Eric J. Bartelink

Quantitative analysis of sharp-force trauma: an application of scanning electron microscopy in forensic anthropology.

Scanning electron microscopy (SEM) has occasionally been used by anthropologists and forensic scientists to look at morphological characteristics that certain implements leave on bone. However, few studies have addressed techniques or protocols for assessing quantitative differences between tool marks on bone made by different bladed implements. In this study, the statistical variation in cut mark width was examined between control and test samples on bone using a scalpel blade, paring knife, and kitchen utility knife. Statistically significant differences (p < .0005) were found between cut marks made by the same knife under control and test conditions for all three knife types used in the study. When the control sample and test samples were examined individually for differences in mean variation between knife types, significant differences were also found (p < .0005). While significant differences in cut mark width were found, caution should be used in trying to classify individual cut marks as being inflicted by a particular implement, due to the overlap in cut mark width that exists between different knife types. When combined, both quantitative and qualitative analyses of cut marks should prove to be more useful in trying to identify a suspect weapon. Furthermore, the application of SEM can be particularly useful for assessing many of these features.

Paleoepidemiological Patterns of Interpersonal Aggression in a Prehistoric Central California Population From CA-ALA-329

Interpersonal aggression is assessed paleoepidemiologically in a large skeletal population from the CA-ALA-329 site located on the southeastern side of San Francisco Bay, California. This comprehensive analysis included all currently recognized skeletal criteria, including craniofacial fracture, projectile injury, forearm fracture, and perimortem bone modification. Craniofacial injury is moderately common, showing an adult prevalence of 9.0% with facial lesions accounting for >50% of involvement. Clinical studies suggest that such separate evaluation of facial involvement provides a useful perspective for understanding patterns of interpersonal aggression. In this group male facial involvement is significantly greater than in females, paralleling the pattern found widely in contemporary populations as well as in African apes. When compared to other North American skeletal samples the prevalence of adult cranial vault injury (3.3%) and especially projectile injury (4.4%) are quite high. However, well documented populations from southern California show markedly higher prevalence for both types of skeletal markers of aggression. Forearm fracture is also assessed using a rigorous radiographic methodology and results suggest that these injuries are not reliable indicators of interpersonal aggression. Lastly, perimortem bone modification was not observed in this population, although it has been recorded from other (older) sites nearby. This study provides an evaluation of multiple skeletal markers of interpersonal aggression in the largest sample from a single site yet reported in North America and, joined with consideration of cultural context, helps further illuminate both geographic and temporal patterns of interpersonal aggression in California.

Sex-Biased Weaning and Early Childhood Diet Among Middle Holocene Hunter-Gatherers in Central California

This article evaluates age of weaning and early childhood diets of eight males and nine females from a Middle Holocene (4300-3000 BP) site in Central California, CA-CCO-548. All individuals died as adults. δ(15) N values from serial sections of dentin collagen in first molars suggest females were fully weaned, on average, by 3.6 years of age, about 0.4 years later than males in the sample, suggesting possible greater parental investment in female offspring. However, throughout childhood females consumed lower trophic-level foods than males. This could indicate greater investment in males through provisioning of higher quality foods, or alternatively, some degree of independent foraging by males starting as early as 2 to 3 years of age. Even as adults, these same males and females consumed a different range of foods as indicated by their bone collagen δ(13) C and δ(15) N values. Overall, the data suggest children were enculturated early into their respective gendered diets, with girls consuming greater amounts of plant foods and boys consuming greater amounts of higher-trophic level fish and meat protein.

Late Holocene Dietary Change in the San Francisco Bay Area

Abstract Scholars of California prehistory continue to debate the importance of different food resources to the native diet during the late Holocene. Resource intensification models for central California predict temporal declines in the abundance of large game relative to smaller fauna, as well as a shift towards greater use of vegetal foods. These changes are commonly linked to human-driven resource depression and overpopulation, although climatic factors may also have played a role. This study uses data from stable carbon and nitrogen isotopes of human bone to evaluate evidence of paleodietary change among late Holocene human populations (ca. 4950-200 cal B.P.) from the eastern shore of San Francisco Bay, California. Carbon and nitrogen isotope values of bone collagen demonstrate significant temporal variation and indicate a shift in emphasis from high trophic-level marine protein toward a greater emphasis on terrestrial resources and lower trophic-level marine foods. Carbon isotope values of bone apatite provide additional information not recorded in bone collagen, and suggest an increased emphasis on vegetal resources during the latter part of the prehistoric sequence (after ca. 2150 cal B.P.). Alternatively, the isotopic data presented here could provide evidence for regionally specific diets or variation due to human population movement throughout the San Francisco Bay area.

A re-examination of cremains weight: sex and age variation in a Northern California sample.

Abstract:  The reduction of modern commercially cremated remains into a fine powder negates the use of traditional methods of skeletal analysis. The literature on the use of cremains weight for estimating aspects of the biologic profile is limited, often with conflicting results. This study re‐evaluates the value of weight in the assessment of biologic parameters from modern cremated remains. A sample of adults was collected in northern California (n = 756), with a cremains weight averaging 2737.1 g. Males were significantly heavier than females ( = 3233.2 g versus  = 2238.3 g, respectively; p < 0.001). Comparison of this sample with other previously reported samples from southern California, Florida, and Tennessee indicates a consistent sex difference, with the most similar mean values to the Tennessee study. Although cremains weight decreases with age as expected, the relationship is weak; thus, cremains weight cannot accurately predict age‐at‐death. While sex estimation shows considerable accuracy (86.3% for males and 80.9% for females), sectioning points may be population specific.

Sexual Dimorphism in Finger Ridge Breadth Measurements: A Tool for Sex Estimation from Fingerprints

Previous research has demonstrated significant sexual dimorphism in friction ridge skin characteristics. This study uses a novel method for measuring sexual dimorphism in finger ridge breadths to evaluate its utility as a sex estimation method from an unknown fingerprint. Beginning and ending in a valley, the width of ten parallel ridges with no obstructions or minutia was measured in a sample of 250 males and females (N = 500). The results demonstrate statistically significant differences in ridge breadth between males and females (p < 0.001), with classification accuracy for each digit varying from 83.2% to 89.3%. Classification accuracy for the pooled finger samples was 83.9% for the right hand and 86.2% for the left hand, which is applicable for cases where the digit number cannot be determined. Weight, stature, and to a lesser degree body mass index also significantly correlate with ridge breadth and account for the degree of overlap between males and females.

The Evolution of a Cemetery: Rapid Change in Burial Practices in a Middle Holocene Site in Central Alta California

Abstract Treating cemeteries as single analytical units masks significant and behaviorally meaningful patterns. With high resolution radiocarbon dating of a large number of burials, we show how interments at CA-CCO-548 in central California shifted spatially, temporally, and stylistically across the site. Some interment attributes such as burial position changed little over time, while others such as orientation drifted markedly. We suggest that the former burial attributes mark stable and perhaps biologically mediated aspects of ancient societies such as generation or birth order, while the latter mark affiliation in groups that vary in popularity such as clan or religious affiliation. Furthermore, the data suggest that variation, not conformity to a single rule, is the norm for interment style.

A probable case of acromegaly from the Windmiller culture of prehistoric Central California

A skeleton excavated from the Blossom Mound (CA-SJO-68), a Late Holocene (4350-2980 BP) site located in the northern San Joaquin Valley of California, exhibits evidence of unusual craniofacial and postcranial features consistent with endocrine disease. Burial 37, an adult male approximately 30-40 years of age, shows pronounced development of the mental eminence, glabellar region, and supraorbital arches, as well as elongation of the mandibular ramus, crowding and malocclusion of the anterior dentition, and periosteal bone formation at several enthesis sites. In addition, abnormal enlargement of the sella turcica as well as pneumatization of the frontal and maxillary sinus and mastoid air cells was observed. These skeletal characteristics are consistent with a diagnosis of acromegaly, an endocrine disorder characterized by the enlargement of bone and soft tissue resulting from a pituitary gland tumor that increases the secretion of growth hormone. Onset typically occurs after epiphyseal fusion, a characteristic that distinguishes it from gigantism. This case study utilizes current clinical criteria for diagnosing acromegaly in human skeletal remains and discusses other evidence of this rare condition in the archeological record.

Application of Portable X-ray Fluorescence (XRF) for Sorting Commingled Human Remains

Abstract Commingled human skeletal remains present complex challenges for medicolegal investigations. In cases of commingling, it is important to accurately segregate the remains of each individual represented and then make a determination of the number of individuals present. Forensic anthropologists are uniquely qualified to make assessments regarding commingling because they routinely employ laboratory methods such as identifying duplicated skeletal elements, visual and osteometric pair-matching of bilateral elements, evaluation of joint congruity between articular surfaces, skeletal age comparisons, and assessment of corresponding pathological changes and taphonomic modifications between different skeletal elements. Recent research using X-ray fluorescence (XRF) spectrometry has shown promise in determining whether a set of remains belongs to a single or multiple individuals by analyzing elemental concentrations in human bones. One advantage to this approach is that it has the potential to provide an inexpensive, rapid, and nondestructive method for assessing small-scale cases of commingling. The development of portable XRF (pXRF) technology has opened the possibility to apply the method to both complete and fragmentary remains not only in a laboratory setting, but also allowing for analyses in the field.

Stable Isotope Forensics as an Investigative Tool in Missing Persons Investigations

Recent forensic applications of stable isotope analysis (SIA) have demonstrated its value as an investigative tool in the identification of unknown decedents. Stable isotope ratios measured in bones, teeth, hair, and nails provide a record of a person’s dietary preferences, travel history, and residence patterns. Stable carbon, nitrogen, and sulfur isotopes of human tissues provide information regarding a decedent’s dietary preferences, which in turn may reflect a person’s geographic region of origin. Additionally, stable oxygen and strontium isotopes in body tissues can be used to provenance human remains, because these isotopes reflect the source of drinking water and local geology, respectively. When combined, a multi-isotope approach provides a powerful geolocation tool for predicting a region of origin or recent travel history for unidentified human remains. In this study, we present on two forensic cases that used SIA to predict the travel history and region of origin of unknown decedents.