Red hair is about as recessive as St. Patrick was Irish
The real truth of Ireland's historical genetics
Out along Europe’s western fringe, Ireland occupies a unique geographical and cultural space, where the continent ends and the vast ocean begins. Separated from Britain by as little as 12 miles (19 km), Ireland’s island history has been inextricably linked to that of its larger, fellow island nation throughout the past, despite their deep current political differences. Curiously, due to the capricious winds of history, today it is the more geographically remote Republic of Ireland that shelters in the fold of the European Union, rather than Britain with its robust record of involvement in the continent’s affairs. Buffered by the seas, Ireland has traditionally been overshadowed by Britain’s geopolitical machinations. In antiquity, when Britain was part of the Roman Empire, Ireland remained a barbarian land of myths, touched by Roman culture and trade, but never Roman politics or armies.
Because of its history, Ireland has become a sui generis creation on Europe’s edge, the furthest bank lapped by a broad stream of Northern European cultures that have flourished since the end of the last Ice Age, its people shaped by its isolation. The Emerald Isle is part of a larger story, but comes bearing its own unique plot twists. It is also an island of unique genetic characteristics, most salient among them the highest frequency of red hair in the world, which is probably a legacy of migrations more than 4,000 years in the past.
The Last Light of the Sun
Ireland remained neutral during World War II, and to this day it stands committed to geopolitical neutrality. But even 2,000 years ago, its remoteness left it uniquely beyond Rome’s reach and geopolitical influence. Christianity did not spread to Ireland through pressure from the Roman Empire, nor did it arrive by winning over a powerful king, as occurred in most of Northern Europe. Rather, Irish Christianity developed organically through contact with Roman Britain (St. Patrick was in fact British), recruiting warlords of the island one by one over several centuries from 400 A.D onward. Ironically, when Rome fell and Britain was conquered by pagan Saxons, Ireland instead remained a redoubt of Christianity, eventually sending missionaries to mainland Europe in the 500’s and 600’s who would founded monasteries in the borderlands between Italy, France and Switzerland. These Irish monks were also instrumental in converting the pagan Saxon kings of England to Christianity.
But Ireland’s remove from the currents of Northwest European history is not an eternal constant. The permanent human occupation of Ireland after the last Ice Age 12,000 years ago began as part of the broader resettlement of Europe’s deglaciated north that defined the early prehistory of Britain, Germany and Scandinavia. The earliest Mesolithic hunter-gatherers relied on fishing and foraging along the maritime fringes after they arrived in Ireland, where the earliest archaeological sites cluster near the ocean. These earliest Irish foragers were genetically identical to their contemporaries in mainland Europe and Britain, and they all descended from small groups of humans who rode out the end of the Ice Age in favorable pockets of Southern Europe. When archaeologists began collaborating with geneticists ten years ago, submitting prehistoric remains to DNA-sequencing technology, they discovered that very little of modern Irish or Northern European heritage more generally, derives from these first settlers, the “Western Hunter-Gatherers” (WHG). One surprising aspect of these earliest inhabitants of Northern Europe was that they were strikingly physically different from today’s people in the region, with blue eyes but very dark skin.