In the 1930s archaeologists working at the site of Zhoukoudian near Beijing recovered an incredible trove of partial skulls and other bones representing some 40 individuals that would eventually be assigned to the early human species Homo erectus. The bones, which recent estimates put at around 770,000 years old, constitute the largest collection of H. erectus fossils ever found. They were China's paleoanthropological pride and joy. And then they vanished. According to historical accounts, in 1941 the most important fossils in the collection were packed in large wooden footlockers or crates to be turned over to the U.S. military for...