BIRM-166’s Thawwater Flora – Emerald Archives

Dateline

31,105 BCE is a modern calendar label, not a year that anyone in Ireland could have named, recorded or remembered. There are no annals, rulers, settlements or archaeological layers that can be assigned to that particular twelve-month span. In radiocarbon convention it falls roughly 33,054 years before AD 1950, within the Late Pleistocene and Marine Isotope Stage 3: a climatically unstable part of the last Ice Age. The responsible history of Ireland at this depth in time is therefore not an event-by-event narrative. It is an account of dated sediments, animal remains, ice-sheet evidence and the limits those traces impose on interpretation.

A Date Within Wide Ranges

The strongest Irish evidence close to this notional date comes from Derryvree, near Maguiresbridge in County Fermanagh. Road works in 1969 cut through a drumlin and exposed an exceptional sequence: freshwater silts and fine sands, including organic material, lay between two separate beds of till, the unsorted sediment deposited by glacier ice. The lower till showed that ice had previously crossed the site; the upper till showed that ice later returned and sealed the intervening deposits. Between those episodes, water and vegetation had persisted long enough to form a local environmental archive.

The principal radiocarbon determination from the organic beds, BIRM-166, was published as 30,500 years BP, with an uncertainty of +1,170 and −1,030 years. Such figures are not calendar dates. Radiocarbon ages must be calibrated against independent records of past atmospheric carbon, and the uncertainty becomes substantial at this antiquity. Expressed cautiously, discussion of the Derryvree result places the deposit broadly around 36,900–31,700 calibrated years BP, approximately 34,950–29,750 BCE. The label 31,105 BCE sits within that broad window, but cannot be matched to a particular season, water level, animal or human action. It is evidence for an interval measured in millennia, not for a day in an Irish calendar.

Older regional terms call this the Derryvree Cold Phase, part of the Middle Midlandian sequence. Such labels are useful shorthand for deposits and changing environments, but they should not imply that all of Ireland experienced one uniform climate or that its timing is fixed to the year. Modern reconstructions of the British–Irish Ice Sheet likewise show a changing, asynchronous system, rather than a single neat advance across every region at once.

Fresh Water Between Glaciers

Derryvree’s importance lies in its contents. Plant macrofossils, pollen, mosses and small animal remains described from the freshwater sediments point to a cold, open and treeless landscape. Sedges, mosses, dwarf shrubs and tundra-associated plants grew around shallow water, wet ground and mineral-rich mud. The assemblage has often been described as muskeg: a waterlogged, mossy and sedgy environment shaped by cold conditions, a short growing season and imperfect drainage. It was not the dense woodland familiar from much later Irish prehistory.

This was nevertheless not simply an empty frozen wilderness. Freshwater vegetation requires liquid water during at least part of the year; pollen and plant remains demonstrate living communities, however low and sparse. Insects and other small fossils add detail to the impression of periglacial conditions—ground exposed to severe seasonal frost, snowmelt and freeze-thaw action rather than permanently buried beneath ice at that locality. The Derryvree evidence is especially valuable because later glacial action destroyed, rearranged or concealed many earlier land surfaces elsewhere in Ireland.

The landscape should not be reconstructed as a single unbroken plain. Drumlins, valleys, wet basins, exposed slopes, snow patches and watercourses would have created local contrasts. Around the Derryvree basin, the waterlogged vegetation was one component of a wider open country. Distant tree pollen, where present in tiny quantities, cannot responsibly be treated as proof of nearby forest: pollen can travel far. The broader assemblage supports a cold, largely treeless environment.

Animals on an Open Range

County Cork cave deposits provide a complementary, though more complicated, record. Castlepook Cave near Doneraile has yielded remains of reindeer, woolly mammoth, giant deer, brown bear, wolf, Arctic fox, hare, lemmings and spotted hyaena. This remarkable fauna establishes that Ireland supported, at different points before the Last Glacial Maximum, cold-adapted mammals and the predators or scavengers associated with them. Reindeer and mammoth particularly indicate open grazing landscapes rather than closed woodland.

Yet Castlepook is not a photograph of one year. Its bones were recovered from a complex cave system and many originated in historic excavations, before modern standards of stratigraphic recording. Radiocarbon dating by the Irish Quaternary Fauna Project showed that specimens once assumed to belong together could date to very different periods. Carnivores may have dragged carcass parts into the cave; water, frost, collapse and earlier digging could also move material. The evidence supports an Ice Age food web in Ireland over a long span, not the claim that every recorded species lived side by side in 31,105 BCE.

Even so, the combined Fermanagh and Cork evidence changes the scale at which this island should be imagined. Ireland was not yet the later green, forested island of popular imagination. It lay on the north-western edge of Europe, repeatedly affected by altered sea levels, shifting ice margins and severe climates. Its animal populations were probably intermittent and vulnerable to environmental change. Presence in the surviving record proves arrival or occupation at some point; absence may simply reflect the loss of deposits or the incompleteness of collection.

The Narrow Human Question

No securely excavated hearth, dwelling, stone-tool assemblage, human burial or settlement surface has been published for Ireland at this age. There is therefore no foundation for describing an Irish community in 31,105 BCE, still less its language, kinship rules, leaders, territorial boundaries or identity. The National Museum of Ireland has long stressed the absence of a conventional, securely documented Palaeolithic occupation record on the island. Substantial, repeated evidence for settlement belongs much later, after the final retreat of the ice, with Mesolithic hunter-gatherers from about the eighth millennium BCE.

A single object makes the question more complicated. A reindeer femur from Castlepook, now in the National Museum of Ireland’s Natural History collections, has been publicly presented by zooarchaeologist Ruth Carden and County Cork heritage publications as bearing a deep mark made with a sharp stone tool while the bone was fresh. The specimen has been assigned approximately to 31,000 BCE. If that identification is confirmed through continuing specialist study and supported by securely stratified material, it could indicate that Upper Palaeolithic people processed a reindeer in Ireland during this broad period.

That is an important possibility, but a narrow one. The radiocarbon age dates the animal bone, not the precise instant of its marking. A single modification does not reveal whether people killed the reindeer, encountered it after death, removed meat, hide, sinew or marrow, or worked the carcass elsewhere before a scavenger transported the bone into a cave. Nor can it establish a permanent population, a regular migration route, a land bridge, boats, or descent from those possible visitors to later inhabitants. Until corroborated by artefacts and excavated context, a short human incursion remains an interpretation rather than a demonstrated settlement history.

No Polities, Trade or Known Cult

Accordingly, there is no evidence for political affairs, warfare, diplomacy, formal trade, agriculture or social institutions in Ireland at this date. There were no states, named peoples, chiefs or borders that archaeology can recover here. Nor is there Irish evidence from this horizon for shrines, graves, monuments, cave art, portable art or a system of learning. Upper Palaeolithic communities elsewhere in Europe made sophisticated stone tools and visual art, but continental parallels cannot be imported as facts about Ireland. They provide context for what possible visitors might have known, not proof of what occurred on this island.

If people did briefly reach Ireland, the most modest inference is that they were highly mobile foragers able to use a sharp stone edge and exploit animal resources. That inference must remain separate from the evidence itself: the evidence is a reportedly modified reindeer bone, not an excavated camp. For the rest, the clearest story is environmental. The freshwater plants at Derryvree, the cold-adapted fauna of Castlepook and the tills enclosing or disturbing older ground together reveal a country repeatedly made available, reshaped and in places erased by Ice Age change.

Approaching the Great Expansion

At about this timescale, Ireland was approaching the major growth phase of the last British–Irish Ice Sheet, although local conditions varied and the chronology remains under active refinement. The ice sheet later achieved its greatest overall volume around 23,000 years ago. Derryvree’s two tills make the longer sequence visible in one place: an earlier glacial advance, an ice-free enough interval for a cold freshwater ecosystem, and a later advance that entombed it. The organic bed is thus both a record of life and a record of interruption.

For 31,105 BCE, that interruption is the history. It offers no named event, but it does preserve a rare glimpse of Irish ground between episodes of ice: shallow water, sedges and mosses under a severe climate; open country capable of supporting distinctive mammals; and, perhaps, the unresolved trace of a human encounter with a reindeer. The uncertainties are not a defect to be concealed. They are the essential fact of Ireland’s deep past, and they define what can responsibly be said about this otherwise calendarless age.

Primary Sources

Tags: British-Irish Ice Sheet, Castlepook Cave, County Cork, Ireland Year by Year, Late Pleistocene, Marine Isotope Stage 3