Remains of the day-preservation of organic micro-residues on stone tools

Here I report on the decay processes of microscopic organic residues left on stone tool surfaces after their use. Residue analysis on ancient stone tools facilitates reconstruction of past activities. This study enables predictions about the circumstances under which ancient residues preserve. Experimental tool sets with modern residues were buried for a year in separate deposits at Sterkfontein, Sibudu (South Africa) and Zelhem (the Netherlands) whose pH and geomorphology varied, they were then analysed using light microscopy. Biological weathering mainly causes residue decay. In unstable environments rich in microbes and micro-organisms, residues decay quickly. From an archaeological perspective this means that sites that are stable, desiccated, waterlogged, extremely acidic or alkaline and extremely cold or hot sites. Different residue types have different preservation optima and this may lead to a preservation and perhaps interpretation bias. The preliminary predictive models presented in this paper could aid in the considered selection of sites and samples.     

Middle Stone Age pièces esquillées from Sibudu Cave,South Africa: an initial micro-residue study

In this paper I present the results of a micro-residue study conducted on ten pièces esquillées (scaled pieces) from Sibudu Cave, South Africa. These artefacts are associated with the Howiesons Poort Industry (∼61.7 and ∼64.7 ka years ago at Sibudu), representing part of the later phase of the Middle Stone Age. Until now, it was unclear on what these pieces were used, and whether they were functional. Previous experimental use-wear work tentatively pointed towards bone processing. However, replication work on stone tool production technology suggests that pièces esquillées are merely the by/end-product of bipolar knapping. I used residue analysis on the Sibudu artefacts because this alternative method has the potential to identify if they were used, and if so, illuminate the specific materials the pieces were used on. Although the sample is small, all the pièces esquillées reveal a clear animal processing signal. There are some bone deposits on the utilised edges that may substantiate bone processing, or perhaps a bone hammer was used with them, but additional study, including Later Stone Age artefacts, is needed to assess the feasibility of these observations. It remains possible that the artefacts are core reduced pieces that were subsequently used as tools or simply knapped with a bone hammer.     

Discerning use-related micro-residues on tools: testing the multi-stranded approach for archaeological studies

In this paper I explore how post-depositional contaminants and non-use related ancient residues may be distinguished from use-related residues directly associated with the application of ancient artefacts. It is assumed that contaminant and unintentional remains have a random distribution over a tool’s surface. Preserved use-related residues, however, are expected to have a consistent spatial distribution around a working edge. To test this, residues on used and unused experimental flakes were recorded after they underwent weathering. The surfaces of the experimental flakes were divided in four quadrants, of roughly equal size. The surface coverage of the residue types per quadrant was then recorded. On used flakes with well preserved residues, the use-related residues are more abundant on portions associated with the sharp edge than on portions associated with blunt sides. On the samples without identified use-related remains and on the unused sample, the distribution of micro-remains is more uniform. This study confirms that by using a contextual approach it is possible to distinguish use-related remains from non-use-related and co-incidental remains.