Site Formation Processes of the Yaalu Archaeological Site during a Period of Anatomically Modern Human Migration

Abstract

Gona, Ethiopia’s sedimentary record spans six million years, containing hominin specimens from Ardipithecus ramidus to Homo sapiens. This record also contains paleosols, or fossilized soil horizons, that provide terrestrial paleoenvironmental reconstructions for archaeological and paleoanthropological sites. A terrestrial-based climate record for East Africa is largely incomplete, as most reconstructions are performed using lacustrine or marine proxies, which fail to deliver a specific, localized reconstruction for hominins, terrestrial mammals. Geologic mapping, sampling, and lab analysis performed using paleosols and other sedimentary deposits from Gona show fluctuation in climate, as wet and dry periods are evident throughout. Recent research suggests that changing climates help to drive and facilitate human evolution and migration, but little is known about Anatomically Modern Human (AMH) migration due to spatially and temporally incomplete records. Ongoing stratigraphic work at Gona shows a high-resolution, intact record of environmental change. A newly discovered site at Yaalu yields a Homo sapiens cranium as well as other fossils and artifacts dating to 85-70 thousand years ago (ka). This corresponds with evidence of AMH migration out of Africa, with Homo activity appearing in the Levant during this time. No geoarchaeological work has been done at Yaalu. A detailed analysis of the site formation processes will tell the story of the climate and environmental conditions of Yaalu before, during, and after the occupation using sediments gathered from a “megatrench” in 2020. Evidence of the Toba supereruption in present day Indonesia, which occurred ~75 ka, may also be present in sediments. The impact of this event on East African populations is relatively unknown, and an isotopic analysis will be performed using sediments collected from this megatrench. These geoarchaeological analyses give a context that is crucial to the understanding of human cultural activities and migration patterns in East Africa at a time period with few archaeological and environmental records