The Koněprusy Caves sit in the Bohemian Karst, a protected limestone landscape about thirty kilometers southwest of Prague.

The karst is riddled with underground systems, many of them still being explored and mapped.

The caves themselves are among the largest in the Czech Republic — passages stretching hundreds of meters, vast chambers adorned with stalactites and stalagmites, and in certain deep sections, the preserved remains of creatures that walked the earth during the last ice age.

Limestone karst landscapes are extraordinary time capsules.

The chemistry of the rock and the hydrology of underground systems create conditions that can preserve organic material — bone, pollen, even DNA — for far longer than most surface environments would allow.

Over hundreds of thousands of years, sediment accumulates in cave passages, capturing whatever organic material was present at each level.

Bones sink into sediment and stay there, gradually mineralized, gradually incorporated into the geological record of the cave system.

In 1950, during excavations connected to a quarrying operation in the Bohemian Karst, human skeletal material was uncovered.

The remains were fragmentary.

A skull in pieces.

Some additional bones.

The site was not ideal for preservation of stratigraphic context — the geological disturbances of karst terrain, combined with the disruption of the quarrying work, meant that pinning down the exact depositional history of the material would prove difficult.

The workers who found the bones recognized them as human.

The question of how old they were would take decades to answer.