Daily Mirror (Northern Ireland)
The Vi-kings of Ireland
Norsemen, French and British have invaded DNA, study reveals 20-30%
THE Irish are much more genetically diverse than previously believed and have Viking and Norman ancestry, research has revealed.
A comprehensive DNA map of people on the island has for the first time revealed lasting contributions from British, Scandinavian and French invasions.
An estimated 80 million people worldwide claim Irish descent – almost half of them Americans who regard it as their main ethnicity.
It has long been assumed this means the blood in their veins is Celtic but geneticists say the truth is much more complicated.
Their latest research has uncovered a previously hidden DNA landscape, shaped through geography and historical migrations.
The findings, published in the journal PLOS Genetics, could also shed fresh light on genetic diseases and lead to better treatments.
For example, in both the UK and Ireland prevalence of multiple sclerosis increases the further North you go.
And compared with the rest of Europe, the Irish have higher rates of coeliac disease and galactosemia, a serious metabolic disorder that prevents the breakdown of sugars in dairy, legumes (beans, lentils etc) and organ meats.
In the 10,000 years since Stone Age cavemen first arrived the Irish have established distinct cultural regions.
But previous studies had identified no clear genetic groups within the population.
Researchers have now found 23 distinct genetic clusters, separated by geography by comparing mutations from almost 1,000 Irish genomes (genetic material of an organism), with more than 6,000 from Britain and mainland Europe.
These are most distinct in western Ireland, but less pronounced in the east, where historical migrations have erased the genetic variations.
When the researchers took into account genetic contributions from people with British ancestry, a clear trend arose, showing this input dropping off in populations to the west.
They also detected genes from Europe and calculated the timing of the historical migrations of the Norse-vikings and the Anglo-normans to Ireland, yielding dates consistent with historical records.
The study paints a new and more complex picture of the genetic landscape of Ireland, and demonstrates the signatures that historical migrations have left on the modern Irish genome.
The findings also show a distinct genetic structure can exist even within small, isolated populations.
The Trinity College Dublin team suggest this newly-revealed structure should be taken into account in future studies that use the Irish population to identify genetics underlying various traits and diseases.
Geneticist Dr Ross Byrne said: “This subtle genetic structure within such a small country has implications for medical genetic association studies.
“As it stands current corrections for population structure in study designs may not adequately account for this within country variation, which may potentially lead to false positive results.
“We feel this will be particularly important in the analysis of rare variants as these are expected to be less uniformly distributed throughout a country.
“We intend to explore this and identify if this structure should be accounted for in corrections.”