Orkney experienced a wave of immigration during the Bronze Age so large that it replaced most of the local population, ancient DNA analysis has revealed.
Experts say that unlike anywhere else, the Bronze Age newcomers to the islands were mostly women.
Although male lineages from the original Neolithic population survived for at least another thousand years, by the Iron Age, which followed the Bronze Age, they were largely replaced and are vanishingly rare today.
Researchers from the Universities of Edinburgh and Huddersfield combined archaeology with the study of ancient DNA from Bronze Age human remains to shed light on this pivotal moment for the islands.
Around 5200 years ago, during the Neolithic period, when farming first took hold, Orkney was a hugely influential cultural centre. Yet, as Europe moved into the Bronze Age around 4500 years ago, the islands' influence dwindled and it supposedly became more insular.
Despite this, after studying human remains from the Links of Noltland site on the remote northern island of Westray, the research team concluded that Orkney experienced large-scale immigration during the Bronze Age.
The new arrivals were probably the first visitors to Orkney speaking Indo-European languages, and carried genetic ancestry derived in part from livestock farmers living on the steppe lands north of the Black Sea.
This migration of people mirrored what was happening in the rest of Great Britain and Europe in the Early to Middle Bronze Age, experts say.
Across most of Europe, the expansion of livestock farmers on the eve of the Bronze Age was typically led by men.
But in Orkney the researchers found exactly the opposite. The Bronze Age newcomers were mainly women. The survival in Orkney of male lineages from the original Neolithic population for at least another thousand years is not seen anywhere else.
Researchers believe Orkney is so different due to the long-term stability and self-sufficiency of farmsteads on the islands, which the genetic data suggest may have been male dominated by the peak of the Neolithic.
When a Europe-wide recession hit towards the end of the Neolithic, Orkney farmers may have been uniquely placed to weather harsher times and maintain their grip on the population as newcomers arrived.
This implies that Orkney was much less insular than has long been assumed. There was a protracted period of integration of the indigenous males with the newcomers from the south over many generations, experts say.
Jim Wilson, Professor of Human Genetics at the University of Edinburgh's Usher Institute, said: "It's absolutely fascinating to discover that the dominant Orcadian Neolithic male genetic lineage persisted at least 1000 years into the Bronze Age, despite replacement of 95 per cent of the rest of the genome by immigrating women. This lineage was then itself replaced and we have yet to find it in today's population."
The study, which appears in Proceedings of the National Academy of Sciences (PNAS), was supported by a Leverhulme Trust Doctoral Scholarship programme, Historic Environment Scotland and the Medical Research Council.
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