Relative Dating of the Piltdown Skull1
Kenneth P. Oakley
Advancement of Science 1950
 In a paper read before Section H in September 1947 attention was called to the analyttical work on fossil bones by Carnot, which had shown that their fluorine content increases with geological age. This conclusion had generally been regarded as having no practical importance, for owing to the wide variation in the relative abundance of this element at different localities it would obviously be impossible to ascribe a geological date to a particular fossil bone merely by determining its fluorine content. However, it was suggested that as a means of differentiating bones of various ages occurring mixed together at a single site fluorinc analysis might be helpful.
: An investigation carried out by Dr. H. J. Twalls in the Home Office S.W. Science Laboratory showed that there is nothing to be gained by using a spectrographic method to determine the rough order of magnitude of fluorine in bone samples. Recourse must be made to a chemical method of estimation. In 1948 the Department of the Government Chemist agreed to collaborate with the Department of Geology, British Museum in exploring further the possible applications of fluorine analysis of bone. Mr. R. H. Settle, Dr. C. R. Hoskins and Mr. E. C. W. Maycock in the Government Laboratory undertook the determination of fluorine in a series of small bone and tooth samples selected by the author. The results obtained have shown that this is a useful means of establishing the relative antiquity of bones at particular sites.
The application of this method to the Galley Hill Skeleton was described to a meeting of Section H in September 1948. A full report has since been published in Bulletin of the British Museum (Nat. Hist.), Geology I, no. 2 (1949). Briefly, it was shown that indigenous fossil bones in the Middle Pleistocene gravels at Swanscombe contain around 2 per cent. fluorine, those from Upper Pleistocene deposits in the same region around 1 percent., and post-Pleistocene bones 0. 05-0.3 per cent; the Galley Hill Skeleton although found in Middle Pleistocene gravels proved to contain about 0.3 per cent. fluorine, and were therefor clearly an intrusive burial. The Swanscombe Skull on the other hand showed the expected 2 per cent. fluorine.
The investigation has now been extended to the famous fossil remains from Piltdown near Fletching, Sussex. The analyses in this case were carried out by Dr. C. R. Hoskins.
The Piltdown gravel has yielded fossil bones and teeth of several ages. The oldest group, which includes Mastodon arocrnensis and Elephas ['Stegodon'] cf. planifrons, is of Villafranchian age, formerly classed as Pliocene but now regarded as Lower Pleistocene. The later types represented in the gravel, such as Cerous elaphu s and Castor fiber, are of Middle or Upper Pleistocene ageindeed it is possible that this post-Villafranchian material represents more than one period, for the gravels have evidently been repeatedly re-arranged.
Whether the bones and teeth referred to Eoanthropus dawsoni, or 'Piltdown Man,' belong to the older or to the younger group has been a matter of controversy since they were first described. Dawson and Smith Woodward considered that Eoanthropus was approximately contemporary with the later group of animal remains, which they called 'early Pleistocene' in contradistinction to the older group which they recognised as 'Pliocene.' E. T. Newton and Sir Arthur Keith regarded Eoanthropus as more probably of the latter age. Similarly Dr. A. T. Hopwood after re-examining all the evidence in 1935 placed it with the Red Crag or Villafranchian group (which, however, he classed as Lower Pleistocene). Mr. A. T. Marston, who considers that the Piltdown mandible and canine tooth are anthropoid, has been inclined to refer these elements to the Lower Pleistocene (i.e. Pliocene of older authors), and the typically human cranial fragments to the Upper Pleistocene.
The fluorine content of every available bone and tooth from Piltdown has now been tested by Dr. C. R. Hoskins in the Government Laboratory. All those of undoubted Lower Pleistocene (Villafranchian) age proved to contain 2-3 per cent. fluorine, while all those which are certainly of later date showed less than 1 6 per cent. fluorine. The Eoanthropus material, including all the cranial fragments, the mandible, the isolated canine tooth, and the remains of the second  skull found 2 miles away, showed extremely little fluorine (average 0 2 per cent.).
It is evident that fluorine has been deficient in the environment since the Piltdown gravels were accumulated, but the fluorine test has shown conclusively that all the specimens referred to Eoanthropus are contemporary, and that their age is not Lower Pleistocene, but considerably later. In fact, they evidently belong to a period immediately preceeding the final re-arrangement of the deposit. From the palaeontological data alone it is not possible to decide whether this took place during Middle or Upper Pleistocene times.
Clement Reid pointed out that the gravels appeared to rest on a low plateau surface (100-120 ft. above O.D.) which was extensively developed in the Weald, but which was nowhere covered by marine deposits of the period of the submergence represented by the Goodwood raised beach (135 ft. above O.D.). It therefore seems unlikely that this surface existed before the phase of base Ievelling which followed the great interglacial period. Viewed as a terrace deposit of the River Ouse, the Piltdown gravel would have to be classed as belonging to the Taplow group (Edmunds 1926). From the temperate character of even the latest faunal elements in the Piltdown faunal melange, it is probable that Eoanthropus lived under interglacial conditions, although the final re-sorting of the gravels may have been brought about in solifluxion. Provisionally Eoanthropus may be referred tothe last interglacial period (the Wùrm).
The results of the fluorine test have considerably increased the probability that the andible and cranium represent a single creature. The relatively late dae 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 this case the peculiarities of the mandible and the excessive thickness of the cranium might well be interpreted as secondary or gernontic developments.
Dayson, C. and Woodward, A. S., 1013: Quart. J. Geol. Soc. London, 69, 124
Edmunds, F. H., 1926: In 'Geology of the County near Lewes,' Mem.Geol. Surv. (N.S. 319), 6 8.
Hopwood, A. T., 1935: Proc. Geol. Assoc. London 46, 47.
Keith, A., 1925: The Antiquity of Man, Vol. II, 508.
Marston, A. T., 1946: Geol. Assoc. London, Circular No. 483, 1, and MS>
Newton, E.T., 1913: In Dawson and Woodward, ibid., 151.
Oakley, K. P., 1948: Adancement of Science , 4, 336-337.
Oakley, K. P. and Montague, M.F.A., 1949: Bull. Brit. Mus. (Nat. Hist.), Geol., 1, 2.
Reid, C., 1913: In Dawson and Woodward, ibid., 149.
1 Substance of a paper read to the Section of Anthropology and Archaeology, at Newcastle, on September 5, 1949. A fuller account of this work will be sent to Nature early in 1950.
Summary of a Note on the Piltdown Skulls 1
Received from Dr. Robert Broom, F.R.S.
During his visit to England in the Spring of 1949 the author took the opportunity of re-examining the remains of the two skulls attributed to Piltdown Man (Eoanthropus). He found that the British Museum also possesses parts of a third fossil human skull found by Charles Dawson in Pleistocene gravel at Barcombe Mills near Piltdown. This has not yet been described, but would probably be worth detailed comparison with the two previously known Piltdown skulls and the Swanscombe skull. The material comprises a large frontal bone (intertemporal measurement 102 mm., interorbital width 28 5 mm.), two malar bones and a slightly worn molar. This tooth (probably M3) shows two marked outer cusps, and two inner, but no distinctly developed 5th cusp. This tootb is not at all anthropoid, nor is it quite typical of modern man.
The author now has scarcely any doubt that the Piltdown mandible belongs to that same individual as the associated brain-case. He considers that Eoanthropus was a big-brained type of man which evolved on a quits different line from true Homo. The 'simian shelf' in the lower jaw is probably not an indication of close affinity with the anth~ poids, but a specialisation due to evolution parallel with that of the modern apes, just as the large brain of this type of man may have been a parallel development to what is found in the Homo lne.:
1 Read by Dr. K. P. Oakley to the Section of Anthropology and Archaeology, at Newcastle, on September 5,