Tens of thousands of years of mammoths, horses, and other Ice Age animals have been found in remarkably complete condition in permafrost deposits — flesh, hair, skin, and internal organs preserved by the continuous freezing in conditions that prevented the bacterial and chemical decomposition that would normally destroy such material within years.

The permafrost of the Yukon and Alaska has yielded specimens of Ice Age animals that are, in biological terms, more complete than the mummified animals of ancient Egypt.

The preservation at Bluefish Caves is not as dramatic as the full-body mummification seen in some permafrost specimens — the caves are not continuously permafrost-frozen throughout their extent, and the bone preservation reflects the variable thermal history of the cave sediments rather than the constant deep-freeze of true permafrost.

But the cold conditions have been sufficient to preserve the collagen in the bones — the protein that is the source of the carbon used for AMS dating — and to maintain the surface texture of the bones well enough to allow taphonomic analysis of the modification marks.