Paleoenvironmental Changes and Human Adaptation: A Multidisciplinary Investigation of Site Abandonment at Qusayrat Aad Archaeological Site, Central Saudi Arabia

This study examines the critical relationship between geoenvironmental changes and human occupation patterns in the central Arabian Peninsula, focusing on the Al-Aflaj region. By integrating geospatial modeling with preliminary archeological excavation results that indicated the site is dated to 5th century BCE to 6th century CE, we evaluate how climatic stressors dictated human adaptation and eventual site abandonment. Late Quaternary climatic fluctuations, particularly the Early Holocene pluvial phases, initially created favorable conditions for settlement through sustained freshwater resources. Subsequent aridification triggered significant migration and settlement contraction, demonstrating a high degree of human resilience. The site of Qusayrat Aad serves as a compelling case study of sophisticated adaptation, evidenced by mudbrick architecture and advanced irrigation systems. Integration of geological, topographic, and paleoclimatic factors indicates that the porous sedimentary layers of the Heet and Al Biyadh Formations were essential for groundwater recharge and spring formation. The geospatial analysis reveals that the settlement was strategically localized on a stable surface with a mean slope of 1.51°. Furthermore, the Topographic Wetness Index (TWI) identifies the site as a significant hydrological function, with a mean value of 8.79 (reaching a 90th percentile of 12.37), which is markedly higher than the regional average of 7.96. These quantitative findings establish a causal necessity for the site’s advanced subsurface canal systems as an engineered response to minimize evaporative losses in high-potential moisture zones. Ultimately, the correlation between the archeological record and climatic proxies suggests that the intensification of late Holocene aridification depleted these specific water resources beyond adaptive capacity, serving as the primary driver for the site’s abandonment and the migration of populations toward the eastern and southern parts of the Peninsula.