TOKYO--New dates for food residue scraped from ancient Japanese pottery have touched off a storm of controversy in Japan's archaeological community. The findings play into the debate over how and when rice paddy agriculture spread from central China. "This could change our understanding of Asian antiquity," says Hideji Harunari, an archaeologist at the National Museum of Japanese History in Chiba, outside Tokyo.
Rice cultivation in paddies is widely believed to have emerged along the Yangtze River in central China about 8000 B.C. How and when it spread eastward is less clear. One theory holds that immigrants fleeing the turmoil of China's Warring States period, beginning about 450 B.C., took the technology overland to present-day Korea, then across the relatively narrow Korea Strait to Japan's Kyushu Island. An alternative theory is that seafaring traders carried the technique to lands bordering the Yellow and East China seas around 1000 B.C. or earlier.
In Japan, the spread of rice cultivation is one of the marks of the beginning of the Yayoi Period, which has been pegged to 500 to 400 B.C., mostly by speculative analysis of evolving pottery techniques. "There have really been very few actual measurements [of artifacts]," says Mineo Imamura, a chemist heading a project at the museum to scientifically date archaeological materials.
To fill this gap, Imamura and his colleagues sent food residue samples from 11 early Yayoi pottery pieces to an accelerator mass spectrometry lab in the United States. Results from 10 of the 11 pots put their ages at 780 to 830 B.C. Because there are more primitive Yayoi pottery samples, they speculate the actual start of the Yayoi period should be about 1000 B.C. Harunari says this indicates that the use of rice paddies spread eastward half a millennia before the Warring States period. The group presented their findings during the spring meeting of the Japanese Archaeological Association here on 25 May.
An earlier start for the Yayoi Period would also mean refiguring an important era in Japanese history. The spread of rice paddy agriculture led to population growth, increasingly large and sophisticated settlements, and chiefdoms. The consolidation of several chiefdoms led to the emergence of a prototypical Japanese nation mentioned in Chinese records of about A.D. 300. Harunari says if their new date for the start of the Yayoi Period is correct, this cultural process took 1200 years instead of the currently accepted 700 to 800 years. But Fujio Oda, an archaeologist at Fukuoka University, and others want more evidence before Japan's history books are rewritten. "We really need a lot more data and not just results from one particular age," Oda says.