Changing middle-Holocene climatic patterns in southern Arabia forced people in the early stages of developing agricultural subsistence economies to adapt cultivation technologies and water management practices to an increasingly arid landscape. RASA (Roots of Agriculture in Southern Arabia) Project fieldwork has provided significant data toward understanding the human-environmental interactions in the remote highlands of southern Yemen during the early Holocene moist phase (ca. 10,000 - 6,000 years ago), characterized by larger population and land management under wetter climate and denser vegetation than today. This period of enhanced activity was followed by settlement abandonment in the increasingly arid mid - late Holocene.

A chronology of paleoenvironments and human activities has been constructed in Wadi Sana and Wadi Idim in the highlands of southern Yemen. Surface scatters of 9000-year-old lithic artifacts signal the arrival of people into the Wadi Sana region. A younger lithic assemblage associated with cattle bones and caprine dung was recovered from numerous hearths dated between 7400 - 5800 14C yr BP. During that time people occupied four large rock shelters adjacent to Wadi Sana. Subsequent people left remains of pit houses, which were abandoned by 5600 14C yr BP, and water management structures built during the middle Holocene phase of enhanced monsoonal precipitation. Preliminary dating of fossil spring deposits in Wadi Idim, ca. 50 km west of Wadi Sana, suggests that there was a gradual southward drying of springs and associated marsh-lacustrine environment beginning as early as 7700 14C yr B.P. However, remnants of that system remain today in the oasis village of Saa', which may have served as a refugium when much of the region became too arid to support agriculture.

Overall, dated materials suggest that aggradation of sediment within the Wadi Sana channel, possibly associated with agricultural activity during a time of enhanced moisture, occurred prior to the middle Holocene monsoon decline, and fluvial incision and sediment erosion have dominated since about 4600 14C yr BP. With additional field sampling and paleohydrologic reconstruction, we hope to document the timing and nature of the transition from the previous monsoonal climate to the present hyper-arid environment.