Derryvree’s Inter-Till Pool

Dateline

The label 31,818 BCE should not be mistaken for a date at which Ireland can be viewed year by year. No written record, settlement sequence or annually resolved environmental archive permits that precision. If converted mechanically to the archaeological convention of years before AD 1950, the label falls around 33,768 calibrated years before present (cal BP). It belongs to the later part of Marine Isotope Stage 3, a long, unstable phase of the last Ice Age. The responsible evidence is therefore a set of broad windows: radiocarbon ranges, sediments between glacial deposits, cave fauna and the changing shape of the British–Irish Ice Sheet.

A Time Window, Not a Date

Radiocarbon ages are not calendar years waiting to be read directly from a bone or piece of peat. Atmospheric carbon-14 varied through time, so measured ages must be calibrated against independently dated records. At roughly 34,000 years ago the calibration curve is necessarily less fine-grained than in recent millennia, and individual determinations can translate into wide, sometimes discontinuous calendar ranges. A nominal BCE year is useful for arranging a chronological archive, but it cannot identify a particular season, migration or human visit.

The most useful Irish environmental evidence near this horizon comes from Derryvree, near Maguiresbridge in County Fermanagh. There, organic freshwater silts and sands were exposed beneath a drumlin, lying between two layers of glacial till. Their position tells a clear relative story: an earlier glacier deposited till; an ice-free interval allowed water, sediment, plants and animals to accumulate; later ice overrode and buried the deposit. A conventional radiocarbon determination associated with the organic sequence has been calibrated broadly to about 36,900–31,700 cal BP. The nominal year considered here lies within that substantial range, not at a known moment within it.

Derryvree is consequently important for what it rules out as well as what it reveals. It makes a simple picture of an island continuously smothered by ice untenable for this part of the cold stage. It does not, however, demonstrate that every Irish district was ice-free, nor that the conditions recorded in Fermanagh prevailed simultaneously in Cork, Kerry or the Irish Sea basin. Ireland’s glacial history was regional and episodic: ice margins advanced, stagnated, thinned and reorganised, while local topography affected water, vegetation and shelter.

Cold Ground and Fresh Water

The biological remains from inter-till deposits indicate a severe but living landscape. Pollen, plant macrofossils and insect evidence point towards open, largely treeless vegetation rather than the oak, ash and hazel woods of later prehistoric Ireland. Sedges, grasses, herbs, mosses and low shrubs could exploit short growing seasons, wet hollows and exposed mineral ground. Permafrost or seasonally frozen soils, strong winds and frost action would have shaped the terrain. Yet Derryvree’s fine sediments also record freshwater: pools, slow channels or marshy margins capable of preserving organic material.

This was not necessarily a featureless snowfield. In summer, damp ground and stream edges could have supported concentrated plant growth, insects and grazing animals; in winter, the same setting could have been locked by frost and snow. The contrast matters. “Tundra” is a useful shorthand for an open cold-stage environment, but it should not be imagined as one unchanging surface. Slope, drainage, shelter and season made different opportunities and hazards across even a small area.

Climate across the North Atlantic changed abruptly during Marine Isotope Stage 3. Greenland ice-core records and marine sediments show repeated shifts between relatively milder interstadials and colder stadials. Irish deposits cannot be matched confidently to every short climatic oscillation, but they fit a broader pattern in which environments and ice limits changed more than once before the Last Glacial Maximum. The fullest ice cover came later, broadly around 27,000–23,000 cal BP, when the Irish sector of the British–Irish Ice Sheet extended across the island and onto the surrounding shelf. Around the date represented here, the decisive story was not yet ice at its maximum, but climatic volatility and the approach of a more extensive glaciation.

Animals in the Cave Record

Caves in southern Ireland provide another, differently imperfect archive. Castlepook Cave near Doneraile, County Cork, produced bones from antiquarian excavations and later investigation. Its faunal assemblage has included reindeer, mammoth, giant deer, brown bear, wolf, fox, Arctic fox, hare, lemmings and spotted hyaena. Modern radiocarbon reassessment has shown that several earlier dates from Irish cave collections were too young, placing important elements of the Castlepook fauna more securely in Marine Isotope Stage 3. The evidence demonstrates that cold-adapted and open-country animals reached Ireland during this long interval.

It must not be used to make an over-detailed animal census for 31,818 BCE. Cave deposits may accumulate over thousands of years; some were disturbed before modern excavation and may mix bones from different episodes. A cave can be a carnivore den, trap, shelter, drainage route and sediment store rather than a single living surface. The age of a bone dates the animal’s death, not automatically the time at which every other bone beside it entered the cave. Still, the combined faunal evidence strongly supports a landscape in which reindeer and other grazing or browsing mammals could move through open habitats, while large predators and scavengers exploited carcasses.

Spotted hyaena are particularly revealing. Their presence in the Irish record should not be read as proof of warm conditions: Late Pleistocene hyaenas ranged far beyond their modern African distribution and scavenged in cold, open environments. Mammoth and giant deer likewise evoke a productive but demanding grass-and-herb landscape, not an Irish forest. Whether the animals arrived across exposed ground, along shifting coastal corridors or during particular low-sea-level phases remains a question of palaeogeography and timing. The sea was lower globally than today as ice accumulated, but changing sea level, isostatic movement and ice barriers mean that no simple permanent ‘land bridge’ should be assumed.

The Human Question

The possibility of people in Ireland at this broad date rests chiefly on a single striking but limited object: a reindeer femur from Castlepook Cave. It has been reported as about 33,000 years old and bears a deep mark interpreted by zooarchaeologist Ruth Carden as a cut made with a sharp stone tool during carcass processing. If that interpretation is sustained, it is potentially the earliest evidence for human activity in Ireland, many millennia before the securely better-attested terminal Pleistocene and Mesolithic record.

The distinction between potential activity and established settlement is essential. The specimen derives from an old cave collection, not from a modern excavation of an intact floor with associated hearths, stone tools, shelters, food remains and repeated occupation layers. Its radiocarbon result dates the animal bone, while the identification of the mark as a tool cut is a separate taphonomic judgement requiring comparison with carnivore damage, trampling, weathering, breakage and excavation damage. One modified bone, even if humanly cut, could record a brief visit to a carcass rather than a resident community.

Recent excavation at Castlepook has sought undisturbed sedimentary contexts and further evidence, including charcoal, lithics and additional modified bone. That work is valuable precisely because it tests, rather than merely repeats, an important claim. At present, no named people, language, population continuity or archaeological culture can responsibly be attached to Ireland at this date. Nor can the island’s later inhabitants be traced back to any possible Ice Age visitors on the basis of this evidence.

No Polities, but Real Lives

There is no evidence for political institutions, diplomacy, territorial kingdoms, formal trade networks, religious monuments or learning in the documentary sense. It would be misleading to manufacture equivalents for a society that may have left no secure settlement evidence at all. If people did reach southern Ireland, comparison with Upper Palaeolithic groups elsewhere in north-west Europe suggests small, mobile bands able to make and use stone tools, understand animal movements and exploit seasonal resources. That is an interpretation drawn from wider European archaeology, not a direct description of an Irish camp.

The likely economic question, if the Castlepook mark proves anthropogenic, was immediate subsistence: obtaining meat, marrow, hide, sinew and perhaps antler from a reindeer carcass. Such an act need not imply organised hunting; people can butcher animals they hunted, found, intercepted from predators or acquired in other ways. There is no Irish evidence from this horizon for farming, herding, pottery, metalwork, houses, burial rites, art or long-distance exchange. Silence in these categories is meaningful only when expressed carefully: later ice erosion, rising seas and the rarity of surviving sites have made the archaeological record exceptionally thin.

For Ireland around 31,818 BCE, then, the central historical development is environmental rather than political. In Fermanagh, a freshwater, open cold-stage landscape existed during an interval between glaciations. Across the island, animal remains attest to an Ice Age fauna adapted to exposed country. In Cork, one reindeer bone raises the serious possibility that people briefly entered this world. The evidence is too fragmentary for a conventional national narrative, but it is enough to replace an older image of a lifeless, uniformly frozen island with a more dynamic and scientifically testable past.

Primary Sources

Tags: County Cork, Derryvree’s Inter-Till Pool, Early Holocene, Ireland Year by Year, Irish Ice Shee, Last Glacial Maximum