Assessing the extent of bone bioerosion in short timescales – A novel approach for quantifying microstructural loss

Abstract

The evaluation of bone diagenetic phenomena in archaeological timescales is well established, but little is known about the extent of bone diagenesis in short forensic timescales. In particular, the use of the Oxford Histological Index (OHI) has become synonymous with assessing bioerosion in archaeological bone samples, but it may not be ideal for use on samples with shorter, forensic post-depositional timescales. Here, we present a novel method of quantifying the extent of bioerosion occurring on samples with short post-depositional periods by counting the number of normal and diagenetic osteocyte lacunae observed within the microstructure of the bone, which enables calculation of the percentage of destroyed bone within the sample. Due to the potential for condition of the remains, or depositional environment to affect bone diagenesis, this study investigated multiple conditions; whole rat carcasses, defleshed rat long bones, and excised fleshed rat limbs that were either placed in soil in plastic boxes or exposed on a clean plastic surface, and left to decompose from four to 28 weeks, to allow bone bioerosion to occur. Statistically significant differences in the number of average diagenetic lacunae observed were found between the three conditions, while a statistically significant difference was observed between OHI scores of samples in the two deposition environments. The number of diagenetic osteocyte lacunae increased in all conditions, showing statistically significant increase in the percentage of destroyed bone over time. Diagenetic changes were seen as early as 4-weeks post-deposition. Comparisons between the OHI scores and the lacunae counts showed that, while the use of OHI could not distinguish between samples with discrete microstructural deterioration, counting the normal and diagenetic lacunae could distinguish such diagenetic changes.