Derryvree’s Intertill Fen – Emerald Archives

Dateline

The label 31,235 BCE is a modern way of locating a point far beyond the reach of annual history. It corresponds approximately to 33,200 calibrated years before AD 1950, within the later part of the Late Pleistocene and Marine Isotope Stage 3. No Irish person could have named this year; there was no writing, calendar, state or continuous archaeological sequence from which an event can be assigned to it. Modern calendar-year precision is not available. The responsible subject is therefore an environmental interval, reconstructed from deposits, fossils and ice-sheet evidence, rather than an imagined episode in a numbered year.

The closest important Irish evidence is the Derryvree sequence near Maguiresbridge in County Fermanagh. During roadworks in 1969, a cutting exposed fine freshwater sands, silts and organic material enclosed between two thick layers of till, the unsorted debris laid down by glacier ice. Organic material from the freshwater bed produced the radiocarbon determination Birm-166, 30,500 +1,170/−1,030 radiocarbon years BP. Calibration places that result broadly around 36,900–31,700 calibrated years BP, or roughly 34,950–29,750 BCE. The modern date in question falls within this wide range, but cannot be pinned to a particular layer, season, animal or human action within it.

A Landscape Between Ice Advances

Derryvree’s value lies first in its order of deposits. An earlier glacier left the lower till. Afterwards, local ice had withdrawn or ceased to occupy this ground long enough for water to collect and for silt, plants and insects to accumulate. A later glacial advance overran and sealed the basin beneath an upper till. This is firm relative evidence for change at one Fermanagh locality: it was not continuously covered by ice throughout the relevant cold-stage interval. It is not proof that every part of Ireland was ice-free at the same time, nor that the whole island had one climate or one surface.

That distinction matters because the British–Irish Ice Sheet was neither static nor uniform. It grew and reorganised across a landscape of mountains, basins and marine channels. The great Last Glacial Maximum, when ice extended across all Ireland and far onto the adjacent continental shelf, came later, chiefly around 27,000–23,000 calibrated years BP. At about 33,200 cal BP, the island was moving through a colder and highly variable glacial world before that maximum. Regional ice margins could advance, thin or retreat at different times. A sheltered wet hollow in south Fermanagh may therefore record conditions unavailable on an exposed upland or beneath an active glacier elsewhere.

The familiar rounded drumlins of Ireland make this history unusually tangible. At Derryvree, the drumlin was not simply a feature of the modern countryside: its glacial sediments both recorded successive ice movements and protected a fragile earlier wetland archive. Later ice destroyed or obscured much of the preceding land surface, but here it also buried the evidence deeply enough for it to survive. The result is a small, precious window rather than a panoramic view.

Cold Water, Low Plants

The biological remains point to an open, severe environment. Pollen was poorly preserved, yet it was predominantly herbaceous. Plant macrofossils included mosses and species associated with cold, wet ground, among them bogbean, mountain-avens and lesser clubmoss; aquatic or waterside plants such as water-milfoil add to the evidence for freshwater. Insect remains also have a cold northern aspect. Taken with the sediments, these finds support the interpretation of a tundra or muskeg-like setting: treeless or nearly treeless ground, shallow pools and waterlogged margins, grasses, sedges, herbs and low shrubs, shaped by frost and seasonal thaw.

“Tundra” is a useful shorthand, but not a picture of an unbroken snowfield. Derryvree indicates living freshwater habitats during at least part of the year. Mosses and aquatic plants grew where water lingered; sedges and herbs occupied saturated edges; exposed mineral ground and low vegetation lay beyond. The short growing season would have been crucial. Winters were long and harsh, while freezing and thawing repeatedly disrupted soil, drainage and vegetation. A few grains of pine or hazel pollen cannot securely demonstrate nearby woodland, since pollen travels and may be redeposited. The strongest local signal remains that of open, cold country.

This was also a changing North Atlantic climate. Marine Isotope Stage 3 was characterised by abrupt climatic oscillations recorded especially clearly in Greenland ice cores and North Atlantic sediments. The Derryvree deposit cannot be correlated to a particular warm pulse or cold pulse with year-by-year certainty. Nevertheless, its position between tills demonstrates that Irish environmental history was episodic: water and vegetation could establish themselves during an interval that was later overwhelmed by renewed ice. The real history is not a single frozen Ireland, but recurrent transformations of ice, water, ground and habitat.

Animals in the Open Country

Other Irish sites help show what kinds of animals could inhabit or visit such landscapes, although they must not be treated as a census for Fermanagh in one precise year. Castlepook Cave near Doneraile, County Cork, is particularly important. Its old collections include remains attributed to woolly mammoth, reindeer, giant deer, brown bear, wolf, Arctic fox, lemmings and spotted hyaena. Improved radiocarbon methods have shown that several southern Irish cave specimens are substantially older than earlier laboratory results suggested, placing significant faunal activity in Marine Isotope Stage 3 and indicating that some species may have disappeared locally before the Last Glacial Maximum.

The collection reflects ecological opportunities rather than a harmonious herd. Reindeer and giant deer browsed or grazed across open habitats; mammoths, where present, belonged to the wider mammoth-steppe world of Pleistocene Europe; wolves and hyaenas competed for prey and carrion. Caves could be shelters, predator dens, traps for bones or places where sediment and remains were washed in. Consequently, Castlepook’s bones show that Ireland supported, at intervals, a striking range of large mammals and carnivores. They do not show that all species met one another, or were alive together, at exactly 31,235 BCE.

The evidence also overturns any assumption that a cold-stage Ireland was biologically empty. It was harsh and probably patchy, but it could sustain food webs of plants, invertebrates, herbivores, scavengers and predators. Wetlands such as Derryvree’s were part of that wider mosaic. Their productivity would have varied sharply by season, water level and temperature. Animals may have moved through favourable corridors and withdrawn as conditions deteriorated; their presence in Irish deposits is evidence of successful arrival, not necessarily of uninterrupted residence.

The Unsettled Human Question

There is no securely excavated settlement, hearth, dwelling floor, burial, stone-tool assemblage or art site that permits a confident account of people living in Ireland at this date. Nor is there evidence for a named people, language, kingship, warfare, diplomacy, religion, farming, exchange network or formal learning. Political and cultural headings appropriate to later history must therefore remain blank. To call any possible visitors “Irish” in an ethnic or national sense would impose identities formed immeasurably later.

One object nevertheless makes the question important. A reindeer femur from Castlepook Cave has been reported as bearing marks consistent with fresh-bone cutting or chopping by a stone implement, and the animal has been publicised as dating to roughly 33,000 years ago. If specialist analysis confirms both that the mark is anthropogenic and that it relates to the animal’s death, it would indicate that one or more Upper Palaeolithic people handled a reindeer carcass in Ireland during the broad period represented here. That would be a major extension of the island’s human record.

It would still not prove permanent settlement. The bone came from an antiquarian cave collection, not from a modern excavation of an undisturbed occupation surface with associated tools and charcoal. Carnivore damage, trampling, sediment abrasion, breakage and excavation damage can complicate the interpretation of bone marks. Recent excavation at Castlepook has located surviving deposits but has not produced a securely stratified Palaeolithic camp. The most defensible formulation is that a very early human incursion is possible and consequential, while sustained human occupation around 31,235 BCE remains unproven.

If people did briefly reach Ireland, their livelihood cannot be reconstructed directly from Irish evidence. By analogy with Upper Palaeolithic groups elsewhere in north-west Europe, small mobile parties could have relied on detailed knowledge of weather, animal movement, hides, fuel and seasonal resources. But analogy is not evidence. Ireland’s lower sea levels exposed additional shelf land, yet its deep surrounding channels meant that access, routes and water crossings remain difficult questions. No boat, camp or crossing route has survived from this period. The environmental archive establishes potential landscapes and animal resources; it does not establish the plans, beliefs or social organisation of any people who may have entered them.

What This Date Can Mean

For this point in deep time, Ireland’s history is best told through thresholds. At Derryvree, water, plants and invertebrates occupied a basin between episodes of glaciation. Across the island, cave faunas show that cold-adapted mammals and formidable predators could live in, or move through, open Pleistocene habitats. At Castlepook, a potentially modified reindeer bone raises the prospect of a fleeting human encounter, but not a demonstrable community. Later ice advance reshaped the land and erased much of what might once have existed.

Thus 31,235 BCE is not an anniversary. It is a useful modern marker within a calibrated range, illuminating an Ireland of periglacial wetlands, open vegetation, shifting ice margins and mobile animal communities. Its most important lesson is methodological as well as historical: sediments can show an ice-free interval, fossils can show former life, and a marked bone can pose an extraordinary question. None allows a responsible historian to invent a year-specific event where the evidence offers only a deep, changing landscape.

Primary Sources

Tags: British-Irish Ice Sheet, Castlepook Cave, County Cork, Derryvree, Ireland Year by Year, Late Pleistocene