Researchers have finished an eight-year study of one of the most infamous forgeries in the history of science - the fake human ancestor Piltdown Man.
They conclude that the forged fossils were made by one man: the prime suspect and "discoverer" Charles Dawson.
The human-like skull fragments and an ape-like jaw, complete with two teeth, shook the scientific world in 1912 but were exposed as a hoax in 1953.
New tests show the bones came from two or three humans and one orangutan.
The research, published in Royal Society Open Science, was a multi-disciplinary collaboration including palaeobiologists, historians, dental experts and ancient DNA specialists.
Comparing the methods used on multiple forged specimens dug up near the Sussex village of Piltdown from 1912 to 1916, the team found what they describe as a highly consistent modus operandi:
- The same reddish-brown stain was applied to make the bones look old
- The specimens had appropriate local gravel packed into their crevices
- Dentist's putty was used to fix the teeth and gravel in place
Such a fixed strategy for fooling the scientific establishment points to a single person conducting the operation, said Isabelle De Groote from Liverpool John Moores University.
Critically, it also links two separate locations: "Piltdown I" where the original jawbone and skull fragments were planted and excavated in 1912, and "Piltdown II" 3km away where Dawson claimed to find a matching tooth and skull pieces in 1915.
"What we've been able to demonstrate is a signature, a fingerprint throughout all of these specimens, even including the second molar from the second Piltdown site," said Dr De Groote, first author of the study.
"Dawson is the only one who ever said there was a Piltdown II site; he's the only one who was ever associated with it and we can clearly link that molar to the original specimens."
That case is clinched by detailed analysis of the various teeth.
The exact shape of molars from the two sites, as well as traces of DNA found in teeth at both Piltdown I and Piltdown II, suggest they all came from the jawbone of a single orangutan - probably belonging to a rare subspecies from Borneo.
Remarkably, Dawson appears to have removed the teeth, breaking the jaw in the process, then ground them down to make them appear more human and stuck two molars back in the jaw with putty and gravel.
But planting a third tooth at Piltdown II, a century before ancient DNA analysis became possible, was his undoing.
"That has to be Dawson, there's no doubt about that. He's the only person uniquely linked with both those sites," said co-author Chris Stringer from London's Natural History Museum.
It is still possible that someone else supplied the specimens for Dawson to "discover", Prof Stringer added. But the amateur collector, anxious for scientific acclaim, was certainly "the central figure".
Made to order
As a consequence, several other suspects are now off the hook, Dr De Groote said, including the French priest Teilhard de Chardin who excavated an isolated canine tooth at the Piltdown I site in 1913.
The new findings place that tooth firmly in the same orangutan jaw as the molars, which are now tied to Dawson.
"It exonerates a number of people who have been accused," Dr De Groote told BBC News.
She and her colleagues' fresh insights into the forger's methods - such as the precisely matching gravel embedded in the bones - also point to Dawson.
"It was very carefully done," she said. "That's another thing that exonerates some others - for example, Sir Arthur Conan Doyle was one of the suspects.
"Obviously he could write a good story, but he probably would never have had the skill or the scientific knowledge to prepare a forgery like this one."
Dawson, on the other hand, had a long-standing interest in antiquity and fossil collecting. He knew that scientists were expecting the earliest human ancestor to have a big brain but an ape-like jaw.
"He listened very carefully," said Dr De Groote, adding that he even tailored subsequent forgeries to the reaction of the scientific community.
"When a jaw and the skull bones were announced, there was a big discussion at the Geological Society about what the canine in such an animal would look like. And, ta-da - six or seven months later, a canine shows up and it looks exactly like what they had predicted."
She says her sleuthing on the Piltdown saga has made her think no evidence should be taken for granted, and scientists must beware their preconceptions.
"If something fits a hypothesis maybe too well, question it again."
The scandal also makes a clear argument for not locking up fossils, Dr De Groote said; for decades after the discovery, scientists were only rarely given access to the Piltdown specimens themselves.
She said even today, her PhD students often face difficulties getting hold of samples.
"The field of palaeoanthropology is still very much a field of fossil hoarding."
By contrast, the recent example of the Homo naledi skeletons being quickly made available as printable 3D files is extremely positive.
"In the last four or five years, this has started to change," Dr De Groote said.
"Open access should include making fossils accessible to people. Now they can be scanned and shared very easily - it would just make for better science."
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