Experimental taphonomy: post-mortem microstructural modifications in Sus scrofa domesticus bone

Histotaphonomic analysis of bone bioerosion reveals a regional framework of diverse deathways in the Neolithic of Southeast Italy

The wide diversity of Neolithic funerary practices is increasingly recognised. In Southeast Italy, recent studies have drawn attention to the co-existence of multiple ways of treating the dead within single sites and across the region. In this study, we address how such diverse deathways form a regional framework of ritual practice through histotaphonomic analysis of bone bioerosion. Samples were obtained from articulated, semi-articulated and disarticulated remains from four sites in Apulia which each presented different modes of treatment and disposal of the dead. Bone thin sections were analysed by light microscopy to characterise microstructural preservation through features including bacterial bioerosion, staining, inclusions, and Wedl tunnelling. We investigate the early post-mortem histories of individuals whose remains ended up in various states of dis/articulation and diverse depositional contexts. Disarticulated remains frequently displayed arrested or extensive bacterial bioerosion, which was also found in articulated and semi-articulated skeletons. Additionally, remains deposited in similar contexts, as well as articulated and disarticulated remains deposited together in the same context, often showed different histotaphonomic characteristics, suggesting diverse early post-mortem trajectories. As a result, we argue that Neolithic deathways in southeastern Italy incorporated a high level of diversity in the early post-mortem treatment of the body. A framework for funerary practices emerges, whereby disarticulated remains probably originated from bodies which had been buried previously and subjected to varying extents of shelter, exposure to invertebrates, and duration of burial. However, we acknowledge the ongoing research into the origins of bacterial bioerosion and the problem of equifinality, which leaves open the possibility for further scenarios of early post-mortem treatment.

Autopsy-Based Comparative Study of Gross and Histopathological Findings at Bone Fracture Surfaces Before and After Death

ABSTRACT

Fractures of bones are commonly encountered in traumatic injuries, and distinguishing between antemortem (AM) and postmortem (PM) bone fractures is crucial for estimating the time since injury and has important medicolegal implications. Correct differentiation enables understanding the dynamics of the injury and, in some cases, the cause of death. The present study aims to evaluate the gross morphological and histopathological characteristics of bony fracture surfaces to determine whether they occurred before or after an individual's death.Fifty-seven sets of bone samples, including both antemortem and artificially created postmortem fractures, were collected from cadavers during medicolegal autopsies, meeting the inclusion criteria. Gross morphological and histopathological features were examined after staining the bony fracture edges with hematoxylin and eosin stain. The study revealed distinct morphological characteristics at fracture surfaces for both antemortem and artificially created postmortem fractures. In addition, signs of vital reaction were observed exclusively in antemortem fracture cases.In conclusion, the findings emphasize the importance of meticulous morphological and histopathological examination of bony fracture surfaces to differentiate between antemortem fractures and artificially created postmortem artifacts. This differentiation holds significant value in forensic investigations and medicolegal cases.

Recognition of the Presence of Bone Fractures Through Physicochemical Changes in Diagenetic Bone

Much research has focused on attempting to understand the drivers of bone diagenesis. However, this sensitive process is easily influenced by various factors, particularly the condition of the remains (i.e., whether they have been subjected to trauma). Previous research demonstrates that trauma can influence soft tissue decomposition, yet to date, no studies have looked at how bone fractures could affect bone diagenesis. To address this gap, two short timescale studies were conducted to investigate the influence of bone fractures on the physicochemical composition of disarticulated, partially fleshed animal remains. Disarticulated porcine bones were either fractured using blunt force or sharp force whilst fresh (producing perimortem damage), at 60 days producing postmortem damage (postmortem interval (PMI)), or left intact and left outside for up to 180 days post-fracture/240 days PMI. Retrieved bone sections were then analyzed for physicochemical differences using non-destructive methods, i.e., scanning electron microscopy energy dispersive spectroscopy and Fourier transform infrared spectroscopy with attenuated total reflectance. It was hypothesized that differences would be found in the physicochemical composition between the bones with fractures and those without after undergoing diagenetic change. The bone fractures significantly affected the elemental composition of bone over time, but structural composition initially remained stable. It was also possible to distinguish between perimortem and postmortem fractures using these two analytical techniques due to physicochemical differences. This research shows bone fractures can significantly alter the physicochemical composition of the bone during the postmortem period and have the potential to facilitate more accurate PMI estimations in forensic contexts.

Bone Diagenesis in Short Timescales: Insights from an Exploratory Proteomic Analysis

The evaluation of bone diagenetic phenomena in archaeological timescales has a long history; however, little is known about the origins of the microbes driving bone diagenesis, nor about the extent of bone diagenesis in short timeframes-such as in forensic contexts. Previously, the analysis of non-collagenous proteins (NCPs) through bottom-up proteomics revealed the presence of potential biomarkers useful in estimating the post-mortem interval (PMI). However, there is still a great need for enhancing the understanding of the diagenetic processes taking place in forensic timeframes, and to clarify whether proteomic analyses can help to develop better models for estimating PMI reliably. To address these knowledge gaps, we designed an experiment based on whole rat carcasses, defleshed long rat bones, and excised but still-fleshed rat limbs, which were either buried in soil or exposed on a clean plastic surface, left to decompose for 28 weeks, and retrieved at different time intervals. This study aimed to assess differences in bone protein relative abundances for the various deposition modalities and intervals. We further evaluated the effects that extrinsic factors, autolysis, and gut and soil bacteria had on bone diagenesis via bottom-up proteomics. Results showed six proteins whose abundance was significantly different between samples subjected to either microbial decomposition (gut or soil bacteria) or to environmental factors. In particular, muscle- and calcium-binding proteins were found to be more prone to degradation by bacterial attack, whereas plasma and bone marrow proteins were more susceptible to exposure to extrinsic agents. Our results suggest that both gut and soil bacteria play key roles in bone diagenesis and protein decay in relatively short timescales, and that bone proteomics is a proficient resource with which to identify microbially-driven versus extrinsically-driven diagenesis.

Harnessing Thor's Hammer: Experimentally induced lightning trauma to human bone by high impulse current

Lightning fatality identification relies primarily on soft tissue traumatic pattern recognition, prohibiting cause of death identification in cases of full skeletonisation. This study explores the effects of high impulse currents on human bone, simulating lightning-level intensities and characterising electrically induced micro-trauma through conventional thin-section histology and micro-focus X-ray computed tomography (μXCT). An experimental system for high impulse current application was applied to bone extracted from donated cadaveric lower limbs (n = 22). μXCT was undertaken prior to and after current application. Histological sections were subsequently undertaken. μXCT poorly resolved micro-trauma compared to conventional histology which allowed for identification and classification of lightning-specific patterns of micro-trauma. Statistical analyses demonstrated correlation between current intensity, extent and damage typology suggesting a multifaceted mechanism of trauma propagation - a combination of electrically, thermally and pressure induced alterations. This study gives an overview of high impulse current trauma to human bone, providing expanded definitions of associated micro-trauma.

•

Combination of thermal, electrical and pressure forces involved in micro-trauma.

•

Micro-fracture sizes and numbers appeared to increase at higher current intensities.

•

New criteria for the classification of bone micro-trauma were developed.

•

Certain micro-fracture types predominated at higher current intensities.

•

Light microscopy of histological section is the preferred method of investigation.

The effect of hydrochloric acid on microstructure of porcine (Sus scrofa domesticus) cortical bone tissue

We evaluated the degradation of cortical bone tissue by hydrochloric acid (HCl) since intentional bone decalcification in a forensic context has not been studied on a histomorphological level. We used 70 pig metatarsal bones split into subsamples and immersed in one of three concentrations of acidic solutions (0.5M, 1M, 2M HCl) for two and four hours. We analyzed the cortical thicknesses on transversal cross-sections, thicknesses of the three histomorphologically distinct zones present in acid-immersed bones, and number and area of crystals present in one of the zones. Furthermore, we analyzed the ratio of calcium to phosphorus (Ca:P). We observed a division of the cortical bone cross section into three distinctive zones: demineralized matrix (DM) in the periosteal part of bone, middle contact zone (CZ), and mineralized matrix (MM) in the endosteal part of bone. With increasing acid concentration and time of immersion (from 0.5M HCl for 2h to 2M HCl for 4h), the thickness of DM increased by 67%, the thickness of CZ increased by 56%, and the thickness of MM decreased by 32%. The Ca:P ratio in the contact zone of acid-treated samples did not change significantly with changing acid concentration and time of immersion. The Ca:P ratio of the CZ decreased by 10% when compared to the Ca:P ratio of MM in acid-treated samples. Moreover, we observed crystals on the outer periosteal border of the DM zone, in the CZ, and in the MM Haversian/Volkmann's canals. The size and number of the crystals in the CZ of acid-treated bones increased with acid concentration and time of acid immersion. Moreover, we also observed significant differences in all analyzed properties between anatomical regions. Due to varying reactions to acid immersion among anatomical regions, bone micro-degradation should be observed separately for each region.

A comparative analysis of microscopic alterations in modern and ancient undecalcified and decalcified dry bones

OBJECTIVES

The present study aims to evaluate the preservation of the microstructure of skeletal remains collected from four different known burial sites (archaeological and contemporary). Histological analysis on undecalcified and decalcified thin sections was performed in order to assess which of the two techniques is more affected by taphonomic insults.

MATERIALS AND METHODS

A histological analysis was performed on both undecalcified and decalcified thin sections of 40 long bones and the degree of diagenetic change was evaluated using transmitted and polarized light microscopy according to the Oxford Histological Index (OHI). In order to test the optical behavior of bone tissue, thin sections were observed by polarized light microscopy and the intensity of birefringence was evaluated.

RESULTS

The more ancient samples are generally characterized by a low OHI (0-1) with extensive microscopic focal destruction; recent samples exhibited a better preservation of bone micromorphology. When comparing undecalcified to decalcified thin sections, the latter showed an amelioration in the conservation of microscopic structure. As regards the birefringence, it was very low in all the undecalcified thin sections, whereas decalcification process seems to improve its visibility.

DISCUSSION

The preservation of the bone microscopic structure appears to be influenced not only by age, but also by the burial context. Undecalcified bones appear to be more affected by taphonomical alterations, probably because of the thickness of the thin sections; on the contrary, decalcified thin sections proved to be able to tackle this issue allowing a better reading of the bone tissue.