The first fine-scale analysis of the population of the UK shows that subtle variations in the genetic make-up of modern Britons reflect the history of their islands’ colonisation by peoples from mainland Europe since the last Ice Age.
‘It has long been known that human populations differ genetically, but never before have we been able to observe such exquisite and fascinating detail’, says Peter Donnelly, Director of WTCHG, who co-directed the work and led the statistical analysis together with Simon Myers, who also works in the WTCHG, Garrett Hellenthal from University College London and Stephen Leslie of Murdoch Childrens Research Institute in Australia.
The results of the People of the British Isles study, just published in the journal Nature, confirm that successive waves of invaders never wiped out the existing populations but interbred with them. The genetic data finds substantial traces throughout the UK of DNA which originated with the earliest settlers of Britain after the last ice age. People in Wales have the highest proportion of this early British DNA, but even in the southern, central and eastern regions settled by Anglo-Saxons after the fall of the Roman Empire, DNA of Anglo-Saxon origin accounts for no more than 40 per cent of people’s genetic inheritance.
The project was devised by Sir Walter Bodmer from the Department of Oncology, who wanted to establish whether there were meaningful levels of genetic differentiation between populations in the UK as a background to studies of genetic disease. He and his colleagues collected DNA samples from 2,039 people in rural areas, all four of whose grandparents were born within 80 km of each other. Effectively this made it possible to sample DNA from the grandparents, who had been born before the major population movements of the 20th century.
The researchers used statistical tools to compare the DNA of the participants at an unprecedented level of detail. They found that the samples could be grouped into 17 clusters, which coincided strongly with geographical areas. People in Orkney, for example, were very different from all other groups; people in Cornwall were different from those in their neighbouring county of Devon.
The researchers went on to compare each cluster’s DNA with samples from 6,209 people in 10 European countries with a history of migration to the British Isles. Orkney’s distinctive signature derived from a strong dose of Norse Viking DNA; in contrast, the Danish domination of northern and eastern England between the 9th and 11th centuries appears to have left no genetic trace.
The study depended on high-performance computing and cutting-edge statistical techniques, recently developed by Simon Myers, Garrett Hellenthal, and two of the other authors, to uncover these subtle effects. ‘In future, increasingly large datasets will allow us to learn even more about the genetic history of the UK, and the similarly rich histories of other world regions, by applying similar techniques’, says Myers.
Other major findings of the study were: