An archeologist works at the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province, Aug. 6, 2022. Photo: Xinhua

An archeologist shows a needle made of bone excavated from the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province, Aug. 6, 2022. Photo: Xinhua

Aerial photo taken on Aug. 6, 2022 shows a view of the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province. Photo: Xinhua

Aerial photo taken on Aug. 6, 2022 shows a view of the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province. Photo: Xinhua

Aerial photo taken on Aug. 6, 2022 shows a view of the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province. Photo: Xinhua

An archeologist cleans recently-excavated stone carvings at the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province, Aug. 6, 2022. Photo: Xinhua

Photo taken on Aug. 6, 2022 shows a view of the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province. Photo: Xinhua

Photo taken on Aug. 6, 2022 shows stone carvings excavated from the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province. Photo: Xinhua

Archeologists measure a recently-excavated stone carvings at the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province, Aug. 6, 2022. Photo: Xinhua

Photo taken on Aug. 6, 2022 shows needles made of bone excavated from the Shimao ruins, an important prehistoric site in Shenmu City, northwest China's Shaanxi Province. Photo: Xinhua