What Pitulko found in 2001, and what his team excavated over the following years, was one of the most extraordinary archaeological sites in the world.

The cultural layer — the stratum of sediment that contains the evidence of human activity — was buried under about nine to ten meters of frozen ground.

That frozen covering, combined with the permafrost that permeates the entire sediment column of the site, is what preserved the evidence so astonishingly well.

The cold had acted as a deep-freeze for three decades of millennia.

Organic materials that would have rotted away in warmer climates had survived in the permafrost: ivory, antler, bone, wood — all of it intact.