Reindeer, Sedges and BIRM-166

Dateline

31,502 BCE is not a year for which Ireland can be described in the manner of later history. No contemporary written record, named ruler, settlement plan or securely dated human occupation belongs to this precise point in the calendar. The number is best understood as a modern way of locating a moment roughly 33,450 calendar years before 1950, within the Late Pleistocene and Marine Isotope Stage 3 (MIS 3), a notably unstable interval of the last Ice Age. At this depth of time, radiocarbon dates must be calibrated and expressed as ranges, not converted into deceptively exact historical anniversaries.

The responsible picture of Ireland around this notional date comes from a small and difficult body of evidence: freshwater sediments sealed between glacial deposits in County Fermanagh; animal bones recovered from caves, especially in north County Cork; pollen, seeds, mosses and insects; and the large-scale record of advancing and retreating ice. These sources illuminate habitats and animal movements much more clearly than they illuminate human life. They also show why Ireland’s earliest possible human story remains both important and unresolved.

A Date Within a Range

The closest useful Irish chronological anchor is the Derryvree deposit near Maguiresbridge, County Fermanagh. Roadworks exposed fine freshwater silts and sands beneath a drumlin, lying between two tills: unsorted sediment left by separate glacier advances. Organic material from the deposit produced the radiocarbon determination BIRM-166, conventionally dated to 30,500 ± 1,100 radiocarbon years before present. Subsequent modelling and calibration place this evidence broadly around 33.5 ± 1.2 thousand calendar years before present. That wide interval encompasses 31,502 BCE, but it does not prove that every fossil in the bed, or every part of Ireland, belonged to that exact moment.

This distinction matters. The Derryvree silts demonstrate that a part of northern Ireland was ice-free when the wetland sediments formed, before the major Late Midlandian or Last Glacial Maximum expansion of the British–Irish Ice Sheet. They do not provide an annual climate diary. Equally, a date from a cave bone establishes the age of that animal’s death, not automatically the date of every event inferred from the bone or the time at which it reached the cave.

Derryvree’s Open Wetland

Even with those cautions, Derryvree offers an unusually vivid environmental glimpse. Its plant remains indicate open, treeless tundra or muskeg rather than forest: grasses, sedges, juniper and cold-adapted herbs occurred with a rich moss flora. Fossils of dwarf willow, mountain avens and bogbean are especially evocative. These were not signs of a barren white wilderness. They point instead to a patchwork of damp ground, shallow freshwater, low vegetation and seasonally exposed mineral soils. Pollen attributed to alternate water-milfoil further indicates freshwater conditions in or near the basin.

Such a landscape would have changed sharply through the year. During a short growing season, sedges and herbs could support grazing animals and insects in sheltered, wet places. Winter conditions were far more severe, with permafrost-related processes, frost action and limited plant cover likely shaping the ground. Wind, snow and meltwater mattered as much as vegetation. The term “tundra” should therefore not conjure a uniform plain: the surviving evidence instead suggests local mosaics of pools, marshy margins, drier ridges and sparsely vegetated surfaces.

Derryvree was not the only surviving archive of environmental fluctuation. At Aghnadarragh in County Antrim, an older interstadial sequence records woodland, swamp and bare ground during a warmer episode earlier in the Midlandian cold stage; above it, later deposits indicate renewed cold and treeless conditions. Together, these sites demonstrate that the Irish climate did not simply progress in a straight line towards maximum glaciation. It oscillated, and habitats expanded, contracted and shifted accordingly.

The Doneraile Fauna

For large animals, Castlepook Cave near Doneraile in the Awbeg Valley of north County Cork is the central Irish site. Also called Mammoth Cave, it yielded an exceptional collection during excavations in the early twentieth century. Its Ice Age fauna includes woolly mammoth, reindeer, giant deer, brown bear, wolf, Arctic fox, lemmings and spotted hyena. This is compelling evidence that Ireland, at different points during MIS 3, supported or received animals normally associated with cold, open Eurasian environments.

However, Castlepook was not a neatly preserved snapshot of one day, season or century. It is a complex cave system in which water movement, carnivore activity, changing sediment and early excavation practices have jumbled contexts. Individual bones have returned dates spanning a long period, and the revised radiocarbon record suggests that some animals formerly thought late in the Ice Age were substantially older. The most defensible conclusion is that the cave preserves a time-depth of faunal history leading towards the Last Glacial Maximum, rather than a single intact community living together in 31,502 BCE.

Spotted hyena is particularly revealing. The animal’s presence suggests that caves could function as carnivore dens and bone accumulators, not merely as shelters awaiting human occupants. Hyenas may have carried carcass parts into the galleries, while carnivore gnawing, trampling, water transport and later disturbance all affected the assemblage. Mammoth and giant deer likewise belong to the broad ecological setting, but their bones cannot be assembled uncritically into one illustrated herd. The evidence supports a cold-country fauna; it does not licence a precise reconstruction of every animal standing together at one place and time.

The Marked Reindeer Bone

Castlepook has a second importance: a fragment of reindeer femur has been interpreted by zooarchaeologist Ruth Carden as bearing a deep mark made by a sharp stone tool during butchery. County Cork heritage material presents the bone as dating to about 31,000 BCE, while public reports have described it more broadly as about 33,000 years old. If the mark was made on fresh bone by a person, it would be extraordinarily early evidence of human activity in Ireland: an Upper Palaeolithic episode more than twenty millennia before the better-established late-glacial and Mesolithic record.

That “if” must remain visible. The object comes from an old cave collection, not from a modern excavation that recorded an undisturbed occupation surface around it. No securely associated hearth, stone-tool assemblage, dwelling, burial, repeatedly used food-processing area or sequence of camps has yet been published for Castlepook at this age. The cave’s role as a carnivore and water-affected bone repository further raises the standard required for interpretation. A marked bone can be a major clue, but it is not a settlement.

The most cautious reading is therefore also the most historically useful. Around the broad interval represented by 31,502 BCE, people may have entered Ireland briefly and processed a reindeer, perhaps during a mobile hunting journey linked to wider Upper Palaeolithic landscapes in Britain or continental Europe. But archaeology cannot yet establish how they arrived, how long they stayed, whether they travelled repeatedly, what language they spoke, or whether they left descendants. It cannot identify a permanent population, a community name or a “first Irish” people.

What Cannot Be Recovered

There is no evidence for political institutions, chiefs, diplomacy, territorial boundaries or organised warfare in Ireland at this date. Nor is there Irish evidence for religious monuments, burials, art, formal learning, farming, pottery, metalworking or trade networks. Upper Palaeolithic people elsewhere in Europe made sophisticated tools and images and maintained far-ranging social connections, but those wider patterns cannot simply be imported into Ireland. The island’s record must be allowed its silence.

If visitors were present, their everyday economy would most plausibly have depended on hunting and scavenging within a highly mobile way of life, with reindeer a potentially valuable animal for meat, hide, fat, sinew and bone. This is an interpretation from the possible butchered femur and the broader European context, not a demonstrated Irish household economy. There is no secure evidence here for tents, clothing styles, seasonally occupied camps or exchange between groups.

Before the Great Ice Expansion

The broader regional development was climatic. Derryvree’s ice-free freshwater environment belongs before the extensive MIS 2 ice-sheet advance that later transformed much of Ireland. Modelling of the British–Irish Ice Sheet places the onset of major build-up after the Derryvree evidence, with maximum extent reached much later, around 27,000 years before present. Glacial erosion and deposition would subsequently remove, bury or disturb much of the older landscape, helping explain why the archaeological record is so sparse.

Thus Ireland around 31,502 BCE should be imagined neither as an empty stage nor as a settled prehistoric country. It was a changeable cold-world landscape of wetlands, open vegetation and large mammals, locally free of ice but moving towards harsher glacial conditions. Derryvree’s silts and Castlepook’s bones are fragments of that world. Their value lies not in supplying a fictional event for a numbered year, but in showing how environmental survival, animal movement and perhaps a fleeting human act preceded the long silence imposed by the advancing ice.

Primary Sources

Tags: Birm-166, Castlepook Cave, County Cork, Ireland Year by Year, Late Pleistocene, Reindeer