Solution for the Sherborne problem
Sir — Since its discovery in quarry debris near Sherborne, Dorset1, the "Sherborne bone" has been the subject of debate, much of it in this journal (for example, refs 2, 3). We have re-studied this artefact, using optical microscopic analyses with image processing and a chemical and mineral textural study, followed by sampling for radiocarbon accelerator dating, to attempt to settle its authenticity once and for all.
This bone, a fragment of mammalian rib, had been engraved with the head and forequarters of a horse, and its resemblance to a Palaeolithic depiction from Creswell Crags, illustrated by Boyd Dawkins4, was used as evidence both for and against its authenticity. More recent exchanges (for example, refs 5, 6) have supported or opposed the authenticity of the engraving as Palaeolithic, while Oakley, in Farrar5, reported relative dating analyses which indicated that the bone itself was fossilized.
Engraved surface and obverse (showing dating sample location) of the Sherborne bone. Photographs by F. d'Errico.
Our analysis of the obverse of the fragment revealed that the spongy bone is still filled with sediment. Micro-roots present in the sediment are trapped in the trabecule of the spongy bone. The sediment and roots are the residue of the original filling adhering to the bone when it was buried and are not the result of fraudulent additions to age a fresh bone artificially. Microanalysis by energy-dispersive X-ray spectrometry, and elemental mapping of the sediment filling the spongy bone and of that still adhering to the engraved side, showed them to be of similar composition, suggesting that the engraved side was also not artificially patinated. The patina covering the bone is therefore the result of the burial environment of the bone fragment.
Analysis of the engraving, however, revealed that almost all the engraved lines are sediment-free and do not show the same patina as the remaining surface of the bone. This is confirmed by optical analysis indicating that engraved lines have gray-value histograms that are different from those obtained from unengraved areas, but similar to those of recently damaged surfaces. Sediment residue also covers eroded areas, suggesting that alteration of the bone surface took place before its engraving.
The engraved lines reveal none of the features that are generally visible on experimental lines produced by lithic tools on fresh bone7, such as sharp edges and multiple parallel striae. In contrast, the engraved surface of the Sherborne bone displays a granular, rough texture, and fractures perpendicular to the groove direction. The edges of the main grooves are frayed by continuous microflaking of the surface lamellae, clearly showing that the engraving took place on an already weathered bone.
Samples for radiocarbon dating were taken from the uncleaned and non-engraved obverse of the rib. The surface was mechanically cleaned and a small quantity (250 mg) of bone removed by drilling. After chemical pretreatment8 and combustion9, the sample yielded an accelerator age (OxA 5239) of 610 ± 45 years, indicating (after calibration10) that the rib had come from an animal that had died some time between the end of the 13th and the start of the 15th centuries ad. It is not possible to say when, after this date, the engraving was carried out, but it now seems inescapable that the Sherborne engraving is a recent fake. It is even possible that the horse head was traced by a metal tool, as no proof of the use of a flint point, such as the presence of minute striations accompanying the main groove7, was found. Oakley's determination that the rib was "fossilized"5 can be attributed to the known limitations of relative dating techniques11.
C. B. Stringer
Department of Palaeontology, The Natural History Museum, London SW7 5BD, UK
Institut du Quaternaire, 33405 Talence, France
C. T. Williams Department of Mineralogy, The Natural History Museum, London SW7 5BD, UK
Department of Archaeology, University of Glasgow, Glasgow G12 8QQ, UK
Radiocarbon Accelerator Unit, Oxford 0X1 3QJ, UK
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