Phytolith evidence for the pastoral origins of multi-cropping in Mesopotamia (ancient Iraq)

Multi-cropping was vital for provisioning large population centers across ancient Eurasia. In Southwest Asia, multi-cropping, in which grain, fodder, or forage could be reliably cultivated during dry summer months, only became possible with the translocation of summer grains, like millet, from Africa and East Asia. Despite some textual sources suggesting millet cultivation as early as the third millennium BCE, the absence of robust archaeobotanical evidence for millet in semi-arid Mesopotamia (ancient Iraq) has led most archaeologists to conclude that millet was only grown in the region after the mid-first millennium BCE introduction of massive, state-sponsored irrigation systems. Here, we present the earliest micro-botanical evidence of the summer grain broomcorn millet (Panicum miliaceum) in Mesopotamia, identified using phytoliths in dung-rich sediments from Khani Masi, a mid-second millennium BCE site located in northern Iraq. Taphonomic factors associated with the region’s agro-pastoral systems have likely made millet challenging to recognize using conventional macrobotanical analyses, and millet may therefore have been more widespread and cultivated much earlier in Mesopotamia than is currently recognized. The evidence for pastoral-related multi-cropping in Bronze Age Mesopotamia provides an antecedent to first millennium BCE agricultural intensification and ties Mesopotamia into our rapidly evolving understanding of early Eurasian food globalization.