The impact of moderate heating on human bones: an infrared and neutron spectroscopy study

Abstract

This study aims to analyse human bones exposed to low/medium temperatures (200–650°C) under experimentally controlled conditions, both oxidizing and reducing, using complementary optical and neutron vibrational spectroscopy techniques. Clear differences were observed between the aerobically and anaerobically heated bones. The organic constituents disappeared at lower temperatures for the former ( ca 300°C), while they lingered for higher temperatures in anaerobic environments ( ca 450–550°C). Unsaturated non-graphitizing carbon species (chars) were detected mainly for anaerobically heated samples, and cyanamide formation occurred only at 650°C in reducing settings. Overall, the main changes were observed from 300 to 400°C in anaerobic conditions and from 450 to 500°C in aerobic environments. The present results enabled the identification of specific spectroscopic biomarkers of the effect of moderate temperatures (less than or equal to 650°C) on human bone, thus contributing to a better characterization of forensic and archaeological skeletal remains subject to heating under distinct environmental settings. In particular, these data may provide information regarding cannibalism or ancient bone boiling and defleshing rituals.

Vibrational spectroscopy to study ancient Roman funerary practices at the “Hypogeum of the Garlands” (Italy)

“…Between the fourth century BC and the first century AD, the cremation rite was prevalent in Ancient Roman civilization and inhumation was rare 23 . By comparing the results obtained here for the archaeological samples with published data previously gathered for modern human bones burned under controlled conditions (regarding temperature and oxygen availability) 14 – 16 , it is possible to estimate the temperatures to which the investigated archaeological samples were subject to. Table 1 summarizes the information gathered from the analysis of the experimental results from the previous section: (i) samples 2, 5, 7, 8, 9 and 10 found inside Aebutia’s sarcophagus, located in the central area of the skeleton, were subject to very mild heating ( ca.…”

“…250 cm −1 . Previous work has shown that the lipid and protein components of bone disappear on heating to about 400 °C (under oxidizing conditions) 14 – 16 . From this evidence, one can conclude that rib1, tibia and carpal appear not to have been burned.…”

“…The second derivative of the data (multiplied by 100), for the 550 to 750 cm −1 range, is included in ( C ). The INS and FTIR-ATR spectra of modern human bone (femur), unburned (F unb ) and burned at 200 °C under controlled aerobic conditions (F200), as well as the INS spectrum of HAp (MAPS, with 5240 cm −1 incident energy), are also shown 14 – 16 . …”

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Figure 4 Vibrational spectra of human skeletal remains from individual A1 (fibula, rib4, cranium2, pelvis, radius, clavicle1, 2 and 3): ( A ) INS, measured at TOSCA (0–2000 cm −1 ); ( B ) INS, measured at MAPS (0–4000 cm −1 , with 5240 cm −1 incident energy); ( C ) FTIR-ATR (400–2100 cm −1 ); ( D ) Raman (100–1250 cm −1 ). The INS and FTIR-ATR spectra of modern human bone (femur) burned at 700 °C (F700), 800 °C (F800) and 900 °C (F900), under controlled aerobic (A) or anaerobic (An) conditions, are also shown 14 – 16 .

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Figure 5 Vibrational spectra of human skeletal remains from individual A1 (radius and cranium2): ( A ) INS, measured at TOSCA (0–2000 cm −1 ); ( B ) INS, measured at MAPS (0–4000 cm −1 , with 5240 cm −1 incident energy); ( C ) FTIR-ATR (400–2100 cm −1 ); ( D ) Raman (100–1250 cm −1 ). The INS and FTIR-ATR spectra of modern human bone (femur) burned at 900 °C (F900) and 1000 °C (F1000), under controlled aerobic (A) or anaerobic (An) conditions, as well as the INS, FTIR-ATR and Raman profiles of reference calcium hydroxyapatite (SRM 2910b, HAp), are also shown 14 – 16 .

Figure 6 FTIR-ATR spectra (400–3750 cm −1 ) of human skeletal remains: ( A ) rib1 fragment from the Aebutia’s sarcophagus and A1; ( B ) cranium1 specimens from the Aebutia’s sarcophagus, with and without white concretions; ( C ) rib1, 2, 3 fragments from Aebutia’s sarcophagus and comparison with modern human bone (femur) burned at 1000 °C (F1000) and unburned; ( D ) comparison of FTIR-ATR spectra of vertebrae2, 3, 4 from Aebutia’s sarcophagus.

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