The shells dug out in Haitong County.

Archeologists have discovered China’s largest shell mound in Haitong County, Yunnan province.

The shells, dug out from a 9-meter-deep pit, belong to a kind of rare spiral shell indigenous to lakes in Yunnan Plateau, but they are extinct today, according to Zhu Zhonghua, an expert from the Yunnan Provincial Institute of Cultural Relics and Archaeology.

"The shells were not deposited naturally in lakes. Ancient people collected them to eat, because the top of the shells had been removed,” Zhu said.

Zhu explained that houses, roads and ash pits that have been unearthed reveal a great deal about the lives of people living 3,000 years ago. The copper ore and its byproducts discovered in the pit indicate that people living beside Qilu Lake had begun to produce bronze wares as early as 3,400 years ago. During excavation, archeologists also found a carbonized acorn, which carbon dating determined to be 3,450 years old.

According to Yang Jie, director of Yuxi Cultural Relics Administration, it is widely believed that the Dian Culture, a bronze culture in Yunnan, dates back to the Warring States Period (475-221 BC). The new discovery in Haitong County proves that the Dian Culture is hundreds of years older than previously believed.