Fermanagh’s Birm-166 Deposit

Dateline

“31,649 BCE” is a modern calendar label, not a date that people in prehistoric Ireland could have recognised or recorded. No event, ruler, settlement foundation or human life can responsibly be assigned to that single year. In archaeological terms, it falls approximately 33,600 calendar years before present (cal BP, where “present” is conventionally AD 1950), in the later part of Marine Isotope Stage 3, a fluctuating interval of the last Ice Age. At this depth in time, radiocarbon measurements carry substantial uncertainty and must be calibrated as ranges. The most useful Irish evidence is therefore not an annual chronicle but a small, uneven archive of buried sediments, fossil plants, insects and animal bones.

The best directly relevant environmental record is at Derryvree, near Maguiresbridge in County Fermanagh. Roadworks in 1969 cut through a drumlin and exposed organic silts and fine sands sealed between two separate sheets of glacial till. The deposit, known from its laboratory radiocarbon determination as Birm-166, produced an uncalibrated age of 30,500 BP with a large uncertainty. Subsequent calibration places the broad age range of the freshwater sequence at roughly 36,900–31,700 cal BP. The notional year 31,649 BCE therefore lies within the wider chronological horizon illuminated by Derryvree, but not at a point that can be distinguished within it.

A Wetland Between Ice Advances

Derryvree matters because the later Irish ice sheet destroyed, reworked or concealed much of the older landscape. Here, however, an earlier freshwater environment survived beneath later glacial deposits. The silts accumulated in a low, wet basin at a time when this part of Fermanagh was not overwhelmed by ice. Mosses, sedges, grasses, herb pollen and insect remains point to a cold, open, periglacial landscape. “Periglacial” does not simply mean frozen solid: it denotes ground shaped by severe cold, seasonal freezing and thawing, sparse vegetation, meltwater and unstable soils around an ice-sheet margin.

The scene was not one of modern Irish pasture, hedgerow or woodland. Trees were at most extremely scarce locally. Plant remains indicate treeless tundra-like vegetation, including damp moss- and sedge-rich ground around shallow water, set beside more exposed mineral soil. Juniper may have occupied favourable patches. The landscape probably changed markedly across short distances: pools and saturated hollows could sit near frost-shattered slopes, wind-blown sediment and seasonally dry ground. Such mosaics supplied particular habitats for insects and small animals, and, in better seasons, grazing for larger mammals.

Yet Derryvree should not be mistaken for a complete map of Ireland. It records one basin in what is now northern Ireland, and its pollen was poorly preserved. A tiny amount of tree pollen cannot prove nearby forest, since pollen can travel long distances or be redeposited. Nor can one freshwater deposit reveal the temperature, snow cover or vegetation of every valley and coast. Its significance is more precise: it securely demonstrates that an ice-free, cold freshwater environment existed in Fermanagh during part of later MIS 3, before a later advance of glacier ice covered it.

Not Yet the Glacial Maximum

At this broad date, Ireland was moving towards, but had not yet reached, the Last Glacial Maximum. The best current reconstructions place the major expansion and maximum extent of the last British–Irish Ice Sheet later, principally within the period from about 27,500 to 19,000 years ago, with extensive Irish glaciation especially evident after roughly 24,000 cal BP. Southern Irish stratigraphic work has shown that many tills once assigned to much older glaciations were in fact laid down during the last glacial cycle. The ice that eventually moulded drumlins, scoured bedrock and deposited widespread till was thus part of Ireland’s future at 31,649 BCE, not a condition that can simply be projected unchanged backwards onto this date.

Climate during MIS 3 was unstable. Greenland ice cores show abrupt alternations between relatively milder interstadials and colder stadials, although the exact local effect in Ireland must be reconstructed cautiously rather than read directly from Greenland. The Derryvree deposit represents an environmentally viable interval amid those larger oscillations. Its open vegetation and cold-adapted insect fauna indicate harsh conditions, but the presence of freshwater sediment and plant life also shows that the region was not an unbroken sterile ice desert. Freeze-thaw processes, snowmelt and waterlogging were likely more consequential to everyday ecology than any single annual temperature figure could convey.

Lower sea levels changed the geography around Ireland as well as its climate. Much of the continental shelf was exposed during colder phases, and Britain remained connected to continental Europe for parts of the last glacial period. Ireland’s own connection to Britain is more complicated. Geological research rejects a simple, enduring southern Irish Sea land bridge; any traversable route depended on sea level, ice extent and local topography, and may have involved ice, temporary islands or northern routes rather than open dry land. For animals—and potentially for people—movement westward was possible only through a shifting, hazardous north-west European frontier. It must not be imagined as a permanent highway.

Animals and the Cave Record

The fossil evidence from Irish caves gives a complementary, if equally imperfect, view. Collections from Castlepook Cave near Doneraile in north County Cork include remains attributed to reindeer, woolly mammoth, giant deer, brown bear, Arctic fox, lemmings, hare, wolf and spotted hyena. The Irish Quaternary Fauna Project showed that a varied mammal fauna reached Ireland during intervals between at least about 45,000 and 20,000 years ago. More recent reassessment has stressed that many old cave collections were excavated before modern stratigraphic standards and that some early radiocarbon determinations need revision. Cave bones establish the presence of species in broad periods; they do not automatically prove that every listed animal shared the same valley, season or generation.

Even so, the fauna is an important corrective to the idea of an empty Ireland. Reindeer and lemmings suit the open, cold conditions suggested at Derryvree. Mammoth and giant deer indicate that, during favourable phases, substantial herbivores used at least parts of the island. Spotted hyenas are especially revealing: a cave may have been a carnivore den, a place into which prey remains were dragged, rather than a natural census of the nearby living landscape. Carnivore damage, water movement, excavation disturbance and later mixing all complicate interpretation. The cave record documents animal mobility and ecological opportunity, not a stable, fully known Ice Age menagerie.

For people, the evidence is far more limited. A reindeer bone from Castlepook has been reported as bearing a possible human-made modification and as dating to around 33,000 radiocarbon years ago. If the mark is confirmed as anthropogenic and securely associated with the dated bone, it may indicate a very early human visit to Ireland during MIS 3. That proposition remains under investigation. It is not a securely excavated camp, and it does not provide a house, hearth, tool assemblage, burial, human DNA or continuous occupation. The best-established direct evidence for human activity in Ireland is much later: a cut-marked brown-bear bone from Alice and Gwendoline Cave in County Clare, dated to the opening of the Younger Dryas around 12,800–12,600 cal BP.

No Kingdoms, No Recorded Communities

Accordingly, there is no responsible account of Irish political affairs, diplomacy, warfare or leadership for 31,649 BCE. There were no known polities, borders, named peoples or institutions on the island, and no writing from which beliefs or social relationships can be recovered. Nor can historians infer a resident community from the Derryvree wetland or Castlepook fauna. The possibility of brief human incursions is different from proof of a population. Any visitors would have entered a landscape in which cold, food availability, snow, predators and the changing route across the surrounding shelf imposed severe constraints.

The same restraint applies to everyday life, religion, culture, learning, economy and trade. No Irish dwelling, hearth, worked lithic assemblage, ornament, grave, ceremonial site or exchange object has been securely dated to this horizon. We may reasonably say that mobile Upper Palaeolithic communities elsewhere in north-west Europe possessed sophisticated knowledge of animals, stone, seasonal movement and changing terrain. But applying their technologies, languages, rituals or social structures to Ireland would be interpretation by analogy, not Irish evidence. There is no basis for describing trade networks, chieftains or religious practice here.

What can be stated is more modest, and more remarkable. Around this broadly defined date, Ireland was a changing Ice Age landscape rather than the familiar island of fields and woods. In Fermanagh, freshwater, sedges, mosses and cold-adapted insects occupied a basin later buried beneath glacial deposits. In the south, caves preserve traces of animals that moved through an intermittently habitable world. Ice sheets were gathering strength but had not yet imposed their later maximum extent. The historical subject is therefore not a lost Irish nation or a forgotten annual event, but the fragile evidence for land, water, animals and possible human movement on Europe’s north-western edge.

Primary Sources

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