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First Sequences of Ancient Irish Human Genomes Support Mass Migration History

NEW YORK (GenomeWeb) – A study of the first sequences of ancient Irish human genomes, published late yesterday in the Proceedings of the National Academy of Sciences, has provided strong new evidence for a history of mass migrations into Ireland and their cultural impact.

A team led by geneticists from Trinity College Dublin and archaeologists from Queen’s University Belfast sequenced the genome of one early farmer woman presumed to live near Belfast about 5,200 years ago, as well as those of three men from from Rathlin Island in the Bronze Age era — around 4,000 years ago.

The results appear to paint a genomic picture of a history of migrations of people from elsewhere into Ireland that parallel specific cultural changes on the island, including a transition to agriculture, the development of bronze metalworking, and potentially even the beginnings of the western Celtic language.

According to the study authors, the archaeological field has been divided as to whether some of the most significant changes — for example from a hunter-gatherer lifestyle to an agricultural one, or from the use of stone tools to metal — occurred in the British Isles as independent local leaps forward, or through the influence of new people migrating into the region.

Although high-throughput sequencing has allowed comparisons of genetic variation in ancient populations elsewhere in Europe that clearly show population movement corresponding with major cultural shifts, the location of the islands of Britain and Ireland and the timing of their shifts in relation to the rest of Europe have left open for debate whether this region was also influenced by successive population influxes in the same way.

But with the new genomic data, it appears that Ireland indeed shares in this greater European migratory history. For example, sequencing results from the study revealed that the early female farmer had a majority ancestry originating in the Middle East, where agriculture was invented.

"She shares higher levels of genetic drift with … samples from Spain rather than those from Germany, supporting a link between the early farming cultures of Atlantic Europe and arguing for the possible passage of farming to Ireland via a southern coastal route rather than via the migrations through central Europe," the authors wrote.

Meanwhile, the Bronze Age male genomes evidenced a second phase of genetic and cultural influx into Ireland. Each sample exhibited the Bronze Age-associated Y chromosome lineage R1b-M269, which has been strongly linked with Steppe incursion into Central Europe. "Thus, it is clear that the great wave of genomic change which swept from above the Black Sea into Europe around 3000 BC washed all of the way to the northeast shore of its most westerly island," they wrote.

The genomic data also indicated that the early farmer had black hair, brown eyes and more resembled southern Europeans, while the three Bronze Age men had alleles for blue eye, as well as the C282Y mutation, a variant for hemochromatosis thatis so frequent in people of Irish descent that it is sometimes referred to as a Celtic disease, the authors wrote.

Finally, though it will require further study to confirm, the authors suggested that the genomes of the three Bronze Age individuals, along with archaeological data, suggest that the influx of migrants with Steppe ancestry may also have been a vector for the introduction of Indo-European language ancestral to Irish.

"There was a great wave of genome change that swept into Europe from above the Black Sea into Bronze Age Europe and we now know it washed all the way to the shores of its most westerly island and this degree of genetic change invites the possibility of other associated changes, perhaps even the introduction of language ancestral to western Celtic tongues," Dan Bradley, a professor of population genetics at Trinity College Dublin, and the leader of the study, said in a statement.