5,200-year-old cereal grains from the eastern Altai Mountains redate the trans-Eurasian crop exchange.

Wheat and barley evolved from large-seeded annual grasses in the arid, low latitudes of Asia; their spread into higher elevations and northern latitudes involved corresponding evolutionary adaptations in these plants, including traits for frost tolerance and shifts in photoperiod sensitivity. The adaptation of farming populations to these northern latitudes was also a complex and poorly understood process that included changes in cultivation practices and the varieties of crops grown. In this article, we push back the earliest dates for the spread of wheat and barley into northern regions of Asia as well as providing earlier cultural links between East and West Asia. The archaeobotanical, palynological and anthracological data we present come from the Tongtian Cave site in the Altai Mountains, with a punctuated occupation dating between 5,200 and 3,200 calibrated years BP, coinciding with global cooling of the middle-late Holocene transition. These early low-investment agropastoral populations in the north steppe area played a major role in the prehistoric trans-Eurasian exchange.