Chinese researchers use CT scanning to trace origins of rice domestication

Chinese researchers have recently revealed how they discovered traces of rice in two ceramic sherds dating back about 10,000 years using CT scanning, shedding new light on the origins of rice domestication.

An Ting, head of the research team at Zhejiang University's School of Art and Archaeology, said that tracing the evolution from wild to domesticated rice poses a significant challenge due to the scarcity of macrobotanical remains, such as seeds, fruits, stems and plant fibers.

Plant imprints on unearthed artifacts, therefore, serve as crucial evidence while tracing the presence of plants, An explained, introducing their research published in the international journal The Holocene.

The two ceramic sherds analyzed with CT scanning were unearthed at the Shangshan site, an ancient ruin located along the lower reaches of the Yangtze River in present-day east China's Zhejiang Province. Discovered in 2000, the site dates back approximately 11,400 to 8,600 years.

The Shangshan culture, named after the site, is recognized as the earliest Neolithic culture in the lower valley of the Yangtze River and is regarded as the cradle of global rice cultivation.

However, identifying well-preserved markers that distinguish wild rice from domesticated varieties in the region remains a central challenge in archaeological research.

The research team led by An has been exploring the use of micro-CT with high resolution to uncover the secrets hidden within the pottery fragments unearthed from the Shangshan site since 2021. Initially, two ceramic fragments showing clear traces of plant carbonization were selected from among the many pottery pieces unearthed at the Shangshan site.

Through micro-CT scanning and computer modeling, researchers identified 184 imprints of rice spikelet bases, the joints between shelled rice seeds and stems, embedded within the two pottery fragments.

The evaluation of the abscission scars on spikelet bases is often considered the most reliable diagnosis marker of rice domestication. The domesticated rice seeds, unlike the wild ones, cannot shed the shells naturally, hence sustaining a "scar" as a result of artificial abscission, whereas the wild ones show no such signs.

The evaluation showed that 12 percent of the 184 imprints displayed domestication traits. According to the research team, this sample size holds statistical significance in the field of archaeology.

Researchers stated in the paper that the identification of the domesticated phenotype, which accounts for 12 percent of the recovered rice imprints, along with other discernible domestication traits of rice spikelets, provides new insights into the early stages of rice domestication.

The research has also resulted in the creation of the most extensive database of early rice remains and it represents a pioneering application of micro-CT analysis on ceramic sherds containing early plant impressions.

The cultivation of rice, a dietary staple for billions worldwide, has profoundly influenced the evolution of Chinese civilization. Scholars from various academic fields have long been captivated by the study of how humans first began cultivating wild rice and the evolutionary journey from wild to domesticated strains.