( The rapid growth of the earliest cities...)Are rice and wheat behind China's population boom?

Although we often associate rice with Chinese agriculture, most archeologists have, until recently, thought it was exclusively millet that was the most important food associated with northern China. However, recent archeological research conducted on the Liangchengzhen site by investigators from the University of Toronto, The Field Museum in Chicago and China's Shandong University in the province of Shandong shows that not only was millet grown, but rice was apparently the prevalent food source, and wheat was also on the scene.

The discovery of wheat - excavated from a pit among ancient house ruins and garbage dumps - was especially intriguing. The Chinese were not known to have contact with western Asia - the likely source of the wheat - until much later.

"Despite all we know about China, we have never had a really good idea about what their agricultural history was," Crawford says. "We had no evidence of what other kinds of crops they grew, their relative popularity across the country and how these people may have been managing their local ecology."

Crawford says what they are seeing now is a very sophisticated knowledge about growing rice - how to intensify yields through the introduction of nutrients in the water and knowledge of water management practices. "By successfully manipulating rice production to the extent that these ancient people did, in combination with millet and wheat, helps explain the foundation of China's huge population today."