Investigating Changes in Middle Stone Age Hunter-gatherer Mobility and Resource Utilisation in Response to Coastline Migration using Archaeological Lithic Provenance in the southern Cape Region, South Africa

List of participants with roles, affiliations, and involvement in the project
1) Jeremy A. Beller, PhD. Postdoctoral Researcher.
European Leaders for Marine Sustainability (SEAS) Programme; Centre for Early Sapiens Behaviour (SapienCE); Department of Archaeology, History, Cultural Studies and Religion (AHKR); University of Bergen.
2) Karen L. van Niekerk, PhD. Principal Investigator and lead supervisor of Jeremy A. Beller.
Centre for Early Sapiens Behaviour (SapienCE); Department of Archaeology, History, Cultural Studies and Religion (AHKR); University of Bergen.
3) Christopher S. Henshilwood, PhD. Director. Support supervisor of Jeremy A. Beller.
Centre for Early Sapiens Behaviour (SapienCE); Department of Archaeology, History, Cultural Studies and Religion (AHKR); University of Bergen.
4) Simon J. Armitage, PhD. Support supervisor of Jeremy A. Beller.
Centre for Early Sapiens Behaviour (SapienCE), University of Bergen. Department of Geography; Royal Holloway, University of London.
Context of study
Anatomically modern humans (hereafter AMH) emerged and spread across the African continent during early MIS 6 (200 ka) (Lombard et al., 2012; McDougall et al., 2005; Stewart & Jones, 2016). Their material culture attest to important adaptations to the diverse environments of Middle Stone Age (200-50 ka, hereafter MSA) Africa and the development of cultural modernity. Cultural modernity refers a suite of behaviours that are thought to distinguish AMH from earlier and contemporary species of human (e.g., Neanderthals) and continue to be exhibited by us today. The components that potentially characterise this critical development in human evolution are not yet fully understood and continue to be debated (McBreaty & Brooks, 2000; Scerri & Will, 2023; Shea, 2011). Among them are a greater exploitation and reliance on marine and coastal resources. The occupation of new econiches was possibly enabled by changes to their mobility and technology.
Mobility is a fundamental aspect of the human experience and is a defining feature of hunter-gatherers (Kelly, 1992; Kuhn, 2020; Kuhn et al., 2016). It presents at several scales, referring to the movement of populations over time, groups throughout the year, and individuals as they forage. It is important to understand the mobility patterns exhibited by a hunter-gatherer society because they have implications for survival, as they are typically a means of mitigating environmental stress (Collard et al., 2013; Hitchcock, 1982), such as a reduction in resources. Mobility is inextricably linked to interaction among groups, subsistence strategies, and the organisation of technology. It is often investigated through reconstructions of resource procurement strategies (Kuhn, 2020), such as those used for stone tools. Stone tools are a major component of hunter-gatherer sites during the Pleistocene and often the means by which they are identified (Potts, 1991). These implements enabled hominins to cope with their environments for the past 2.5 million years and, for archaeologists, provide high resolution evidence of behavioural change throughout human evolution. Procurement encompasses the suite of decisions and activities involved in the acquisition of raw material (Wilson, 2007), which have implications for the subsequent reduction, transport, utility, and longevity of the tools. The variability and distribution of natural resources, both terrestrial and marine, often force hunter-gatherers to confront decisions regarding the nature of procurement and their mobility.
The southern Cape Region in South Africa provides a significant opportunity in which to investigate the relationship between hunter-gatherer mobility and coastal subsistence. It encompasses high plant biodiversity and landscape variability, including an exposed rocky coastline on the south Atlantic Ocean with multiple caves and shelters. Several of these caves were occupied during the MSA. One important site, Blombos Cave, has been excavated and studied by Prof. Christopher Henshilwood (now of the SapienCE group from the University of Bergen, Norway) since 1991. These efforts have revealed clear oscillations in the occupational intensity and use of both terrestrial and marine resources (Archer et al., 2015; Discamps & Henshilwood, 2015; Haaland et al., 2021; Reynard & Henshilwood, 2017).
Blombos Cave contains a long sequence of MSA occupation (100-72 ka). Early occupation occurs when the coast was 2.3 km from the site with nearby access to predictable marine and coastal resources (Fisher et al., 2010; Jacobs et al., 2020). By 72 ka, the coastline has gradually receded to 32.5 km, reducing access to these resources (Fisher et al., 2010; Jacobs et al., 2020). The regression of the sea opened up a large geographic area (today submerged) off the southern coast of Africa, known as the Palaeo-Agulhas Plain (Marean et al., 2020). The proximity to marine resources, predominantly shellfish (De Vynck et al., 2020), is reflected in the nature of the ecocultural niches of the sites. In particular,
Blombos Cave shifts from being a coastal site to a continental (interior) one (Discamps & Henshilwood, 2015; Reynard & Henshilwood, 2017). Consequently, it is becoming clearer that the shifting coastlines of southern Africa had a noticeable impact on the nature of subsistence in the region (d’Errico et al., 2017), and further begs inquiry into which other aspects of human behaviour were affected.
The lithics assemblage from Blombos Cave contains tools and debitage made from quartz, quartzite, cryptocrystalline silicates, and silcrete. Blombos Cave contains layers with the Still Bay techno-tradition, signalled by bifacial foliate points (Soriano et al., 2015). The Still Bay tradition has been discovered at other MSA sites throughout South Africa (Henshilwood, 2012), indicating their likely importance for subsistence, networking, and regional identity. For hominins congregating in a region with shifting coastlines, the development of effective foraging and lithic procurement strategies was essential to their survival. The procurement of raw materials, specifically silcrete which is not found locally, likely required hunter-gatherer groups to be mobile across the landscape, especially during sea level regression. A reconstruction of raw material procurement strategies will lend insight into critical questions regarding the nature of hunter-gatherer mobility and the ecocultural niches that humans occupied during the MSA in the southern Cape Region.
Questions and objectives
The research will be guided by the following questions:
1) Where are the silcrete sources from which the stone tools at Blombos Cave are manufactured? What sources of silcrete might have been available during the MSA in what are now in offshore regions, such as the Palaeo-Agulhas Plain?
2) What are the specific marine-related signatures that can be identified when investigating patterns of hunter-gatherer mobility and resource utilisation during the MSA at coastal and inland sites and can these be identified and correlated with changes in raw material types?
3) What evidence is there for connections among MSA sites of the southern Cape, West Cape Coast, and the Karoo interior, and can these be related through past mobility patterns, particularly in relation to marine resources?
The corresponding objectives of this project are threefold:
1) Investigate the provenance of silcrete materials at Blombos Cave, through linkages to potential terrestrial and marine sources.
2) Reconstruct patterns of resource utilisation and movement across the terrestrial and coastal landscape of the southern Cape Region and Palaeo-Agulhas Plain during the MSA.
3) Situate the mobility of hunter-gatherers with the corresponding econiches during each econiche, particularly in reference to sea regression and transgression.
Materials and methods
The project integrates a number of advanced analyses at the frontier of scientific investigation. The largest component is a provenance analysis of the silcrete and quartzite stone tools. A provenance analysis relies on the geochemical and/or petrographic consistency between tested data (stone tools) and known data (sources of raw material). The geological durability and near ubiquity of stone tools at hunter-gatherer sites makes them an ideal material for such study. Although the characterisation is very challenging, provenance analyses have been applied with success by archaeologists on silcrete (e.g., Nash et al., 2022; Nash et al., 2013; Nash et al., 2016) and quartzite (e.g., Prieto et al., 2019; Prieto et al., 2021). This provenance analysis mirrors them.
First, geological maps and literature were consulted to identify silcrete and quartzite sources within the southern Cape Region. Representative samples were collected during a vehicle and pedestrian survey with Pieter-Jan Gräbe, a local geologist from Terra Search Geological Consults. Geographic variables, such as GPS coordinates, proximate streams, topographic features, vegetation locales, were documented at each source.
Second, samples of silcrete and quartzite tools were selected from the lithic assemblage from Blombos Cave at the Witwatersrand satellite laboratory in Cape Town (Table 1 and Table 2). These were extracted from the lowest phase of occupation, M3, which correspond to high sea levels. Priority was given to the largest artefacts (e.g., chunks, cores) and debitage. The presence of large and cortical debitage indicates that raw material was likely transported as blank and that manufacture occurred on site; its absence indicates that stone tools were likely made elsewhere, possibly at the source.
Third, the petrographic, geochemical, and isotopic profiles of silcrete and quartzite sources and artefacts will be generated through several innovative and reliable techniques. The major oxides and base metals concentrations will be generated by the inductively coupled plasma-optical emission spectrometry (ICP-OES) or X-ray fluorescence spectrometry (XRF) in the Department of Earth Science at the University of Bergen. Date on the rare earth elements will be generated by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), also in the Department of Earth Science at the University of Bergen. The mineralogy will be identified using petrographic thin sections. These will be analysed using the cross polarised microscope in the SFF Centre for Early Sapiens Behaviour (SapienCE) laboratory at the University of Bergen. Secondary ion mass spectrometry (SIMS) will be applied to produce the O2 isotopic profiles and solution nebulization-inductively coupled plasma-mass spectrometry (SN-ICP-MS) will be used to produce the Pb isotopes. SIMS has been shown to be considerably more reliable at producing isotopic profiles than LA-ICP-MS (Košler et al., 2002). Both instruments are housed with the Earth Materials and Archaeometry Center (EMAC) at the University of Manitoba.
Fourth, the petro-geochemical profiles of the stone artefacts are cross-referenced with those of the sources in order to identify consistencies among them. This will be performed through statistical evaluations (e.g., PCA, bivariate scatterplots, cluster analyses) applied with JMP software. The identification of sources will, at minimum, provide a Euclidean distance of raw material movement.
Lastly, the results of the provenance analysis will be integrated into a digital spatial model in order to further visualise and evaluate the movement of humans throughout the landscape. This will include
models of the reconstructed Palaeo-Agulhas Plain to identify potential routes taken to locations of marine and coastal resources, both lithic and other resources. It will base them on the periodisation at Blombos Cave for a longue durée perspective corresponding to sea level fluctuation.
Rationale for requested export
This study cannot be conducted in South Africa as some of the specialised instruments and laboratories for sample preparation and analysis are located at foreign institutions: the University of Bergen, Norway, and the University of Manitoba, Canada. The samples will be co-analysed by specialists Prof. Desiree Roerdink (Bergen) and Prof. Mostafa Fayek (Manitoba). Prof. Roerdink has experience analysing trace and rare earth elements through LA-ICP-MS and major elements through ICP-OES. Prof. Fayek operates the SIMS laboratory through which Pb and O2 isotopes can be analysed. He also has performed research on landscape weathering and evolution in South Africa. Together, their expertise and input are vital to the success of the project.
The preliminary results on the sources will be presented at the Southern African Society of Quaternary Research (SASQUA) XXIV biennial congress in the Cango Valley, South Africa. Results on the artefacts will be presented at the PanAfrican Archaeological Association congress and the Society of Africanist Archaeologists biennial meeting. Meetings outside Africa where the results will be disseminated include the European Association of Archaeologists and the Society for American Archaeology. We are also collaborating with the Gouritz Cluster Biosphere Reserve, based in Riversdale, to make the results relevant to issues of nature sustainability and heritage protection.
Mode of transportation
The samples will be transported via DHL courier services, arranged by the Curator, Samantha Mienies, at Wits satellite Laboratory, 167 Buitenkant street, Gardens, Cape Town, South Africa to the University of Bergen, Norway.