Integrative geochronology calibrates the Middle and Late Stone Ages of Ethiopia’s Afar Rift

Abstract

Significance Understanding the evolution, dispersals, behaviors, and ecologies of early African Homo sapiens requires accurate geochronological placement of fossils and artifacts. We introduce open-air occurrences of such remains in sediments of the Middle Awash study area in Ethiopia. We describe the stratigraphic and depositional contexts of our discoveries and demonstrate the effectiveness of recently developed uranium-series dating of ostrich eggshell at validating and bridging across more traditional radioisotopic methods ( 14 C and 40 Ar/ 39 Ar). Homo sapiens fossils and associated Middle Stone Age artifacts are placed at >158 and ∼96 ka. Later Stone Age occurrences are dated to ∼21 to 24 ka and ∼31 to 32 ka, firmly dating the upper portion of one of the longest records of human evolution.