Birm-166’s Wide Horizon – Emerald Archives

Dateline

31,542 BCE is a useful point on a modern chronological scale, but it was not a year that anyone living in Ireland could have named, counted or recorded. No political chronicle, settlement sequence or human biography can be attached to it. At this depth of time, calendar-year precision is unavailable: the responsible subject is Ireland during the later part of Marine Isotope Stage 3, a fluctuating phase of the last Ice Age. The numbered year corresponds approximately to 33,500 calibrated years before present, conventionally before 1950, but it must be treated as an illustrative point within much broader dated ranges rather than as the date of an event.

The most directly relevant Irish evidence is a freshwater deposit exposed in 1969 at Derryvree, near Maguiresbridge in County Fermanagh. Its laboratory reference, Birm-166, has become important precisely because it records an interval between two separate glacial deposits. That sequence gives Ireland a rare glimpse of an ice-free local landscape before a later advance buried it beneath till. It does not supply an anniversary. It supplies a window.

A Date With Broad Edges

Organic silts and fine sands at Derryvree produced a conventional radiocarbon result of 30,500 years BP, with a substantial uncertainty of +1,170 and −1,030 years. Radiocarbon years are not calendar years: changing atmospheric carbon-14 levels mean that results must be calibrated against internationally maintained curves. Modern calibration places the determination broadly within about 36,900–31,700 calibrated years BP, or roughly 34,950–29,750 BCE. That wide interval includes 31,542 BCE, but it cannot locate that notional year in a particular layer, season or episode at the site.

There is a second chronological caution. The North Greenland ice-core record places Greenland Interstadial 6 between about 33,740 and 33,360 years before AD 2000. The date considered here falls approximately within that short, comparatively milder North Atlantic interval. Yet this does not prove that conditions changed in Fermanagh on precisely the same day, decade or even century as the Greenland signal. Ice cores are a superb framework for regional climatic comparison, not a licence to impose exact synchrony on a sparse Irish deposit. In this article, Derryvree’s calibrated range is evidence; its possible relationship to wider North Atlantic oscillations is interpretation.

Freshwater Beneath A Drumlin

The Derryvree road cutting revealed a simple but powerful sequence. A lower till had been laid down by glacier ice. Above it, in a non-glacial interval, freshwater silts, sands and organic material accumulated in or beside still water. An upper till then sealed the deposits as ice returned. The organic bed held plant and animal remains characteristic of a cold, open environment. Its pollen, seeds and other microfossils included sedges, mosses and plants such as bogbean, water-milfoil and mountain avens; dwarf willow and juniper were also identified. These remains indicate a wet, treeless tundra or tundra-steppe setting, not an Irish landscape of closed woodland, farms or bogs in their modern form.

That conclusion needs local limits. Derryvree was a freshwater basin in what is now inland Fermanagh, and its plant record describes vegetation growing around that particular wetland. It does not demonstrate that every coast, upland and lowland of Ireland looked identical. Nor does an ice-free interval at the site establish that all of Ireland was free of ice. Ireland’s glaciers expanded and retreated unevenly, their form governed by altitude, snowfall, temperature, sea margins and the changing behaviour of ice streams. What the deposit securely shows is that, during part of its broad age range, open ground, freshwater and cold-adapted vegetation existed at Derryvree between two glacial episodes.

Such a place was severe but productive. In the brief growing season, shallow pools, sedge margins and damp mineral soils could support flowering plants, mosses and insects. During the long cold season, frost, snow cover, frozen ground and strong winds would have made the locality exposed. The term “periglacial” is useful here: it denotes a climate strongly shaped by repeated freezing and thawing beside or beyond glacier ice. It does not mean a lifeless white desert. The sediment’s biological remains are the reason that it can be recognised as a functioning wetland landscape.

The Irish Faunal Record

Other Irish evidence gives this setting an animal dimension, though not a single, neatly contemporaneous community. Caves in the south, especially Castlepook Cave near Doneraile in County Cork, yielded a remarkable assortment of Late Pleistocene bones: mammoth, reindeer, giant deer, brown bear, wolf, Arctic fox, hare, lemmings and spotted hyaena among them. Improved ultrafiltration and radiocarbon work has shown that several earlier dates from these collections were too young. The revised results place important elements of the Castlepook fauna in Marine Isotope Stage 3, and suggest that giant deer and spotted hyaena had disappeared locally before the Last Glacial Maximum.

The cave assemblage is invaluable, but it must not be turned into a census for 31,542 BCE. Castlepook was used by carnivores as well as receiving bones by natural processes; nineteenth- and early twentieth-century excavations also removed deposits before modern methods were available. Different animals may have died or been carried in at different times, and some later material entered the cave. A mammoth bone, a hyaena tooth and a reindeer limb found in the same cave system do not automatically prove that the animals met one another on a particular day. Nevertheless, the assemblage establishes that Ireland was intermittently accessible to a broader cold-stage fauna than its later historical wildlife would suggest.

Reindeer are especially relevant to the open habitats indicated at Derryvree. Their presence in the Irish Pleistocene record is compatible with grass- and sedge-rich ground, while lemmings and Arctic fox point towards cold conditions. Giant deer, despite the misleading popular name “Irish elk”, was not uniquely Irish; it was a widespread Eurasian deer. Research on a much later Irish giant-deer tooth has found evidence consistent with seasonal movement. That cannot demonstrate the movements of animals thousands of years earlier at Derryvree, but it is a reminder that Pleistocene animals could respond to seasonal stress by mobility rather than remaining within one small territory.

People: Possibility, Not Settlement

There is no securely excavated house, hearth, stone-tool assemblage, human burial or enduring settlement in Ireland dated to around 31,542 BCE. Accordingly, there can be no responsible account of Irish political affairs, leaders, diplomacy, warfare, social classes, religion, trade networks or learning at this date. The evidence is simply not there. Terms such as “tribe”, “chief” or “Irish people” would import later assumptions into a period for which even a human presence remains uncertain.

One object explains why the question remains open. A reindeer femur from Castlepook Cave has been presented as dating to about 31,000 BCE and bears a deep surface mark interpreted by Ruth Carden as a cut made by a sharp stone tool while fresh bone was being processed. If that interpretation is sustained, it would indicate a human visit or hunting activity far earlier than Ireland’s previously accepted Palaeolithic evidence. It would not, by itself, prove a resident population, a camp at Castlepook, or the identity and culture of those visitors. The bone’s age dates the animal; interpretation of the incision requires separate taphonomic judgement; and the old cave context limits certainty.

The more widely discussed direct evidence for people in Ireland remains much later: a cut-marked brown-bear kneecap from Alice and Gwendoline Cave, County Clare, has calibrated ranges around 12,810–12,590 years BP. The contrast matters. A possible MIS 3 reindeer butchery signal and a securely dated terminal-Pleistocene modified bear bone are not equivalent kinds of evidence. Around 31,542 BCE, the safest conclusion is that transient human incursions are possible, perhaps linked to following game across the then-expanded landscapes of the Irish Sea region, but that permanent occupation is unproven.

Land, Ice And Connection

Sea level was far lower than today because much water was held in northern ice sheets. Ireland was therefore not yet the fully isolated island familiar from later prehistory and history, although routes through the Irish Sea basin were shaped by changing sea level, rivers, topography and ice. Animals could enter during favourable windows; any people who reached Ireland would have done so through the same larger north-west European world, not across the modern coast. This was a landscape in transition rather than a fixed land bridge.

The future was harsh. The Last Glacial Maximum, when ice ultimately covered Ireland and its continental shelf much more extensively, lay ahead, with maximum expansion generally dated to about 27,000–23,000 calibrated years BP. Glacial erosion and deposition would remove, bury or scramble much earlier evidence. That geological history partly explains the extraordinary thinness of Ireland’s record: the absence of sites is not proof that no animal or person ever crossed the region, but neither is it evidence for a lost flourishing society.

For Ireland around this notional year, Birm-166 offers the clearest lesson. Beneath later ice lay freshwater mud, sedges, mosses and the residues of an open cold landscape. The archaeological story is not one of kingdoms or monuments, but of a land repeatedly made habitable and then remade by climate. Its surviving witnesses are a buried wetland in Fermanagh, scattered cave bones in the south, and dated samples whose uncertainty is not a weakness to conceal, but the measure of what can honestly be known.

Primary Sources

Tags: Castlepook Cave, County Cork, County Fermanagh, Ireland Year by Year, Marine Isotope Stage 3, Radiocarbon Dating