Charred bone: Physical and chemical changes during laboratory simulated heating under reducing conditions and its relevance for the study of fire use in archaeology
“…The BPI and OH/P values followed the same trend observed in previous works (Thompson et al, ; Lebon et al, ; Snoeck et al, ; Reidsma et al, ), although, in general, with the already mentioned higher values. The BPI decreased uninterruptedly until the 1000°C mark, but very slightly after 800°C.…”
Section: Discussionsupporting
confidence: 89%
“…This supports the hypothesis that species differences may be responsible for different CI trends. Reidsma et al (), in turn, experimentally burned cow bones and found an increasing CI trend similar to the one currently reported. This may go against the human vs fauna hypothesis but reliable comparisons cannot be made because their experiment was carried out under oxygen reducing conditions and did not replicate ours entirely.…”
Section: Discussionsupporting
confidence: 82%
“…Although quite a few studies, using several techniques, have discussed the variability of bone composition as a function of incremental heating (e.g., Von Endt & Ortner, ; Person, Bocherens, Mariotti, & Renard, ; Rogers & Daniels, ; Hiller, Thompson, Evison, Chamberlain, & Wess, ; Etok et al, ; Piga, Malgosa, et al, 2008; Piga, Thompson, et al 2009; Lebon et al, ; Wang et al, ; Marques et al, ; Reidsma, Hoesel, van Os, Megens, & Braadbaart, ; Zohar, Ovadia, & Goren‐Inbar, ; Cascant et al, ; Chen et al, ; Ellingham, Thompson, & Islam, ), little research has been focused on the intrabone, intraskeleton, and interskeleton variability of chemometric indices. Those scarce studies reported important variations that may have a significant impact on subsequent analyses (Thompson et al, ; Snoeck et al, ).…”
The relatively large heterogeneity, especially at the intrabone level, is possibly the consequence of microstructural bone differences. The dissimilarities observed between our investigation and other published studies are probably due to the fact that the samples used here came from human rather than faunal bones. Also, our samples were buried previously to the experimental burning so this may also partly explain our contrasting results, since previous research was mostly performed on fresh bone. Future inferences based on vibrational spectroscopy analyses should take into account the possible effect of all these sources.
“…The BPI and OH/P values followed the same trend observed in previous works (Thompson et al, ; Lebon et al, ; Snoeck et al, ; Reidsma et al, ), although, in general, with the already mentioned higher values. The BPI decreased uninterruptedly until the 1000°C mark, but very slightly after 800°C.…”
Section: Discussionsupporting
confidence: 89%
“…This supports the hypothesis that species differences may be responsible for different CI trends. Reidsma et al (), in turn, experimentally burned cow bones and found an increasing CI trend similar to the one currently reported. This may go against the human vs fauna hypothesis but reliable comparisons cannot be made because their experiment was carried out under oxygen reducing conditions and did not replicate ours entirely.…”
Section: Discussionsupporting
confidence: 82%
“…Although quite a few studies, using several techniques, have discussed the variability of bone composition as a function of incremental heating (e.g., Von Endt & Ortner, ; Person, Bocherens, Mariotti, & Renard, ; Rogers & Daniels, ; Hiller, Thompson, Evison, Chamberlain, & Wess, ; Etok et al, ; Piga, Malgosa, et al, 2008; Piga, Thompson, et al 2009; Lebon et al, ; Wang et al, ; Marques et al, ; Reidsma, Hoesel, van Os, Megens, & Braadbaart, ; Zohar, Ovadia, & Goren‐Inbar, ; Cascant et al, ; Chen et al, ; Ellingham, Thompson, & Islam, ), little research has been focused on the intrabone, intraskeleton, and interskeleton variability of chemometric indices. Those scarce studies reported important variations that may have a significant impact on subsequent analyses (Thompson et al, ; Snoeck et al, ).…”
The relatively large heterogeneity, especially at the intrabone level, is possibly the consequence of microstructural bone differences. The dissimilarities observed between our investigation and other published studies are probably due to the fact that the samples used here came from human rather than faunal bones. Also, our samples were buried previously to the experimental burning so this may also partly explain our contrasting results, since previous research was mostly performed on fresh bone. Future inferences based on vibrational spectroscopy analyses should take into account the possible effect of all these sources.
“…Bands in the 1,500–1,700 cm −1 region of the spectra for samples burned at temperatures above 500 °C are indicative of aromatic compounds of char residues from burned organic matter. This is expected in bone samples that have not been ashed completely (Figs 3 and 4) 32 .Figure 3FTIR Spectra of Salmon and Codfish Bones Heat Treated through a Ramping Temperature Sequence between 200 °C and 1,000 °C. ( A ) Atlantic Salmon; note the loss of the HPO 4 /CO 3 peak and appearance of strong βMgTCP peaks at 600 °C; ( B ) Atlantic Cod; the loss of the HPO 4 / CO 3 peak and appearance of weak βMgTCP peaks occurs at 800 °C; abbreviations: Tgy = triglyceride ester; Am = amide; Alk = alkene; Pr = proline; CO 3 = carbonate; PO 4 = phosphate; HPO 4 = hydrogen phosphate; Arom = aromatic char compounds; WH = whitlockite; β = beta magnesium tricalcium phosphate.Figure 4FTIR Spectra of Caribou and Duck Bones Heat Treated through a Ramping Temperature Sequence between 200 °C and 1,000 °C.…”
Ichthyoarchaeological evidence is uncommon at ancient hunter-gatherer sites from various regions and timeframes. This research contributes to the development of microarchaeological techniques useful for identifying fishing economies in situations where classifiable bones are unavailable. Specifically, traces of heat altered bone mineral in domestic hearths are expected to provide markers for discarded fish remains. We used a series of laboratory incineration experiments to characterize the mineralogy of burned salmonid vertebrae. Fourier transform infrared spectroscopy and x-ray diffraction distinguished the formation of beta magnesium tricalcium phosphate (βMgTCP) at temperatures as low as 600 °C. Bones from a sample of game mammals and birds did not form this phase at temperatures below 1,000 °C. We propose that this neoformed mineral can serve as a proxy for hunter-gatherer salmonid fishing when typical ichthyoarchaeological evidence is absent. Using Fourier transform infrared spectroscopy, it will be possible to rapidly and inexpensively determine the presence of βMgTCP in fragmentary burned bone remains associated with combustion features. The occurrence of βMgTCP in archaeological hearth features will offer a new means of further evaluating the temporal, geographic, and cultural scope of salmonid harvesting. We also acknowledge the value of biphasic hydroxylapatite-βMgTCP recovered from Atlantic salmon vertebrae as a bioceramic.
“…Exposure to heat leads to colour changes that are correlated with burning temperature (Shipman et al, ; Etxeberria, ; Mayne Correia, ; Devlin and Herrmann, ; Walker, Miller, & Richman, ; but see Walker et al, , and Reidsma, van Hoesel, van Os, Megens, & Braadbaart, , who show that similar heat‐induced colours may occur when bones are burned at different temperatures due to differences in oxygen availability and duration of exposure to heat). Thus, heat‐induced colour changes were used to tentatively infer the intensity of the cremation.…”
The Iberian Chalcolithic displayed a remarkable variety of funerary practices, which has been related to interpopulation differences, intrapopulation social‐cultural differences, and complex multistage funerary rituals. Perdigões, a Chalcolithic set of ditched enclosures, reflects such diversity including a wide array of funerary practices. Among those practices is cremation, which, despite relatively rare, is represented in different structures in Perdigões. One of these structures (Pit 40) presents an unparalleled high minimum number of individuals (n = 240), contrasting with nearby and coeval structures. In this study, we analyse heat‐induced bone changes and other archaeothanatological variables to tentatively assess the preburning condition of the human remains. The results of Pit 40 are also compared with other comparable contexts to assess if this unique context presents further funerary differences relative to those other contexts in, for example, body processing. Our results suggest preferential cremation of fleshed human remains, but burning of at least a minority of skeletonised remains and deposition of possibly unburned remains also likely occurred. Body processing appears to be comparable with that of the cremation contexts of Perdigões but contrasts with that of another nearby context (Dolmen of Olival da Pega 2b) in which burned bones were also found.
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