Later Stone Age toolstone acquisition in the Central Rift Valley of Kenya: Portable XRF of Eburran obsidian artifacts from Leakey's excavations at Gamble's Cave II (original) (raw)
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Two-million-years of obsidian extraction, utilization, and exchange in eastern Africa
Eastern Africa hosts the longest record of human evolutionary and cultural change on the planet. Archaeological sites across what are today Kenya and Tanzania preserve evidence for the emergence of bipedal hominins, our ancestors’ earliest experiments with stone tools, technological and social innovations, and expansions of diverse forms of food production. Here, we present a synthesis of recent advances in geochemical methodologies, source identifications, and applied sourcing studies that have enhanced our understanding of human-obsidian relationships across the volcanic landscapes of Kenya and Tanzania over the last two million year
Proceedings of the 2021 International Obsidian Conference. Regents of the University of California , 2024
We characterized 42 obsidian samples from the Baantu obsidian source in southwestern Ethiopia, including 25 outcrop samples and 17 surface artifacts, using portable X-ray fluorescence (pXRF) spectroscopy. We then compared these source data to 116 obsidian artifacts from Mochena Borago Rockshelter. Results indicate that at least three geo-chemical source clusters are represented at the Baantu source: one derived from sampled outcrops and two deriving from as-yet unknown source locations. Comparing these data to obsidian artifacts at Mochena Borago excavated from levels dated to > 50 ka and ~44 ka BP, early levels dating to > 50 ka preserve obsidian from as many as six as-yet unidentified sources, while Baantu obsidians were in the minority. By ~44 ka cal BP, Mochena Borago occupants procured most, if not all, of their obsidian from the Baantu source. Compar-ison to regional published obsidian source data suggests little, if any, procurement from northern sources within the Ethiopian Rift. We need more regional survey and artifact characterizations to identify the spatial scale and directionality of stone procurement in this area, but these data provide evidence that the occupants of Mochena Borago Rock-shelter engaged with a variety of stone raw materials across periods of major ecological and likely social change in the Late Pleistocene Horn of Africa.
2017
The East African Rift system created one of the world's most obsidian-rich landscapes, where this volcanic glass has been used to make tools for nearly two million years. In Kenya alone, there are > 80 chemically distinct obsidians along a 800-km north-south transect. Recently Brown et al. (2013) published their Kenyan obsidian database assembled since the 1980s. Specifically, they report elemental data measured by EMPA, ICP-MS, and WDXRF, providing a rich basis for future sourcing studies. Here we report our use of portable XRF (pXRF), calibrated specifically and directly to the database in Brown et al. (2013), to examine interactions between Later Stone Age forager-fishers and pastoralists near Lake Victoria. Regarding our calibration to the WDXRF and EMPA datasets of Brown et al. (2013), the elements of in- terest have very high correlations (R2 = 0.96–0.99) to our pXRF values, which show, on average, only a 2–5% relative difference from the published values. Use of pXRF data specifically calibrated to the datasets from Brown et al. (2013) greatly expands the impact of their work over three decades to catalog and characterize a multitude of Kenyan obsidians. Our focus here is investigating social contacts and exchange between late Holocene populations that included Kansyore forager-fishers and Elmenteitan pastoralists. Similarities and differences in their obsidian access provide new insights into long-term interactions between foragers and food producers in eastern Africa. We report new sourcing results for obsidian artifacts from six late Holocene rock shelters along the Winam Gulf of Lake Victoria. The patterns in obsidian access are consistent with changing interaction spheres that are relevant to understanding forager-fisher social identities and subsistence strategies during periods of economic and demographic change.
Twenty-sixMiddle Stone Age obsidian artifacts from the Gademotta Formation were instrumentally characterized by energy dispersive X-ray fluorescence. Analysis of artifacts from the type locality enabled sampling of a greater time depth while avoiding the uncertainties in previous results on artifacts sampled from a “disturbed” context at Kulkuletti. Moreover, the analysis here of source samples from Alutu, Worja, and the previously unstudied Bora and Ficke sources in the broader region offers a better understanding of prehistoric lithic raw material procurement. The local Worja source, an aphyric obsidian excellent for tool production, substantially dominates the assemblage. Bora, another aphyric obsidian in the wider region, is also present, but not common. The vitrophyric Ficke and Alutu obsidian sources with abundant sanidine phenocrysts were not present in the archaeological assemblage, and likely did not compete withWorja and Bora for tool production. At least one artifact appears to be from an as yet unknown source, thus confirming results of previous studies. A few artifacts share similar geochemical composition with the Worja and Bora sources, thus highlighting the complexity of obsidian source studies in this part of the rift where multiple geographically close sources may share similar crustal material.
The Pleistocene Stone Artifact Record of Africa: Technologies, Typologies, and Analytic Approaches
Handbook of Pleistocene Archaeology in Africa, 2023
Flaked stone (lithic) artifacts are a ubiquitous cultural material at Pleistocene sites and first appear in the archaeological record 3.3 million years ago (Ma) in East Africa (Harmand et al., 2015). The African stone artifact record thus covers the longest time span of human prehistory compared to other world regions. Lithic artifacts preserve well, and they are often the only cultural materials remaining at a site. Archaeologists have therefore dedicated considerable effort to describing stone artifacts and to developing theory to interpret them in light of the behavioral and biological evolution of hominins. Below we briefly describe the major lithic technologies that appeared in Africa during the Pleistocene. Additionally, this chapter reviews the common analytical approaches that researchers employ when studying lithic assemblages from diverse contexts. We then discuss how archaeologists have used lithic artifacts to interpret other aspects of hominin evolution and the issues that confound these interpretations. Here, stone “artifacts” are preferred as opposed to stone “tools” to refer to all intentionally flaked stones because the term “artifact” does not presume their use as tools per se.
Earliest long distance obsidian transport: Sibilo School Road Site, Baringo, Kenya
This study presents the earliest evidence of long-distance obsidian transport at the ~200 ka Sibilo School Road Site (SSRS), an early Middle Stone Age site in the Kapthurin Formation, Kenya. The later Middle Pleistocene of East Africa (130e400 ka) spans significant and interrelated behavioral and biological changes in human evolution including the first appearance of Homo sapiens. Despite the importance of the later Middle Pleistocene, there are relatively few archaeological sites in well-dated contexts (n < 10) that document hominin behavior from this time period. In particular, geochemically informed evidence of long-distance obsidian transport, important for investigating expansion of intergroup interactions in hominin evolution, is rare from the Middle Pleistocene record of Africa. The SSRS offers a unique contribution to this small but growing dataset. Tephrostratigraphic analysis of tuffs encasing the SSRS provides a minimum age of ~200 ka for the site. Levallois points and methods of core preparation demonstrate characteristic Middle Stone Age lithic technologies present at the SSRS. A significant portion (43%) of the lithic assemblage is obsidian. The SSRS obsidian comes from three different sources located at distances of 25 km, 140 km and 166 km from the site. The majority of obsidian derives from the farthest source, 166 km to the south of the site. The SSRS thus provides important new evidence that long-distance raw material transport, and the expansion of hominin intergroup interactions that this entails, was a significant feature of hominin behavior ~200 ka, the time of the first appearance of H. sapiens, and ~150,000 years before similar behaviors were previously documented in the region.