Lynne S. Bell

Differentiating Human Bone from Animal Bone: A Review of Histological Methods

ABSTRACT: This review brings together a complex and extensive literature to address the question of whether it is possible to distinguish human from nonhuman bone using the histological appearance of cortical bone. The mammalian species included are rat, hare, badger, racoon dog, cat, dog, pig, cow, goat, sheep, deer, horse, water buffalo, bear, nonhuman primates, and human and are therefore not exhaustive, but cover those mammals that may contribute to a North American or Eurasian forensic assemblage. The review has demonstrated that differentiation of human from certain nonhuman species is possible, including small mammals exhibiting Haversian bone tissue and large mammals exhibiting plexiform bone tissue. Pig, cow, goat, sheep, horse, and water buffalo exhibit both plexiform and Haversian bone tissue and where only Haversian bone tissue exists in bone fragments, differentiation of these species from humans is not possible. Other primate Haversian bone tissue is also not distinguishable from humans. Where differentiation using Haversian bone tissue is undertaken, both the general microstructural appearance and measurements of histological structures should be applied. Haversian system diameter and Haversian canal diameter are the most optimal and diagnostic measurements to use. Haversian system density may be usefully applied to provide an upper and lower limit for humans.

The Application of Remote Sensing for Detecting Mass Graves: An Experimental Animal Case Study from Costa Rica

Abstract:  Detection of mass graves utilizing the hyperspectral information in airborne or satellite imagery is an untested application of remote sensing technology. We examined the in situ spectral reflectance of an experimental animal mass grave in a tropical moist forest environment and compared it to an identically constructed false grave which was refilled with soil, but contained no cattle carcasses over the course of a 16‐month period. The separability of the in situ reflectance spectra was examined with a combination of feature selection and five different nonparametric pattern classifiers. We also scaled up the analysis to examine the spectral signature of the same experimental mass grave from an air‐borne hyperspectral image collected 1 month following burial. Our results indicate that at both scales (in situ and airborne), the experimental grave had a spectral signature that was distinct and therefore detectable from the false grave. In addition, we observed that vegetation regeneration was severely inhibited over the mass grave containing cattle carcasses for up to a period of 16 months. This experimental study has demonstrated the real utility of airborne hyperspectral imagery for the detection of a relatively small mass grave (5 m2) within a specific climatic zone. Other climatic zones will require similar actualistic modeling studies, but it is clear that the applications of this technology provide the international community with both an early detection tool and a tool for ongoing monitoring.

The mineralized osteocyte: A living fossil

We report here on an enigmatic and biologically mysterious event in which a single cell, the osteocyte, mineralizes in vivo and in this process the cells organelles, cytoskeleton and membrane, are mineralized in a dying state. That the bony lacuna in which the lone osteocyte resides becomes infilled with mineral in vivo is not a new observation and was noted by early microscopists. This study has applied scanning and transmission electron microscopy to modern, archaeological, and fossil bone to investigate the mineral and organic structure and content of this cell. The results from this study revealed that within this mineral lies a visibly identifiable cell, which has an apoptotic-like morphology. The mechanisms by which this cell mineralizes are so intimate chemically that remnant cell organelles, membranes, cytoskeleton, and potentially nucleic bodies are morphologically identifiable. We have further identified mineralized osteocytes surviving in archaeological and fossil mammal bone up to 5 million years BP. The significance of our findings demonstrates that a single cell may itself mineralize in vivo via an unknown set of biochemical events. Importantly, the location and survival of extra cellular and cellular proteins, including nuclear and mitochondrial DNA in bone after death, has been an area of some speculation, and this unique fossil cell provides a preservation locus within human and mammalian bone, which might be fruitfully targeted in future biomolecular studies.

Remote Sensing as a Tool for the Detection of Clandestine Mass Graves

ABSTRACT Mass graves in both an international and domestic setting often present a difficult, time-consuming and complicated detection problem. Historically, witness testimony has been relied upon to determine location. Other detection methods such as geophysical resistivity, magnetometry and ground penetrating radar may be, and have been, employed for the detection of graves with some success. However, these methods require that the grave locale is known fairly precisely and that personnel can physically walk the grave site to undertake data collection. Remote sensing (i.e. airborne and satellite imagery) is a detection tool that can be used to search larger geographical areas without placing investigative personnel at risk. Hyperspectral imagery acquired from aircraft or satellite provides over a hundred layers (bands) of data that can be selectively examined and analyzed to detect subtle changes in the reflectance spectra of the surface. Work presented here indicates, from an ongoing long-term experimental mass grave and an actual mass grave site, that remote sensing is a powerful detection tool, one which has the capacity to discriminate a mass grave from its surroundings in real-time or in certain cases even retrospectively.

Deep Coastal Marine Taphonomy: Investigation into Carcass Decomposition in the Saanich Inlet, British Columbia Using a Baited Camera

Decomposition and faunal colonization of a carcass in the terrestrial environment has been well studied, but knowledge of decomposition in the marine environment is based almost entirely on anecdotal reports. Three pig carcasses were deployed in Saanich Inlet, BC, over 3 years utilizing Ocean Network Canada’s VENUS observatory. Each carcass was deployed in late summer/early fall at 99 m under a remotely controlled camera and observed several times a day. Dissolved oxygen, temperature, salinity, density and pressure were continuously measured. Carcass 1 was immediately colonized by Munida quadrispina, Pandalus platyceros and Metacarcinus magister, rapidly scavenged then dragged from view by Day 22. Artifacts specific to each of the crustaceans’ feeding patterns were observed. Carcass 2 was scavenged in a similar fashion. Exposed tissue became covered by Orchomenella obtusa (Family Lysianassidae) which removed all the internal tissues rapidly. Carcass 3 attracted only a few M. quadrispina, remaining intact, developing a thick filamentous sulphur bacterial mat, until Day 92, when it was skeletonized by crustacea. The major difference between the deployments was dissolved oxygen levels. The first two carcasses were placed when oxygen levels were tolerable, becoming more anoxic. This allowed larger crustacea to feed. However, Carcass 3 was deployed when the water was already extremely anoxic, which prevented larger crustacea from accessing the carcass. The smaller M. quadrispina were unable to break the skin alone. The larger crustacea returned when the Inlet was re-oxygenated in spring. Oxygen levels, therefore, drive the biota in this area, although most crustacea endured stressful levels of oxygen to access the carcasses for much of the time. These data will be valuable in forensic investigations involving submerged bodies, indicating types of water conditions to which the body has been exposed, identifying post-mortem artifacts and providing realistic expectations for recovery divers and families of the deceased.

MAPPING HUMAN MOVEMENT USING STABLE OXYGEN ISOTOPIC RATIO MASS SPECTROMETRY: POTENTIAL APPLICATION TO FORENSIC SCIENCE DEMONSTRATED BY A MODERN HORSE-HUMAN STUDY

ABSTRACT The utility of stable oxygen isotope analysis for demonstrating human migration has been developed and demonstrated on archaeological human populations. The application of this approach to tracking human movement has seldom been applied within forensic science. This paper gives results from a stable oxygen isotope assessment of extant modern human and horse enamel δ18O values recovered from tooth enamel. The human and horses were all constrained to known geographic locales for the period of tooth formation and compared to UK and global precipitation values for δ18O. It was found that human and horse values track one another and horse can be used with some confidence as a human proxy. UK values were constrained geographically and outlier values to the UK were identified between Iceland and the Sudan. For application within the realm of forensic science more research is required to understand the regionalized contribution of hydrology to a catchment and the potentially confounding contribution of mixed water sources. However, as a tool to track human movement within forensics there is clear utility.

Impact of Marine Submergence and Season on Faunal Colonization and Decomposition of Pig Carcasses in the Salish Sea

Pig carcasses, as human proxies, were placed on the seabed at a depth of 300 m, in the Strait of Georgia and observed continuously by a remotely operated camera and instruments. Two carcasses were deployed in spring and two in fall utilizing Ocean Network Canada’s Victoria Experimental Network under the Sea (formerly VENUS) observatory. A trial experiment showed that bluntnose sixgill sharks could rapidly devour a carcass so a platform was designed which held two matched carcasses, one fully exposed, the other covered in a barred cage to protect it from sharks, while still allowing invertebrates and smaller vertebrates access. The carcasses were deployed under a frame which supported a video camera, and instruments which recorded oxygen, temperature, salinity, density, pressure, conductivity, sound speed and turbidity at per minute intervals. The spring exposed carcass was briefly fed upon by sharks, but they were inefficient feeders and lost interest after a few bites. Immediately after deployment, all carcasses, in both spring and fall, were very rapidly covered in vast numbers of lyssianassid amphipods. These skeletonized the carcasses by Day 3 in fall and Day 4 in spring. A dramatic, very localized drop in dissolved oxygen levels occurred in fall, exactly coinciding with the presence of the amphipods. Oxygen levels returned to normal once the amphipods dispersed. Either the physical presence of the amphipods or the sudden draw down of oxygen during their tenure, excluded other fauna. The amphipods fed from the inside out, removing the skin last. After the amphipods had receded, other fauna colonized such as spot shrimp and a few Dungeness crabs but by this time, all soft tissue had been removed. The amphipod activity caused major bioturbation in the local area and possible oxygen depletion. The spring deployment carcasses became covered in silt and a black film formed on them and on the silt above them whereas the fall bones remained uncovered and hence continued to be attractive to large numbers of spot shrimp. The carcass remains were recovered after 166 and 134 days respectively for further study.

Reply to “Ichthyosaur embryos outside the mother body: not due to carcass explosion but to carcass implosion” by van Loon (2013)

In his recent discussion on the taphonomy of ichthyosaurs, van Loon (2013) supported—at least partially—the view of Reisdorf et al. (2012) and emphasized that explosion of vertebrate carcasses on the sea floor should not be considered as a taphonomically reasonable scenario. Carcass explosion is thus not a process that can be used to explain both the disarticulation of certain ichthyosaur skeletons and the displacement of their bones in the geological record. Van Loon (2013), however, did suggest that, as an alternative hypothesis, implosion could have led to the displacement of bones on the sea floor. Van Loon (2013) focussed his explanation of the implosion hypothesis on the example of a maternal ichthyosaur having embryonic ichthyosaurs around and within its body cavity (Staatliches Museum fur Naturkunde Stuttgart, specimen number SMNS 50 007). Reisdorf et al. (2012) outlined that

Comparison of Faunal Scavenging of Submerged Carrion in Two Seasons at a Depth of 170 m, in the Strait of Georgia, British Columbia

The taphonomy of carcasses submerged in the ocean is little understood, yet it is extremely important ecologically and forensically. The objectives of this study were to determine the fate of pig carcasses as human proxies in the Strait of Georgia at 170 m in spring and fall. Using Ocean Networks Canada’s Victoria Experimental Network Underseas (VENUS) observatory, two carcasses per season were placed under a cabled platform hosting a webcam and instruments measuring water chemistry. Two minutes of video were recorded every 15 min. In spring, Lyssianassidae amphipods and Pandalus platyceros were immediately attracted and fed on the carcasses, the amphipods removed the bulk of the soft tissue from the inside whilst the shrimp shredded the skin and tissue. The carcasses were skeletonized on Days 8 and 10. In fall, Metacarcinus magister was the major scavenger, removing most of the soft tissue from one carcass. Amphipods did not arrive in large numbers until Day 15, when they skeletonized the scavenged carcass by Day 22 and the less scavenged carcass by Day 24. Amphipods remained for some days after skeletonization. This skeletonization was very different from previous experiments at different depths and habitats. Such data are very valuable for predicting preservation, planning recoveries, and managing family expectations.

Identifying Postmortem Microstructural Change to Skeletal and Dental Tissues using Backscattered Electron Imaging

A number of papers have been published over a 100 year period describing postmortem microstructural change to bone and teeth in humans and other mammals. Much of the work is descriptive and has used a number of microscopic methods, which introduce changes during preparation, and are limited by the resolving power of that technique. Backscattered electron imaging in a scanning electron microscope (BSE/SEM) has been used successfully applied to on normal skeletal tissues and is an excellent method to document postmortem changes to bone and tooth microstructure. In forensic science, archaeology, and paleontology there is a collective interest in understanding early death history and subsequent treatment and deposition of the body. To this end the main microstructural changes are provided as a means of identification, and practical suggestions to circumvent misinterpretation due to artifacts created by employing the BSE imaging method.