Birm-166’s Tundra Record – Emerald Archives

Dateline

A Date Beyond Calendars

31,623 BCE is a modern chronological label, not a year that anyone in prehistoric Ireland could have named, counted or recorded. Expressed in the archaeological convention of years before AD 1950, it lies roughly 33,570 calendar years before present, within the Late Pleistocene and Marine Isotope Stage 3, a climatically unstable part of the last Ice Age. At this depth in time, neither radiocarbon dating nor glacial stratigraphy can resolve Irish history to a single year, season or generation. The responsible approach is therefore to ask what dated deposits can illuminate the broad interval around this point, and what they cannot.

The evidence is exceptionally sparse. Ireland has no securely dated house, hearth, tool assemblage, grave, monument or settlement from this notional year. There are no written sources, named peoples, rulers, territories or institutions. Claims about politics, diplomacy, warfare, formal religion, trade or an enduring population would consequently go well beyond the record. Yet the island was not necessarily an empty white space. Sediments beneath a Fermanagh drumlin and bones from north Cork caves preserve rare, partial evidence for a cold but living landscape before the greatest expansion of the British–Irish Ice Sheet.

The Freshwater Layer at Derryvree

The most useful Irish archive for the broad environmental setting is Derryvree townland, near Maguiresbridge in County Fermanagh. Roadworks in 1969 cut through a drumlin and exposed an extraordinary sequence: organic freshwater silts and fine sands lay between two thick, distinct beds of till, the debris left by moving ice. The sequence establishes a relative order with unusual clarity. An earlier glacier had deposited the lower till; a period without local glacier cover then allowed water, plants, invertebrates and sediment to accumulate; later ice buried the deposit beneath the upper till.

A radiocarbon determination, Birmingham laboratory sample Birm-166, gave an age of 30,500 radiocarbon years BP, with a substantial error range. Modern calibration is essential because radiocarbon years are not identical to calendar years. Published discussion places the broad calibrated span at approximately 36,900–31,700 cal BP, or roughly 34,950–29,750 BCE. The nominal date of 31,623 BCE falls within that large range. That overlap permits Derryvree to illuminate the general world of this article, but it does not demonstrate that any particular pond, plant, animal or human action existed in the precise numbered year.

The biological remains indicate open tundra vegetation and a periglacial climate. Pollen, plant macrofossils, mosses and insects point towards wet, mossy ground with sedges, grasses, herbs, low shrubs and shallow pools rather than woodland. The original investigators described a muskeg-like environment: waterlogged, plant-rich terrain broken by open water and damp margins. Winters were severe and the growing season short. Nevertheless, the deposit is important precisely because it records biological productivity. Cold Ireland was not uniformly lifeless, nor was it necessarily covered everywhere by permanent ice.

A Patchwork Rather Than an Ice Blanket

Derryvree must not be turned into a complete map of Ireland. It is one preserved locality in the north of the island, and its sediments accumulated over an interval rather than in a single instant. Conditions in Cork, the west coast, uplands and the Irish Sea basin could have differed substantially. Ice sheets advance, thin, stagnate and reorganise unevenly; local relief affects drainage, shelter and snow retention. Still, Derryvree decisively complicates the older image of Ireland as continuously smothered by ice throughout the later Pleistocene.

The major maximum of the last British–Irish Ice Sheet lay ahead. Large-scale reconstructions indicate considerable ice-sheet growth from about 31,000 years ago, with its maximum overall extent reached much later, around 27,000–23,000 cal BP, although timing differed across regions. Around the horizon represented by 31,623 BCE, Ireland was therefore entering a long transition towards harsher and more extensive glaciation, not standing at the maximum itself. The eventual ice advance both shaped the island’s familiar drumlin landscapes and destroyed or disturbed much older ground surfaces. That destructive history helps explain why a thin freshwater bed trapped beneath a drumlin is so valuable.

Castlepook and the Animal World

At Castlepook Cave, also known as Mammoth Cave, near Doneraile in north County Cork, excavations and later reassessment have produced Ireland’s most important collection of pre-Last Glacial Maximum vertebrate remains. The cave yielded a remarkably varied fauna, including woolly mammoth, reindeer, giant deer, brown bear, wolf, hare, arctic fox and spotted hyaena. Not all bones are contemporary, and cave deposits are difficult archives: carnivores can drag remains into dens; water can move material; early excavations did not meet modern recording standards; and later disturbance can mix deposits. Individual dates and contexts must therefore be assessed separately.

Even with those cautions, Castlepook demonstrates that parts of Ireland supported, or were visited by, a substantial cold-stage animal community over the wider Late Pleistocene. Reindeer and mammoth suggest open grazing country with enough vegetation to sustain large herbivores. Predators and scavengers indicate food chains more complex than modern Irish fauna might imply. Spotted hyaenas should not be imagined as misplaced modern African animals: during the Pleistocene they ranged through cold, open parts of Europe. A cave packed with bone need not have been a hunting camp; it may chiefly record carnivore activity and the chance preservation of carcass remains.

Recent sedimentary ancient-DNA work at Castlepook has added a further line of evidence, detecting taxa not all represented among identifiable bones and linking several faunal lineages to wider western Eurasian populations. This supports the interpretation that Ireland was biologically connected, at intervals, to neighbouring lands before the Last Glacial Maximum. It does not settle the exact route. Lower sea levels altered coastlines, but they did not automatically create a single, dry and easily traversed land bridge between Ireland, Britain and continental Europe. Animal movement may have depended on changing corridors, exposed shelves, short water crossings or combinations of these conditions.

The Limited Human Question

One Castlepook object has particular importance: a reindeer femur in the historic collection has been reported as about 33,000 years old and bears a deep mark interpreted by zooarchaeologist Ruth Carden as damage made with a sharp stone tool while fresh bone was being processed. If that interpretation and association are confirmed through continuing research, it would be evidence that Upper Palaeolithic people handled a reindeer in Ireland during this broad part of the Ice Age. It would push possible human activity on the island far earlier than the long-established record of post-glacial settlement.

It remains a striking but limited item of evidence, rather than proof of a permanent colony at Derryvree, Castlepook or anywhere else in Ireland. No associated stone tools, hearth, dwelling floor, grave or repeated occupation surface has yet been securely recovered from the relevant period. Nor can the femur identify the language, ancestry, numbers or social organisation of the people who may have made the mark. The safest conclusion is that a human visit or brief episode of carcass processing is possible, perhaps increasingly plausible, but continuous settlement cannot presently be demonstrated.

Everyday Life, Without Invention

If people did reach Ireland around this broad horizon, they would have belonged to the Upper Palaeolithic world of mobile hunter-gatherers known elsewhere in north-west Europe. Their survival would have depended on detailed knowledge of animals, weather, fuel, shelter, routes and the seasonal availability of water and plants. Reindeer could have provided meat, hides, sinews, antler and bone; however, no Irish camp has yet shown such a full range of activities. These are reasonable comparisons with contemporary European lifeways, not direct observations from an Irish household.

For the same reason, there is no responsible political narrative. There is no evidence for chiefs, territorial boundaries, alliances, raids, diplomacy or organised war. There is likewise no evidence for shrines, burials, ritual objects, visual art or formal religious practice in Ireland at this date. Caves can gain spiritual significance in later societies, but their use by carnivores or their capacity to preserve fossil bone does not make Castlepook a sanctuary. “Trade” is also the wrong word for the evidence. At most, faunal and possible human movement points to connectivity across the wider north-west European world.

An Archive of Survival

The significance of 31,623 BCE for Irish history lies not in an event assigned to that year, but in the survival of evidence from a period usually erased by ice. Derryvree’s freshwater layer shows that a periglacial wetland, with pools and tundra vegetation, existed during an ice-free interval between glacial advances. Castlepook’s bones show that cold-adapted mammals formed part of Ireland’s Late Pleistocene ecology, while the marked reindeer femur raises an important yet unresolved possibility of early human presence. Together, these archives replace a simplistic tale of an eternally frozen island with one of environmental fluctuation, intermittent habitats and uncertain movement.

They also set a high standard for restraint. Modern calendar precision is unavailable; calibrated ranges, geological relationships and carefully assessed fossils are stronger than dramatic certainty. Ireland around this notional date was a changing Ice Age landscape, perhaps with temporary corridors to a wider world, certainly with plants and animals resilient enough to occupy its cold ground. Whether people were only nearby, briefly present, or absent altogether remains one of the most consequential unanswered questions in Irish prehistory.

Primary Sources

Tags: Birm-166, Castlepook Cave, County Cork, Ireland Year by Year, Late Pleistocene, Marine Isotope Stage 3