Research done into the DNA of the Irish has shown that our old understanding of where the population of Ireland originated may have been misguided. Although the modern Irish have been shown to share many genetic similarities with Scottish and Welsh populations, and to differ somewhat from the English, due to repeated waves of migration to the island they also have close genetic relations with people further afield. In fact, some of the Irish's closest DNA links are with regions further afield!
This article is based upon the latest research sequencing the genomes of the remains of ancient Irish people, published at the end of 2015
Where Did the Early Irish Come From?
For a long time the myth of Irish history has been that the Irish are Celts. Many people still refer to Irish, Scottish, and Welsh as Celtic culture. The assumption has been that they were Celts who migrated from central Europe around 500BCE.
Keltoi was the name given by the Ancient Greeks to a 'barbaric' (in their eyes) people who lived to the north of them in central Europe. While early Irish art shows some similarities of style to central European art of the Keltoi, historians have also recognized many significant differences between the two cultures.
Recent research into Irish DNA at the beginning of the twenty-first century suggests that the early inhabitants of Ireland were not directly descended from the Keltoi of central Europe. Genome sequencing performed on remains of early settlers in Ireland by researchers at Trinity University in Dublin and Queens University has revealed at least two waves of migration to the island in past millennia. Analysis of the remains of a 5,200 year-old Irish farmer suggested that the population of Ireland at that time was closely genetically related to the modern-day populations of southern Europe, especially Spain and Sardinia. Her ancestors, however, originally migrated from the Middle East, the cradle of agriculture.
Meanwhile, the research team also examined the remains of three 4,000 year-old men from the Bronze Age and revealed that another wave of migration to Ireland had taken place, this time from the edges of Eastern Europe. One third of their ancestry came from the Steppe region of Russia and Ukraine, so their ancestors must have gradually spread west across Europe. These remains, found on Rathlin Island also shared a close genetic affinity with the Scottish, Welsh, and modern Irish, unlike the earlier farmer. This suggests that many people living in Ireland today have genetic links to people who were living on the island at least 4,000 years ago.
Most interestingly, the book says that the group which then came to Ireland and fully established itself as rulers of the island were the Milesians—the sons of Mil, a soldier from Spain. Modern DNA research has actually suggested that the Irish are close genetic relatives of the people of northern Spain.
What we do know is that the modern Irish are descended from a number of waves of migration with some ancestors coming from as far away as the Middle East and the Russian Steppes. Although it might seem surprising, it is worth remembering that in ancient times the sea was one of the fastest and easiest ways to travel. When the land was covered in thick forest, coastal settlements were common and people travelleled around the seaboard of Europe quite freely.
DNA testing through the male Y chromosome has shown that Irish males have the highest incidence of the haplogroup 1 (or Rb1) gene in Europe. While other parts of Europe have integrated continuous waves of new settlers from Asia, Ireland's remote geographical position has meant that the Irish gene-pool has been less susceptible to change. The same genes have been passed down from parents to children for thousands of years. The other region with very high levels of this male chromosome is the Basque region.
This is mirrored in genetic studies which have compared DNA analysis with Irish surnames. Many surnames in Irish are Gaelic surnames, suggesting that the holder of the surname is a descendant of people who lived in Ireland long before the English conquests of the Middle Ages. Men with Gaelic surnames, showed the highest incidences of Haplogroup 1 (or Rb1) gene. This means that those Irish whose ancestors pre-date English conquest of the island are descendants (in the male line) of people who probably migrated west across Europe, as far as Ireland in the north and Spain in the south.
Some scholars even argue that the Iberian peninsula (modern-day Spain and Portugal) was once heavily populated by Celtiberians who spoke at now-extinct Celtic language. They believe some of these people moved northwards along the Atlantic coast bringing Celtic language and culture to Ireland and Britain, as well as France. Although the evidence in not conclusive, the findings on the similarities between Irish and Iberian DNA provides some support for this theory.
However, research into both British and Irish DNA suggests that people on the two islands have much genetically in common. Males in both islands have a strong predominance of the Haplogroup 1 gene, meaning that most of us in the British Isles are descended from the same stone age settlers.
The main difference is the degree to which later migrations of people to the islands affected the population's DNA. Parts of Ireland (most notably the western seaboard) have been almost untouched by outside genetic influence since early times. Men there with traditional Irish surnames have the highest incidence of the Haplogroup 1 gene - over 99%.
At the same time London, for example, has been a mutli-ethnic city for hundreds of years. Furthermore, England has seen more arrivals of new people from Europe - Anglo-Saxons and Normans - than Ireland. Therefore while the earliest English ancestors were very similar in DNA and culture to the tribes of Ireland, later arrivals to England have created more diversity between the two groups.
Irish and Scottish people share very similar DNA. The obvious similarities of culture, pale skin, tendency to red hair have historically been prescribed to the two people's sharing a common Celtic ancestry. Actually, in my opinion, it seems much more likely that the similarity results from the movement of people from the north of Ireland into Scotland in the centuries 400 - 800 AD. At this time the kingdom of Dalriada, based near Ballymoney in County Antrim extended far into Scotland. The Irish invaders brought Gaelic language and culture, and they also brought their genes.
These genes were then brought to the British Isles by the original settlers, men and women who would have been relatively tall, with little body fat, athletic, fair-skinned and who would have had red hair. So red-heads may well be descended from the earliest ancestors of the Irish and British.
The ambiguity comes in when trying to determine whether dark-haired Irish people are genetically distinct from Irish with lighter coloring. Dark hair is common in Ireland, while dark complexions are more rare.
One theory about the origins of the term is that it describes Irish people who descend from survivors of the Spanish Armada. There are other hypotheses, mostly placing Irish ancestors on the Iberian peninsula or among the traders that sailed back and forth between Spain, North Africa, and Ireland, particularly around the Connemara region.
Some "Black Irish" are of Irish-African descent, tracing their ancestry back to the slave trade. Many of these people live on Barbados and Montserrat.
Some readers, writing below, with typical Black Irish coloring have had genetic testing done to confirm that they have Spanish, Portuguese, and Canary Island heritage.