtaining large repositories of documented subadult material, forcing Australian practitioners to rely on North American, arguably antiquated reference standards for age estimation. This study assessed the temporal pattern of ossification of the cranium and provides recalibrated probabilistic information for age estimation of modern Australian children. Fusion status of the occipital and frontal bones, atlas, and axis was scored using a modified two‐ to four‐tier system from cranial/cervical DICOM datasets of 585 children aged birth to 10 years. Transition analysis was applied to elucidate maximum‐likelihood estimates between consecutive fusion stages, in conjunction with Bayesian statistics to calculate credible intervals for age estimation. Results demonstrate significant sex differences in skeletal maturation (p < 0.05) and earlier timings in comparison with major literary sources, underscoring the requisite of updated standards for age estimation of modern individuals.     

A Bayesian Approach to Age Estimation in Modern Americans from the Clavicle*

Abstract: Clavicles from 1289 individuals from cohorts spanning the 20th century were scored with two scoring systems. Transition analysis and Bayesian statistics were used to obtain robust age ranges that are less sensitive to the effects of age mimicry and developmental outliers than age ranges obtained using a percentile approach. Observer error tests showed that a simple three‐phase scoring system proved the least subjective, while retaining accuracy levels. Additionally, significant sexual dimorphism was detected in the onset of fusion, with women commencing fusion at least a year earlier than men (women transition to fusion at approximately 15 years of age and men at 16 years). Significant secular trends were apparent in the onset of skeletal maturation, with modern Americans transitioning to fusion approximately 4 years earlier than early 20th century Americans and 3.5 years earlier than Korean War era Americans. These results underscore the importance of using modern standards to estimate age in modern individuals.     

A Bayesian approach to estimate skeletal age-at-death utilizing dental wear

In the forensic context, teeth are often recovered in mass disasters, armed conflicts, and mass graves associated with human rights violations. Therefore, for victim identification, techniques utilizing the dentition to estimate the first parameters of identity (e.g., age) can be critical. This analysis was undertaken to apply a Bayesian statistical method, transition analysis, based on the Gompertz-Makeham (GM) hazard model, to estimate individual ages-at-death for Balkan populations utilizing dental wear. Dental wear phases were scored following Smith's eight-phase ordinal scoring method and chart. To estimate age, probability density functions for the posterior distributions of age for each tooth phase are calculated. Transition analysis was utilized to generate a mean age-of-transition from one dental wear phase to the next. The age estimates are based on the calculated age distribution from the GM hazard analysis and the ages-of-transition. To estimate the age-at-death for an individual, the highest posterior density region for each phase is calculated. By using a Bayesian statistical approach to estimate age, the population's age distribution is taken into account. Therefore, the age estimates are reliable for the Balkan populations, regardless of population or sex differences. The results showed that a vast amount of interpersonal variation in dental wear exists within the current sample and that this method may be most useful for classifying unknown individuals into broad age cohorts rather than small age ranges.     

A Bayesian Approach to Age‐at‐Death Estimation from Osteoarthritis of the Shoulder in Modern North Americans

Osteoarthritis (OA) is a marker of degeneration within the skeleton, frequently associated with age. This study quantifies the correlation between OA and age‐at‐death and investigates the utility of shoulder OA as a forensic age indicator using a modern North American sample of 206 individuals. Lipping, surface porosity, osteophyte formation, eburnation, and percentage of joint surface affected were recorded on an ordinal scale and summed to create composite scores that were assigned a specific phase. Spearman's correlation indicated a positive relationship between each composite score and age (right shoulder = 0.752; left shoulder = 0.734). Transition analysis revealed a tendency toward earlier degeneration of the right shoulder. Bayesian statistics generated phase‐related age estimates based on highest posterior density regions. Best age estimates were into the seventh decade at the 90th and 50th percentile. The proposed method supplements traditional techniques by providing age estimates beyond a homogenous 50+ age cohort.     

Estimation of age-at-death for adult males using the acetabulum, applied to four Western European populations

Methods to estimate adult age from observations of skeletal elements are not very accurate and motivate the development of better methods. In this article, we test recently published method based on the acetabulum and Bayesian inference, developed using Coimbra collection (Portugal). In this study, to evaluate its utility in other populations, this methodology was applied to 394 specimens from four different documented Western European collections. Four strategies of analysis to estimate age were outlined: (a) each series separately; (b) on Lisbon collection, taken as a reference Coimbra collection; (c) on Barcelona collection, taken as a reference both Portuguese collections; and (d) on London collection taken as reference the three Iberian collections combined. Results indicate that estimates are accurate (83-100%). As might be expected, the least accurate estimates were obtained when the most distant collection was used as a reference. Observations of the fused acetabulum can be used to make accurate estimates of age for adults of any age, with less accurate estimates when a more distant reference collection is used.     

New formulae for estimating age-at-death in the Balkans utilizing Lamendin's dental technique and Bayesian analysis

The present study analyzed apical translucency and periodontal recession on single-rooted teeth in order to generate age-at-death estimations using two inverse calibration methods and one Bayesian method. The three age estimates were compared to highlight inherent problems with the inverse calibration methods. The results showed that the Bayesian analysis reduced severity of several problems associated with adult skeletal age-at-death estimations. The Bayesian estimates produced a lower overall mean error, a higher correlation with actual age, reduced aging bias, reduced age mimicry, and reduced the age ranges associated with the most probable age as compared to the inverse calibration methods for this sample. This research concluded that periodontal recession cannot be used as a univariate age indicator, due to its low correlation with chronological age. Apical translucency yielded a high correlation with chronological age and was concluded to be an important age indicator. The Bayesian approach offered the most appropriate statistical analysis for the estimation of age-at-death with the current sample.     

A Bayesian approach to the group versus individual prediction controversy in actuarial risk assessment

Recent attempts to indict the use of actuarial risk assessment instruments have relied on confidence intervals to demonstrate that risk estimates derived at the group level do not necessarily apply to any specific individual within that group. This article contends that frequentist confidence intervals are inapposite to the current debate. Instead, Bayesian credible intervals are necessary-in principle-to accomplish what commentators are concerned about: describing the precision of an actuarial risk estimate. After illustrating both the calculation and interpretation of credible intervals, this article shows how such intervals can be used to characterize the precision of actuarial risk estimates. It then explores the legal implications of wide and overlapping intervals. Contrary to what detractors claim, the fact that risk estimate intervals overlap is not a germane to legal (logical) relevance, and therefore actuarial risk estimates cannot be per se "inadmissible" on this basis.     

Evaluation of age estimation technique: testing traits of the acetabulum to estimate age at death in adult males

This study evaluates the accuracy and precision of a skeletal age estimation method, using the acetabulum of 100 male ossa coxae from the Grant Collection (GRO) at the University of Toronto, Canada. Age at death was obtained using Bayesian inference and a computational application (IDADE2) that requires a reference population, close in geographic and temporal distribution to the target case, to calibrate age ranges from scores generated by the technique. The inaccuracy of this method is 8 years. The direction of bias indicates the acetabulum technique tends to underestimate age. The categories 46-65 and 76-90 years exhibit the smallest inaccuracy (0.2), suggesting that this method may be appropriate for individuals over 40 years. Eighty-three percent of age estimates were ±12 years of known age; 79% were ±10 years of known age; and 62% were ±5 years of known age. Identifying a suitable reference population is the most significant limitation of this technique for forensic applications.     

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.     

Palatine Sutures as Age Indicator: A Controlled Study in the Elderly

Abstract:  Vault sutures have proven their low reliability for estimating age at death in individual forensic science cases. We broke down the palatine sutures of 134 skulls (with known sex and age at time of death) into 15 subparts and 5 stages of fusion to obtain a mean coefficient of obliteration ( C p) which was then linked to five age classes. We completed this study with multiple regression equations of total palatine suture scores. We compared our results with those obtained using the Mann method on the one hand and classically segmented and scored ectocranial suture age determination methods on the other. Palatine sutures generally do not estimate age at death any better than cranial vault sutures. Despite the partly subjective aspect of suture study, palatine suture observation contributes additional information to age-range estimation, especially in old and very old subjects where other methods lose their effectiveness.     

Weight References for Burned Human Skeletal Remains from Portuguese Samples

Weight is often one of the few recoverable data when analyzing human cremains but references are still rare, especially for European populations. Mean weights for skeletal remains were thus documented for Portuguese modern cremations of both recently deceased individuals and dry skeletons, and the effect of age, sex, and the intensity of combustion was investigated using both multivariate and univariate statistics. The cremains from fresh cadavers were significantly heavier than the ones from dry skeletons regardless of sex and age cohort (p < 0.001 to p = 0.003). As expected, males were heavier than females and age had a powerful effect in female skeletal weight. The effect of the intensity of combustion in cremains weight was unclear. These weight references may, in some cases, help estimating the minimum number of individuals, the completeness of the skeletal assemblage, and the sex of an unknown individual.     

Utility of the Frontonasal Suture for Estimating Age at Death in Human Skeletal Remains*

Abstract: This project evaluated the utility of the frontonasal suture for estimating age at death. Utilizing human remains of known age at death with varying degrees of fusion, curated at the American Museum of Natural History in New York City and the Smithsonian Institution’s National Museum of Natural History in Washington, DC, data were collected from the ectocranial surface of 522 crania; 68 of these were sagittally sectioned, allowing collection of internal data and observation of suture closure through the bone. Degree of ectocranial suture closure does not significantly predict age, even when sex and ancestry are accounted for. Suture closure progression data were converted into a Hershkovitz ratio (sum of the measurement of open portion divided by the total suture length), and regression models demonstrate that the effect of age accounts for only 13% of variation in suture closure.     

Maxillary suture obliteration: a visual method for estimating skeletal age.

The purpose of this study was to develop a method of estimating the age of an individual based on obliteration of the four maxillary (palatal) sutures. A sample of 186 individuals of known age, race, and sex were examined. It was found that males of both races (black and white) exhibit more suture obliteration than females at the same age. During the early adult years, maxillary suture obliteration progresses at nearly the same rate in both sexes; however, the age of old individuals may be greatly overestimated using this method. Although this method cannot be used for exact estimates of individual age, it is valuable in establishing the age range, sorting commingled remains, and estimating skeletal age when only the maxilla is present.     

Ossification Degrees of Cranial Sutures Determined with Flat‐Panel Computed Tomography: Narrowing the Age Estimate with Extrema

Abstract: Since Broca’s time (1824–1880), ossification of the neurocranial sutures has been used as a characteristic of age. Current approaches include the visual macroscopic examination of ecto and endocranial sutures. The evaluation of the cross‐section of sutures usually necessitates the destruction of the neurocranium. In a nondestructive alternative approach that was tested within the context of the “Digital Forensic Osteology” project that ran in cooperation with the Virtopsy^®‐Project, it emerged that the resolution of conventional multi‐slice computed tomography data sets was not high enough to image sutures. Thus for the experiments presented here, the eXplore Locus Ultra flat‐panel computed tomography scanner from GE Healthcare was used. Calottes were scanned during autopsy and then immediately returned to the corpse. So far, the skullcaps of 221 individuals have been scanned. The cross‐sections of 14 suture segments could be assessed for seven previously defined stages of ossification. In a converse step, the 14 highest and lowest age estimate values corresponding to the individual stages of suture closure found were estimated for each calotte. The obtained ranges narrowing down the age estimate were evaluated with statistics. A mean value of 43.31 years for the range of narrowed age estimates shows that this method can be a useful aid in estimating age. The results of intra‐ and inter‐observer tests showed good overall agreement between the findings of three observers. This method is suitable for a nondestructive age estimation and can be used for the entire calotte.     

The sensitivity of the Bayesian HPD method to the choice of prior.

Statistical sampling error is present in every statistical calculations using DNA because all such statistics rely on a sample (database) of individuals, which is used to estimate the population frequencies of alleles. Curran et al.gave a method for estimating the sampling error of the statistics based on the region of the highest density of the Bayesian posterior (HPD). The Bayesian HPD method relies on the assumption of a prior distribution for the population allele frequencies as well as Monte Carlo simulation. In this paper we answer three pivotal questions. Firstly we address the question of how many Monte Carlo iterations are required to get sufficient accuracy in our estimates of sampling error. Secondly, we address the question of the appropriate choice of the prior distribution for the population allele frequencies. Thirdly, we demonstrate the flexibility of the Bayesian HPD over other methods.     

Evaluation of post-mortem estimated dental age versus real age: a retrospective 21-year survey

The aim of the study was to evaluate the reliability of methods used for forensic dental age estimation. We analysed all cases over the last 21 years (1984-2004) of unidentified bodies that were examined for identification purposes (including age assessment), and of which secure identification was subsequently achieved. In total, the study included 51 cases and 7 different methods had been used for dental age estimation, with the Bang/Ramm and the Gustafson/Johanson methods being the most frequently applied. The age estimates had usually been recorded as 10-year intervals. Factual ages at death were in the range of 6-76 years, with the largest concentration of cases being in the age interval of 25-55 years (34 cases). There was good agreement between estimated age interval and factual age at death in 37/51 (72%) of the cases. In eight cases the factual age at death deviated up to +/-5 years from the estimated age, and in six cases by more than 6 years. The average difference between factual age at death and estimated age was 4.5 years. The four subadults in the material were all correctly estimated within an age range of +/-3 years. Our study showed that forensic odontological age estimates are reliable. However, the implementation of the specific methods may need to be adjusted concerning age ranges. In the future we recommend to register anamnestic information and the different steps in the methods used. Clinical evaluation should contain more details about attrition, colour, number and presumed age of the restorations and periodontal status.     

Analysis of age-at-death estimation through the use of pubic symphyseal data

The question of whether age parameters derived from an American population will reliably estimate age-at-death for East European skeletal populations is important since the ability to accurately estimate an individual's age-at-death hinges on what standard is used. A reference sample of identified individuals with known ages-at-death from the regions of the Former Yugoslavia (n = 861) is used to determine the age structure of victims and serves as the prior in the Bayesian analysis. Pubic symphyseal data in the manners of Todd (Am J Phys Anthropol, 3 [1920], 285; Am J Phys Anthropol, 4 [1921], 1) and Suchey-Brooks (Am J Phys Anthropol, 80 [1986], 167) were collected for n = 296 Balkan males and females and for n = 2078 American males and females. An analysis of deviance is calculated using an improvement chi-square to test for population variation in the aging processes of American and East European populations using proportional odds probit regression. When males and females are treated separately, there is a significant association among females and the population (df = 1, chi-square likelihood ratio = 15.071, p = 0.001). New age estimates for Balkan populations are provided and are based on the calculated age distribution from the Gompertz-Makeham hazard analysis and the ages-of-transition. To estimate the age-at-death for an individual, the highest posterior density regions for each symphyseal phase are provided.