It also has a different relationship with contaminating materials.

The problem that emerged when both proteins were dated from the Arlington Springs bone was striking: the ages disagreed.

By thousands of years.

The osteocalcin date, extracted using formic acid, came in at 6,610 ± 60 radiocarbon years BP.

The collagen date, extracted using XAD purification — a more refined chemical method that removes contaminants more thoroughly — came in at 10,960 ± 80 radiocarbon years BP.

Two different proteins from the same bones, dated by the same method, producing results that differed by more than four thousand radiocarbon years.