The Geoarchaeology Team at the Center for Archaeological Science, Sichuan University reveals evidence of rice farming integrated with marine adaptation in the early Holocene coastal zone of the lower Yangtze River.

Recently, He Keyang, a specially appointed associate researcher at the Geochronology Archaeology Laboratory of the Center for Archaeological Science, Sichuan University, published an article entitled "Early Holocene rice cultivation integrated into marine adaptation in eastern China" in the international journal *Journal of Archaeological Science: Reports*. He Keyang, a specially appointed associate researcher at our center, is the first author and corresponding author, and Wang Yonglei, curator of the Zhejiang Provincial Institute of Cultural Relics and Archaeology, is the co-corresponding author. This research was primarily funded by the National Natural Science Foundation of China key project "Microfossil Research on the Relationship between the Origin of Rice Agriculture and Environmental Changes in the Yangtze River Basin" (41830322).

Figure 1: Location of the Jingtoushan site and microfossil assemblage map

Coastal areas play an important role in human migration, population growth, and social interaction. Early Holocene warming and sea-level rise fostered a variety of human adaptive behaviors in coastal areas, including the use of marine resources and the origin of agriculture. However, the relationship between the two, especially the transition of subsistence patterns from hunting-gathering to agriculture, remains unclear. To this end, we conducted a detailed phytolith and diatom microfossil analysis (Figure 1) of the Jingtoushan site, the earliest Neolithic shell midden site in the lower Yangtze River region. The results showed that as early as 8,000 years ago, rice cultivation in the coastal zone of the lower Yangtze River was integrated into the marine-adapted subsistence pattern represented by shell middens, but the rice domestication process at the Jingtoushan site was significantly delayed compared to the contemporaneous Kuahuqiao site.

Figure 2: Morphology and morphometric data of rice bulliform phytoliths

Morphological and morphometric data of rice bulliform phytoliths showed that the overall variation of rice bulliform phytoliths at the Jingtoushan site was small (Figure 2), with lengths and widths close to those of the contemporaneous Kuahuqiao site, and a B/A ratio close to *japonica* rice. However, the proportion of rice bulliform phytoliths with squamate ornamentation 鈮�9 was only ~41.7%, far lower than that of the contemporaneous Kuahuqiao site, indicating a delayed rice domestication process in the Ning-Shao area. Microfossil assemblage evidence indicates that the start and end of rice cultivation at the Jingtoushan site corresponded to the appearance of freshwater diatoms and the expansion of marine diatoms, respectively (Figure 1c), indicating a close relationship between sea-level rise and rice cultivation. On the one hand, rising groundwater levels caused by sea-level rise may have led to an increase in wetlands, leading to the expansion of wild rice. On the other hand, the submergence of coastal areas may have led to a decrease in population size, thereby weakening labor input and artificial selection pressure (Figure 3a). All of these factors may have ultimately led to de-domestication of rice and a prolonged domestication process.

Figure 3: Rice domestication and subsistence patterns at the Jingtoushan site

Considering that rice domestication at the Jingtoushan site was still in its primary stage, the subsistence pattern at the Jingtoushan site was still dependent on a hunting-gathering economy represented by acorns and shellfish (Figure 3b). In addition to the Jingtoushan site, coastal shell midden sites in southern China are mainly distributed in the Lingnan region of Guangdong and Guangxi and the southeastern region of Fujian. Among them, the shell midden sites in the Guangdong and Guangxi regions are of the freshwater estuary type, and the age or nature of rice remains is questionable; in the Fujian region, definite evidence of rice dating back to about 5,000 years ago has been found at several coastal shell midden sites, such as Zhuangbianshan and Huangguashan. Contrary to the previous view that coastal shell midden sites in southern China relied solely on marine adaptation without rice cultivation, our research shows that at the Jingtoushan site around 8,000 years ago, rice cultivation had been integrated into marine adaptation and subsequently spread to southeastern China around 5,000 years ago. Therefore, the Jingtoushan site is not only the ancestor of the Hemudu culture, but also possibly a precursor to the Neolithic Austronesian maritime expansion.