Tag Archives: Geoarchaeology

Challenging our assumptions about the antiquity of trade and social networks in Middle Stone Age Africa

Nature human behavior has just published a research highlight written John Carson about work at the Sibilo School Road Site in Kenya done by Nick Blegen, Harvard University, that has recovered large quantities of obsidian along with Middle Stone Age (MSA) tools . The finds are thought to date back at least 200 kyr.

As Carson summarizes: “Geochemical analyses demonstrated that the majority of obsidian pieces had their provenance at a source site >160 km away, indicating long-distance transport of raw materials during the MSA.” Previously, East African sites evidencing long-distance resource transport have all be less than <50 kyr old.

Evidently known MSA sites of this age are rare in East Africa. If more sites can be found and excavated, the “big story” usually told about the evolution of human social behavior may need updating: far-reaching resource networks and/or intergroup trade in raw materials could have developed earlier than generally believed in the history of our species. If so, then in Carson’s words: “we may gain greater insight into the timeline of social evolution that eventually led to our modern group behaviours.”

Blegen’s report was just published (unfortunately behind a paywall) in the Journal of Human Evolution. Here is the abstract you will find available there for free:


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 (130–400 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.

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