Understanding tool use at the oldest occupational layers at the Blombos Cave through use-wear and residue analysis.

Overview
The project, part of a comprehensive study at the Centre for Early Sapiens Behaviour (SapienCE),
aims to unravel the usage patterns of stone tools during the Middle Stone Age (MSA) in South
Africa, with a particular emphasis on plant gathering and utilisation. It focuses on the tools found
in the oldest layers (M3 phase) of Blombos Cave.
The proposed research is based on large-scale use-wear analysis. It allows reconstructing an
artefact's life history from production through use, deposition or discard, and post-depositional
processes. The research will investigate several important questions: What types of activities
were undertaken at the site? Do we observe a change between the layers, and if so, what could
be the cause? Is there a preference for a material type in relation to a specific task? Finally, how
can all these patterns be related to the broader context of environmental adaptation and shifts in
site use?
To achieve this goal, a series of analyses will be performed. Toolsselected for export were already
analysed in Cape Town at low magnifications (up to 50×) using a stereo microscope. Detailed
examination of the tool's surface will be conducted through reflected light microscopy at
magnifications between 50 and 500×. Observed polish characteristics will be quantified through
confocal microscopy. A Scanning Electron Microscope with energy-dispersive X-ray
spectroscopy will be employed to test the composition of observed residues. It will allow an
understanding of the trace's nature and origin.
Aim/Objective
The proposed research aims to trace possible activities undertaken at the Blombos Cave by
studying the use-wear traces on lithics from the M3 phase dated to ~100ka – 85ka. The goal is to
describe the frequency of different wear traces and verify their importance. This would allow us

to begin a discussion about these tasks and compare different assemblages as well as the
relation between techno-typological tool types and their function. The obtained results will be
compared to the available environmental data to estimate the impact of climate change on
subsistence strategies and possibly link some of the shifts to certain technological innovations.
By combining these observations with what is known about hunting and mollusc gathering, it will
be possible to create compelling and evidence-based stories of site use, settlement dynamics
and human-environment interaction.

Materials
Artefacts selected for export were initially analysed in the Wits Satellite Laboratory, 167
Buitenkant Street, Cape Town. The selection was based on the edge alterations detected with the
naked eye and through low magnifications. In total, 74 tools were chosen, and the list is provided
in the attached file.
Raw materials
Tools selected for this research are made from 4 raw material types, namely quartz, quartzite,
silicrete and chert (fig. 1). Non-flint lithic materials pose a challenge due to the more complex
nature of the raw material and the relatively low number of studies conducted (Aleo, 2022;
Clemente Conte et al., 2015; Pedergnana & Ollé, 2017). Use-wear traces form at different rates
on each of them and have varying characteristics (for example, in terms of polishing development
or appearance/lack of striations). Individual characteristics of the trace formation on the 4 raw
materialsinfluence the methodsselected forthis project. The proposed combination of three
main microscopic approaches will allow for the best understanding of both use-wear traces and
post-depositional processesthat could influence artefact preservation.
Almost half of the selected tools were made from silcrete (fig. 1). It is a heterogeneous rock
consisting of quartz grains in a microcrystalline silica matrix. In the Cape Coastal zone of South
Africa, it occurs as caprocks on deeply weathered bedrock plateaus. It is highly variable in terms
of thickness, colour and texture (Webb & Nash, 2020). Polish develops irregularly on the tool's
surface and is usually found in small, randomly distributed patches. Edge removals happen
relatively quickly, whereas edge rounding, striation and polish develop at a slower rate (Munt et
al., 2023; Stephenson–Gordon, 2021).
Quartzite is a coarse-grained metamorphic rock with quartz grains being an essential component
(at least 95%), and various types of mica, feldspars, and heavy minerals of a detritic origin are
present in low amounts at different proportions. It varies in colour (based on the presence of
minerals) and texture. The traces develop at crystals, and the matrix at different rates, and the
trace development is influenced by the material roughness and uniformity. Moreover, surface
irregularities and varying orientations of the crystalsurfaces, creating further variation in surface
relief, are regarded as major obstacles while conducting use-wear analyses (Pedergnana & Ollé,
2017; Antonella Pedergnana, 2019 pp. 2‐4). During work, especially at the initial stages,
a significant material loss is observed at the first stage of the trace development due to the brittle
nature of quartzite. This rapid crystal detachment causes quick edge dulling and rounding. At the
same time, traces that would develop on the tool edge disappear due to use (Clemente Conte &
Gibaja Bao, 2009).
Quartz is an important component of the above-mentioned raw materials and was also

frequently used at the Blombos Cave. Ten artefacts selected for this study were made from fine-
grained quartz. Functional analysis of this raw material has grown in popularity in recent years,

and the trace formation processes are relatively well understood (de la Peña et al., 2018; Ehlert
et al., 2022; Knutsson et al., 2015; Taipale & Rots, 2018). Quartz is a highly reflective,
heterogeneous material (Driscoll, 2011). Both qualities pose a challenge during use-wear
analysis. Additionally, diagnostic traces such as striations, polish, or fractures may appear on
different parts of the tool being analysed (Lemorini et al., 2014; Venditti, 2012). Consequently, all
edges and adjacent areas of the tool must be examined thoroughly to identify and interpret any
potential traces properly.
Only one tool in the sample was made from fine-grained chert. Traces developing on its surface
are comparable to well-studied ones on flint, although they can be characterised by a lower
development degree after the same amount of working time. Polish distribution is highly
dependent on the natural topography of this raw material. Traces are often localised and display
lesslinkage than flint (Aleo, 2022; Schmidt et al., 2020).

Methods
All of the proposed methods are non-destructive. During the initial analysis conducted at the Wits
Satellite Laboratory, selected artefacts were not washed. After screening for potential residues
and conducting analysis on them, selected artefacts will be cleaned using a solution of ultrapure
water and starch-free, no-fragrance soap.
The identification of use-wear traces on archaeological material is based on a comparison with
the experimental reference collection. Experiments were conducted on bone processing, cutting
reeds and wild grasses, fish butchering, and ochre processing. The experimental collection is
currently stored at the University of Bergen.
Optical light microscopy
This method is based on the qualitative observations of the tool's surface and the identification
of traces. Characteristic traces are formed on the edges and surface of the artefact during
contact with another material, such as different plants, wood, hide, meat, bone, and antlers.
First, the low-power approach using a stereomicroscope with magnifications up to 100× is
applied. Several types of modification of the lithic surface, so-called macro traces, can be
noticed using this method. Heavy edge damage, such as chipping and fracturing, can be the first
indicator ofthe use of the tool but could also be the result of the post-depositional processes.

Edge scarring (fig. 2 d) and rounding are usually the most visible use patterns and can sometimes
be noticed even with the naked eye. The second type of trace would be some of the biggest
striations of varying dimensions. In general, this method is better suited to observe the amount
and location of the use-wear traces, hardness of the material and direction of movement without
obtaining specific information about the type of the material worked (Jensen, 1994 pp. 12‐14;
Marreiros et al., 2015 p. 9). In the case of the proposed project, it is essential to broadly screen
the tools to understand general wear patterns (fig. 2 a, c, d) and sample relevant specimens for
the next stage.

The sample is studied using high-power magnifications (50–500×) under a metallurgical
microscope in the second step. The method is based on the recognition of distinctive morphology
and texture patterns of wear (fig. 2 b) formed on the tool's surface (Clemente Conte et al., 2015).
Modification of the surface of the flint called micro polish is, in most cases, possible to observe
only in high magnification from 100 to 500×. The only exception is heavily developed harvest
polish, the so-called ‘sickle gloss’, which can be easily observed without professional equipment
(D’Errico, 2017). Polish formed on the tool's surface can be defined by texture, pattern and degree
of development. The texture is understood as the arrangement of traces and their regularity. The
distribution and location of the polished areas and the relation between them create a pattern.
Finally, development is understood as a proportion between the polished surface and the area
not affected by use (González‐Urquijo & Ibáñez-Estévez, 2003 p. 483). The analysis includes

identifying and interpreting three things: the location of the use wear on the surface, the mode of
use, and the worked material.
Very weak use-wear traces can be formed on the surface of a tool after a few minutes of work.
It will first develop on the zones near the edge or on the most elevated parts, such as ridges, of
the used tool and will continuously spread into the surface and lower areas, for example, into the
bottom of the scars. Progression and development of the polish depends not only on the length
and intensity of work but also on several other factors such as hardness of the material, water
content and specific movement of the tool (Jensen, 1994 p. 13). Less invasive and restricted in
terms of surface distribution, polish will form on the tool used on dry and hard material, whereas
softer and wet material would produce a more irregular texture going deeper into the tool's
surface. However, very soft materialssuch as meat, fat or vegetables usually develop only generic
weak polish (González‐Urquijo & Ibáñez-Estévez, 2003 pp. 484-485; Knutsson et al., 2015). It is
also important to note that the rate of polish development is affected by the type and quality of
the lithic material and its initial surface roughness (Aleo, 2022).
Laser scanning confocal microscopy (LSCM)
A quantitative approach will be applied after locating and understanding the use-wear traces.
LSCM is used to obtain a 3D surface model of a selected spot with well-developed polish. The
results are processed to calculate a range of surface texture parameters in ISO standards
describing features such as surface roughness or furrow depth (Evans & Donahue, 2008). This
method has been successfully applied in other studies to show differences between polish
generated through working with various materials: bone, antler, wood, hide cereals and reeds
(Ibáñez et al., 2018;Ibáñez & Mazzucco, 2021).
LSCM has two main benefits when applied to the use-wear analysis of coarse-grained rocks. It
allows for the quantification of observed traces and statistical comparison both within the
sample and with the experimentally reproduced traces (Stemp, 2023). Additionally, a confocal
microscope equipped with an optical one can be used to work on highly reflective or uneven raw
materials, providing better-quality photos of the observed areas (Pedergnana, Calandra, et al.,
2020).
Scanning Electron Microscope (SEM) with Energy-dispersive X-ray spectroscopy (EDX)
Using SEM for use-wear analysis provides an advantage in terms of visualisation, obtained
magnifications, and the possibility of residue detection. Compared to optical light microscopy,
SEM offers a greater depth of field, which leads to the acquisition of better-focused pictures,
especially at high magnifications (Borel et al., 2014; Taipale & Rots, 2018). Less developed
polish or low contrast traces, which is often the case for most of the raw materials analysed in
this study, are also better visible under SEM. Due to this method's lengthy procedure and high
cost, a small sub-sample of tools will be selected for this stage. It will include artefacts with
clearly distributed ochre residue and some tools with the most promising polishes. All analyses
will be performed in low vacuum conditions, so covering the artefacts with carbon or gold layers
will not be needed.
The biggest advantage of using SEM isthe ability to detect and analyse the chemical composition
of particles adhering to the tools. Residues are an important element of use identification, clearly
inferring past tool function. Depending on their size and nature, some can be observed through
optical light microscopy, but chemical elemental analysis is important to infer their origin clearly
(Borel et al., 2014; Pedergnana & Ollé, 2017).

Rationale for Requested Export
The equipment required for the analysis is available in the laboratories at the University of Bergen in Norway and the University of Bordeaux in France. After
the initial study carried out at the Wits Satellite Laboratory, more detailed examination of selected tools is needed. The proposed research combining 3 main
microscopic methods will allow the best understanding of observed traces and residues. Additionally, an experimental reference collection that will be
analysed using the same methods is stored at the University of Bergen.
Mode of Transport
The samples will be transported via DHL courier services (arranged by the Curator, Samantha Mienies), Wits Satellite Laboratory, 167 Buitenkant Street,
Cape Town. For travels between Bergen and Bordeaux, artefacts will be transported in Marzena Cendrowska's personal luggage.