Collagen, properly extracted, avoids most of these problems because it is a large structural protein whose molecular bonds are resistant to exchange with environmental carbonate.

The collagen does not exchange its carbon atoms with passing groundwater in the way that bone mineral does.

Its carbon, once incorporated during the organism’s life, stays fixed in the protein’s amino acid sequence.

This is why the XAD-purified collagen date is more reliable than either the mineral fraction or the osteocalcin fraction for Arlington Springs.

Osteocalcin, as a small protein, is more vulnerable to contamination by humic acids and other environmental organic matter than collagen.

The mineral fraction is subject to carbonate exchange.