Is naked barley an eastern or a western crop? The combined evidence of archaeobotany and genetics

Forms of Hordeum vulgare ssp. vulgare (barley) that possess a naked caryopsis are an important human staple and are mainly found today in eastern Asia. However, naked barley has not always been an eastern crop: archaeobotanical data show that it was prevalent in Europe and the Near East during various periods in prehistory. In this review we have collated data on the incidence of hulled and naked barley at archaeological sites in Europe and the Near East from two sources: archaeobotanical literature reviews and an archaeobotanical database, both assembled by Helmut Kroll. We have also examined the incidence of hulled and naked barleys in extant germplasm collections. Our compilation of this archaeobotanical data has enabled us to elucidate long-term changes in the ratio of hulled to naked barley under cultivation in these regions; specifically, these records show that naked barley begins to disappear from the archaeobotanical record from the Chalcolithic/Bronze Age onwards in the Near East, and from the Iron Age/Roman periods onwards in Europe. We discuss the possible causes of this decline in naked barley cultivation in these regions, along with the present-day prevalence of naked barley landraces in eastern Asia, particularly in relation to genetic evidence, which shows that naked barley has a single origin.