Obsidian dating and source exploitation studies in Africa: Implications for the evolution of human behavior

Obsidian occurs in the eastern Rift Valley region of Ethiopia, Eritrea, Kenya, and Tanzania, and in a restricted region of West Africa, in Cameroon. Source locations and chemical compositions are best documented in Kenya and Tanzania, and significant advances are now being made in Ethiopia. Several sites have been dated by obsidian hydration, one by fission tracks and four by radiogenic argon isotope ratios. Hydration dating appears to be limited to sites younger than 120,000 years. Although the most advanced methods of hydration dating have not been applied in this region, radiometric dating demonstrates that the Middle to Later Stone Age transition in eastern Africa is substantially older than the Middle to Upper Paleolithic transition in western Eur asia. Obsidian was first used for flaked stone-tool manufacture during the Early Stone Age (Oldowan), more than 1.7 million years ago. Rare instances of long-distance transport of obsidian occurred during the Oldowan at Olduvai Gorge and during the early Acheulean in Kenya and Ethiopia. However, substantial amounts of obsidian were not transported long distances until the second half of the Middle Stone Age (MSA). The increase in long-distance transport of obsidian during the late MSA reflects the African origin and development of large-scale regional social networks, which is an important milestone in the evolution of modern human behavior. Patterns of obsidian use in Kenya and Tanzania during the Holocene may reflect adaptations to changing environments by hunter-gatherers, and exchange patterns and territorial boundaries of Neo lithic pastoralists. Obsidian in Egyptian sites as early as the Predynastic era reflect long-distance contacts with Ethiopia and Eritrea.