For forty years the missing link was an orangutan

For forty years, England's most famous human fossil was half an orangutan jaw with its teeth filed down by hand. It was called Piltdown Man and it was displayed as a plaster cast at the British Museum.

It was presented by Charles Dawson, a Sussex solicitor and amateur fossil hunter, to the Geological Society of London on 18 December 1912. He said labourers had handed him pieces of a skull dug out of a gravel pit at Barkham Manor, near the village of Piltdown, and that he had later found the jaw there himself. Arthur Smith Woodward, the museum's keeper of geology, assembled the specimen, reconstructed the face and gave it a scientific name: Eoanthropus dawsoni, Dawson's dawn man.

The find fitted far too well. The fashionable English theory held that in human evolution the brain had grown first and the face had followed, and Piltdown delivered exactly that: a large, modern-looking braincase and an ape's jaw. It also delivered something that was no small matter in 1912: England finally had an ancestor of its own, against the Neanderthals of Germany and France.

The doubts began at once. In 1915 the American zoologist Gerrit Smith Miller wrote that the jaw belonged to a fossil ape, probably a chimpanzee, and was being joined to a skull that did not go with it. It made no difference: the specimen was kept under lock and key and researchers worked from plaster casts, which show neither the real wear on the teeth nor the colour of the bone.

The first technical crack came in 1949. Kenneth Oakley applied the fluorine test to the specimen, which measures how much fluorine a bone has absorbed from groundwater and rises with the years it has spent buried. The result, published in March 1950, did not denounce a fraud: it said the remains were recent, some fifty thousand years old. That was enough to bring down the missing link and not enough to uncover the forgery, which is why the specimen lasted four more years.

On 21 November 1953, Joseph Weiner, Oakley and Wilfrid Le Gros Clark published the full dismantling. The new tests also measured the nitrogen in the bone and showed that skull and jaw could not have lain buried for the same length of time. The skull was human and medieval. The jaw was an orangutan's and a few centuries old. The molars had been filed with a tool to flatten the chewing surface in the human manner, and the pieces had been stained with potassium dichromate and iron salts to give them the dark colour of old bone. The canine tooth that Pierre Teilhard de Chardin had found at the site in 1913 was painted.

In February 1925 the anatomist Raymond Dart described in Nature the skull of a child from Taung that had reached him the year before, with a small brain and already human teeth: the exact opposite of Piltdown, and this time genuine. The British scientific establishment treated it for two decades as an ape of no interest, because it contradicted the fossil from Sussex.

In 2016 a team led by Isabelle De Groote drilled into the specimens and found dental filler and gravel from the site itself inside them, and established that every piece of jaw came from a single orangutan, probably from Borneo. The conclusion pointed to one hand working with one animal.

Dawson died in 1916. Nothing ever turned up at the Piltdown site again.