A rubbing of a solar deity is among exhibits at the ongoing rock art show in Beijing. Photos by Wang Kaihao / China Daily

An ancient stone carving is among exhibits at the ongoing rock art show in Beijing. Photos by Wang Kaihao / China Daily

"While there's little evidence of intercultural communication from back then, comparative studies are looking for common links," says Zuo.

Meanwhile, rock art in Ningxia did not end after early-stage civilization. For instance, a lot of the art belonged to the Western Xia (1038-1227) era, which is evident from the written characters found on them. And, shepherds from different eras up to the early 20th century left their artistic impressions.

In China, rock art is found in 28 provincial-level administrative regions, and Zuo says that most of it in northern China is "carved" on rocks, while in the south you see the painted kind.

"We know of people's changing beliefs, thinking and cultural models through this art," says Zuo.

"It plays important roles in ethnology and studies of world art history as well as religions," he adds.

Studies by the Ningxia Rock Art Research Center show that there are about 50,000 pieces of rock art scattered over 31 major sites in the autonomous region's mountainous areas.

Most of the art was discovered by archaeologists in the 1980s.

In 2010, the research center began digitizing and constructing a database of rock art with the help of the State Administration of Cultural Heritage.

As of now, approximately 22,000 pieces of rock art are recorded in the database, but Zuo says that more money is needed to continue with the project.

"The digital resources will be useful to the public. Perhaps, one day we'll be able to have a digital display instead of rubbings."

Speaking of the ongoing exhibition, Huang Jikai, the director of the museum, which was set up in 2014, says the event is the first exhibition that is not directly connected to the history of overseas Chinese.

"But, the rock art represents early civilizations along the Silk Road," he says, explaining why the institution chose to host the event.

"Our ancestors' courage in struggling against nature and their spirit of adventure coincide with the goals of our museum: To show the overseas Chinese' perseverance, though they belong to different eras."

On Friday, when the Zuojiang Huashan Rock Art Cultural Landscape in southern Guangxi Zhuang autonomous region was added to UNESCO's world heritage list, an exhibition in Beijing kicked off to show people its cousin in Northwest China's Ningxia Hui autonomous region.

Ancient Echo: The Special Exhibition of Ningxia Rock Art opened in the capital's Overseas Chinese Museum of China, and will run through Sept 15.

About 60 rubbings and ancient stone carvings from the Helan Mountains are on display.

A rubbing of a solar deity is a highlight of the show, says Zuo Changying, the deputy director of the Ningxia Rock Art Research Center, China's only provincial-level entity dedicated to the study of rock art.

There are also pieces on hunting, rituals and the breeding of animals.

The earliest art can be roughly dated to 10,000 years ago in the late Paleolithic Age, but a unanimous conclusion has yet to be reached due to difficulties in judging the age of rock art.

Some experts believe that the art is from the Bronze Age, which is at least 6,000 years later.

Weighing in on the age issue, Zuo says: "Unlike ancient tombs where there are often funeral articles that can be used as references, rock art leaves little information for us."

She also says that some patterns found in the rock art are similar to those discovered in Mesopotamia.