J. Hum. Evol. 103, 1–19 (2017)

The East African Rift Valley was a significant region in hominin evolution and has produced many of the most important fossil discoveries. However, the evidence for behavioural evolution during the emergence of Homo sapiens in this region 200 kyr (thousand years) ago is scarce.


Nick Blegen, of Harvard University, reports the excavation of large amounts of obsidian alongside finds of middle stone age (MSA) tools at the Sibilo School Road Site (SSRS) in Kenya. Tephrochronological analyses of volcanic layers at SSRS dated the finds as at least 200 kyr old. 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. Until now, the well-dated East African sites showing evidence of long-distance resource transport have been much younger (<50 kyr old). Blegen suggests that wide resource networks and/or intergroup trading of raw materials could have developed very early in the evolution of Homo sapiens.

MSA sites of this age remain rare in East Africa. As more sites are discovered and excavated, we may gain greater insight into the timeline of social evolution that eventually led to our modern group behaviours.