Prof Christopher Ramsey

Abstract:

This update on radiocarbon calibration results from the 19th International Radiocarbon Conference at Oxford in April 2006, and is essential reading for all archaeologists. The way radiocarbon dates and absolute dates relate to each other differs in three periods: back to 12 400 cal BP, radiocarbon dates can be calibrated with tree rings, and the calibration curve in this form should soon extend back to 18 000 cal BP. Between 12 400 and 26 000 cal BP, the calibration curves are based on marine records, and thus are only a best estimate of atmospheric concentrations. Beyond 26 000 cal BP, dates have to be based on comparison (rather than calibration) with a variety of records. Radical variations are thus possible in this period, a highly significant caveat for the dating of middle and lower Paleolithic art, artefacts and animal and human remains.

Abstract:

The question of the coexistence and potential interaction between the last Neanderthal and the earliest intrusive populations of anatomically modern humans in Europe has recently emerged as a topic of lively debate in the archaeological and anthropological literature. Here we report the results of radiocarbon accelerator dating for what has been reported as an interstratified sequence of late Neanderthal and early anatomically modern occupations at the French type-site of the Chatelperronian, the Grotte des Fées de Châtelperron, in east-central France. The radiocarbon measurements seem to provide the earliest secure dates for the presence of Aurignacian technology - and from this, we infer the presence of anatomically modern human populations - in France. © 2005 Nature Publishing Group.

Abstract:

Accelerator mass spectrometry (AMS) determinations of rat bones from natural and cultural sites in New Zealand have produced ages at odds with the accepted date for early human settlement by over 1000 yr. Since rats are a human commensal, this implies either an earlier visitation by people or problems with the reliability of the AMS determinations. One explanation for the extreme ages is dietary variation involving movement of depleted radiocarbon through dietary food chains to rats. To investigate this, we ¹⁴C dated fauna from the previously well-dated site of Shag River Mouth. The faunal remains were of species that consumed carbon derived from a variety of environments within the orbit of the site, including the estuary, river, land, and sea. The ¹⁴C results showed a wide range in age among estuarine and freshwater species. Terrestrial and marine organisms produced ages within expectations. We also found differences between bone dated using the Oxford ultra-filtration method and those treated using the filtered gelatin method. This implies that contamination could also be of greater importance than previously thought. © 2005 by the Arizona Board of Regents on behalf of the University of Arizona.

Abstract:

Radiocarbon dating of individual samples only yields limited chronological precision (typically of the order of 150–200 years for 95% confidence). This is in large part due to the complex nature of the calibration curve. Only by using large numbers of radiocarbon determinations together can we hope to resolve chronological issues at the sub-century level. Interpretation of such datasets is very difficult to do accurately by eye and for this reason statistical methods are needed. The methods most often employed are those of Bayesian analysis. Such methods do indeed allow us to improve our precision beyond that which is possible for single age determinations by radiocarbon but, critically, they also allow us to see the limitations in our data. In cases where statistical analysis shows that the radiocarbon measurements cannot resolve the chronological issues we need to accept that we must rely on other forms of archaeological information and interpretation. The conference at Yarnton was very closely focussed on specific chronological issues in the Iron Age of the Levant. These issues are of critical importance to the understanding of the interrelationship of the polities of the region and would be of academic interest in any other region under archaeological investigation. However, in this case the arguments are given even more prominence because of the implications for our interpretation of the nature of King Solomon's political impact.