A new statistical approach for determining the crystallinity of heat-altered bone mineral from FTIR spectra

The crystallinity of bone mineral represents an established method of measuring heat-induced change and is of importance to fields including material science, clinical science, anthropology and archaeology. A commonly used technique involves the calculation of the Crystallinity Index (CI) using selected peaks from Fourier Transform Infrared (FTIR) absorbance spectra. However, the choice of peaks has to date not been statistically justified. In this study a novel application of statistical techniques to the FTIR spectra of bone samples burned in the range 100 °C–1100 °C has been used to identify 5 new spectral indices of heat-induced crystallinity change. The validity of the new indices was tested by using a statistical classification model (LDA) to predict the burning temperature of a set of 108 bone samples burned between 100 °C and 1100 °C. A correct classification rate (CCR) of 97.2% was obtained when a combination of 4 indices including the CI was used. This was significantly better than the CCR of 66.7% which was obtained when the CI was used on its own.     

Investigation of the ‘canopy effect’ in the isotope ecology of temperate woodlands

Anomalously ¹³C-depleted carbon stable isotope values from closed forest ecosystems have been termed the ‘canopy effect’. Originally this was ascribed to recycling of depleted carbon from forest floor decomposition of organic material, although others have suggested that it is equally likely to be due to variations in leaf-level processes in response to increased shade. This depletion in the heavier carbon isotope is passed on to woodland herbivores feeding within the forest environments. A similar isotopic depletion has also been reported in the archaeological literature from more open temperate woodland settings, but no measurements have been made on the plants at the base of the food chain in order to quantify the effect. In this study we attempt this by examining the carbon and nitrogen stable isotopic values of different species of grasses from a range of open to closed habitat settings within Wytham Wood, Oxfordshire, UK. We find a strong relationship between carbon isotopic depletion of plant tissue and lowered light intensity with an up to 5‰ shift between grass grown in open and closed locations. In order to follow this up the food chain, we also report data on wool from sheep grazing in open pastures near the Wood, and on fallow deer living within the woodland, but which turn out not to show a strong canopy effect, probably related to their feeding strategies. We conclude that there is indeed a strong ‘canopy effect’ in temperate woodland, probably related to differential light levels, but that not all apparently woodland-dwelling mammals show such an effect. We also show considerable isotopic variation at the base of the food chain, which should counsel caution when attempting to interpret dietary isotopes using mixing models.     

Experimental patterns of hammerstone percussion damage on bones: implications for inferences of carcass processing by humans

The common occurrence of hammerstone percussion damage (pits, striae, notches and impact flakes) on the fossil limb bones of ungulates indicates that marrow extraction has been an important component of hominid butchery for over two million years. Beyond this level of basic inference, it would be behaviorally informative if three deeper aspects of marrow harvesting were understood more clearly: (1) whether inter-element patterns of bone fragmentation vary when processing intensity is held constant; (2) whether butcher investment in marrow extraction correlates positively with the number of percussion marks generated; (3) whether taphonomic effectors can be identified based on percussion mark morphology, frequency and placement. Some experimental work has been conducted previously in service of exploring these questions, but we set out here to address them explicitly through the analysis of a large sample of white-tailed deer (Odocoileus virginianus) limb elements fractured by hammerstone percussion. Our results indicate that (1) measures of bone fragmentation, which supposedly reflect processing intensity, are highly contingent on the research question being posed. This stresses the fact that researchers must be explicit in their definition of processing intensity. (2) In addition, hypothesized covariance between number of hammerstone blows and percussion mark frequencies are not met in our sample, corroborating previous conclusions of a lack of covariance between cutting strokes and cutmark frequencies. These results highlight the contingent nature of butchery mark production, and emphasize the need to investigate carcass resource exploitation by posing questions that do not rely on mark frequencies, but instead utilize other zooarchaeological measures. (3) Finally, our results—showing high incidences of impact notches and flakes created by direct anvil contact and “anvil scratches” created by direct hammerstone contact—suggest caution in using specific categories of percussion damage to infer their taphonomic effectors.     

Neo-Liberalism as Creative Destruction

Neoliberalization has swept across the world like a vast tidal wave of institutional reform and discursive adjustment, entailing much destruction, not only of prior institutional frameworks and powers, but also of divisions of labor, social relations, welfare provisions, technological mixes, ways of life, attachments to the land, habits of the heart, ways of thought, and the like. To turn the neoliberal rhetoric against itself, we may reasonably ask: in whose particular interests is it that the state take a neoliberal stance and in what ways have these particular interests used neoliberalism to benefit themselves rather than, as is claimed, everyone, everywhere? Neoliberalism has spawned a swath of oppositional movements. The more clearly oppositional movements recognize that their central objective must be to confront the class power that has been so effectively restored under neoliberalization, the more they will likely themselves cohere.     

Confocal laser scanning microscopy: a flexible tool for simultaneous polarization and three-dimensional fluorescence imaging of archaeological compact bone

Wide-field polarized light and epifluorescence microscopy have been used to enhance analysis of archaeological bone tissue, providing information on bone formation, modeling, pathology, preservation, age estimation, and biomechanics. Though valuable, these techniques are limited by their inability to remove out-of-focus light and view multiple levels of a sample, restricting our understanding of the three-dimensional (3-D) microarchitecture of compact bone. Modern technological advances, such as microscopic computerized tomography, allow increasing resolution in 3-D bone imaging, but do not allow fluorescence labeling or polarized-light analysis. Confocal laser scanning microscopy (CLSM) is a valuable tool for 3-D histology. However, its application to the study of compact bone is lacking, especially in archaeological and forensic sciences. The current study investigated CLSM as a tool for fluorescence and polarized-light microscopy of archaeological compact bone in order to demonstrate its advantages. Standard techniques and CLSM are compared in their suitability for imaging well preserved archaeological bones from the Dakhleh Oasis, Egypt. CLSM's high resolution, multi-channel, two- and three-dimensional capabilities augment the flexibility and creativity of compact bone imaging and have the potential to increase the accuracy of quantitative medical and anthropological histomorphometric techniques. CLSM is specifically suggested as a useful tool for the investigation of ancient bone fluorescence caused by the presence of tetracycline and/or other fluorochromes.     

Palaeoenvironmental and chronological investigations of the Magdalenian sites of Goyet Cave and Trou de Chaleux (Belgium), via stable isotope and radiocarbon analyses of horse skeletal remains

Trou de Chaleux and Goyet are caves situated less than 30 km apart in Belgium that contain stratified Magdalenian artefacts and butchered faunal remains. Published radiocarbon dates suggest that both sites were contemporaneously occupied during to the Late-glacial interstadial. It has previously been suggested that the Trou de Chaleux Late-glacial faunal remains might be slightly older than those at Goyet Cave, and that Trou de Chaleux has two phases of occupation during the Late-glacial interstadial. However, the limited number of radiocarbon dates currently available makes it impossible to determine whether the sites are truly contemporaneous, and the assessment of their absolute chronologies is complicated by a plateau in the calibration curve. In this paper, bone collagen δ¹³C and δ¹⁵N signatures of horse bones from the two sites are used to reconstruct local palaeoenvironments. We hypothesise that if occupations at the two sites were contemporaneous, the horse collagen δ¹³C and δ¹⁵N isotope signatures from both sites will be similar, since comparable carbon and nitrogen isotopic values would reflect similar diets, ecologies and environments. To provide clear dating parameters, new AMS radiocarbon determinations are also presented. Results show that horse collagen δ¹³C and δ¹⁵N isotope signatures at the two sites are different, indicating that the populations were not subject to similar diets, ecologies and environments. The new radiocarbon dates confirm that the horse bones from Trou de Chaleux date to the Late-glacial interstadial, but they also show that in Goyet Cave Horizons 1 and 2, older horse remains dating to ca. 32?000–27?000 ¹⁴C yr BP are mixed with Late-glacial horse remains. The δ¹⁵N values of the Goyet Cave horse bones radiocarbon dated to the Pleniglacial are substantially higher than those that have Late-glacial radiocarbon dates. Therefore, we now hypothesise that the majority of the horse bones isotopically analysed from Goyet Cave Horizon 1 are Pleniglacial in age. Statistical analysis of the radiocarbon dates indicates that the Late-glacial occupation at the two sites was contemporaneous, and that while there may appear to be two phases of occupation at Trou de Chaleux, this may be an artefact of the radiocarbon calibration curve.     

Assessing the function of early hominin bone tools

Bone tools from early hominin sites in southern Africa continue to intrigue researchers interested in the development of early human technology and cognition. Sterkfontein, Swartkrans and Drimolen have all yielded bone tools dated to between 1 and 2 Mya associated with numerous Paranthropus robustus and few early Homo remains. The bone tools are described by different authors as implements used to excavate tubers from the ground and termites from their nests, work hides and strip bark from trees. The purpose of this research was to develop a more powerful analytical tool for the study and interpretation of bone surface modifications in general, and early hominin bone tool function(s) in particular. We used an optical interferometer to scan the worn areas of a sample of bone tools from Swartkrans and Drimolen, an ethnographic collection of implements used for defleshing marula fruits, and a set used experimentally to excavate in the ground and in termite mounds. The 3D rendering of archaeological and experimental wear patterns better highlights previously described differences between these patterns, and demonstrates the pertinence of this analytical tool to visually discriminating between different bone modifications. Analysis of selected 2D and 3D roughness variables indicates that the wear pattern on the early hominin bone tools from Drimolen is significantly different from that of tuber digging, very similar to termite foraging, and not unlike marula fruit processing. Marked differences are detected between the Swartkrans and Drimolen wear patterns, which suggests that the tools from these sites may have been used with different motions, in contact with abrasive particles of different size, or in different tasks. Principal component analyses conducted on 2D and 3D variables suggest that early hominin bone tools from southern Africa may have been used to forage for termites, extract tubers in a motion parallel to the tool main axis, process fruits and conduct other, as yet unidentified, tasks.     

Archaeological collagen: Why worry about collagen diagenesis?

DNA appears to decay by random chain scission resulting in a predictable range of fragment lengths. Collagen decay has also been modelled in this same way, although it has become increasingly evident that collagen decay does not follow this same pattern. Radiocarbon and stable isotope analysis now use ultra-filtration to isolate large fragments (>30% of original polymer length) even in Pleistocene bone. How then does collagen decay? This study contrasts experimentally degraded samples with collagen extracted from forensic, archaeological and fossil bone. In experimentally degraded bone, values for amino acid and elemental (C:N) composition, bulk δ ¹³C, δ ¹⁵N, and aspartic acid racemisation (AAR) changed very little until 99% of the collagen was lost, suggesting that the collagen triple helix and polypeptide chains remained remarkably intact. This suggestion was demonstrated directly by examining the integrity of individual polypeptide chains using cyanogen bromide (CNBr) cleavage followed by SDS-PAGE electrophoresis. In ancient samples, AAR values remain remarkably stable and the pattern of CNBr-cleavage was only replaced with a smear of smaller polypeptides in the oldest (Pleistocene) bones investigated. Smearing may reflect both modification of the methionine resides (the sites of CNBr-cleavage) and/or partial hydrolysis of the collagen molecule. The findings reveal why it is not usually necessary to worry about collagen diagenesis; it is mostly intact. However, evidence of partial deterioration of the oldest bone samples suggests that alternative purification strategies may increase yields in some samples.     

Restrictions on fluorine depth profiling for exposure age dating in archaeological bones

Archaeological fragments of bone and teeth that are exposed to a humid environment take up fluorine from the surrounding soil. The fluorine ion replaces the hydroxyl group in the mineral phase of the bone, forming chemically more stable fluorapatite. In cortical parts of the long bone diaphysis a fluorine concentration profile can be observed, which decreases from the outer surface and the marrow cavity towards the inner parts of the bone matrix. Geological time spans are needed for this process to reach equilibrium and for the distribution to become uniform. As the shape of the profile, which can be described by a diffusion model, contains information on the exposure duration of the fossil object, several attempts to use fluorine profiling as a dating method have been undertaken. The distribution of fluorine in an archaeological sample however is strongly influenced by environmentally induced processes of bone diagenesis, i.e. alteration in the structure and composition of the mineral phase and degradation of organic components that may make the time information indistinct. The primary chemical composition of bones can thus be obscured by diagenesis within tens, hundreds or thousands of years. This depends more on the diagenetic environment than on the geological age. To observe the impact of environmental influence on the profile shape, samples from several burial sites featuring various soil conditions have been analyzed for their fluorine distribution and preservation state. This paper provides an overview on the restrictions that have to be considered when attempts are undertaken to relate a fluorine diffusion pattern to the archaeological age of a bone specimen.