Introduction to the 13th site: The 13th site of the Zhoukoudian site is located about 1 km south of Longgu Mountain. It was discovered in October 1933 under the leadership of Bu Dasheng. 161 boxes of fossils and a small number of stone tools were unearthed, including mammals. There are 36 species of animal fossils, most of which are large animals. The more significant species include the wolf wolf, the Chinese hyena, the last saber-toothed tiger, the Shangding's zokor, the Burkin's vole, the Larvae's porcupine, the three-door horse, and the plum. The cultural relics include gravels and stone flakes with smash marks, trapezoidal stone flakes made of flint, and clear traces of use on the lower edge; A single straight-edged scraper made of vein quartz small gravel, which can be used for cutting; a primitive pointed tool and a small chopper. From these few stone tool materials, it can be seen that people at that time used two methods to break pieces: smashing method and hammering method, and used hammering method to repair tools. There were already three types of tools: scrapers, pointed tools and chopping tools. The era is equivalent to the early stage of Chinese ape-man culture.