Castlepook’s Uncertain Visitors
Radiocarbon dates are normally expressed in years before AD 1950 and must be calibrated against independently dated records of past atmospheric carbon. Calibration produces ranges rather than a single exact historical year, and the uncertainties become especially important this far back. The modern IntCal20 calibration curve reaches to 55,000 calibrated years before present, but it does not convert an Ice Age bone into evidence for activity in one numbered BCE year. The numerical date in this article should thus be read as an approximate pointer within a much longer span.