That a person stood in this cave and butchered a reindeer at some point during the Old Stone Age is, on its face, an extraordinary thing to sit with.

The bones were identified from an assemblage of faunal material recovered at Castlepook Cave, and the cut marks are the critical detail. In zooarchaeology, cut marks on bone are direct evidence of human activity, typically from butchering or hide removal using stone tools, and they distinguish deliberate human presence from, say, the accumulated debris of a predator's den. The Palaeolithic in Ireland is a period about which almost nothing was known until relatively recently; the island's acidic soils destroy organic material with uncommon efficiency, and the repeated glaciations of the last ice age scoured away much of what might otherwise have survived. Caves, by contrast, can preserve bone over vast timescales. The evidence from Castlepook places human or human-adjacent activity in Ireland at a point when reindeer, now long absent from the island, still roamed a landscape that would have looked nothing like the one we know.