Environment and collapse: Eastern Anatolian obsidians at Urkesh (Tell Mozan, Syria) and the third-millennium Mesopotamian urban crisis

The Early to Middle Bronze Age transition in Northern Mesopotamia has received great attention for the apparent concurrence of aridification, deurbanisation, and the end of the Akkadian empire around 2200 BCE. Our understanding of the " crisis" has been almost exclusively shaped by ceramics, demography, and subsistence. Exchange and the associated social networks have been largely neglected. Here we report our sourcing results for 97 obsidian artefacts from Urkesh, a large urban settlement inhabited throughout the crisis. Before the crisis, six obsidian sources located in Eastern Anatolia are represented among the artefacts. Such a diversity of Eastern Anatolian obsidians at one site is hitherto unknown in Mesopotamia. It implies Urkesh was a cosmopolitan city with diverse visitors or visitors with diverse itineraries. During this crisis, however, obsidians came from only two of the closest sources. Two to three centuries passed before varied obsidians reappeared. Even when an obsidian source reappears, the raw material seems to have come from a different collection spot. We discuss the likely exchange mechanisms and related social networks responsible for the arrival of obsidians at Urkesh and how they might have changed in response to climatic perturbations and regional government collapse.