The people who were in eastern Beringia 24,000 years ago were not doing something unusual for their time — they were doing exactly what modern human populations were doing everywhere in the cold northern latitudes during this period.

The Radiocarbon Calibration Story

The process of converting the raw radiocarbon date from the Bluefish Caves horse mandible into a calibrated calendar age — the approximately 24,000 calibrated years BP figure — involves a calibration curve that has a specific history and that carries specific uncertainties that are worth describing in more detail.

The IntCal calibration dataset — the standard reference for converting radiocarbon years to calendar years in the Northern Hemisphere — is maintained by an international consortium of researchers who compile measurements from a variety of independently dated sources.

The most important source is tree rings, which provide a continuous, year-by-year record of atmospheric radiocarbon going back more than 14,000 years.