Burned Bone

The role of degradational processes that act on archaeological faunal assemblages after burial has attracted less attention than it warrants, in part because many of the changes take place over time scales that are not amenable to experimental investigation. We propose a straightforward method for evaluating the level of post-depositional degradation in a stratified archaeological faunal assemblage based primarily on trends in the burning composition of the assemblage. The twin foundations of the method are: 1) the experimentally verified changes in physical properties that occur in bone as it is progressively burned through carbonized to calcined stages: and 2) postulated contrasts between burning stages in susceptibility to a suite of degradational processes that operate in the burial context, including a range of microbial, fungal, thermal and chemical processes. We present data from seven archaeological sites from Australasia and three ethnographic assemblages from Papua New Guinea, including sites in open-air, rockshelter and cave contexts, and sites with both acidic and alkaline soil conditions. Each of the archaeological sites is treated as a temporally-seriated assemblage that documents the potential impacts of post-depositional degradation on the faunal assemblage. We compare the relative abundance of un-burned, burned/carbonized or calcined bone through each sequence and identify commonalities of pattern that are highly suggestive of post-depositional degradation. For each assemblage, these patterns are verified by visual inspection and identification of classic signs of surface degradation such as pitting and root channelling. In each of the acidic contexts there was a clear trend of increasing degradation of bone with excavation depth (= age). Assemblages from alkaline deposits were more complex, but some also provided more subtle evidence of degradation within the profile. Investigation of burning profiles in combination with careful examination of bone macro-damage provides a useful tool for identifying the pattern of post-depositional degradation within a stratified sequence and for distinguishing this from other various kinds of taphonomic patterning, and from signals produced by human behaviour.

Abstract:  In view of the difficulties in extracting quantitative information from burned bone, we suggest a new and accurate method of determining the temperature and duration of burning of human remains in forensic contexts. Application of the powder X-ray diffraction approach to a sample of human bone and teeth allowed their microstructural behavior, as a function of temperature (200–1000°C) and duration of burning (0, 18, 36, and 60 min), to be predicted. The experimental results from the 57 human bone sections and 12 molar teeth determined that the growth of hydroxylapatite crystallites is a direct and predictable function of the applied temperature, which follows a nonlinear logistic relationship. This will allow the forensic investigator to acquire useful information about the equilibrium temperature brought about by the burning process and to suggest a reasonable duration of fire exposure.

Divers facteurs sont à l'origine de ces doutes, notamment un enregistrement incomplet des données de fouilles, une documentation insuffisante, et une analyse trop peu précise des stigmates (stries, fractures, traces de feu) et de la disposition des déchets. En particulier, on peut ...

Forensic anthropologists are tasked with interpreting the sequence of events from death to the discovery of a body. Burned bone often evokes questions as to the timing of burning events. The purpose of this study was to assess the progression of thermal damage on bones with advancement in decomposition. Twenty-five pigs in various stages of decomposition (fresh, early, advanced, early and late skeletonisation) were exposed to fire for 30 min. The scored heat-related features on bone included colour change (unaltered, charred, calcined), brown and heat borders, heat lines, delineation, greasy bone, joint shielding, predictable and minimal cracking, delamination and heat-induced fractures. Colour changes were scored according to a ranked percentage scale (0-3) and the remaining traits as absent or present (0/1). Kappa statistics was used to evaluate intra- and inter-observer error. Transition analysis was used to formulate probability mass functions [P(X=j|i)] to predict decomposition...

The faunal assemblage from the open-air site of Saint-Antoine at Vitrolles (Hautes-Alpes, Epigravettian) has
yielded an atypical composition of burned bones (NRT = 23%), being composed mainly of charred compact
bones. While in an experimental context a high proportion of charred bones is typical of the use of skeletal
remains as fuel, their representation in archaeological contexts is generally low, particularly in comparison to
that of the less intensely burned elements. Contrary to this general principle, the Saint-Antoine deposit shows a
strong representation of charred bones in a difficult taphonomic context characterised by an acid sediment and
by the intensive action of different taphonomic phenomena (weathering, sediment compaction, dissolution). The
high representation of charred bones seems to result from a combination of various factors, including the purpose
of the combustion (camp maintenance and/or use as fuel) and their intense fragmentation, together with a higher
preservation potential for burned bones (compact and spongy), including charred bones, compared to unburned
bone elements when they are buried in acid sediments.