The Irish Sea Threshold
Archived: 15 September 2026
31,675 BCE is a modern label, not a datable Irish event, representing late Pleistocene Marine Isotope Stage 3 as the British–Irish Ice Sheet began sustained growth. Ireland contained ice-free tundra, wetlands and freshwater habitats, preserved beneath glacial deposits at Derryvree and Greenagho. Castlepook Cave's imperfect bone assemblage records reindeer, mammoth, giant deer and predators, indicating an ecologically active landscape. A cut-marked reindeer femur may signal Ireland's earliest human activity, but cannot prove settlement, culture or continuity. Glacial erosion, uncertain radiocarbon dates and changing sea geography limit conclusions. The period is an environmental threshold, illuminated by fragmentary evidence rather than events.