Castlepook’s Ancient Femur – Emerald Archives

Dateline

31,559 BCE is not a recoverable year in Ireland’s human past. No community on the island kept a calendar that can be correlated with a modern date, and neither radiocarbon dating nor glacial stratigraphy can identify an event within one year so far back. In calendar arithmetic, the date lies about 33,509 years before AD 1950, the conventional reference point for ‘before present’. That does not mean it was 33,509 radiocarbon years ago: radiocarbon ages require calibration and normally come with substantial ranges at this depth of time.

The appropriate setting is therefore not an imagined annual episode but later Marine Isotope Stage 3 (MIS 3), a long and climatically volatile part of the last Ice Age. Ireland was approaching, but had not yet reached, the Last Glacial Maximum, when ice would cover the island and much of its surrounding shelf between roughly 27,000 and 23,000 calibrated years before present. Evidence from County Fermanagh and County Cork shows that at different points in MIS 3 parts of Ireland supported open, cold environments and large mammals. It also raises the important, still cautious possibility that people reached the island long before its better-attested post-glacial settlement.

A Date Range, Not a Day

The closest useful Irish chronological marker is an organic deposit exposed at Derryvree near Maguiresbridge, County Fermanagh. There, freshwater silts and fine sands lay between two tills: sediments left by an earlier ice advance below and a later one above. The intervening organic layer produced the legacy radiocarbon determination Birm-166, 30,500 ± 1,100 radiocarbon years BP. Published calibrations place it broadly at about 36,900–31,700 calibrated years BP. The modern label 31,559 BCE, approximately 33,509 calibrated years BP, falls within that wide range, but it cannot be assigned to the beginning, end or any particular season of the deposit.

This stratigraphy is valuable because it establishes a sequence rather than merely an isolated fossil: glacial conditions, an ice-free freshwater and periglacial environment, then renewed glaciation. It decisively complicates any picture of Ireland as continuously buried beneath ice throughout the later Ice Age. Yet Derryvree was a local basin, not a weather station for the whole island. Its deposits demonstrate that this part of Fermanagh could sustain wetland life during a cold interval; they do not prove identical conditions in Cork, Connacht, the east coast or every upland district at the same time.

Derryvree’s Open Wetland

The Derryvree plant and insect evidence permits a carefully grounded reconstruction. Fossil remains point to a treeless, open tundra or muskeg landscape: wet ground with pools, mosses, sedges, grasses, herbs and dwarf shrubs. Finds include bogbean (Menyanthes trifoliata) and mountain avens (Dryas octopetala), plants now strongly associated with wet, cold or Arctic-alpine settings. Juniper and herb pollen, together with moss-rich vegetation and aquatic material, indicate neither dense woodland nor a lifeless polar desert. Water, vegetation and exposed mineral ground existed together in a harsh periglacial mosaic.

Such a landscape would have been intensely seasonal. Long, cold winters, frost action and sparse cover limited plant growth, while short growing seasons concentrated food in marshes, stream margins and sheltered hollows. The insects suggest open pools rich in plant material and surrounded by mossy ground. These are observations derived from preserved organisms. The further idea that animals would have moved between productive patches, or that people would have favoured river corridors and sheltered limestone country, is reasonable ecological interpretation rather than a directly observed Irish itinerary.

Environmental change was the dominant ‘political’ force in this world. There is no evidence for polities, chiefs, diplomacy, territories, formal warfare or named peoples. Ice margins expanded and retreated over longer spans; abrupt North Atlantic climatic shifts altered the extent of habitable ground, vegetation and animal range. For any small human party, access to food, fuel, shelter and a safe route mattered more than borders in the later historical sense.

The Castlepook Fauna

At Castlepook Cave, near Doneraile in north County Cork, an old cave collection offers Ireland’s most important pre-Last Glacial Maximum animal archive. The limestone cave system yielded remains attributed to woolly mammoth, reindeer, giant deer, brown bear, spotted hyaena, wolf, fox, hare, stoat and lemmings. These are not the contents of one simultaneous herd or a single day’s deposit. Cave assemblages accumulated through carnivore occupation, animals dying in or near caves, water movement, sediment disturbance and early twentieth-century excavation. Revised accelerator dating has also shown that some older determinations from southern Irish caves underestimated the ages of MIS 3 bones by thousands of radiocarbon years.

Nevertheless, the fauna establishes that Ireland was linked to wider north-west European animal geography during parts of MIS 3. Mammoths and reindeer imply open grazing country; lemmings and Arctic fox fit severe conditions; hyaenas, wolves and bears show that the food web included formidable scavengers and predators. Giant deer should not be treated as the familiar emblem of a later Irish bog landscape alone: its presence belongs to a far longer and changing Pleistocene history. The animal record makes a cold, biologically active Ireland more credible than an empty wilderness, while its mixed chronology warns against arranging every species into one neat scene.

The Mark on a Reindeer Bone

Castlepook is especially relevant to this notional date because a reindeer femur from its collection has been reported as about 33,000 years old and as bearing a deep mark interpreted as damage from a sharp stone tool used on fresh bone. County Cork heritage publications present the specimen as evidence for Palaeolithic butchery, and the interpretation has drawn attention because it could extend Irish human activity more than 20,000 years earlier than the formerly accepted record.

The finding deserves emphasis, but also restraint. A dated bone is not a dated settlement: the measurement gives the age of the animal, not a precise moment when a person made a mark. Nor does one modified femur prove that hunters killed the reindeer, rather than encountered a carcass after another predator had fed. Crucially, the bone comes from an old cave collection, not a modern excavation of an undisturbed occupation floor. No securely associated hearth, lithic assemblage, dwelling, human burial, food store or repeated butchered surface has yet been published for Ireland at this age. The mark may represent a brief Upper Palaeolithic visit, but it cannot demonstrate a permanent population or continuous occupation.

That distinction matters for everyday life. If people did process the animal, reindeer could have supplied meat, marrow, hide, sinew and bone: resources well known from Upper Palaeolithic economies elsewhere in north-west Europe. But those wider comparisons cannot fill the evidential gap at Castlepook. There is no securely Irish evidence around 31,559 BCE for tents, clothing, fire-making practice, family size, hunting weapons, language, kinship, exchange networks or routes of travel. The responsible conclusion is modest: an isolated act of animal processing is possible; a settled society is unproven.

Sea, Land and Movement

Lower global sea levels exposed extensive areas now submerged around north-west Europe, but this should not be simplified into a certain, broad land bridge on which people simply walked to Ireland. Irish relative sea level depended not only on global ice volume but also on the changing weight of nearby ice sheets and the response of the Earth’s crust. Reconstructions of insularity remain complex. At this earlier MIS 3 date, the configuration of coast, shallow sea, exposed shelf and ice was different from today, but the evidence does not permit a precise route for humans or animals to be drawn.

The faunal record itself shows that some animals reached Ireland during favourable intervals. Whether people followed the same paths, crossed short sea gaps, travelled over frozen terrain, or arrived by another route cannot presently be resolved. It would be unsafe to call them ‘Ireland’s first settlers’, to attach a modern ethnic identity, or to assume that any visiting group survived the subsequent worsening of climate. The later Last Glacial Maximum was an overwhelming break in the island’s environmental history.

Culture Beyond the Evidence

There is no evidence for religion, art, monuments, writing, formal learning, trade or diplomacy in Ireland at this point. Upper Palaeolithic people elsewhere in Europe made sophisticated stone and bone tools, ornaments and images, but no such cultural material has been securely associated with a 33,500-year-old Irish occupation. Absence is not proof that no person ever made, carried or believed such things here; it is a statement about the present record, much of which may have been destroyed, displaced or concealed by later ice and sea-level change.

For Ireland around 31,559 BCE, the greatest historical development is therefore the survival of fragile evidence itself. Derryvree preserves a cold wetland between glacial episodes. Castlepook preserves a time-averaged fauna and a reindeer femur whose marked surface may record human intervention. Together they replace an older, simpler story of an entirely ice-bound and humanly irrelevant island. They do not yet yield a named community, a settlement map or a year-by-year narrative. Their real achievement is to show how much of Ireland’s deepest past remains open to discovery, testing and revision.

Primary Sources

Tags: Castlepook Cave, County Cork, County Fermanagh, Ice Age, Ireland Year by Year, Marine Isotope Stage 3