Dawson claimed to have discovered an ancient hominid skull in Piltdown quarry, near Uckfield in Sussex in England, and gave it the Latin name reproduced above ("Dawson's Dawn Man" in translation). The find was written up by mainly British paleontologists as the 'missing link' between ape and man, seeming as it did to feature a human-like cranium and an ape-like jaw. There was considerable scepticism until a second similar skull (Piltdown II) was uncovered in 1915. However, it became increasingly difficult to reconcile Piltdown Man with later (genuine) hominid finds and by the late 1930s it was effectively ignored. Following fluorine absorption tests in 1949 and redating of the Piltdown gravel beds it was finally revealed as a hoax on 21 November 1953.
Piltdown Man turned out to be literally half-ape, half-man: it consisted of the skull of a medieval human, the 500-year-old lower jaw of a Sarawak orangutan and chimpanzee fossil teeth. The appearance of age had been created by staining the bones with a iron solution and chromic acid. To remove the evidence for the lack of fit the jawbone was carefully broken and the teeth filed and patched to fit. This filing of the teeth, in fact, led to doubt being cast of the skull's veracity - by chance it was noticed that the top of one of the molars sloped at a very different angle to the other teeth. Microscopic examination revealed scratch-marks on the teeth. Filing was necessary as apes chew their food in a different way to humans.
Two aspects aided the survival of the hoax for forty years. It satisfied European expectations that the earliest humans would be found in Eurasia. And professional jealousy kept the faked skull and jaw securely locked away from public gaze. The discoverers were well respected, the skull matched expectations (brain development before the jaw) and it was a well-executed forgery for its time. Even though it was quickly shown to be out of place and was relegated to the status of an unimportant curiosity, it was not dismissed as a forgery.
Assigning responsibility for the hoax has been a minor academic industry for a number of years. Charles Dawson was naturally the prime suspect, but a number of prominent persons had been to the site at various times, including Arthur Conan Doyle and Pierre Teilhard de Chardin, and various theories were proposed naming them. The general idea was that a practical joke had been played on Dawson, or on paleontologists generally, but the locking away of the specimen had prevented immediate discovery, and the huge publicity for the discovery had caused the hoaxer to keep silent.
The perpetrator has never been discovered with absolute certainty, and, short of finding a diary recording the forging, never will be, but the candidate on whom most suspicion has recently fallen is one Martin A.C. Hinton. In 1970, a trunk bearing his name and containing letters to him was discovered in storage at the Natural History Museum in London: the trunk also contained animal bones and teeth that had been carved and stained in a manner identical to the Piltdown artifacts.