Mammoth Cave’s Reindeer Passage
The apparent precision of 31,821 BCE must therefore not be mistaken for a precise archaeological moment. Radiocarbon determinations measure radiocarbon years before present, conventionally before 1950, and must be calibrated against changing atmospheric carbon levels to create calendar-age estimates. At great age the calibrated intervals can be wide, and old cave collections introduce further problems: bones may have been moved by animals, water, earlier excavation or later disturbance; material from different episodes can lie close together; and improved preparation techniques have revised some earlier Irish results substantially. The current IntCal20 calibration curve is especially important for the last glacial period, where revisions can alter calendar placement materially.