Daniel J. Wescott

Estimation and Evidence in Forensic Anthropology: Age‐at‐Death

Abstract:  A great deal has previously been written about the use of skeletal morphological changes in estimating ages‐at‐death. This article looks in particular at the pubic symphysis, as it was historically one of the first regions to be described in the literature on age estimation. Despite the lengthy history, the value of the pubic symphysis in estimating ages and in providing evidence for putative identifications remains unclear. This lack of clarity primarily stems from the fact that rather ad hoc statistical methods have been applied in previous studies. This article presents a statistical analysis of a large data set (n = 1766) of pubic symphyseal scores from multiple contexts, including anatomical collections, war dead, and victims of genocide. The emphasis is in finding statistical methods that will have the correct “coverage.”“Coverage” means that if a method has a stated coverage of 50%, then approximately 50% of the individuals in a particular pubic symphyseal stage should have ages that are between the stated age limits, and that approximately 25% should be below the bottom age limit and 25% above the top age limit. In a number of applications it is shown that if an appropriate prior age‐at‐death distribution is used, then “transition analysis” will provide accurate “coverages,” while percentile methods, range methods, and means (±standard deviations) will not. Even in cases where there are significant differences in the mean ages‐to‐transition between populations, the effects on the stated age limits for particular “coverages” are minimal. As a consequence, more emphasis needs to be placed on collecting data on age changes in large samples, rather than focusing on the possibility of inter‐population variation in rates of aging.

Assessing Craniofacial Secular Change in American Blacks and Whites Using Geometric Morphometry

American crania have changed significantly in the past 150 years. In the sagittal plane, most of the change is associated with a downward movement of the cranial base, especially at basion. Secular change in American crania is proximately related to a decrease in cranial base breadth and an increase in cranial capacity, and ultimately a reflection of improved infant growth due to better health and nutrition. The environment of 20th century Americans has no parallel in history. Activity levels are at an all-time low, and diet has improved to the point where overnutrition has surpassed undernutrition as our most serious malnutrition problem (Flegal et al., 1998). In addition, epidemic infectious diseases are now mostly controlled, and mortality is at an all-time low (Armstrong et al., 1999). It is not surprising that there is a biological response to this unparalleled environmental change.

Sex variation in the second cervical vertebra.

The second cervical vertebra can be used to estimate sex with 83% accuracy in unidentified human skeletal remains. Reported here are the necessary statistics, based on 8 dimensions taken from 400 second cervical vertebrae, for the computation of customized discriminant functions. Discriminant function equations developed using variables selected in a stepwise procedure are also presented here as an example of the usefulness of this bone in estimating sex.

Estimation of adult skeletal age-at-death using the Sugeno fuzzy integral

Age-at-death estimation of an individual skeleton is important to forensic and biological anthropologists for identification and demographic analysis, but it has been shown that the current aging methods are often unreliable because of skeletal variation and taphonomic factors. Multifactorial methods have been shown to produce better results when determining age-at-death than single indicator methods. However, multifactorial methods are difficult to apply to single or poorly preserved skeletons, and they rarely provide the investigator with information about the reliability of the estimate. The goal of this research is to examine the validity of the Sugeno fuzzy integral as a multifactorial method for modeling age-at-death of an individual skeleton. This approach is novel because it produces an informed decision of age-at-death utilizing multiple age indicators while also taking into consideration the accuracies of the methods and the condition of the bone being examined. Additionally, the Sugeno fuzzy integral does not require the use of a population and it qualitatively produces easily interpreted graphical results. Examples are presented applying three commonly used aging methods on a known-age skeletal sample from the Terry Anatomical Collection. This method produces results that are more accurate and with smaller intervals than single indicator methods.

Population Variation in Femur Subtrochanteric Shape

Use of proximal femur shape to determine ancestry has appeal, but its validity is problematic because of unaddressed issues associated with skeletal plasticity, within- and between-population variation, sample selection, and interobserver error. In this paper, I inspect within- and between-group variation in proximal femur shape using five groups (American Blacks, American Whites, Hispanics, Native Americans, and Polynesians), and examine the affect of three environmental variables (subsistence strategy, physical terrain, and geographical region). Finally. I consider the validity of using the proximal femur to assess ancestry. The results show that there is significant within-group variation in proximal femur shape. Among Native Americans, both geographical location and subsistence strategy have a significant affect on proximal femur shape. Nevertheless, this study generally verifies the assertion that the proximal femur can be used reliably to distinguish Native Americans from American Blacks and Whites, but its precision may be reduced in some geographical regions.

Stature Estimation Based on Dimensions of the Bony Pelvis and Proximal Femur

Abstract:  Pelin et al. recently showed that sacral height measured on lateral magnetic resonance images can be used with moderate accuracy to reconstruct stature in males. In most forensic anthropological cases, however, sacral dimensions must be obtained from dry bones. In this study, the relationship between stature and sacral height, hip height, and femur head diameter measured on dry bone was evaluated for American Blacks and Whites of both sexes (n = 247). There are significant correlation between stature and these three dimensions, but the results suggest that none of the dimensions predict stature with the accuracy needed to be useful in forensic anthropological investigations.

Metric Variation in the Human Occipital Bone: Forensic Anthropological Applications

Sex and race variation of the occipital bone have been previously investigated, but particular examination of the effect of age and ancestry on sexual dimorphism has not been addressed. This paper examines morphological variation associated with sex and ancestry in the condylar region of the occipital bone and the effect of age and ancestry on the estimation of sex. Models previously published by Holland are also tested, and methodological problems are addressed. The results indicate that age does not have an effect on sexual dimorphism, but that whites exhibit greater, although not significantly, more sexual dimorphism than blacks. Significant sex and ancestry variation is present in the condylar region of the occipital bone, but neither sex nor ancestry could be estimated accurately using measurements of this anatomical region defined by Holland.

Still More “Fancy” and “Myth” than “Fact” in Students’ Conceptions of Evolution

College students do not come to biological sciences classes, including biological anthropology, as “blank slates.” Rather, these students have complex and strongly held scientific misconceptions that often interfere with their ability to understand accurate explanations that are presented in class. Research indicates that a scientific misconception cannot be corrected by simply presenting accurate information; the misconception must be made explicit, and the student must decide for him or herself that it is inaccurate. The first step in helping to facilitate such conceptual change among college students is to understand the nature of the scientific misconceptions. We surveyed 547 undergraduate students at the University of Missouri-Columbia on their understanding of the nature and language of science, the mechanisms of evolution, and their support for both Lamarckian inheritance and teleological evolution. We found few significant sex differences among the respondents and identified some common themes in the students’ misconceptions. Our survey results show that student understanding of evolutionary processes is limited, even among students who accept the validity of biological evolution. We also found that confidence in one’s knowledge of science is not related to actual understanding. We advise instructors in biological anthropology courses to survey their students in order to identify the class-specific scientific misconceptions, and we urge faculty members to incorporate active learning strategies in their courses in order to facilitate conceptual change among the students.

Extension of the fuzzy integral for general fuzzy set-valued information

The fuzzy integral (FI) is an extremely flexible aggregation operator. It is used in numerous applications, such as image processing, multicriteria decision making, skeletal age-at-death estimation, and multisource (e.g., feature, algorithm, sensor, and confidence) fusion. To date, a few works have appeared on the topic of generalizing Sugenos original real-valued integrand and fuzzy measure (FM) for the case of higher order uncertain information (both integrand and measure). For the most part, these extensions are motivated by, and are consistent with, Zadehs extension principle (EP). Namely, existing extensions focus on fuzzy number (FN), i.e., convex and normal fuzzy set- (FS) valued integrands. Herein, we put forth a new definition, called the generalized FI (gFI), and efficient algorithm for calculation for FS-valued integrands. In addition, we compare the gFI, numerically and theoretically, with our non-EP-based FI extension called the nondirect FI (NDFI). Examples are investigated in the areas of skeletal age-at-death estimation in forensic anthropology and multisource fusion. These applications help demonstrate the need and benefit of the proposed work. In particular, we show there is not one supreme technique. Instead, multiple extensions are of benefit in different contexts and applications.

Effect of obesity on the reliability of age-at-death indicators of the pelvis

During medicolegal investigations, forensic anthropologists commonly use morphological changes in the auricular surface of the ilium and the symphyseal face of the pubis to estimate age. However, obesity may impact the reliability of age estimations based on pelvic joints. Over the past several decades, the prevalence of obesity has dramatically increased in the United States (US). Since the rate of progression through age-related stages of weight-bearing joints may be influenced by excessive body mass, it is important that anthropologists understand how obesity affects age-related morphological changes in the skeleton. This study investigates the effects of obesity on the validity of the estimated age-at-death based on the Buckberry-Chamberlin and Suchey-Brooks methods by comparing US adults considered normal BMI (BMI 18.5-24.9) and obese (BMI ≥ 30). The obese group exhibits overall greater bias (overestimation of age) and inaccuracy, less precision, and lower correlations between estimated and known age than the normal BMI group using both methods, although differences in the pubic symphysis are not statistically significant. For the auricular surface the age of transition from one phase to the next is lower and the standard deviations are greater for the obese as compared to normal weight individuals. This study helps to elucidate how obesity affects the rate of age-related skeletal change of the human pelvis, and shows that the pubic symphysis may be a more reliable indicator of age in obese individuals and that greater standard deviations are needed for obese individuals when estimating age-at-death from the pelvis.