A landmark study into the genetic makeup of the British Isles has created the first fine-scale genetic map of any country in the world.
The analysis, led by Australians Stephen Leslie and Peter Donnelly, reveals significant insights into the history of movements of people into the UK over the last 10,000 years. According to the 2011 Census, over half (55%) of Australians nominate their heritage as English, Scottish, Welsh or Irish.
The international team of researchers, including lead author Dr Stephen Leslie from Murdoch Children's Research Institute, used DNA samples collected from more than 2,000 people from the UK and compared this information with DNA samples from over 6,000 Europeans.
The team, whose findings were published in Nature, were able to identify clear traces of the population movements into the UK since the last major ice age. Their work confirmed, and in many cases shed further light on, known historical migration patterns. Their findings show that prior to the mass migrations of the 20th century there was a striking pattern of rich but subtle genetic variation across the UK, with distinct groups of genetically similar individuals showing remarkable geographical clustering.
“Rich genetic information such as this tells us a great deal about our history and augments what we know already from archaeology, linguistic and historical records,” said Dr Leslie.
“Much of what we’ve learned about our history comes from the successful people of society, as they leave the strongest marks on history and archaeology. By using genetics and sophisticated statistical methods, we have been able to tell the story of the masses.”
The researchers were able to “zoom in” to examine the genetic patterns in the UK in levels of increasing resolution. At the broadest scale, the population in Orkney (islands to the north of Scotland) emerged as the most genetically distinct, reflecting their history of settlement by Norse Vikings. The next level shows Wales to form a distinct genetic group, followed by a further division between north and south Wales. Subsequently the north of England, Scotland, and Northern Ireland collectively separate from southern England. At the next level, Cornwall forms a separate cluster, followed by Scotland and Northern Ireland separating from northern England. The study then focused at the level where the UK was divided into 17 genetically distinct clusters of people, whose genomes were found to contain a cocktail of DNA from different European groups.
Selected key findings from the study show;
- There was not a single “Celtic” genetic group. In fact, the Celtic parts of the UK, (Scotland, Northern Ireland, Wales and Cornwall), are amongst the most different from each other genetically. For example, the Cornish are much more similar genetically to other English groups than they are to the Welsh or the Scots.
- The vast majority of central and southern England is made up of a single, relatively homogeneous, genetic group with a significant DNA contribution from Anglo-Saxon migrations (between 10-40% of total ancestry). This also settles a historical controversy in showing that the Anglo-Saxons intermarried with, rather than replaced, the existing populations.
- The Welsh appear more similar to the earliest settlers of Britain after the last ice age than do other people in the UK.
- There is no obvious genetic signature of the Danish Vikings, who controlled large parts of England (“The Danelaw”) from the 9th century, suggesting they did not leave much DNA behind.
- Many of the genetic clusters show similar locations to the tribal groupings and kingdoms around at the time of the Saxon invasion (from the 5th century), suggesting these tribes and kingdoms may have maintained a regional identity for many centuries.
- The population in Orkney emerged as the most genetically distinct, with 25% of DNA coming from Norwegian ancestors (most likely from the invasion of the Norse Vikings in the 9th century).
Using a recently developed and highly sophisticated statistical method, called fineSTRUCTURE, the researchers were able to analyse the DNA variation at more than 500,000 positions within the genome to detect subtle genetic differences. They then separated the samples into genetically similar individuals, without knowing where in the UK the samples came from. By plotting each person onto a map of the British Isles, using the centre point of their grandparents’ birth places, they were able to see how this distribution correlated with their genetic groupings.
The People of the British Isles study sampled 2,039 people from rural areas of the UK, whose four grandparents were all born within 80km of each other. Because a quarter of our genome comes from each of our grandparents, the researchers were effectively sampling DNA from these ancestors, allowing a snapshot of UK genetics in the late 19th Century. They also analysed data from 6,209 individuals from 10 modern European countries.
Michael Dunn from the Wellcome Trust, one of the world’s largest private funders of research, added, “This study used modern genetic techniques to provide answers to the centuries’ old question - where do we come from? Beyond the fascinating insights into our history, this information could prove very useful from a health perspective. Building a picture of population genetics at this scale may in future help us to design better genetic studies to investigate disease.”
The study was co-led by Sir Walter Bodmer from the University of Oxford, who conceived the People of the British Isles study, and Professor Peter Donnelly, Director of the Wellcome Trust Centre for Human Genetics at the University of Oxford.