Genetic history of the British Isles

The genetic history of the British Isles is the subject of research within the larger field of human population genetics. It has developed in parallel with DNA testing technologies capable of identifying genetic similarities and differences between both modern and ancient populations. The conclusions of population genetics regarding the British Isles in turn draw upon and contribute to the larger field of understanding the history of the human occupation of the area, complementing work in linguistics, archaeology, history and genealogy.

Research concerning the most important routes of migration into the British Isles is the subject of debate. Apart from the most obvious route across the narrowest point of the English Channel into Kent, other routes may have been important over the millennia, including a land bridge in the Mesolithic period, as well as maritime connections along the Atlantic coasts.

Genetic studies have revealed multiple migration waves into Britain and Ireland from the Palaeolithic onwards, with detectable regional differences among present-day populations. After the Last Glacial Maximum, hunter-gatherer groups carrying two distinct ancestries (GoyetQ2-related and Villabruna-related) repopulated Britain and Ireland, with the latter eventually becoming dominant. This hunter-gatherer ancestry was substantially replaced during the Neolithic revolution, c. 4000 BC, by groups carrying Early European Farmer (EEF) ancestry from the European mainland, who admixed to a certain extent with the existing hunter-gatherer population in some regions. At the start of the Bronze Age, another major population replacement occurred when migrating Bell Beaker groups, carrying a high proportion of Steppe-related ancestry, replaced around 90% of the Neolithic gene pool. Throughout the Bronze and Iron Ages, further migration from mainland Europe raised the proportion of Early European Farmer ancestry in southern Britain. This has been proposed as one possible mechanism for the introduction of Celtic languages.

Other potentially important historical periods of migration that have been subject to consideration in this field include the Roman era, the period of early Germanic influx, the Viking era, the Norman invasion of 1066, and the era of the European wars of religion.