The first complete skull of “Beijing Ape Men” of Zhoukoudian was discovered in December 1929 by Pei Wenzhong, a Chinese anthropologist. Later, large-scale excavations were done on several occasions,  amounting to 25, 000 cubic meters of earthwork. Fossils of men and vertebrates were found. Of men fossils alone, a total of 152 pieces were uncovered of skulls, fragments of skulls, facial bones, lower jawbones and teeth belonging to over 40 individuals of different ages and sexes. 
    The site was listed by the United Nations' Education, Science, and Culture Organization (UNESCO) as one of the world's heritages in 1987.