A genetic population study across Scotland has been found to reflect the boundaries of the medieval kingdoms.

Population studies can give a window into human history as migrations, invasions and hardships all leave a genetic signature. For example, Britain was first invaded by the Vikings in AD 793. Interbreeding between the Vikings and the Anglo-Saxons is reflected in the British population today as Nordic ancestry is still observed in modern British populations.

Genetic data was taken from 2,544 individuals from all over Scotland, including from isolated areas such as Shetland and the Herbrides. 341,924 common genetic markers were compared between the individuals. This was to identify genetic similarities between people and see if these correlated with location.

The researchers found that there were six distinct genetic subtypes of the Scottish population clustered in different areas of the country; the northeast, the southwest, the Borders, the Hebrides, Orkney, and Shetland. The geographic population structure was therefore found to correlate with the borders of the medieval kingdoms of Scotland. For example, the northeast cluster appears to mirror the boundaries of an ancient Pictish kingdom. The researchers state that this was a surprising find, given the high prevalence of migration in modern day Britain.

The northern islands of Scotland demonstrated long periods of geographic isolation. The current population here showed similar genetic variants and low gene flow. This means that for long periods these areas were cut off from mainland and the island population would interbreed with each other, reducing the genetic variation.

The researchers also found genetic correlation between Icelanders with Gaelic ancestry and current day populations from Northwest Britain and Ireland, suggesting that Gaelic people may have migrated to Iceland during the Viking invasion.

However, population genetics also has application in genetic research. By showing what disease variants are common in particular locations, treatments can be personalised towards patients.

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