[blam]

Chinese, Japanese Started Prehistoric Exchanges 7,000 Years Ago: Archaeologists

"They compared archeological findings in China's Xinglonggou Relics Site in north China's Inner Mongolia Autonomous Region, also popularly known as "China's first primitive village", and findings in Japanese sites from the Neolithic age, about 10,000 to 4,000 years ago

. The cultural exchanges occurred on a route from northeast China through coastal Russian areas to Japan's Hokkaido and Honshu over 7,000 years ago, noted Wang Wei, deputy director of the Institute of Archaeology of the Chinese Academy of Social Sciences"

[Fedora]

Interesting article. This part would also seem relevant to the issue of possible connections with the Olmecs:

The relic site is the earliest and most well-preserved of primitive villages in China and pushed estimates of the country's jade production history back to some 8,000 years ago.