14 dating 23
L.) is one of the world’s most important staple foods, sustaining more than half of the global population (1).Questions surrounding its origins and domestication have led to a considerable amount of attention in the last decade (e.g., refs.
However, debate exists as to whether the rice is domesticated, wild, or transitional (12, 13).When the domestication of rice began in its homeland, China, is an enduring and important issue of debate for researchers from many different disciplines.Reliable chronological and robust identification criteria for rice domestication are keys to understanding the issue.We also discuss the characteristics of these earliest rice remains with respect to their wild or domesticated status using established rice bulliform phytolith morphological differences (25) (To assess the efficiency of phytolith-extracting protocols, we used multichecking methods, such as optical microscopy; scanning electron microscopy and energy-dispersive spectrometer (SEM-EDS); and X-ray diffraction (XRD). S3), indicating the efficiency of the phytolith extraction protocol.Thus, the measured C values of the phytoliths are shown with a high level of confidence to be from the phytolith samples themselves.Phytoliths can occlude some organic carbon during their deposition, which is captured through photosynthesis from atmospheric CO–19).
A number of studies have recently shown that phytoliths can be confidently dated using rigorous phytolith isolation techniques that do not alter phytolith carbon or cause its leakage from silicified cell, and where suitable plant sources are used (i.e., from nonvolcanic environments) (16–18, 22, 23).
Here we directly dated phytoliths using adjusted extracting protocols (22).
We further validated the phytolith dates by comparing them with known radiocarbon ages of seeds and charcoal recovered from the same stratigraphic levels from a nearby site, Huxi (N 28°52′27.768′′, E 120°1′5.052′′, 92 m above sea level) (Fig.
Direct dating of the rice remains might serve to clarify their age.
Here, we first validate the reliability of phytolith dating in the study region through a comparison with dates obtained from other material from the same layer or context.
Our phytolith data indicate that rice remains retrieved from early stages of the Shangshan and Hehuashan sites have ages of approximately 9,400 and 9,000 calibrated years before the present, respectively.