Climate change and world history: Evidence from the site of Sym-Ota 1 in the Aral Sea Basin

Humans responded to a climatically induced river avulsion in the Amu Darya delta beginning ca. 400 CE by re-engineering the river’s main channel to flow west of the Aral Sea. This change, which we refer to as the “Khorezmian pivot,” altered the cultural geography of the Aral Sea Basin (ASB) for over a millennium, influencing major events in world history including the formation of the Seljuk Empire in the 11 th century CE and the Mongol conquests of western Asia in the 13 th century CE. In this study, we present new radiocarbon dating and environmental data from the river-adjacent site of Sym-Ota 1 at the base of the Khorezmian pivot that indicates inhabitants were able to modify the main channel of the Amu Darya 700 years earlier than previously known, by ca. 300 BCE. This suggests that the hydromorphology of the Amu Darya delta has been shaped by over 2,000 years of human ecosystem engineering. The riparian agricultural strategies documented at Sym-Ota 1 were likely important features of adaptation to the 400 CE avulsion and the integration and maintenance of culture groups in the ASB such as the Seljuks and Mongols that played major roles in world history.