CARBON-14 141 FIG. 5 (far left): Calibration curve (blue) and interval of calibrated dates (grey peak). Radiocarbon age: 730 ± 20 BP. Calibrated dates: AD 1260– 1290 AD (95.4% probability). FIG. 6 (near left): Calibration curve (blue) and interval of calibrated dates (grey peak). Radiocarbon age: 190 ± 20 BP. Calibrated dates: AD 1661– 1684 (20.4% probability); AD 1735–1806 (54.0% probability); AD 1930– 1954 (21.0% probability). FIG. 7: Standing figure. Tellem, Mali. Wood, ritual surface. H: 47.5 cm. Courtesy of Galerie Alain Bovis. FIG. 8: Mask. Kwele, Gabon. Wood, pigment. H: 30.5 cm. Private collection. Reproduced by kind permission of Didier Claes, Brussels. This example illustrates the limitations of carbon-14 testing for dating art in general and for tribal art in particular. The scientific analyses cannot be considered conclusive but instead represent a complement to the research done by art historians and dealers. It can be thought of as technical assistance or scientific support. It is not the calculation of probabilities alone that points to the most likely interval but rather an exchange with art professionals that allows for the identification of one interval as being more credible than another. BEFORE OR AFTER 1954 Carbon-14 allows for definitive determination of whether the tested material existed before or after 1954. This artificial “cutoff” line is man-made. The atomic bombs over Nagasaki and Hiroshima, and especially the extensive nuclear testing that ensued in the 1950s, resulted in a near doubling of the amount of carbon-14 in the atmosphere. In recent objects, that is to say objects made after 1954, one finds abnormally elevated concentrations of carbon-14, at levels higher than ever before in history. Since the halt of nuclear testing in the atmosphere, which took place in the early 1960s, the diminution of the amount of carbon-14 has been very regular. This has made it possible to date recent materials very precisely, with an error margin of only one to two years, and this has made the method useful for dating wine, among other things.
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