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

M P M Marques,L A E Batista De Carvalho,E Cunha,S F Parker,D Gonçalves

doi:10.1098/rsos.210774

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.

Highlights

This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance
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
Two different settings were probed: (i) combustion, in the presence of oxygen—aerobic (A) and (ii) absence of oxygen—anaerobic (An)—in a sealed chamber not allowing the release of the volatiles formed during the burning process, which enables a reequilibrium to be attained within the bone matrix

Summary

Introduction

This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance. Low to medium heating does not cause significant changes in bone’s mineral components, which leaves the variations in the organic constituents (collagen and lipids) as the only biomarkers of the impact of temperature, with an emphasis on collagen fibril unpacking and fragmentation which arise well before collagen loss and change in mineral crystallinity (that take place at higher temperatures) Spectroscopic relationships such as the crystallinity index (splitting factor), or the carbonate/phosphate and OH/phosphate ratios, which were reported to be highly valuable in the analysis of heavily burned bones [15,17,20,21,22,27], are useless in the characterization of bones subject to temperatures below 600°C

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