Cranial morphometric analysis of early wet-rice farmers in the Yangtze River Delta of China

The Yangtze River Delta is the best-known homeland of wet-rice agriculture. From the Middle Neolithic, rice farming expanded from the Yangtze region to both the north and the south. However, poor preservation of ancient human skeletal remains in the region has meant that the population history of these expansions has not been fully understood. In order to clarify the ancestry of early wet-rice farmers in East Asia, we conducted a cranial morphometric analysis and comparison of a Middle Neolithic skeletal assemblage excavated from the Guangfulin site, Shanghai. The results of bivariate and multivariate analyses showed that: (1) Neolithic wet-rice farmers from the lower Yangtze retained local morphological characteristics, but were nevertheless morphologically more similar to Neolithic and later populations in northern China, which was home to early millet farmers, than to Neolithic populations in south China; and (2) Neolithic and later agricultural populations in East Asia were morphologically homogeneous compared to pre-Neolithic hunter-gatherer groups even though the area occupied by both was equally vast. These results suggest, respectively, that: (1) Middle Neolithic wet-rice farmers in the Yangtze Delta experienced significant gene flow from regions of northern China such as the Central Plains and Shandong even though there is currently no evidence that millet cultivation itself had yet reached the delta region; and (2) Neolithic populations resulting from interaction between the Yangtze Delta and northern China dispersed widely across much of East Asia including the Japanese archipelago together with the spread of wet-rice agricultural technologies. These two proposals are paralleled by recent stable isotope analyses using tooth enamel and bone collagen, as well as archaeological evidence from Shandong. Finally, a facial approximation was conducted using a cranium (M252) excavated from Guangfulin for the purpose of visually expressing the results of this study.