MOLECULAR CARBON AND HYDROGEN ISOTOPE PROFILES FROM THE NEOLITHIC TIANLOUSHAN SITE IN CHINA: IMPLICATIONS FOR CLIMATE CHANGE DURING RICE DOMESTICATION

Isotopic analysis of molecular carbon (δ¹³C) and hydrogen (δD) of n-alkanes from a sedimentary sequence spanning 7,000 years of China’s eastern coastal region revealed environmental changes that coincided with the domestication of rice during Neolithic times. Analysis on the sedimentary sequence shows an obviously synchronized positive shift of both hydrogen and carbon isotopic values for n-C₂₇ alkane δD (-114‰) and δ¹³C (-28.9‰) during a prehistoric sea transgression period dated from 4445±85 to 4340±110 BC that separated two periods of ancient rice cultivation horizons associated with more-negative isotope values of n-C₂₇ alkane δD (-207‰) and δ¹³C (-32.5‰) (4340±110 to 2650±190 BC) and n-C₂₇ alkane δD (-192‰) and δ¹³C (-33.0‰) (5080±140 to 4445±85 BC). In order to test the environmental significance and sensitivity of our isotope data, we plot our new data against known paleontological data of diatoms, seeds, and phytoliths as well as archaeological analysis on artifacts from the Neolithic society that relied on hunting, gathering, and rice cultivation to sustain their diets. Sediments characterized by the more positive isotopic shift correlate well with low tide coastal mudflats that have been identified by remains of plentiful salt-tolerant plant seeds and abundant offshore, coastal, and intertidal diatom species. Strata characterized by more negative isotopic values couple well with wetland or marsh environments that have been suggested by phytoliths indicative of wetland ecosystems, abundant freshwater diatom species, and wild and domesticated rice remains. Our isotope data along with paleontological and archaeological analyses illustrate the influence of sea-level change on land usage for rice farming during the process of early rice domestication. Continual rice cultivation in eastern China was interrupted by a sea transgression that lasted more than a century which forced Neolithic rice farmers to rely on hunting and gathering techniques when rice fields became inundated. An isotopic profile with higher resolution may be able to separate local climate variations from regional and global climate trends that may have directly controlled rice domestication in eastern China.