Derryvree’s Bogbean Waters – Emerald Archives

Dateline

The label 31,643 BCE is a modern chronological convenience, not a date that can be identified in Ireland’s prehistoric record. No one living then used this calendar, and neither radiocarbon dating nor glacial deposits can isolate a particular Irish event, person or season in a single year nearly 34,000 years ago. In calendar terms it is approximately 33,592 years before AD 1950. The responsible historical frame is the later part of the Last Glacial period, within Marine Isotope Stage 3, and it must be measured in broad intervals rather than annual entries.

On the Greenland ice-core chronology, that nominal point falls within Greenland Interstadial 6, a short milder pulse conventionally placed at about 33.69–33.31 thousand calendar years before present. This does not mean that Ireland shared Greenland’s weather day for day, or that an Irish deposit can be assigned exactly to the interval. It does show that the North Atlantic climate system was capable of rapid, large changes. The dating uncertainty attached to the Irish evidence is wider than the 380-year duration of that named interstadial.

A Landscape Between Ice Advances

Ireland was not yet in the fullest grip of the Last Glacial Maximum, the phase when an ice sheet covered all or almost all of its low ground, conventionally around 26–21 thousand years ago. But this was no settled, benign interval before the ice. Research increasingly depicts the British–Irish Ice Sheet as an unstable system which had already grown and changed repeatedly during Marine Isotope Stage 3. Its limits, thickness and timing varied by region, while later ice advance destroyed, buried or rearranged much of the earlier terrestrial record.

Thus, it is not responsible to draw a single coastline, ice margin or vegetation boundary for all Ireland in 31,643 BCE. Sea level was substantially lower than today, so the modern island formed part of a wider, changing north-west European land-and-sea margin. Connections between Ireland, Britain and the exposed continental shelf could at times have facilitated the movement of land mammals, though routes were constrained by channels, coasts, ice and climate. The National Museum of Ireland summarises the broader evidence as indicating the arrival of spotted hyena and other mammals from Britain sometime around 45,000–30,000 years ago. That is a long chronological window, not evidence for a migration in this particular year.

The Derryvree Evidence

The most illuminating Irish environmental evidence relevant to this broad period comes from Derryvree, near Maguiresbridge in County Fermanagh. There, organic-rich freshwater sediments were discovered between two layers of glacial till beneath a drumlin. The lower till belongs to an earlier ice advance; the upper till records a later one. Between them survives a remarkable, if limited, record of a time when water, plants, insects and sediment accumulated in a local basin rather than being overridden by ice.

A conventional radiocarbon determination from the organic layers was 30,500 years BP, with an uncertainty of roughly a millennium. That is a radiocarbon age, not an unmediated calendar date: it requires calibration against changing atmospheric carbon-14, and its uncertainty creates a wide calendar interval. IntCal20 provides a Northern Hemisphere calibration curve to 55,000 calendar years BP, but calibration does not make Derryvree an annual diary. The deposit is best treated as evidence for conditions in a broad Middle Midlandian interval close in geological terms to the assigned date, not as proof of the landscape on 31,643 BCE itself.

What does survive is unusually vivid. Pollen, plant remains, freshwater mosses and sedges, together with insects of cold northern aspect, point to open tundra or tundra-like wetland, not a forested Ireland. A seed of bogbean, Menyanthes trifoliata, is especially revealing. It indicates shallow freshwater or wet margins capable of sustaining aquatic vegetation. Mosses, sedges and small pools would have formed a patchwork within a generally exposed periglacial setting: ground affected by severe seasonal freezing and thawing, but not necessarily covered by glacier ice at that locality when the deposits formed.

Open Ground, Not Empty Ground

Treeless does not mean lifeless. The Derryvree flora and insect fauna suggest cold, damp ground with vegetation sufficient to support small food webs. Elsewhere in Ireland, cave deposits provide the complementary evidence of larger animals. Castlepook Cave, also known as Mammoth Cave, near Doneraile in north County Cork, has produced remains of woolly mammoth, reindeer, giant deer, brown bear, wolf, Arctic fox, mountain hare, lemmings and spotted hyena. Many bones bear tooth damage, and the cave was used over time by carnivores, especially hyenas, rather than representing one tranquil animal community or one single moment.

These animals establish that parts of Ireland supported a cold-stage fauna during the long period before the Last Glacial Maximum. They should not, however, be assembled into a fictional tableau for 31,643 BCE. Castlepook’s old excavations recovered material from disturbed and complex deposits. Modern re-dating has shown that some earlier determinations underestimated the true ages of bones by approximately 5,000–12,000 radiocarbon years. Individual specimens therefore have their own dates and contexts, while the collection as a whole spans many millennia.

The calibrated dates demonstrate this caution clearly. One brown-bear specimen from Castlepook has published calibrated ranges of 38,041–34,320 and 39,416–37,153 cal BP, depending on the treatment of the determination; another directly dated Castlepook bone has a published range of 35,703–34,384 cal BP. Such ranges are invaluable for placing animals within Late Pleistocene Ireland, but they do not securely document those animals at the nominal 33,592 cal BP represented by this entry. Evidence and interpretation must remain separate.

People: A Possibility, Not a Population

The question of people is the most arresting and the most easily overstated. A reindeer femur from Castlepook has a deep incision that zooarchaeologist Ruth Carden has interpreted as a mark made during processing with a sharp stone implement. If that interpretation is upheld, it would indicate human activity in Ireland during the Upper Palaeolithic, vastly earlier than the formerly accepted evidence for settlement after the last ice age. It would suggest a brief visit, hunt or carcass-processing episode by highly mobile hunter-gatherers moving through the wider north-west European zone.

But the bone does not demonstrate a permanent community, a village, a named people, or a population continuous with later inhabitants of Ireland. No securely associated hearth, dwelling floor, stone-tool assemblage or human remains from a contemporary, stratified Irish occupation has been recovered at Castlepook. Its old cave context is disturbed. Nor is the specimen an exact date for 31,643 BCE. The honest conclusion is narrower: human presence in pre-Last-Glacial-Maximum Ireland is a serious possibility supported by a potentially modified bone, but the scale, frequency and duration of such presence remain unresolved.

No Politics, No States, No Recorded Religion

There can be no account here of kingship, diplomacy, warfare, law or political boundaries. There were no recorded states in Ireland and no documentary archive. Equally, no evidence permits identification of religious rites, artistic traditions, spoken languages, kin groups or formal territories. If people did reach the island in this period, they would have relied on social knowledge, cooperation and mobility to survive in a dangerous environment, but that is an inference from the requirements of Upper Palaeolithic lifeways elsewhere, not a directly observed Irish institution.

Nor can economy and trade be described in their later senses. The relevant exchanges were ecological: the movement of animals, people and materials across a wider landscape periodically reshaped by sea, ice and climate. Reindeer and other herbivores could have offered meat, hide, sinew, bone, antler and fat to any visiting hunters; caves offered shelter and dens to carnivores. Yet the Irish evidence does not establish organised procurement, recurring trade routes or a local tool-making tradition at this date.

A Fragile Archive

The principal historical development around this notional year was therefore environmental instability. A brief North Atlantic warming pulse, local wetlands preserved beneath later glacial deposits, animal movements through a changing Irish Sea world, and the prospect of fleeting human visits are more consequential than invented stories of settlement. Ireland’s archive is sparse precisely because later ice sheets eroded and buried landscapes, while the evidence that survived often lay in caves or sealed sediment pockets.

Derryvree’s bogbean waters matter because they prevent the Ice Age from becoming a blank white backdrop. They show that, during one broad interval between glacial advances, there were freshwater margins, mosses, sedges, insects and open ground in what is now County Fermanagh. Castlepook shows that a diverse cold-stage fauna reached Ireland at different times before the maximum ice advance. Together they offer a disciplined picture of 31,643 BCE: not a year with a recoverable event, but a point within a volatile prehistoric world whose traces must be read with precision, restraint and respect for uncertainty.

Primary Sources

Tags: Castlepook Cave, County Cork, Derryvree, Ireland Year by Year, Late Pleistocene, Marine Isotope Stage 3