There is no doubt that Piltdown man was a hoax, but there is still little agreement on who was responsible, writes Geoff Watts.
The Piltdown hoax is to palaeontology what Jack the Ripper is to criminology: a classic whodunit. The events may be different - skilful forgery as opposed to brutish murder - but the similarities are striking: an enduring public interest; a succession of popular books and learned articles; and a cast of likely or unlikely suspects ranging from the obscure to the celebrated. There is little reason to suppose that the theorising about either mystery will ever reach a definitive conclusion.
To master the contending theories about Piltdown - the evidence, actual and circumstantial, and its multiple and contradictory interpretations - takes a week of solid reading. But to itemise the agreed facts is simple enough.
The discoveries, which took place between 1912 and 1914 near Piltdown in Sussex, were all made by or in the presence of Charles Dawson. An amateur geologist and antiquarian, Dawson was familiar with fossil hunting, having collected material for the British Museum.
The first and most celebrated finds, from a gravel pit at Barkham Manor, comprised a jaw and fragments of a skull, various animal fossils and also some flint and bone tools. Arthur Smith Woodward, keeper of natural history at the British Museum, was among those eminent scientists who made much of the finds. On the face of it, they provided evidence for a then widely held belief about our ancestry: that we represent the end point of a very ancient lineage in which the first modern feature to emerge was a large brain. Finding an obviously advanced skull together with a primitive and far more ape-like jaw played well to this view. Others disagreed.
Dawson died in 1916, but controversy over the interpretation continued until 1953, when the fraud was exposed. Chemical and other analyses by Oxford anthropologist Joseph Weiner (whose 1955 book on Piltdown is about to be reissued) revealed that the skull was only 600 years old and that the jaw came from an orang-utan. This and the rest of the material had been assembled and treated to give a bogus impression of great antiquity. But by whom? Although Dawson was the most obvious candidate, all sorts of people, with even the most tenuous connections, fell under suspicion.
The next significant development came in the mid-1970s when builders working in the roof space of the Natural History Museum found a canvas trunk marked with the initials of Martin Hinton, a curator at the museum at the time of the fraud. A close examination carried out a few years later showed it to contain bones that had been stained and carved in the same way as much of the Piltdown material.
Here, it seemed, was clear evidence of the guilt of one man: Hinton. Brian Gardiner - then professor of palaeontology at King's College London - used his 1996 presidential address to the Linnaean Society to discuss the find and its significance. Instead of settling the matter, however, the discovery simply reminded people of it.
Gardiner still believes that the perpetrator was Hinton - and not only because of the material in the trunk. He describes contacting Hinton's executor and friend, the late Bob Savage of Bristol University. "Hinton was a garrulous character. He and Savage used to drink together. Savage told me how he would give Hinton lots of port and try to persuade him to own up to the Piltdown forgery. But Hinton never did."
Among the mountain of papers and artefacts hoarded by Hinton and examined after his death was a tin containing a number of human teeth. These too had been stained. Gardiner arranged for a chemical analysis. It showed that the staining had been performed using another technique employed on some of the Piltdown material.
"I believe that Hinton was probably in cahoots with a friend of his at the museum, a chap called Michael Oldfield Thomas. I think the two of them together decided they would play this marvellous hoax on the rather upright Arthur Smith Woodward." They thought it would be a great joke to put together the jaw of an ape with the skull of a human. Acquiring an orang-utan skull would not have been a problem - JOldfield Thomas collected them.
By this reckoning, Dawson was not the perpetrator but one of the victims.
He hadn't the brains or the cunning to have done it himself, Gardiner says.
Chris Stringer, also of the Natural History Museum, doesn't buy this view. He still sees Dawson as the most likely culprit, though probably not working alone. "Dawson was there when most of the material was found, and if you don't involve him, you end up having to imagine that someone was going ahead, dropping stuff for him to find."
Dawson certainly had form as a faker of antiquities. "I think he was someone who was in it for the glory. He wanted to be a member of the Royal Society, and this was part of a strategy to achieve it."
Stringer finds it difficult to judge the significance of the material in Hinton's trunk. "He did have a long-standing interest in the way things became fossilised. So you could argue that some of it was his own experiments to find out how it happened. Or, if he did suspect Piltdown was a hoax, he might have been trying to replicate how it had been done.
"There is a view, which I've got some sympathy for, that Dawson wasn't expert enough. So you could bring in Hinton there, though we don't have a good link between him and Dawson."
Andy Currant, the museum's curator of Ice Age mammals, takes another view.
He thinks the forgery was an ingenious attempt to establish the validity of what are known as eoliths or "dawn stones". These were supposed to be the earliest of early man's stone tools. But the workmanship was crude, and sceptics claimed that any resemblance they bore to tools was due to chipping produced by natural processes. "Today we've forgotten about the eolith debate," Currant says. "But at that time it was the red-hot issue.
It divided the scientific community.
"Looking at the material, and thinking about what was going on at the time, it's my contention that creating what we call Piltdown man wasn't the original intention of the forger." The real purpose of the hoax, according to Currant, was to create evidence in support of eoliths. As he says: "It happened at a time when the debate about eoliths had gone rather badly for people who believed in them."
In the 1860s, there were suggestions that human-like animals might have been making flint artefacts as far back as the Miocene epoch, which began 25 million years ago. This was debunked to the satisfaction of most experts in the early years of the 19th century - but not to that of believers, Currant says. "Some of the people involved could well have gone over the top. Some of the amateurs involved were severely bonkers," he says.
The hoaxer's original intention, he thinks, was to create a site showing evidence of a primate-like animal that could have been making eoliths. But all the hoax created was a muddle. The evidence was found, as planned; but the interpretation was not the intended one because the jaw became associated with the skull. "Once the jaw and the skull were put together, everyone ignored the artefacts and the mammals."
Instead of being taken as evidence for the human origin of eoliths, the find was treated as the remains of a human ancestor. But who would have perpetrated the fraud?
"I can believe that Hinton might have been involved," Currant says. "But I can't really see him as the prime mover."
His candidate for this role is William Lewis Abbott, a jeweller from St Leonard's near Hastings. He had a large collection of fossils and human artefacts, and he had written extensively on them. Currant has read some of his correspondence. "He was a massively self-deluding and incredibly arrogant man, prone to saying and doing some very stupid things. And he believed passionately in eoliths. He was completely unbalanced. You read his correspondence and you think, 'what a nutter!'"
If Currant is right about Lewis Abbott, Piltdown would be what is known in police circles as "noble cause corruption": the planting of evidence to prove a case you sincerely believe to be watertight but cannot prove. As Currant observes: "Opinion sometimes goes against you when the evidence itself hasn't changed at all. This can be too frustrating for some people to deal with."
There is some circumstantial evidence to support the view. In a letter to the Morning Post , Lewis Abbott seems to be trying, almost desperately, to push the interpretation of the evidence in the direction he had intended.
"It was a nasty letter basically saying, 'You're all a bunch of idiots, I know far more than you do.'" Which, if he was indeed the forger, is scarcely less than the truth.
Anything else? "A man called Alfred Kennard, a quite famous mollusc worker, always said he knew who had perpetrated the hoax but would never tell anybody. He was a protege of Lewis Abbott and very loyal to him. Hinton was a close associate of Lewis Abbott and might have fed him material or even advised him. I cannot believe that Hinton didn't know what was going on."
Along with the Ripper saga, Piltdown has something in common with that other enduring mystery, the Loch Ness monster. Much as unequivocal proof of the existence of Nessie would spoil the thrill of the chase, so too with Piltdown.
Of course we all want to know who really did it and why... but, please, not just yet.
Piltdown is the subject of the Pfizer Annual Science Forum to be held at the Natural History Museum on November 25 at 7.30pm.