Pseudofossils are inorganic objects, markings, or impressions that might be mistaken for fossils. Pseudofossils may be misleading, as some types of mineral deposits can mimic lifeforms by forming what appear to be highly detailed or organized structures. One common example is when manganese oxides crystallize with a characteristic treelike or dendritic pattern along a rock fracture. The formation of frost dendrites on a window is another common example of this crystal growth. Concretions are sometimes thought to be fossils, and occasionally one contains a fossil, but are generally not fossils themselves. Chert or flint nodules in limestone can often take forms that resemble fossils.

Pyrite disks or spindles are sometimes mistaken for fossils of sand dollars or other forms (see marcasite). Cracks, bumps, gas bubbles, and such can be difficult to distinguish from true fossils. Debates about whether specific forms are pseudo or true fossils can be lengthy and difficult. For example, Eozoon is a complex lumpy form found in some rocks that was long thought to be a fossil algae until "specimens" were identified in recent lavas.

Pseudofossil hoaxes

Piltdown Man

Perhaps the best known pseudofossil was Piltdown Man, which fooled the famous philosopher Pierre Teilhard de Chardin and the author Arthur Conan Doyle.

Piltdown Man (Eoanthropus dawsoni) was a fraud which was perpetrated, possibly by Charles Dawson and/or others, on paleontologists from November 1912 until its exposure in 1953.

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 since it fitted the prevailing theory of such a link having 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, such as the Taung child which had a small cranium and human-like jaw. By the late 1930s, the Piltdown Man 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 an 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 from humans.

A number of aspects aided the survival of the hoax for forty years. It satisfied European expectations that the earliest humans would be found in Eurasia, and the British also wanted a "first Briton" due to national identity, leading to the dismissal of the first Frenchmen and Germans that the French and Germans already had (see Neanderthals). 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 artefacts.

In November 2003, the Natural History Museum held an exhibition to mark the 50th anniversary of the exposure of the hoax.

Although now clearly discredited, Piltdown Man is a bit of a cause celebre for creationists, who claim it shows evidence of corruption in the scientific community, and points to the possibility that other hominid fossils are hoaxes.

Popular Culture

Mike Oldfield, in his 1973 album Tubular Bells, lists "Piltdown man" as one of the instruments he plays in the album. This refers to one part of the album (found in the second track) that is undoubtedly inspired by early hominids and sung in a raw voice. In the 2003 reworking of the album, this part is titled "Caveman".

The Apple Macintosh computer game Marathon 2 has a computer terminal with the word "piltdown" in a transmission's header. It is argued that this usage implies that the message from the terminal was not entirely true, and that the supposed 'sender' did not exist at all.

In his book Scientology: A History of Man, Scientology founder L. Ron Hubbard lists Piltdown Man as one of the ancestors of humanity, describing him as having "enormous" teeth and being "quite careless as to whom and what he bit." Piltdown Man was exposed as a hoax just months after the publication of Hubbard's book.