Geographic mosaics of rice domestication in the lower Yangtze River indicated by morphological characteristics of rice bulliform phytoliths

The lower Yangtze River valley has widely been regarded as centres of rice domestication, tracing back to 10,000 cal a BP or even earlier in the late Pleistocene. Despite recent advances in both evidence of genetics and archaeology had shed light on the process of rice domestication, including its initiation, acceleration, and completion, the spatial pattern and intra-regional differences of rice domestication in the lower Yangtze River remain unclear. Here, rice bulliform phytoliths were selected as a proxy of the domestication trait and applied to Jingtoushan, Hemudu, Yushan and Xiawangdu sites, ranging from 8000 to 5000 cal a BP in the Ningshao Plain, along with accumulated phytolith data in the Jinqu Basin and Taihu Plain. Rice domestication in the lower Yangtze River exhibited a geographic mosaic pattern rather than the presumed synchronous process among different regions. Rice domestication was initiated during the Shangshan culture (10–8.5 cal ka BP) in the Jinqu Basin and increased rapidly, which reached even higher level than the subsequent Jingtoushan culture (8.3–7.8 cal ka BP) in the Ningshao Plain. During the middle Holocene, rice domestication in the Taihu Plain was generally higher than that in the contemporaneous Ningshao Plain which may finish hundreds of years later. In contrast to the accomplishment of rice domestication around 6000 cal a BP in the Taihu Plain, the delayed process of rice domestication in the Ningshao Plain may result from frequent marine inundation induced by sea-level fluctuation during the Jingtoushan and Hemudu cultures (7–5 cal ka BP).