Archaeologists have unearthed relics that suggest prehistoric humans lived along the Silk Road long before it was created about 2,000 years ago as a pivotal Eurasian trade network.

An excavation project that started in 2010 on ruins in northwest China's Gansu Province has yielded evidence that people who lived on the west bank of the Heihe River 4,100 to 3,600 years ago were able to grow crops and smelt copper, the researchers said.

The site is believed to date back to the Han Dynasty (202 BC - AD 220).

Over the past three years, archaeologists have discovered a variety of copper items, as well as equipment used to smelt metal, said Chen Guoke, a researcher with the Gansu Provincial Institute of Archaeology.

"People back then mainly dealt with red metal. They also began to make alloys," said Chen, who is in charge of the excavation project.

Chen added that a rare copper-smelting mill was also found in the ruins.

"The mill is the earliest of its kind that has been unearthed. It will be of great help for studies of the history of Chinese craftmanship," said Zhang Liangren, a professor at Northwest University in Xi'an, capital of Shaanxi Province.

The researchers also discovered carbonized barley and wheat seeds, as well as stone hoes and knives used for farming, said Zhang, adding that some adobe houses were also found this year.

The finds indicate that east-west exchanges started prior to the Han Dynasty, as adobe architecture, barley and wheat originated in central and west Asia, according to Zhang.

A series of previous discoveries during the past decade have also provided evidence of the existence of prehistoric civilization along the Silk Road.

From 2003 to 2005, archaeologists excavated the Xihetan ruins in Gansu's city of Jiuquan.

"We were surprised to find a pen for cattle and sheep preserved in the ruins. The find was unprecedented," said Zhao Congcang, another professor at Northwest University.

Footprints of the livestock and their skeletons were also found at the site.

In 2005, researchers from China and Japan completed a three-year excavation project at the Mozuizi ruins in Gansu's city of Wuwei, finding traces of a primitive tribe that lived about 4,500 years ago.

Starting from the ancient city of Chang'an, now known as Xi'an, the ancient Silk Road extends to the Mediterranean region in the west and the Indian subcontinent in the south. Its total length is over 10,000 km, with 4,000 km located within China.

In January, China, Kazakhstan and Kyrgyzstan jointly submitted an application to the UNESCO for adding the Silk Road to the World Heritage List for 2014.