Undated file photo provided by Zhengzhou Municipal Institute of Archaeology shows the silkworm carving unearthed in Gongyi City, central China's Henan Province. A boar tusk carving of a silkworm, dating back over 5,000 years, was unearthed in the Shuanghuaishu Remain in Gongyi City. The carving, 6.4cm long, nearly 1cm wide and 0.1cm thick, was believed to be China's earliest carving depicting silkworms. (Xinhua)