A biodiverse package of southwest Asian grain crops facilitated high-elevation agriculture in the central Tien Shan during the mid-third millennium BCE

We report the earliest and the most abundant archaeobotanical assemblage of southwest Asian grain crops from Early Bronze Age Central Asia, recovered from the Chap II site in Kyrgyzstan. The archaeobotanical remains consist of thousands of cultivated grains dating to the mid-late 3rd millennium BCE. The recovery of cereal chaff, which is rare in archaeobotanical samples from Central Asia, allows for the identification of some crops to species and indicates local cultivation at 2000 m.a.s.l., as crop first spread to the mountains of Central Asia. The sites inhabitants cultivated two types of free-threshing wheats, glume wheats, and hulled and naked barleys. Highly compact morphotypes of wheat and barley grains represent a special variety of cereals adopted to highland environments. Moreover, glume wheats recovered at Chap II represent their most eastern distribution in Central Asia so far identified. Based on the presence of weed species, we argue that the past environment of Chap II was characterized by an open mountain landscape, where animal grazing likely took place, which may have been further modified by people irrigating agricultural fields. This research suggests that early farmers in the mountains of Central Asia cultivated a high diversity of southwest Asian crops during the initial eastward dispersal of agricultural technologies, which likely played a critical role in shaping montane adaptations and dynamic interaction networks between farming societies across highland and lowland cultivation zones.