Comment on “Bacterial bioerosion of bones is a post-skeletonisation phenomenon and appears contingent on soil burial” [Quat. Int. 660 (2023) 75–83]

Abstract

Histotaphonomic analysis, through thin section microscopy, SEM and micro-CT scanning, has become an increasingly popular approach for archaeologists in recent years. The method relies on assessing the character of degradation in bone microstructure, placing particular importance on the degree and nature of bacterial bioerosion. However, there remains considerable disagreement about the origins and timing of bacterial bioerosion and this has major ramifications for the interpretative potential of the approach. Turner-Walker et al. (2023) p resent a firm case for the origins of bacteria being exclusively exogenous (from the soil) with bioerosion occurring only after skeletonisation. This scenario means that information gained from analysis of histotaphonomy relates entirely to the nature of the burial environment and its suitability for collagenolytic bacteria to thrive and thus provides very little useful information about human behaviour and mortuary practice. This contrasts with the common position that the origins of bacteria can be enteric (from the gut) and can effect bioerosion during putrefaction in the early post-mortem phase, thus potentially informing on mortuary practice.In this response, we present the alternative view to Turner-Walker et al. (2023) and demonstrate strong and wide-ranging evidence for bacteria from the gut microbiome to have the potential to cause bioerosion. A review of previous studies is used to evidence the impact of mortuary practice on variable microstructural preservation. We counter some of Turner-Walker et al.‘s key lines of evidence and present alternative, evidence-based explanations. Importantly, we acknowledge that the origins of bacteria are not always enteric and that current interpretations that only consider bacteria as either enteric or exogenous cannot account for the variability seen in the archaeological record.