The Doneraile Femur
Radiocarbon dating does not translate automatically into a calendar year. A laboratory measures remaining carbon-14 in organic material and produces an age in radiocarbon years before present, where “present” conventionally means 1950. That result must then be calibrated against records of past atmospheric carbon-14. At this antiquity calibration produces ranges, sometimes broad or irregular ones, rather than an annual date. The internationally used IntCal20 curve extends to 55,000 calibrated years before present, but its older section necessarily combines several kinds of environmental archive and retains uncertainty.