From 1928 to 1937 numerous remains of Peking Man were discovered including five skulls, and specimens from more than 40 individuals.

"But this enormous success dramatically turned into the biggest loss in the history of paleoanthropology," Kundrat says.

In 1941, the whole collection, including the holotype, disappeared just before it was due to be shipped to the United States for safekeeping.

Of all the specimens collected prior to the war, only the two teeth sent to Uppsala in 1924, had survived. However, many crates of Zhoukoudian material that had been shipped to Uppsala University in the 1920s remained unstudied, and these were eventually to yield further specimens: In 1951, Zdansky found a third tooth, a right lower fourth premolar, and in 2011, Kundrat found the fourth one.

"Theoretically more specimens of Peking Man could be possibly found in the crates. I will check the contents again," says Kundrat.

This tooth, he explained, is unique as it is one of the very first pieces of evidence proving the existence of the Peking Man.

Though excellent casts and descriptions of the original fossils still exist, Liu says, the original fossils would give so much insight into ancient humans.