## 1 Introduction  
The relationship between sociocultural environments and natural geographical settings is intricate and interconnected, with human societies and civilizations profoundly shaped by the landscapes they inhabit [1, 2, 3, 4, 5, 6]. Geography forms the foundation of cultural development, and, in turn, human activities leave enduring imprints on the natural world [7, 8]. Over the past several decades, advancements in research on environmental change and archaeology have reinvigorated interest in the distribution, evolution, and transformation of prehistoric settlements. This interaction between environment and culture is especially evident in historically rich regions, where scientific studies have yieldedinvaluable insights into the interplay between geography, settlement patterns, and social evolution [7; 8; 9; 10; 11; 12; 13; 14; 15]. The middle and lower reaches of the Yuanjiang River have long held significant historical importance, emerging as central hubs for the development of Chinese civilization [16; 17]. Archaeological evidence suggests that human activity in this region dates back approximately 300,000 years [18; 19]. Early artifacts, including stone tools, pottery, and ancient dwellings, offer crucial glimpses into the lives of the prehistoric societies that once flourished here. The region's prominence was deeply connected to the unique geographical features of the Yuanjiang catchment area, which greatly influenced settlement patterns and human activities. The middle reaches of the river, surrounded by mountainous terrain, provided a relatively secluded environment, while the lower reaches open up into the expansive Dongting Lake area, known for its rich ecological diversity. These varied ecological zones were ideal for agriculture, hunting, and tool-making. Moreover, the river itself served as a natural corridor, facilitating both cultural exchange and migration between the Yangtze and Pearl Rivers [16]. Positioned between China's second-tier plateau and the central southern hills, the Yuanjiang River offers a distinctive environmental context for studying the region's ancient human history. Despite the region's historical and archaeological importance, systematic prehistoric research in the Yuanjiang River Basin began relatively late in comparison to neighboring areas, such as the Lishui River Basin. Major archaeological discoveries in the Yuanjiang Basin only emerged in the 1970s [16]. However, from the 1980s onwards, the scope and intensity of archaeological efforts, particularly led by the Hunan Provincial Museum, greatly expanded. Key sites, such as the Gaomiao and Daqiaoxi settlements, underscore the region's critical role in Paleolithic studies [16; 17; 18; 20]. Scholars have observed that Paleolithic cultures in central and southern China often developed near river confluences, where the availability of water, fertile soil, and flat land provided a conducive environment for human settlement [19; 21; 22]. In subsequent research, a rich and complex cultural history emerged, with multiple Neolithic phases documented across the region. These phases include the Lower Zaoshi Culture, Daxi Culture, Qujiang Culture, and Shijiahe Culture [23; 24; 25; 20; 26; 27; 28]. To date, over 804 prehistoric settlements have been recorded along the Yuanjiang River [28; 29; 30; 31; 32]. While significant progress has been made in understanding the ancient cultures of the Yuanjiang River Basin, several key challenges remain in fully appreciating its historical significance. A major gap in research is the absence of a comprehensive, integrated analysis of the entire catchment area, which has limited the exploration of inter-site interactions and broader cultural patterns that may have existed across the region. Additionally, the factors driving cultural evolution in the Yuanjiang Basin remain inadequately understood. Of particular interest is the ancient cultural landscape of the lower reaches of the river, located between the middle reaches of the Yuanjiang River and the Lishui River.