Piltdown Man was one of the biggest archaeological discoveries in history when it was discovered in 1912.

It was hailed as the missing evolutionary link between apes and humans, giving us a better understanding of how we evolved. There was just one problem though: it was a hoax.

Of course, we had already known that since 1953, but we didn't know who was truly behind it. Now, thanks to multi-disciplinary collaboration between experts ranging from palaeobiologists, historians and even ancient DNA specialists, we know who the culprit is: Charles Dawson, the one who "discovered" the skull and just him alone.

The research, published in Royal Society Open Science, details how the team compared the methods used on multiple forged specimens dug up near the Sussex village of Piltdown from 1912 to 1916, and eventually found what they describe as highly consistent modus operandi:

 – The same reddish-brown stain that was used 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 experts at the time points to the fact that a single person conducted the operation, said Isabelle De Groote from Liverpool John Moores University.

Of course, to appreciate this conclusion, you have to understand the hoax.

A Hoax Of Historic Proportions

The story begins in 1912, when Charles Dawson, a professional lawyer and amateur fossil hunter, discovered fragments of a human-like skull, an ape-like jawbone with two worn molar teeth, various stone tools and fragments of animal fossils at Plitdown in East Sussex, England. All of these fossils had the same feature: a reddish-brown stain (which we know is a product of Dawson trying to pass these off as real human fossils).

Since Dawson wasn't in the field himself, he brought his findings to someone who was, paleontologist Arthur Smith Woodward, and together, they announced their find. The discovery was monumental for two primary reasons: for the scientific community, the skull suggested that humans evolved large brains early on and entirely reset what researchers thought they were looking for from a "missing link." In fact, it was hailed as the missing evolutionary link between apes and humans. For England, however, it was a matter of pride. Germany had just discovered Homo heidelbergensis a few years, and increased their attempts to find a human ancestor in their own country as a result.

Unfortunately, Dawson didn't get to enjoy his rise to fame as he died four years later in 1916. However, one year before doing so, he wrote to Woodward claiming that he discovered three more fossil fragments (including a molar) from another skull at a second site just a couple miles from the first one.

However, there was something off about the "findings" this time around.

The Hoax Exposed

As with most scientific discoveries, there were some doubts about the discovery of the Piltdown Man. It was accepted as the real deal, but there was one particular cause for concern: the site of the second excavation, Piltdown 2, was never discovered, and Woodward never submitted the findings until after Dawson's death.

Time passed, and in 1953, the scientific community was met with upsetting news: Dawson's "historic finding" was a hoax.

Using the then-new technique of fluorine dating, a team of researchers at the British Museum found that the bones were not all of the same age. Specifically, they found that 50,000 years old and the ape-like jawbone was just a few decades old — far younger than the 500,000 years of age at which Dawson tried to pass them off. As for how he managed to pass them off at the age? Potassium Dichromate, giving the bones the previously-mentioned reddish-brown appearance.

Now, with his lie exposed, what was poised to be one of the greatest archaeological finds of all time became one of the greatest scientific hoaxes of all time.

Who Was Behind It?

In the world of science, answering one question often leads to several more being asked in this place. It was very much the same in this instance, though the question became: "Who was behind it?"

Dawson was obviously the prime suspect, but there were several more who were eyed for their possible involvement.

Leading the list was Woodward, the same man who brought forward the initial discovery. There was one problem with this hypothesis, though: up until his death in the 1940s, he had spent the majority of his time search for more of those same fossils.

Other suspects, were Martin Hinton, a British Museum staffer who held a grudge against Dawson, a French priest named Pierre Teilhard de Chardin, and even Sherlock Holmes creator Sir Arthur Conan Doyle, who lived near Piltdown and was opposed to the theory of evolution.

In the end, however, it was Dawson, and Dawson alone who was found to be responsible for the hoax: not only was he the only person to ever find these fossils while he was alive, but no more Piltdown fossils were ever discovered after his death. He knew that scientists were looking for "a large brain, ape-like face and jaws, and heavily fossilized materials that indicated great antiquity" — so, that's what he gave them.

In fact, it turns out Dawson had experience at doing this, too, as he was apparently responsible for at least 38 forgeries, such as a stone axe, a fake flit mine at the Lavant Caves and what he claimed was one of the first bronze statuettes linked to Roman times.

"He clearly had been doing this for a very long time," Groote said.

Why?

A hoax this great would have no doubt left his career in shambles had he lived long enough to see it exposed, so why bother taking that risk in the first place? 

Some suggest that it was for the scientific recognition, particularly his goal to become a member of the Royal Society. For what it's worth, he certainly tried to earn recognition through legitimate means, having previously written more than 50 publications. In fact, he and and his wife wrote letters asking for his recognition, and while he was nominated a fellow, his nomination for election was not successful. The only time his career made any notable progress was after Piltdown.

Amusingly enough, the paper outing him as the sole perpetrator was published on the 100th anniversary of his death.