First Humans in Ireland

During the Last Glacial Maximum, between about 26,000 and 20,000 years ago, ice sheets over 3,000 meters thick covered Ireland, dramatically reshaping its landscape. By 24,000 years ago, these glaciers extended beyond Ireland's southern coast. However, as the climate warmed, the ice began to retreat. By 16,000 years ago, only an ice bridge connected Northern Ireland to Scotland. By 14,000 years ago, Ireland stood isolated from Britain, with the glaciation period ending around 11,700 years ago, transforming Ireland into an arctic tundra landscape. This glaciation is known as the Midlandian glaciation.

Between 17,500 and 12,000 years ago, the Bølling-Allerød warming period allowed northern Europe to be repopulated by hunter-gatherers. Genetic evidence points to reoccupation starting in southwestern Europe, while faunal remains suggest an Iberian refugium extending into southern France. Reindeer and aurochs migrated north during this pre-boreal period, attracting humans who hunted migratory game at glacial termini as far north as Sweden.

As the Holocene began around 11,500 years ago, humans reached the northernmost ice-free zones of continental Europe, including areas near Ireland. Despite a warming climate, early Holocene Ireland remained inhospitable, limiting human settlement to possible fishing activities. Although a hypothetical land bridge may have connected Britain and Ireland, it likely disappeared around 14,000 BCE due to rising sea levels, preventing most terrestrial flora and fauna from crossing. Conversely, Britain remained connected to continental Europe until around 5600 BCE.

The earliest known modern humans in Ireland date back to the late Paleolithic. Radiocarbon dating in 2016 of a butchered bear bone from Alice and Gwendoline Cave in County Clare revealed human presence around 10,500 BCE, shortly after the ice retreated. Earlier discoveries, such as a flint found in Mell, Drogheda, and a reindeer bone fragment from Castlepook Cave, suggest human activity dating back as far as 33,000 years ago, though these instances are less definitive and might involve materials carried by ice.

Evidence from an 11,000 BCE site on the British coast of the Irish Sea suggests a marine diet including shellfish, indicating that people may have colonized Ireland by boat. However, due to few resources beyond coastal areas, these early populations may not have permanently settled. The Younger Dryas (10,900 BCE to 9700 BCE) brought a return of freezing conditions, possibly depopulating Ireland and ensuring the land bridge with Britain never reappeared.