Framing the Middle Stone Age of bed V at Mumba Rock Shelter, Tanzania, using electron spin resonance and uranium series

Abstract

Eastern Africa is a key region for studying the origin and dispersal of early Homo sapiens. In particular, in the Lake Eyasi basin located in northern Tanzania, Mumba Rock Shelter yielded a long stratigraphic sequence documenting lithic assemblages from the Middle Stone Age (MSA) and the Later Stone Age (LSA). The site was excavated by Margit Kohl-Larsen in 1934 and 1938. Despite having been the object of multiple dating studies, the chronology of Bed V, attributed to the MSA, was poorly defined. This work presents new ages obtained using Electron Spin Resonance (ESR) dating combined with uranium series (230Th/U) on eight herbivore teeth from Bed V of the MSA, selected from the Kohl-Larsen collection curated at the University of Tübingen in Germany. Following the 2022 excavation campaign, we were able to correlate the initial location of the teeth discovered in the 1930s with the standing section and reconstruct the environmental dose rate with in situ gamma spectrometry measurements. The ages, ranging from 72 ± 8 ka to 54 ± 3 ka, fall within marine isotopic stage (MIS) 4 and the beginning of MIS 3, framing the human occupation recorded in Bed V during the Late Pleistocene.