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.     

A Test of the Revised Auricular Surface Aging Method on a Modern European Population

The accurate age estimation of adults is an important step in the construction of the biological profile of skeletonized remains. The auricular surface of the ilium as it was developed in 1985 by Lovejoy et al., is one of the methods employed for age estimation. This study presents the results of a blind test of the revised auricular surface aging method developed by Buckberry and Chamberlain. A sample of 120 individuals from the Athens Collection was used to test this revised aging technique. Almost all features and composite score were positively correlated with known age‐at‐death. The calculation of bias demonstrated no obvious trend for either overestimation or underestimation of age when all individuals were pooled together. Inaccuracy showed that absolute errors of estimated ages against known ages are substantial. The data generated from this study suggest that the revised method can be reliable for age estimation on a modern European population.     

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.     

Improving Nonmetric Sex Classification for Hispanic Individuals

Current techniques used by forensic anthropologists for the identification of unknown human skeletal remains have largely been created using U.S. Black and White samples. When applied to Hispanics, these techniques perform poorly and can lead to misclassifications; consequently, there is an imperative need for population‐specific standards for Hispanics. This research examines the classification accuracies obtained by the original Walker (Am J Phys Anthropol, 136, 2008) and Klales et al. (Am J Phys Anthropol, 149, 2012) methods for nonmetric sex estimation and provides recalibrated regression equations specifically for Hispanics. Ordinal data were collected for five skull and three pelvic traits from a sample of 54 modern Hispanic individuals. Recalibration of the Klales et al. equation improved accuracy (90.3% vs. 94.1%), while recalibration of the Walker method equation decreased accuracy (81.5% vs. 74.1%), but greatly improved sex bias (22.2% vs. ?7.4%), thereby making the recalibrated equations more appropriate for use with Hispanics.     

Secular Change in Morphological Pelvic Traits used for Sex Estimation

This research evaluates secular change in Phenice's (Am J Phys Anthropol, 30, 1969 and 297) three morphological traits of the pubis, as described by Klales et al. (Am J Phys Anthropol, 149, 2012 and 104): medial aspect of the ischio‐pubic ramus, subpubic contour, and ventral arc. Ordinal scores were collected for these traits and compared between a sample of innominates from the historical Hamann–Todd Collection (n = 170) and modern Bass Donated Collection (n = 129). Using the Freeman–Halton test, significant differences between temporal sample score frequencies were found for all traits in females and for the subpubic contour and ventral arc in males. Despite these findings, classification accuracy using logistic regression between the temporal periods remained low (68.7%). These results suggest that secular changes in trait expression are occurring; however, sex estimation methods using these traits and created with historical samples are still applicable to modern forensic cases. In fact, the secular changes occurring in these traits contribute to better classification accuracy between sexes in modern populations.     

A Test of a Recently Devised Method of Estimating Skeletal Age at Death using Features of the Adult Acetabulum

Estimation of age at death from adult skeletal remains is highly problematic, due in great part to interpopulation variability in skeletal age changes. Thorough testing of aging methods is therefore of key importance. A method recently devised by Calce (Am J Phys Anthropol 148 (2012): 11–23) for placing adult skeletons into three broad age at death classes (17–39, 40–64, 65+ years) on the basis of acetabular morphology is tested on a collection of 18–19th century AD skeletons (N = 185) of documented age at death from London. Results showed that 45% were correctly assigned to age class using this method. This compares with 81% reported by Calce on 20th century North American material. This indicates significant interpopulation differences in the relationship between the Calce acetabular variables and age, even between populations of European ancestry. Until the sources of this variation are better understood, caution should be used before applying this method to estimate age in unknown skeletons.     

Pronasale Position: An Appraisal of Two Recently Proposed Methods for Predicting Nasal Projection in Facial Reconstruction

This study examines two recently proposed methods for predicting nose projection from the skull, those developed by Stephan et al. (Am J Phys Anthropol 122, 2003, 240) and Rynn et al. (Forensic Sci Med Pathol 6, 2010, 20). A sample of 86 lateral head cephalograms of adult subjects from Central Europe was measured, and the actual and predicted dimensions were compared. Regarding nose projection (the anterior and vertical position of the pronasale), in general, the method of Rynn et al. (Forensic Sci Med Pathol 6, 2010, 20) was found to perform better and with less error variance than the method of Stephan et al. (Am J Phys Anthropol 122, 2003, 240), but the mean difference between the actual and predicted values did not exceed 2.2 mm (6.5% of the actual dimension) in most of the variables tested. The vertical dimensions of the nose were predictable with greater accuracy than the horizontal dimensions. Although the mean error of both methods is not great in practice and thus both methods could be considered to be “accurate,” the real variance of error should not be overlooked.     

Reliability of the Walker Cranial Nonmetric Method and Implications for Sex Estimation

The cranial trait scoring method presented in Buikstra and Ubelaker (Standards for data collection from human skeletal remains. Fayetteville, AR: Arkansas Archeological Survey Research Series No. 44, 1994) and Walker (Am J Phys Anthropol, 136, 2008 and 39) is the most common nonmetric cranial sex estimation method utilized by physical and forensic anthropologists. As such, the reliability and accuracy of the method is vital to ensure its validity in forensic applications. In this study, inter‐ and intra‐observer error rates for the Walker scoring method were calculated using a sample of U.S. White and Black individuals (n = 135). Cohen's weighted kappas, intraclass correlation coefficients, and percentage agreements indicate good agreement between trials and observers for all traits except the mental eminence. Slight disagreement in scoring, however, was found to impact sex classifications, leading to lower accuracy rates than those published by Walker. Furthermore, experience does appear to impact trait scoring and sex classification. The use of revised population‐specific equations that avoid the mental eminence is highly recommended to minimize the potential for misclassifications.     

Assessment of age at death by microscopy: unbiased quantification of secondary osteons in femoral cross sections

The microscopic method of age at death determination was introduced by Kerley in 1965 [E.R. Kerley, The microscopic determination of age in human bone, Am. J. Phys. Anthropol, 23 (1965) 149-163.]. However, even though the method has been revised several times, there remain some fundamental issues concerning the reliability of the methods. This is because several basic histological features seen in a cross section of a bone have to be quantified according to the method, but the definition, and hence quantification, of these features leaves room for subjectivity. In a previous study we found that some of these features (osteon fragments and Haversian canals) could not be identified reliably. Only secondary osteons could be identified with a low inter and intra observer error. Furthermore, since the histological features are quantified in only parts of an entire bone cross section, the selection of these parts or areas is a potential source of bias. Finally, unless an unbiased method is used for addressing features on the borders of the selected areas, this will also introduce error. These issues have not been addressed specifically in previous studies. In this study, we used the methods of stereology to choose the regions of interest, as well as for dealing with border phenomena, and we only counted secondary osteons. Our results show a statistically significant increase in the median number of osteons per area unit with increasing age at death. However, this was after exclusion of one outlier. This result is probably due to the limited sample size (N = 24). As such, this study is preliminary, but does warrant applying the described techniques to a larger sample.     

The Issue of Age Estimation in a Modern Skeletal Population: Are Even the More Modern Current Aging Methods Satisfactory for the Elderly?,

The main idea behind age assessment in adults is related to the analysis of the physiological degeneration of particular skeletal structures with age. The main issues with these procedures are due to the fact that they have not been tested on different modern populations and in different taphonomic contexts and that they tend to underestimate the age of older individuals. The purpose of this study was to test the applicability and the reliability of these methods on a contemporary population of skeletal remains of 145 elderly individuals of known sex and age. The results show that, due to taphonomic influences, some skeletal sites showed a lower survival. Therefore, the methods with the highest percentage of applicability were Lovejoy (89.6%) and Rougé‐Maillart (81.3%), followed by Suchey‐Brooks (59.3%), and those with the lowest percentage of applicability were Beauthier (26.2%) and Iscan (22.7%). In addition, this research has shown how for older adults the study of both acetabulum and auricular surface may be more reliable for aging. This is also in accordance with the fact that auricular surface and the acetabulum are the areas more frequently surviving taphonomic insult.     

A Test of Hartnett's Revisions to the Pubic Symphysis and Fourth Rib Methods on a Modern Sample

Estimating age at death is one of the most important aspects of creating a biological profile. Most adult age estimation methods were developed on North American skeletal collections from the early to mid‐20th century, and their applicability to modern populations has been questioned. In 2010, Hartnett used a modern skeletal collection from the Maricopia County Forensic Science Centre to revise the Suchey‐Brooks pubic symphysis method and the ??can et al. fourth rib methods. The current study tests Hartnett's revised methods as well as the original Suchey‐Brooks and ??can et al. methods on a modern sample from the William Bass Skeletal Collection (N = 313, mean age = 58.5, range 19–92). Results show that the Suchey‐Brooks and ??can et al. methods assign individuals to the correct phase 70.8% and 57.5% of the time compared with Hartnett's revised methods at 58.1% and 29.7%, respectively, with correctness scores based on one standard deviation of the mean rather than the entire age range. Accuracy and bias scores are significantly improved for Hartnett's revised pubic symphysis method and marginally better for Hartnett's revised fourth rib method, suggesting that the revised mean ages at death of Hartnett's phases better reflect this modern population. Overall, both Hartnett's revised methods are reliable age estimation methods. For the pubic symphysis, there are significant improvements in accuracy and bias scores, especially for older individuals; however, for the fourth rib, the results are comparable to the original ??can et al. methods, with some improvement for older individuals.     

Variability of the pattern of aging on the human skeleton: evidence from bone indicators and implications on age at death estimation

Age at death assessment of adult skeletons is one of the most difficult problems in forensic and physical anthropology. Two fundamental sources of error are described: the complex variability in the process of skeletal aging and methodological bias. Taking into account these limits, we developed a new scoring system for the auricular surface of the ilium and the pubic symphysis. In order to address a large variability, we examine reference samples from Europe, North America, Africa, and Asia. Data were processed using Bayesian prediction in order to classify specimens in age range categories. Results show that combining indicators do not perform better than the auricular surface used as a single indicator. Morphological changes with aging are variable between Asian, African, and European populations, confirming the necessity to use population-specific standards. Bayesian prediction produces reliable classification and is applicable for subjects over 50 years old, a real methodological improvement.     

A Comparison of Different Age Estimation Methods of the Adult Pelvis

The adult human pelvis is useful to estimate age because it contains three age indicators—the pubic symphysis, auricular surface, and acetabulum. This study tested the accuracy, inaccuracy, and bias of age estimation from the Suchey‐Brooks pubic symphysis, Osborne auricular surface, Rissech and Calce acetabulum aging methods, and a summary age of these indicators. The study sample consisted of 212 White individuals with known age and sex from the William M. Bass Donated Skeletal Collection. The Rissech method performed the best, was the most accurate method with smallest inaccuracy and bias, followed by the Osborne, Suchey‐Brooks, summary age, and then Calce methods. Though the Pearson correlation showed only the Suchey‐Brooks method to correlate significantly with known age, it is likely the Suchey‐Brooks study sample coincidentally reflected the age distribution of this test sample. Results suggested that Bayesian prediction may improve age estimation and should be applied to other age indicators.     

A test of the auricular surface aging technique

A recently developed technique used in the estimation of age at death is based upon the metamorphosis of the auricular surface of the ilium. This technique was designed to be used in seriation to estimate the age distribution of a skeletal sample. However, the technique has also been used in forensic science cases, which must be analyzed on a case-by-case basis. The present study examines the use of the auricular surface technique as the single aging factor. Two hypotheses are tested using a sample of 189 individuals drawn from the Terry Collection, housed at the Smithsonian Institution. The hypotheses are (1) is the method equally applicable across race and sex, and (2) how well does the method perform as the single aging factor? The results indicate that the amount of degenerative change in the auricular surface is not dependent upon race or sex in any given age category. However, the rate of degenerative change is too variable to be used as a single criterion for the estimation of age; the range of estimation error is simply too large for forensic science purposes.     

A simple technique for imaging the human skeleton using a flatbed scanner

A simple technique for imaging the human skeleton with a flatbed scanner is presented using the auricular surface of the ilium as an example. A flatbed scanner with resolution capabilities of 600 dpi or greater allows for images of human bones. The auricular surface of the ilium was selected to demonstrate this technique as it is a fairly three-dimensional area that can be difficult to record photographically. Fifty left ilia of various ages at death from the Athens Collection were selected from which three observers (SCF, CE, and IM) scored the morphology of the auricular surface using a well-established aging method. Observations were taken of the dry bone, of digital photographs of the bone, and of scanned images of the bone, and in that sequence. Results indicate that scores of scanned images are equivalent or better than digital images of the same ilia. This technique allows for sharing data electronically with ease.     

Determination of male age at death in Chinese Han population: using quantitative variables statistical analysis from pubic bones

Determination of age at death by skeletal features is difficult, but important, both in forensic and physical anthropology. Pubic symphysis is a widely accepted morphological indicator, which provides the best result for personal age identification. Age prediction in this study used nine indicators of morphological changes, viz: ridges and furrows on the symphysial surface, ridge of pubic tubercle, lower extremity, ventral beveling, ossific nodules, dorsal margin, ventral rampart, general macroscopic changes of symphysial surface, and bone density of the symphysial surface. Samples were drawn from 262 male individuals. The study procedures are as follows: Firstly, we examined the morphological features of pubic symphysis using criteria similar to Hanihara's and Suchey-Brooks (SB). Secondly, we evaluated each stage with an appropriate score. Thirdly, we deduced four equations of male age assessment of morphological features by statistic analysis. The results were compared with Hanihara's and Suchey-Brooks method; the similarities and differences among them were discussed objectively. The method produced consistent results as well as developing the criteria of Hanihara's and Suchey-Brooks'.     

Age estimation from the human os coxa: a test on a documented Italian collection*

Current standards for age at death estimation from the pelvis are based on Americans of European and African ancestry. Our limited understanding of population variability hampers our efforts to apply these techniques to the various skeletal populations around the world, especially in global forensic contexts. However, documented skeletal samples are rare, limiting our ability to test our techniques. This study tested the Suchey-Brooks pubic symphysis aging method and the auricular surface method originally developed by Lovejoy et al. on a large sample (n = 404) of known sex and age from the Sassari Collection, housed at the Museum of Anthropology at the University of Bologna, Italy. The results indicate that for both methods, bias and inaccuracy increased with age and actual age tended to be underestimated over the age of 40. The auricular surface method performed slightly better, exhibiting slightly lower levels of bias and inaccuracy, especially for males.     

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.