The G-force awakens: the influence of gravity in bone heat-induced warping and its implications for the estimation of the pre-burning condition of human remains

Abstract

In forensics, assessing the pre-burning condition is important to determine the circumstances of death. Heat-induced warping (HIW) occurs more frequently on non-dry bone but is not a reliable indicator of the pre-burning condition of human remains. Several factors have a significant effect on warping (e.g. maximum temperature) but others are still unknown. We investigated the effect of Earth’s force of gravity on HIW by experimentally burning 23 human long bones from 4 different unidentified skeletons at different temperatures. Only 56% of the warped bones (n = 16) presented HIW compatible with gravity. These bones presented larger masses than the bones presenting warping incompatible with gravity, thus suggesting that bone mass plays a role in HIW. Probably, the intrinsic contractile forces caused by heated collagen are at the origin of warping and such bending may be compatible with gravity depending on bone mass. Possibly, incompatibility occurs when intrinsic bending is counteracted by gravity whenever bone mass produces a stronger force. We therefore conjecture that HIW results from a combination of at least two different forces. HIW is multifactorial and finding a reliable indicator of the pre-burning condition of human remains may be only possible at the microscopic and elemental levels.

Keywords:

• Forensic anthropology
• bioarchaeology
• taphonomy
• heat-induced changes
• burned bone

Acknowledgements

The authors thank Calil Makhoul for his aid with the experimental burnings. They also thank the reviewers for their valuable comments on a previous version of the paper.