fossil discoveries since 1917 contradicted the 19th-century idea that humans had an ancestor with a modern brain and ape jaw, and actually suggested the opposite relationship. The Java fossils are currently housed in the Senckenberg Museum with the financial support of the Werner Reimers Foundation of Bad Homburg. In 1937, Von Koenigswald hosted paleontologist Franz Weidenreich's visit to Java to examine recent discovery sites. Also in 1937, Von Koenigswald became a Dutch citizen. In 1938 Von Koenigswald and Weidenreich together announced the discovery of a new skull of Pithecanthropus (P. robustus). Early in 1939, Von Koenigswald took several Javanese hominin specimens to Weidenreich in Peking, China. Comparing the Sangiran and Choukoutien hominids led the two scientists to conclude that the specimens were closely allied. They decided to abandon the genus Sinanthropus, combining all the specimens into the earlier-named genus Pithecanthropus. Later, Pithecanthropus was incorporated into the genus Homo as Homo erectus. World War II World War II brought difficulty and danger to Von Koenigswald in Java. He managed to hide his fossils from the invading Japanese, and although he, being a Dutch citizen, was interned in a prisoner-of-war camp, only one fossil skull was confiscated by the Japanese soldiers. It was presented to Emperor Hirohito but was recovered after the war. During the war years, Weidenreich's description of Sinanthropus was published. In a borrowed office at the American Museum of Natural History, Weidenreich added to their earlier work and reviewed the fossil record of human evolution, merging Sinanthropus and Pithecanthropus into a new taxon, Homo erectus, with various geographic sub-species. He published descriptions and assigned scientific names to some of Von Koenigswald's discoveries, as he and others presumed that Von Koenigswald was dead at the hands of the Japanese. After the war, Von Koenigswald worked with Weidenreich at the American Museum of Natural History in New York City for 18 months. Netherlands For the next 20 years, Von Koenigswald filled a Chair of Palaeontology created for him at the Rijksuniversiteit at Utrecht, Netherlands. During his academic career, he visited sites in North and South Africa (1951–52), the Philippines, Thailand and Borneo (1957), and Pakistan (1966–67). In Pakistan, Von Koenigswald and his students found specimens which included a palate assigned to a new species of the hominoid genus Sivapithecus and teeth considered to belong to Ramapithecus. In 1950 he became member, and in 1968 foreign member of the Royal Netherlands Academy