Greenagho’s Buried Lake – Emerald Archives

Dateline

“31,666 BCE” is a useful modern label, not a date that can be matched to a recorded Irish event. No written calendar, named community, ruler or securely dated human settlement allows history to be told year by year at this depth of time. The responsible approach is to place the notional year within the later part of Marine Isotope Stage 3, an unstable phase of the last Ice Age. Radiocarbon results must be calibrated, and their ranges are often measured in centuries or millennia rather than single years. On that basis, this date falls within a period when parts of Ireland were probably still open to plants and animals, even as major expansion of the British–Irish Ice Sheet was approaching.

A Landscape Before the Maximum Ice

The crucial evidence comes not from a settlement but from sediment buried beneath later glacial deposits. At Derryvree, near Maguiresbridge in County Fermanagh, road works exposed freshwater silts and fine sands trapped between two layers of till. The organic material within them produced a radiocarbon determination of 30,500 ± 1,100 radiocarbon years BP. Calibrated estimates cited in later glacial reconstructions place the deposit broadly between about 36,900 and 31,700 calendar years BP. That wide range embraces a notional date of 31,666 BCE, but it does not identify a particular season, year or even human generation.

The Derryvree deposits demonstrate something important: north-central Ireland had not yet been continuously overwhelmed by the later ice sheet. Freshwater sediments, plant remains and small animal evidence accumulated in a local wetland or shallow-water setting before advancing ice covered and preserved them. The very survival of this archive is exceptional. Subsequent glaciers scoured much of Ireland’s older surface record away, while caves, sheltered hollows and sediments sealed beneath till retained rare fragments of the earlier world.

Greenagho, also in County Fermanagh, supplies a related clue. Organic lake deposits beneath till there have yielded an age of 32,500 ± 300 radiocarbon years BP, calibrated broadly to around 37,200–35,700 calendar years BP. The precise relationship between these sites, climatic phases and ice advances remains debated, but together they show that inland water, vegetation and ice-free ground existed in this part of Ireland during the middle to later last glacial cycle. They do not show that the whole island was hospitable at once. Conditions varied sharply by region, altitude, season and proximity to ice.

Cold Wetlands and Open Ground

The flora recorded at Derryvree is the basis for a cautious reconstruction of its environment. Fossil remains include plants associated with cold, open and wet ground: sedges, mosses, dwarf willow, mountain avens and bogbean. These species do not recreate a single uniform scene. Rather, they indicate a mosaic of damp hollows, shallow pools, mineral-rich marshes and exposed ground under a cold climate. Trees were absent or extremely scarce locally. This was not the later, familiar Ireland of oak woodland, blanket bog and enclosed fields, but a treeless periglacial landscape shaped by frost, wind, seasonal thaw and changing water levels.

Such ground could nevertheless be productive. Short growing seasons can sustain sedges, herbs and low shrubs; watercourses and wetlands create distinct ecological niches; and sheltered limestone districts may have offered cover unavailable on exposed uplands. The words “tundra” and “mammoth steppe” are useful broad comparisons, but neither should be treated as a complete map of Ireland in this period. The evidence is site-specific, and climate shifted repeatedly across the North Atlantic world. An interval favourable to plants and grazing animals could be followed, in geological terms rapidly, by renewed cold and encroaching ice.

At the scale of the island, the approaching transformation mattered more than any local continuity. New reconstructions of the British–Irish Ice Sheet suggest major growth in its northern sectors around 32,000–31,000 years ago. The ultimate maximum came later, around 27,000 years ago, but its build-up was already remaking routes, drainage systems and habitats. Around the notional year considered here, Ireland was therefore not simply “before the Ice Age”: it was already deep within an Ice Age, in a landscape where ice margins and ice-free refuges could alter dramatically.

Castlepook’s Animal World

County Cork provides the richest, though complicated, glimpse of larger animals in Ireland during this broad period. Castlepook Cave near Doneraile, long known as Mammoth Cave, was excavated in the early twentieth century by Richard Ussher and colleagues. Its collections include remains attributed to woolly mammoth, reindeer, giant deer, spotted hyaena, brown bear, wolf, fox, Arctic fox, mountain hare and lemmings. A mammoth bone formerly dated to about 33,500 radiocarbon years BP and later reassessment of faunal dates place significant elements of the cave record in Marine Isotope Stage 3, before the Last Glacial Maximum.

This assemblage is evidence that an Ice Age fauna reached or lived in southern Ireland at various times. It does not prove that every listed animal shared the same valley in the same century. Castle deposits accumulated through natural processes: animals died or were dragged in, carnivores used chambers, water moved sediment, and excavators working more than a century ago could not recover modern standards of stratigraphic information. Individual fossils have also been re-dated as laboratory methods improved. The cave is best understood as a long, disturbed archive rather than a snapshot.

Even so, the animal record suggests food webs more varied than Ireland’s modern terrestrial fauna. Reindeer could have exploited open grazing, while giant deer browsed or grazed where vegetation permitted. Hyaenas and wolves were predators and scavengers; bears may have used caves as dens or winter refuges. Mammoths imply access, at least intermittently, to extensive open habitats with enough forage for very large herbivores. The missing evidence matters too: not every mainland European Ice Age species is securely known from Ireland. Faunal movement depended on changing sea levels, ice barriers, coastal plains and passages through Britain, not on a permanently available land bridge.

The Human Question

The most arresting possible human evidence is also the most limited. A reindeer femur from Castlepook, recovered from old collections, has been reported as roughly 33,000 years old and bears a deep mark interpreted by zoologist Ruth Carden as the product of a sharp stone tool used in carcass processing. If that diagnosis and association are sustained, it would indicate that Upper Palaeolithic people reached Ireland during this general phase of the last glacial cycle and handled a reindeer here.

That is not the same as evidence for an Irish population. No securely associated hearth, stone-tool assemblage, shelter floor, burial, repeated camp or settlement of comparable age has been excavated at Castlepook. The date obtained from bone measures the animal’s death, not automatically the moment of cutting; the bone’s recovery from a historically excavated cave makes its original context especially difficult to reconstruct. Nor can one mark establish whether people stayed for hours, days or seasons. The interpretation is important precisely because it is testable: new excavation, microscopic study of surface modification, direct dating and securely stratified finds may clarify it.

It is reasonable to say that small, mobile hunter-gatherer groups were present elsewhere in north-west Europe at this time, equipped with stone technologies and capable of exploiting large animals. It is not reasonable to project their particular languages, identities, ritual practices, art or social organisation into Ireland without Irish evidence. The Castlepook femur permits a narrow economic inference only: if its incision is genuinely anthropogenic, someone understood the practical value of a reindeer carcass—meat, hide, sinew, marrow or bone. It cannot yet support claims of trade, regular diplomacy, territorial polities or a continuous colonisation.

No Kingdoms, No Monuments

Political affairs, warfare and diplomacy leave no identifiable Irish record for 31,666 BCE. There were no states, kingdoms, towns, farms, churches, monuments or writing systems from which to reconstruct institutions. Nor is there evidence for long-distance exchange involving Ireland at this point. The distant Atlantic façade was instead a shifting ecological frontier, its routes altered by low sea levels, cold seas and advancing ice. Any human visitors, if present, would have moved through landscapes and connections very unlike the later island world.

Religion, culture and learning are equally beyond recovery in specifically Irish terms. Upper Palaeolithic communities in continental Europe made art, ornaments and sophisticated tools, but no comparably dated Irish artefact permits us to claim equivalent practices here. Silence is not proof of absence; it is a reminder that survival and discovery are uneven. Caves preserve bones better than camps, and glaciers remove evidence more efficiently than they preserve it.

The enduring importance of this notional year lies in that distinction between evidence and interpretation. Derryvree and Greenagho show that cold freshwater environments persisted in parts of Ireland before later ice advance. Castlepook confirms an unexpectedly rich Ice Age fauna in the south and raises the serious possibility of very early human activity. Together, these traces replace an older picture of an empty, uniformly frozen Ireland with a more dynamic one: an exposed, treeless and seasonally harsh land, intermittently capable of supporting wetlands, herds, predators and perhaps brief human incursions, before the expanding ice sheet erased much of what came before.

Primary Sources

Tags: Castlepook Cave, County Cork, County Fermanagh, Greenagho, Ireland Year by Year, Marine Isotope Stage 3