Houchengzui stone ruins offer glimpse into prehistoric civilizations

During the news conference on Friday, the Bicun site in Xingxian county, Shanxi province, dating back 4,200 to 3,800 years, was also highlighted. Zhang Guanghui, a researcher with the Shanxi Archaeology Academy who led the ongoing excavation, said this stone city site about 50 km from Shimao was probably a frontier border pass.

"Outposts were everywhere in the city, and its structure was rigidly planned," Zhang said. "It might have been a key strategic passageway connecting central and western China, which was pivotal for society then."

Unearthed jades and potteries provided a glimpse of different aspects of people's daily lives then.

Chen Xingcan, director of the Chinese Academy of Social Sciences' Institute of Archaeology, said, "The Houchengzui, Bicun and Shimao sites composed a cultural system that is crucial for the study of how a complicated society was formed in the first place.

"Many questions remain unanswered. If these sites were military fortifications, who did they defend against?" Chen said. "The work has just started, and there's a long way to go to more clearly figure out their connections."