Arlington Springs, with its terminal Pleistocene island bones, was a contribution to this post-Clovis environment: evidence from a specific place and time that coastal presence was a reality by 13,000 years ago, even if it could not specify what route was taken to get there.

The Radiocarbon Calibration — Understanding The Curve

The conversion of the Arlington Springs radiocarbon age to calendar years is worth examining in more detail, because the calibration curve for the terminal Pleistocene has its own interesting history and its uncertainties have sometimes been underappreciated.

The IntCal calibration curves — the internationally recognized standards for converting radiocarbon ages to calendar ages — are regularly updated as new data are incorporated.

The curves available when the Arlington Springs revision was published in the early 2000s were less precise in the terminal Pleistocene than later versions, because the tree-ring record that provides the most reliable calibration data did not extend back 13,000 years, and calibration for that period relied more heavily on other materials with larger age uncertainties.