Later, more sheep bones, over 4,000 years old, were found in sites in Shanxi, Henan and Shandong provinces.

DNA tests showed Chinese sheep had a close genetic link to those that first appeared in western Asia.

"So domesticated sheep were introduced from western Asia to China along a road much earlier than the so-called Silk Road," says Yuan.

Archaeological discoveries also indicate the important role of mutton in ancient Chinese cuisine.

In a pit at the site of the Palace of the Tang Dynasty (618-907) in Xi'an, capital of northwest China's Shaanxi Province, archaeologists found a large number of animal bones, most of them from sheep. Before the Tang Dynasty, most animal remains found in the ruins of palaces were pigs.

"It means from the Tang Dynasty, mutton became popular in royal cuisine. That continued in the later Song Dynasty (960-1279)," Yuan says.

The ancients kept sheep not only for meat and milk, but also for wool. So when did Chinese start shearing?

Archaeologists unearthed many sheep bones in the Taosi relic site dating back 4,000 years in Shanxi Province, and most of the bones belong to old sheep.

"Apparently, those old sheep were not raised for meat or milk. A similar phenomenon was also found in a 3,900-year-old relic site in Zhengzhou, and in the 3,700-year-old Erlitou relic site in Henan Province," Yuan says.

"We assume that the ancients of Taosi acquired the technique of shearing 4,000 years ago," Yuan says.