A large team of researchers reported this week that it had sequenced the whole genomes of four prehistoric Irish individuals: a Neolithic woman (3343 – 3020 BC) from a tomb in Ballynahatty near Belfast, and three Early Bronze Age men (2026 – 1534 BC) from a cist burial in Rathlin Island.

According to the team, led by Trinity College Dublin scientist Prof. Dan Bradley, Ireland has intriguing genetics.

“It lies at the edge of many European genetic gradients with world maxima for the variants that code for lactose tolerance, the western European Y chromosome type, and several important genetic diseases including one of excessive iron retention, called hemochromatosis. However, the origins of this heritage are unknown,” the scientists explained.

“We address this issue by using the first whole genome data from prehistoric Irish individuals,” they wrote in a study published December 28 in the Proceedings of the National Academy of Sciences. The study is the first time ancient human genomea have been recovered and sequenced from Ireland.

Prof. Bradley and co-authors said the newly sequenced genomes each show unequivocal evidence for massive migration.

“A Neolithic woman from a megalithic burial possessed a genome of predominantly Near Eastern origin. She had some hunter-gatherer ancestry but belonged to a population of large effective size, suggesting a substantial influx of early farmers to the island,” they said.

“Three Bronze Age individuals from Rathlin Island showed substantial Steppe genetic heritage indicating that the European population upheavals of the third millennium manifested all of the way from southern Siberia to the western ocean.”

“This turnover invites the possibility of accompanying introduction of Indo-European, perhaps early Celtic, language.”

“It is clear that this project has demonstrated what a powerful tool ancient DNA analysis can provide in answering questions which have long perplexed academics regarding the origins of the Irish,” added co-author Dr Eileen Murphy, of Queen’s University Belfast.

Whereas the early farmer had black hair, brown eyes and more resembled southern Europeans, the genetic variants circulating in the three individuals from Rathlin Island had the most common Irish Y chromosome type, blue eye alleles and the most important variant for hemochromatosis.

The latter C282Y mutation is so frequent in people of Irish descent that it is sometimes referred to as a Celtic disease.

“Genetic affinity is strongest between the Bronze Age genomes and modern Irish, Scottish and Welsh, suggesting establishment of central attributes of the insular Celtic genome some 4,000 years ago,” said study first author Lara Cassidy, of Trinity College Dublin.

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Lara M. Cassidy et al. Neolithic and Bronze Age migration to Ireland and establishment of the insular Atlantic genome. PNAS, published online December 28, 2015; doi: 10.1073/pnas.1518445113