With the contamination problem addressed and the authenticity of the collagen confirmed, the AMS measurement itself was made on a tiny fraction of the purified material — just a few milligrams of carbon, converted to carbon dioxide and then to graphite, and measured in the particle accelerator.

The result: 10,960 ± 80 radiocarbon years before present.

This date, calibrated to calendar years, places the Arlington Springs individual at approximately 12,710 to 13,010 calendar years before present — the terminal Pleistocene, as the geological context independently confirmed.

The Sex Assessment — A Long And Careful Revision

There is a chapter of the Arlington Springs story that has sometimes been reported in sensationalized terms — as a dramatic revelation that “he was actually a she” — but which is more accurately understood as a lesson in the difficulty of biological sex assessment from fragmentary remains, and in how science revises its conclusions as evidence accumulates.

Phil Orr, when he found the femora in 1959 and published his account in 1962, called the remains those of a man.