At a meeting of the Geologists Association in 1947, Alvan T. Marston delivered a paper on the Piltdown mandible and canine tooth, both of which he described as pure ape. During the ensuing discussion, Kenneth Oakley, of the British Museum of Natural History's Geology Department, suggested that it might be feasible to subject the Piltdown fossils to a test for fluorine content. This test would be the undoing of Piltdown Man.
Fluorine had first been detected in teeth in 1802. By 1844, it was known that teeth and bones absorbed the element from an environment that had it. Absorption of fluorine changes the phosphate hydroxy-apatite (the main component of teeth and bones) to fluorapatite. The test can't determine an absolute date, but can reveal whether two relics in the same fluorine-rich environment have been there for the same amount of time. If two or more pieces from the same site were to contain radically different amounts of fluorine, that would mean that they had arrived there at different times. If they show the same amount, then they could have been deposited together.
The femur, skullcap, and tooth from Java checked out as having the same amount of fluorine, which was not inconsistent with the thesis that they had all come from the same possessor. Applied to Galley Hill, the test showed that the skeleton contained the same amount of fluorine (0.3 percent) as post-Pleistocene fossils, and had not, therefore, been a Pleistocene burial. The Swanscombe skull and accompanying Elephas relies had absorbed the same amount of fluorine (2 percent) since they had come to rest on the Thames bank in the middle of the Pleistocene. The test knocked out the antiquity of hominid fossils from Bury St. Edmunds, Dartford, Baker's Hole, and London.
In September 1948, the British Museum's Department of Geology gave permission for Oakley and his associates to drill into Piltdown Man.  This wasn't as much of a desecration as drilling into the Crown Jewels, but the fossils had been protected from German bombs during two wars, from being molested by inquisitive scientists for forty years, and even from the public, who viewed not the fossils themselves, but casts.
The drill bit into the mammalian fossils. The pit was shown to have contained populations from different ages: the older, Lower Pleistocene, or Villafranchian, was represented by the mastodon and elephas fossils (2-3 percent fluorine); the more recent, Middle or Upper Pleistocene, by deer and beaver fossils (less than 1.6 percent). It bit into Eoanthropus, cranium and jaw. Eoanthropus checked in at 0.2 percent.
Piltdown Man was thus deposed as the earliest Englishman, genealogical priority going to Marston's Swanscombe Man. But the conclusion that the cranial and jaw fragments had about the same amount of fluorine in them suggested that all the parts had slept in the pit through the same long night, absorbing fluorine at the same rate. This result did not coerce the conclusion that the two parts had belonged to one individual, but it did not deny that. Oakley wrote in January 1949:
The results of the fluorine test have considerably increased the probability that the mandible and cranium represent a single creature. The relatively late date indicated by the summary of evidence suggests moreover that "Piltdown Man," far from being an early primitive type, may have been a late specialised hominid which evolved in comparative isolation.
In a collaborative paper that year, Oakley and C. Randall Hoskins again gave heart to Piltdown fans: the cranial and jaw fragments could well have come from the same individual. Pleased with the settling of one of the big Piltdown problems, the age of Eoanthropus, Marston remained dissatisfied with the conclusions about the other big problem, the unity of Eoanthropus. Piltdown Man still hung tenaciously onto both his head and his jaw. In June 1949, Marston read a paper, "On Piltdown Man" to the Royal Anthropological Institute; the paper was incorporated into an article, "The Relative Ages of the Swanscombe and Piltdown Skulls, with Special Reference to the Results of the Fluorine Estimation Test," published a year later (Marston, 1950). He went over the history of the finds, anatomical and geological difficulties, the growing skepticism about Piltdown Man's authenticity, still arguing
It is evident that many mistakes have been made concerning Piltdown Man-many mistakes by many highly qualified and highly placed men. To err is human and none of these men have been divine.
 The British Museum of Natural History continued to display Piltdown Man as though he were one being. In September 1949, Kenneth Oakley read a note to an anthropological meeting at Newcastle; this note, from Robert Broom, the famous finder of australopithecine remains, stated Broom's conviction that the canine tooth "is not at all anthropoid. The author now has scarcely any doubt that the Piltdown mandible belongs to the same individual as the associated brain case." As for the simian shelf, Broom thought that a specialization due to parallel evolution.
Vallois and Movius were compiling their Catalogue des Hommes Fossiles. Oakley wrote the section on "Royaume-Uni" fossil remains. For the Piltdown fossils, he listed the bones; dated them as contemporary with deer and beaver fossils; and noted that Site II was probably Sheffield Park. He rejected any validity to the conjecture (which Weinert among others had offered) that the bones from Site II had belonged to the skull from Site I, that possibility being to Oakley "infinitely remote." He also gave an inventory of the various taxonomies proposed for Eoanthropus: those who thought that skull and jaw belonged together called the whole thing Eoanthropus dawsoni, though Kleinschmidt had in 1922 recommended Homo sapiens dawsoni,. (2) those who separated the two gave different labels to cranium (Miller, Eoanthropus dawsoni, Marston, Homo sapiens) and to jaw (Miller, Pan vetus; Friederichs, Boreopithecus dawsoni, and we could add Boule's Troglodytes dawsont). This exuberance of taxonomic labeling reflects a good deal of uncertainty about what any of it was.
The Catalogue, with Oakley's tacit acceptance of Piltdown Man as authentic, was published in 1952. At a Wenner-Gren International Symposium in June 1952, Oakley told his colleagues that Piltdown Man had lived not a million years ago, as Osborn had estimated; not even 200,000 years ago, Keith's estimate; but only about 50,000 years ago. But Eoanthropus had lived. To the American anthropologist Ruth Moore, the test proved that "there has been no miracle mixing of bones.... Oakley emphasizes that it is still possible that the remains represent two creatures, though this does not now seem likely" (Moore, 1953). Hans Weinert found support for his theory: that the two parts belong together, the lower jaw as hominid as the cranium, but an atavistic structure.
Oakley's continued defense of Piltdown Man's integrity and rationalizations like Weinert's atavistic jaw and Broom's convergency of shelf strut failed to discourage the skeptics. At a 1950 talk to the Oxford University Anthropological Society (Daniel, 1983), Oakley described his test and its  results. In the audience sat J. S. Weiner, of the Department of Anatomy of Oxford University. The two met each other for the first time and discussed the Piltdown problem. Later, Wilfred Le Gros Clark, a colleague of Weiner in the Department of Anatomy, discussed it with Oakley. Weiner had his doubts about the accuracy of the first test-based on small samples, it could not detect minute differences in fluorine content.
Ashley Montagu's contribution (Montagu, 1951) severed cranium and jaw. Marston returned to the fight with his 1952 "Why the Piltdown Canine Tooth and Mandible Could Not Belong to Piltdown Man." As 1953 approached, at an international congress held in London, no one read any papers on Piltdown Man. He was welcomed with a degree of hospitality not seen since Banquo's ghost came to dine.
JUST A MISTAKE
The team of Weiner, Oakley, and Le Gros Clark went to work refining and reapplying the fluorine test. Here are the results:
|Piltdown pit fluorine content|