Investigating the Timing and Extent of Juvenile and Fetal Bone Diagenesis in a Temperate Environment.

It is well understood that intrinsic factors of bone contribute to bone diagenesis, including bone porosity, crystallinity, and the ratio of organic to mineral components. However, histological analyses have largely been limited to adult bones, although with some exceptions. Considering that many of these properties are different between juvenile and adult bone, the purpose of this study is to investigate if these differences may result in increased degradation observed histologically in fetal and juvenile bone. Thirty-two fetal (n = 16) and juvenile (n = 16) Sus scrofa domesticus femora subject to different depositions over a period of two years were sectioned for histological observation. Degradation was scored using an adapted tunneling index. Results showed degradation related to microbial activity in both fetal and juvenile remains across depositions as early as three months. Buried juvenile remains consistently showed the greatest degradation over time, while the blanket fetal remains showed more minimal degradation. This is likely related to the buried remains' greater contact with surrounding soil and groundwater during deposition. Further, most of the degradation was seen in the subendosteal region, followed by the subperiosteal region, which may suggest the initial microbial attack is from endogenous sources.

Midfacial Morphology and Neandertal-Modern Human Interbreeding.

Ancient DNA from, Neandertal and modern human fossils, and comparative morphological analyses of them, reveal a complex history of interbreeding between these lineages and the introgression of Neandertal genes into modern human genomes. Despite substantial increases in our knowledge of these events, the timing and geographic location of hybridization events remain unclear. Six measures of facial size and shape, from regional samples of Neandertals and early modern humans, were used in a multivariate exploratory analysis to try to identify regions in which early modern human facial morphology was more similar to that of Neandertals, which might thus represent regions of greater introgression of Neandertal genes. The results of canonical variates analysis and hierarchical cluster analysis suggest important affinities in facial morphology between both Middle and Upper Paleolithic early modern humans of the Near East with Neandertals, highlighting the importance of this region for interbreeding between the two lineages.

Recent Advances in Forensic Anthropological Methods and Research.

This Special Issue, "Recent Advances in Forensic Anthropological Methods and Research", with thirteen articles covers a wide range of highly diverse topics within forensic anthropology [...].

Identifying Blunt Force Traumatic Injury on Thermally Altered Remains: A Pilot Study Using Sus scrofa.

In forensic scenarios involving homicide, human remains are often exposed to fire as a means of disposal and/or obscuring identity. Burning human remains can result in the concealment of traumatic injury, the creation of artifacts resembling injury, or the destruction of preexisting trauma. Since fire exposure can greatly influence trauma preservation, methods to differentiate trauma signatures from burning artifacts are necessary to conduct forensic analyses. Specifically, in the field of forensic anthropology, criteria to distinguish trauma from fire signatures on bone is inconsistent and sparse. This study aims to supplement current forensic anthropological literature by identifying criteria found to be the most diagnostic of fire damage or blunt force trauma. Using the skulls of 11 adult pigs (Sus scrofa), blunt force trauma was manually produced using a crowbar and flat-faced hammer. Three specimens received no impacts and were utilized as controls. All skulls were relocated to an outdoor, open-air fire where they were burned until a calcined state was achieved across all samples. Results from this experiment found that blunt force trauma signatures remained after burning and were identifiable in all samples where reassociation of fragments was possible. This study concludes that distinct patterns attributed to thermal fractures and blunt force fractures are identifiable, allowing for diagnostic criteria to be narrowed down for future analyses.

Ethical dilemmas in skeletal collection utilization: Implications of the Black Lives Matter movement on the anatomical and anthropological sciences.

The Black Lives Matter (BLM) movement has brought to the public eye longstanding issues of social and racial injustice which have permeated the experiences of individuals of African ancestry in the United States and abroad for centuries. Motivated by a desire to disassemble a framework of systemic racism, the BLM movement has infiltrated numerous social and political arenas including the sciences, demanding change. The impact of the BLM movement is evident in the attention recently garnered by protests of museum skeletal collections' acquisition and handling of African/African American human remains. It is from this vantage point that we explore the ethical issues pervasive within United States skeletal collections and forensically relevant issues surrounding the unclaimed decedents of marginalized populations; colonial/imperial ideological formations, which construct and sustain power differentials in anatomization; and conceive of a path forward that prioritizes personhood.

The need to incorporate human variation and evolutionary theory in forensic anthropology: A call for reform.

In 1992, Norm Sauer called for a language shift in which practitioners would move away from the socially loaded term "race" and replace it with the less provocative term "ancestry." While many heeded the call and moved towards ancestry in their research and reports, the actual approach to research and analysis did not change. In response to this change, there was a large growth in ancestry estimation method development in the early decade of the 2000s. However, the practice of ancestry estimation did not adequately incorporate evolutionary theory in interpretation or trait selection and continued with little critical reflection. In the past decade, there has been an increase in ancestry validation methods with little critique of the "race" concept or discussion of modern human variation or reference samples. To advance, forensic anthropologists need to reckon with the practice of ancestry estimation as it is currently practiced. We are calling for another reform in the axiom focusing on evolutionary theory, population history, trait selection, and population-level reference samples. The practice needs to abandon the terms ancestry and race completely and recalibrate to an analysis of population affinity. Population affinity is a statistical approach based on the underlying population structure that would allow the understanding of how microevolutionary forces act in concert with historical events (e.g., colonization, the Transatlantic Slave Trade, etc.) to shape modern human variation. This is not to be confused with geographic ancestry that all too often can be perceived as interchangeable with social race and as an affirmation of the biological concept of race. It is time to critically evaluate the social and scientific implications of the current practice of ancestry estimation, and re-frame our approach to studying and analyzing modern human variation through a population structure approach.

Ancestry Studies in Forensic Anthropology: Back on the Frontier of Racism.

One of the parameters forensic anthropologists have traditionally estimated is ancestry, which is used in the United States as a proxy for social race. Its use is controversial because the biological race concept was debunked by scientists decades ago. However, many forensic anthropologists contend, in part, that because social race categories used by law enforcement can be predicted by cranial variation, ancestry remains a necessary parameter for estimation. Here, we use content analysis of the Journal of Forensic Sciences for the period 2009-2019 to demonstrate the use of various nomenclature and resultant confusion in ancestry estimation studies, and as a mechanism to discuss how forensic anthropologists have eschewed a human variation approach to studying human morphological differences in favor of a simplistic and debunked typological one. Further, we employ modern geometric morphometric and spatial analysis methods on craniofacial coordinate anatomical landmarks from several Latin American samples to test the validity of applying the antiquated tri-continental approach to ancestry (i.e., African, Asian, European). Our results indicate groups are not patterned by the ancestry trifecta. These findings illustrate the benefit and necessity of embracing studies that employ population structure models to better understand human variation and the historical factors that have influenced it.

Faces Divulge the Origins of Caribbean Prehistoric Inhabitants.

The origins of the first peoples to colonize the Caribbean Islands have been the subject of intense debate for over 30 years. Competing hypotheses have identified five separate migrations from the mainland with a separate debate concerning the colonization of The Bahamas. Significant differences in the facial morphology of the pre-Columbian inhabitants of Hispaniola and Cuba led to the present study of Lucayan skulls from The Bahamas. The goal was to determine which group the native Lucayans more closely resembled to resolve this long-standing dispute. The results indicate that they are related to groups from Hispaniola and Jamaica and not to Cuban inhabitants. This study clarified the larger picture of Caribbean migrations and supports evidence for a Carib invasion of the Greater Antilles around AD 800.

Complex Nature of Hominin Dispersals: Ecogeographical and Climatic Evidence for Pre-Contact Craniofacial Variation.

Coordinate data analysis of ancient crania from the New World reveals complexity in interpretation when addressing ancient population dispersals. The results of this study generally support a geographic patterning for the New World; however, it also revealed a much more complex and multifactorial mechanism shaping craniofacial morphology that should be considered when investigating ecogeographic models for hominin dispersals. We show that craniofacial variation is not the result of a single mechanism but is a much more complex interaction of environmental and microevolutionary forces.

Morphology of the Homo naledi femora from Lesedi.

OBJECTIVES: The femoral remains recovered from the Lesedi Chamber are among the most complete South African fossil hominin femora discovered to date and offer new and valuable insights into the anatomy and variation of the bone in Homo naledi. While the femur is one of the best represented postcranial elements in the H. naledi assemblage from the Dinaledi Chamber, the fragmentary and commingled nature of the Dinaledi femoral remains has impeded the assessment of this element in its complete state. MATERIALS AND METHODS: Here we analyze and provide descriptions of three new relatively well-preserved femoral specimens of H. naledi from the Lesedi Chamber: U.W. 102a-001, U.W. 102a-003, and U.W. 102a-004. These femora are quantitatively and qualitatively compared to multiple extinct hominin femoral specimens, extant hominid taxa, and, where possible, each other. RESULTS: The Lesedi femora are morphologically similar to the Dinaledi femora for all overlapping regions, with differences limited to few traits of presently unknown significance. The Lesedi distal femur and mid-diaphysis preserve anatomy previously unidentified or unconfirmed in the species, including an anteroposteriorly expanded midshaft and anteriorly expanded patellar surface. The hypothesis that the Lesedi femoral sample may represent two individuals is supported. DISCUSSION: The Lesedi femora increase the range of variation of femoral morphology in H. naledi. Newly described features of the diaphysis and distal femur are either taxonomically uninformative or Homo-like. Overall, these three new femora are consistent with previous functional interpretations of the H. naledi lower limb as belonging to a species adapted for long distance walking and, possibly, running.

Bone Mineral Density Adult Age Estimation in Forensic Anthropology: A Test of the DXAGE Application.

Estimating age-at-death of individuals represented only by skeletonized human remains is a fundamental aspect of forensic anthropological casework. Recently, several researchers have proposed that bone mineral density (BMD) is a useful predictor of age-at-death in forensic contexts. Navega et al. (JFS 63(2):497-503) developed an online application called DXAGE for calculating age-at-death from BMD parameters. This study tests the utility of DXAGE by utilizing data from the National Health and Nutrition Examination Survey (NHANES). BMD data from a female subsample (n = 470) of the NHANES 2007-2008 dataset were analyzed, and the relationship between predicted age and real age was examined. Inaccuracy was 14.25 years, and bias was -7.20 years. Results show that there is a weak correlation between predicted and actual age (r = 0.47) using the DXAGE application. While BMD data are potentially useful for predicting age age-at-death, the DXAGE application should be used cautiously in forensic anthropological contexts.

Biological sex variation in bone mineral density in the cranium and femur.

OBJECTIVES: Sex and age trends in bone mineral density (BMD) play an important role in the estimation of age-at-death (AAD) of unidentified human remains. Current methodologies lack the ability to precisely estimate age in older individuals. In this study, BMD of the cranium and femur measured by DXA were examined to establish their applicability for age estimation in older adults. BMD as measured by DXA, is most commonly used clinically for prediction of osteoporotic fracture risk. We hypothesized that weight-bearing and non-weight-bearing bones, the femur and cranium, respectively, would provide valuable insights for aging. METHODS: The sample consists of 32 sets of excised cranial fragments from the Regional Forensic Center, Johnson City, Tennessee and 41 associated crania and femora from the North Carolina Office of the Chief Medical Examiner. All crania and femora were scanned using a Hologic (R) DXA scanner and data were analyzed using Student t-tests, Loess regression, and ANOVA. RESULTS: Student t-tests indicate a significant relationship between the sexes and cranial BMD and a significant relationship between age cohorts and femoral neck BMD. The Loess regression showed different aging patterns in the cranium for females and males older than 55. And the ANOVA showed changes in femoral neck after age 55. CONCLUSIONS: These results indicate age and sex dependent changes in BMD especially for individuals over the age of 55, which offers improvement from current aging methods for older individuals. Further research using a larger sample size could improve the predictive capabilities of the model.

Scanning Skeletal Remains for Bone Mineral Density in Forensic Contexts.

The purpose of this paper is to introduce a promising, novel method to aid in the assessment of bone quality in forensically relevant skeletal remains. BMD is an important component of bone's nutritional status and in skeletal remains of both juveniles and adults, and it can provide information about bone quality. For adults remains, it can provide information on pathological conditions or when bone insufficiency may have occurred. In juveniles, it provides a useful metric to elucidate cases of fatal starvation or neglect, which are generally difficult to identify. This paper provides a protocol for the anatomical orientation and analysis of skeletal remains for scanning via dual-energy X-ray absorptiometry (DXA). Three case studies are presented to illustrate when DXA scans can be informative to the forensic practitioner. The first case study presents an individual with observed longitudinal fractures in the weight bearing bones and DXA is used to assess bone insufficiency. BMD is found to be normal suggesting another etiology for the fracture pattern present. The second case study employed DXA to investigate suspected chronic malnutrition. The BMD results are consistent with results from long bone lengths and suggest the juvenile had suffered from chronic malnutrition. The final case study provides an example where fatal starvation in a fourteen-month infant is suspected, which supports autopsy findings of fatal starvation. DXA scans showed low bone mineral density for chronological age and is substantiated by traditional assessments of infant health. However, when dealing with skeletal remains taphonomic alterations should be considered before applying this method.

Decomposition of juvenile-sized remains: a macro- and microscopic perspective.

There is currently a dearth of research investigating the progression and rate of decomposition for juvenile remains. It is thought that juveniles and infants decompose at an increased rate relative to adults due simply to body mass and that skeletal preservation is commonly dependent on intrinsic levels of bone mineral density (BMD). This study investigates the environmental variables important in driving juvenile decomposition as well as examining if currently accepted methodology for quantifying adult decomposition can be applied to juvenile remains. Furthermore, histological analysis is undertaken to test the Histological Index (HI) as a semi-quantitative indicator of decomposition. Thirty-five Sus scrofa ranging between 1.8 and 22.7 kg were deposited to simulate body mass of human infant and juvenile remains. Pigs were deposited every season over two years in the southeastern US with five depositional types: bagged, blanket wrapped, and surface control foetal remains, surface, and buried juvenile remains. Remains were scored quantitatively throughout soft tissue decomposition. Following study completion and skeletonization, a femur was selected from each set of remains for histological analysis. Thick sections were assessed under standard brightfield light and scored using Oxford Histological Index (OHI). Results indicate that seasonal variation is an important factor to consider even when using a standardized time variable such as accumulated degree days (ADD), particularly variation in soil moisture. Soil moisture was a consistent significant variable in the mixed effects model. The pattern of decomposition using total body score (TBS) was similar to that observed by others prior to log transformation with a rapid incline early in decomposition with levelling off. The correlation between time in days, ADD, and TBS was not as strong as those previously reported (R 2 = 0.317 and 0.499, respectively) suggesting that TBS as it is currently formulated cannot be directly applied to juvenile remains. Finally, the OHI model performed moderately well, but was variable even within seasons across multiple years.

The virtual approach to the assessment of skeletal injuries in human skeletal remains of forensic importance.

While assessing skeletal injuries in human skeletal remains, forensic anthropologists are frequently presented with fractured, fragmented, or otherwise modified skeletal remains. The examination of evidence and the mechanisms of skeletal injuries often require that separate osseous elements be permanently or temporarily reassembled or reconstructed. If not dealt with properly, such reconstructions may impede accurate interpretation of the evidence. Nowadays, routine forensic examinations increasingly incorporate digital imaging technologies. As a result, a variety of PC-assisted imaging techniques, collectively referred to as the virtual approach, have been made available to treat fragmentary skeletal remains. The present study employs a 3D virtual approach to assess mechanisms of skeletal injuries, and provides an expert opinion of causative tools in three forensic cases involving human skeletal remains where integrity was compromised by multiple peri- or postmortem alterations resulting in fragmentation and/or incompleteness. Three fragmentary skulls and an incomplete set of foot bones with evidence of perimortem fractures (gunshot wounds) and sharp force trauma (saw marks) were digitized using a desktop laser scanner. The digitized skeletal elements were reassembled in the virtual workspace using functionalities incorporated in AMIRA® version 5.0 software, and simultaneously in real physical space by traditional reconstructive approaches. For this study, the original skeletal fragments were substituted by replicas built by 3D printing. Inter-method differences were quantified by mesh-based comparison after the physically reassembled elements had been re-digitized. Observed differences were further reinforced by visualizing local variations using colormaps and other advanced 3D visualization techniques. In addition, intra-operator and inter-operator error was computed. The results demonstrate that the importance of incorporating the virtual approach into the assessment of skeletal injuries increases with the complexity and state of preservation of a forensic case. While in relatively simple cases the virtual approach is a welcome extension to a traditional approach, which merely facilitates the analysis, in more complex and extensively fragmentary cases such as multiple gunshot wounds or dismemberment, the virtual approach can be a crucial step in applying the principles of gunshot wounds or sharp force traumatic mechanisms. The unrestricted manipulation with digital elements enabling limitless repairs and adjustments to a "best-case scenario" also produced smaller inter-operator variation in comparison to the traditional approach.

The Impact of Freezing on Bone Mineral Density: Implications for Forensic Research.

It is common for researchers using animal or human remains for scientific study to freeze samples prior to use. However, effects of freezing on bone macro- or microstructure are relatively unknown. The research objective of this study was to determine whether freezing could potentially bias experimental results by analyzing changes in bone mineral density (BMD) with the freezing of remains over time. Eight fetal pigs were scanned to determine their initial BMD before freezing. Three piglets underwent a freeze-thaw cycle to assess the effects of the freezing process. Four piglets were frozen and scanned weekly for 20 weeks to assess freezing over time. The overall average between the fresh initial scan and final frozen scan was significantly different (p < 0.001). Per contra, the final thawed BMD scans did not differ from the initial fresh scan (p = 0.418). Thus, completely thawed remains are recommended for experimental studies.

Bone mineral density and wounding capacity of handguns: implications for estimation of caliber.

Methodologies that improve estimation of caliber from cranial bone defects are necessary to meet the ever increasing admissibility standards. The relationship between caliber, wound diameter, and bone mineral density (BMD) was examined. The formation of the permanent cavity is influenced by bullet yaw, velocity, distance, and tissue properties. The hypothesis was that including BMD, wound diameter could be explained by differences in caliber. The sample consists of 68 autopsy sections and 101 specimens from Phelps (1898). A subsample of 18 was scanned using dual energy x-ray absorptiometry (DEXA) for BMD measurement to test whether an increase in BMD affects wound diameter. Pearson product-moment correlations of the subsample indicate the strongest correlation is between BMD and minimum diameter (r = 0.7101), followed by a correlation between minimum diameter and caliber (r = 0.6854). Despite the previous use of thickness as a proxy for BMD, no correlation was found between BMD and thickness (r = 0.0143). A multivariate analysis of variance (MANOVA) detected a significant influence of BMD and minimum diameter on caliber size (Prob > F = 0.0003). The logistic regression shows that caliber can be estimated from minimum diameter. Using the subsample, the results show that the inclusion of BMD strengthens the model for estimating caliber from entrance gunshot defects.