The darkness prevents the UV-driven oxidation that damages organic molecules.

The ice itself seals the material from the air.

The result, if the ice remains stable, is a kind of natural deep freeze that can preserve not just bone but soft tissue, hair, clothing, and even stomach contents for centuries or, under the right conditions, for millennia.

The glacier at Tatshenshini-Alsek had apparently done exactly this.

The man who was found by the hunters in 1999 had been preserved in the ice for what would later be estimated to be somewhere between approximately 300 and 550 years, with different materials and different dating methods producing different results within this general range.

He had died, for reasons that remain unknown, in or near the glacier, and the ice had taken him in and kept him in a state of preservation that no burial in soil or cave sediment in this environment could have matched.