The big-brained, ape-jawed Piltdown Man was hailed as a major missing link in human evolution when he was discovered in a gravel pit outside a small U.K. village in 1912. The find set the pace for evolutionary research for decades and established the United Kingdom as an important site in human evolution. The only problem? Piltdown Man turned out to be one of the most famous frauds in scientific history—a human cranium paired with an orangutan’s jaw and teeth. Now, scientists think they’ve figured out once and for all that a single hoaxer was responsible, not a duplicitous cabal.

The saga of Piltdown started in 1907. That year, a sand mine worker in Germany discovered the jaw bone of Homo heidelbergensis—a 200,000-to-600,000-year-old hominin now recognized as a likely common ancestor to both modern humans and Neandertals. The find, compounded by rising national tensions that would eventually lead to World War I, sparked something of an inferiority complex among U.K. naturalists. So it seemed fortuitous when, 5 years later, Charles Dawson, a professional lawyer and amateur fossil hunter in Sussex, U.K. (now East Sussex, U.K.), wrote to his friend, paleontologist Sir Arthur Smith Woodward, announcing that he had uncovered a “thick portion of a human(?) skull which will rival H. heidelbergensis in solidity” near the Sussex village of Piltdown.

Smith Woodward and Dawson jointly presented their findings to the Geological Society of London in 1912. From their first excavation, they claimed to have discovered several pieces of a humanlike skull, an apelike mandible, some worn molar teeth, stone tools, and fossilized animals. Excavations over the following 2 years by the team revealed canine teeth that were somewhere in between a human’s and an ape’s in size. Based on the bones’ color and the fossilized animals surrounding them, Dawson and Smith Woodward speculated that the individual lived some 500,000 years ago. The U.K. human evolution research community enthusiastically embraced Eoanthropus dawsoni, better known as Piltdown Man. Its large braincase and apelike jaw and teeth were exactly what these scientists expected to find from a “missing link.”

As more and more hominin fossils were discovered over the next few decades in Africa, China, and Indonesia, however, Piltdown Man lost its significance as a singular missing link. The hoax came to light in 1953 when scientists at the University of Oxford in the United Kingdom, using the then-new technique of fluorine dating—which relies on the fact that older bones absorb more fluoride from groundwater over time—revealed that Piltdown Man’s bones were not all the same age. Further analysis revealed they were an amalgam of carefully carved and stained human and ape bones.

The potential perpetrators included Dawson and Smith Woodward, naturally, but also Pierre Teilhard de Chardin, a French Jesuit priest who assisted the excavation, and Martin Hinton, a volunteer who worked with Smith Woodward, among others. Even Sherlock Holmes creator Sir Arthur Conan Doyle was considered. So whodunit?

Isabelle De Groote, a paleoanthropologist at Liverpool John Moores University in the United Kingdom, began looking into the question in 2009, applying modern scanning technology and DNA analysis to the original materials. She and colleagues compared computer tomography (CT) scans of the mandible and teeth to known ape specimens and concluded that all these pieces originated from an orangutan. DNA sequencing of the teeth suggested they all came from the same orangutan, which De Groote suspects the forger or forgers might have obtained from a curiosities shop.

The human bones, already recognized to be from at least two individuals, revealed fewer secrets. Although these bones are unusually thick—a fact initially used to argue for their prehistoric origin—De Groote says they aren’t outside the range of normal human variation. Unfortunately, the researchers were unable to extract DNA from the bones, and radiocarbon dating failed.

Examining the CT scans, De Groote also noticed a strange, off-white putty on the surface of virtually every bone. This putty had been painted over and stained, and in some cases was used to fill in cracks and gaps that the forger accidentally created. Inside the crania and teeth, she found tiny pebbles stuffed inside hollow chambers sealed over with the same putty. De Groote thinks the hoaxer used these pebbles to weigh down the bones, as fossilized bones are noticeably heavier than recent bones.

Taken together, the consistency of technique used across all the Piltdown Man fragments suggests that a single person pulled off the hoax, the team reports today in Royal Society Open Science . “Throughout the whole assemblage, there’s evidence of one hand, one maker, one signature,” De Groote says.

The likeliest hand belonged to Charles Dawson, who died almost exactly 100 years ago, De Groote says. An amateur geologist, archaeologist, and historian, he regularly attended meetings of geologists and anthropologists, she notes. He was an inveterate fossil hunter with access to collections and the knowledge of what prehistoric finds should look like. He also had a habit of small-time forgery, with several other of his less-celebrated findings later being shown to be fakes. More than anything, he was desperate for acceptance and recognition within the U.K. scientific community, De Groote says. Letters reveal his persistent, but ultimately fruitless, attempts to join the Royal Society.

“It now appears that the chemical data supports the abundant circumstantial evidence that Dawson was the brains behind the hoax,” says geologist Stephen Donovan of the Naturalis Biodiversity Institute in Leiden, the Netherlands, who did not participate in the current study.

Dawson was able to fool the experts of the day by employing the same trick used by successful con artists since time immemorial: He showed them what they wanted to see. “Dawson really played a very clever card,” De Groote says. “With the findings coming out of Germany, and Britain wanting to be at the forefront of science, there was this sense that, ‘We must have these fossils in Britain, as well.’”

Miles Russell, an archaeologist in Bournemouth, U.K., who wrote the book The Piltdown Man Hoax: Case Closed in 2012, says the study adds scientific certainty to his and others’ conclusions that Dawson alone committed the hoax. “Having an accomplice in this … would have been extremely dangerous, opening the forger up to potential blackmail, or worse, exposure and ridicule,” he says. “The new report confirms the likelihood that the forger, who we can now no longer doubt was Dawson, acted alone.”

De Groote says Piltdown’s other prime suspect, Smith Woodward, was merely an unwitting participant in Dawson’s gamble for fame. Although he helped with the excavation, he always let Dawson guide the work, she says.

Still, others remain convinced that Dawson had help. Francis Thackeray, a paleoanthropologist at the University of the Witwatersrand in Johannesburg, South Africa, says he “strongly suspects” Teilhard de Chardin was in on the hoax. Teilhard de Chardin was known as a bit of a prankster, he says. “My view is that Teilhard [de Chardin] was an adviser to Dawson, and that the motive behind the forgery was that it was initially a joke against [Smith] Woodward,” Thackeray says. “It was a joke that went seriously wrong.”

Dawson’s calculated chicanery underscores why studying Piltdown Man is still important to modern science, De Groote says. Although such a brazen hoax is unlikely to occur again in physical anthropology because of the sophistication of modern analytical techniques, she says, there’s still a danger of being too quick to accept interpretations that adhere to what scientists expect to find. That’s especially true when anthropologists hoard their collections, De Groote says, which remains all too common in her field.

“Piltdown Man sets a good example of the need for us to take a step back and look at the evidence for what it is,” she says, “and not for whether it conforms to our preconceived ideas.”