Explanations of variability in Middle Stone Age stone tool assemblage composition and raw material use in Eastern Africa

Abstract

The Middle Stone Age (MSA) corresponds to a critical phase in human evolution, overlapping with the earliest emergence of Homo sapiens as well as the expansions of these populations across and beyond Africa. Within the context of growing recognition for a complex and structured population history across the continent, Eastern Africa remains a critical region to explore patterns of behavioural variability due to the large number of well-dated archaeological assemblages compared to other regions. Quantitative studies of the Eastern African MSA record have indicated patterns of behavioural variation across space, time and from different environmental contexts. Here, we examine the nature of these patterns through the use of matrix correlation statistics, exploring whether differences in assemblage composition and raw material use correlate to differences between one another, assemblage age, distance in space, and the geographic and environmental characteristics of the landscapes surrounding MSA sites. Assemblage composition and raw material use correlate most strongly with one another, with site type as well as geographic and environmental variables also identified as having significant correlations to the former, and distance in time and space correlating more strongly with the latter. By combining time and space into a single variable, we are able to show the strong relationship this has with differences in stone tool assemblage composition and raw material use, with significance for exploring the impacts of processes of cultural inheritance on variability in the MSA. A significant, independent role for terrain roughness for explaining variability in stone tool assemblages highlights the importance of considering the impacts of mobility on structuring the archaeological record of the MSA of Eastern Africa.

A spatiotemporally explicit paleoenvironmental framework for the Middle Stone Age of eastern Africa

“…Their results stressed the influence of environmental settings over the spatiotemporal distribution of MSA sites, with pulsed patterns of occupation intensity occurring during interglacial stages 10 . Significant relationships between raw material and stone tool types and geographic and environmental variables were reported 11 , with the strongest relationships with topographic ‘roughness’, emulating earlier hypotheses by King and Bailey 31 . These results validate the emphasis placed by earlier studies on ecology and the physical landscape 12 ; however, it remains to be tested whether Blinkhorn and Grove’s 10 , 11 use of arid and humid models as representations of the extremes of variability observed within an interglacial-glacial cycle effectively characterise change throughout the MSA.…”

“…Tryon and Faith 13 made important advances in the quantitative assessment of eastern African MSA lithic assemblage composition, though they lacked the means to make similar developments in the characterisation of MSA environments, acknowledging the mismatched geographies and scales of archaeological and environmental records 18 . Blinkhorn and Grove 10 , 11 in a suite of quantitative analyses, brought together ecology and archaeology using an expanded dataset of MSA lithic artefact typology alongside modern environmental datasets and models for the Last Glacial Maximum (LGM) and Last Interglacial (MIS 5e). Their results stressed the influence of environmental settings over the spatiotemporal distribution of MSA sites, with pulsed patterns of occupation intensity occurring during interglacial stages 10 .…”

“…As such, our understanding of Middle to Late Pleistocene diachronic change has been greatly improved by high-resolution climatic records, whilst a series of regional syntheses of MSA assemblages has encouraged considerations of the ecological implications of prehistoric climate change 9 , the quantitative assessment of MSA archaeology 13 , and their integration 10 , 11 . However, as also stressed in a recent review by Patalano et al .…”

Integrative geochronology calibrates the Middle and Late Stone Ages of Ethiopia’s Afar Rift

“…Indeed, from eastern to western Africa, understanding the nature of the relationship between the MSA and LSA remains incomplete, with little consensus on issues ranging from timing to geography to technology. Understanding the temporal and spatial variation in technologies (51)(52)(53), subsistence (54), mobility (55,56), and potential ecosystem modifications (57) of Middle and Late Pleistocene human populations is best accomplished via comprehensive research on stratified, calibrated sequences of timesuccessive, geographically limited archaeological occurrences associated with skeletal remains. The rapidly expanding nexus of MSA localities in the Afar thereby creates additional opportunities for progress in testing the modes and tempos of biological and cultural change and the causes of observed variation (58)(59)(60)(61).…”

Lithic variability and raw material exploitation at the Middle Stone Age (MSA) site of Gotera, southern Ethiopia: A combined technological and quantitative approach

“…East Africa has generally been considered as an area of great importance for the evolution of the genus Homo (Blome et al 2012;Mirazón Lahr & Foley 2016;Mounier & Lahr 2019;Stringer 2016), although older specimens of Homo sapiens have been recently discovered in Morocco (Hublin et al 2017;Richter et al 2017;Stringer & Galway-Witham 2017), and a model of genetically structured population of Homo sapiens across the whole African continent has been recently proposed (Bergström et al 2021;Scerri 2018;Scerri et al 2018). Notwithstanding recent re-evaluation of modern human origin and expansion (Bergström et al 2021), according to paleoanthropological, archaeological, and genetic data East Africa still remains an important area to investigate for the worldwide expansion of Homo sapiens (Blinkhorn & Grove 2021;Grove & Blinkhorn 2020), and the region is still central in the debate (Blinkhorn & Grove 2018;2021;Brooks et al 2018;Grove & Blinkhorn 2020;Mirazón Lahr & Foley 2016;Neubauer et al 2018;Potts et al 2018) as a potential source for ancient population as well as a gateway for the Out of Africa (Groucutt et al 2015;Lamb et al 2018;Petraglia et al 2010). In fact, East Africa with its archaeological record provides the richest source of information about the evolution of modern humans (Stringer 2016).…”