Xiacaowan Cultural Relics, known as the earliest site of ancient humans discovered in Jiangsu Province, lie on the eastern bank of the Xiacaowan irrigation channel about 8 kilometers from the southeast of Shuanggou Town in Sihong County, facing Huaihe River in the south and Hongze Lake in the north. Now the Relics look like an ordinary river slope, confirmed in 2002 by the Municipal Government as the Municipal-Level Key Cultural Heritage Protection Unit. In June 1954, Professor Yang Zhongjian, Academician of China Academy of Science, Geologist and Paleontologist, collected a length of 15.27-centimeter ape femur fossil when he went on a inspection in Suqian. The fossil was believed to be the human fossil in Late Paleocene dating from 40 to 50 thousand years ago and belonged to intelligent human beings in the Age of Late Paleocene. They have been named as “Neo- People in Xiacaowan”.

In recent years, experts have for many times conducted archaeological surveys and scientific excavations in Xiacaowan Area and discovered hundreds of vertebral mammal fossils dating back to the Pleistocene Epoch and Miocene Epoch, a large number of which are new species of the new genera and called “Xiacaowan Fauna”. The fossils unearthed including Shuanggou Intoxicated Apes and ? Huai Wide-Tine Apes play a valuable role in the researches into evolution from apes to human beings. Ecologists found out when they inspected Xiacaowan Relics that the soil layer structure in the area is the lacustrine facies sedimentary section, called “Xiacaowan Kaolin Clay Strata” and denominated as “Xiacaowan Series” together with the strata of the same type. They have been recorded in China Geology.