British Genetic Study 2015

A study into the genetic makeup of the British population was published in the journal Nature in March 2015.

NATURE Abstract     Nature 519, pp 309–314 (19 March 2015)

Fine-scale genetic variation between human populations is interesting as a signature of historical demographic events and because of its potential for confounding disease studies. We use haplotype-based statistical methods to analyse genome-wide single nucleotide polymorphism (SNP) data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom. This reveals a rich and detailed pattern of genetic differentiation with remarkable concordance between genetic clusters and geography. The regional genetic differentiation and differing patterns of shared ancestry with 6,209 individuals from across Europe carry clear signals of historical demographic events. We estimate the genetic contribution to southeastern England from Anglo-Saxon migrations to be under half, and identify the regions not carrying genetic material from these migrations. We suggest significant pre-Roman but post-Mesolithic movement into southeastern England from continental Europe, and show that in non-Saxon parts of the United Kingdom, there exist genetically differentiated subgroups rather than a general ‘Celtic’ population.

The study used a detailed DNA analysis of 2,000 mostly middle-aged Caucasian people living across the UK, each of whom had all four of their grandparents living close to each other in a rural area. This selection criterion enabled the Oxford University-led researchers to filter out 20th-century immigration and to look back to earlier migration patterns. They compared genetic patterns now with the map of Britain in about AD 600, after the Anglo Saxons had arrived from what is now southern Denmark and Northern Germany and by which time they occupied much of central and southern England. They also compared the analysis with the genetic data on 6,000 people from ten European countries.

• Modern Britain can be divided into 17 distinct genetic groups.
• The expectation of a uniform Celtic fringe extending from Cornwall through to Wales into Scotland was not supported by the data and is the first genetic evidence to confirm the archaeological theory that Celts represent a tradition or culture rather than a genetic or racial grouping.
• Genetically there is not a unique Celtic group of people in the UK, but there is a genetic basis for regional identities in the UK. Many of the genetic clusters in the west and north are similar to the tribal groupings and kingdoms around, and just after, the time of the Saxon invasion, suggesting these kingdoms maintained a regional identity for many years.
• The invading Anglo Saxons did not wipe out the Britons of 1,500 years ago, but mixed with them.
• Those of Celtic ancestry in Scotland and Cornwall are more similar to the English than they are to other Celtic groups.
• In Orkney, around 25% of DNA is Norwegian, reflecting the Viking settlement of the Islands around 800 AD which remained part of their country for the next 600years), but this persists at fairly low levels, suggesting that the Vikings and the existing populations coexisted and intermingled more than people had expected.
• People in the north of England are genetically more similar to people in Scotland than they are to those in the south of England.
• There are subtle but distinct differences between those sampled in West Yorkshire and the rest of the country.
• There is a marked division between the people of Cornwall and Devon that almost exactly matches the county border.
• The people of Devon are distinct from those from neighbouring Dorset.
• English genomes are around a quarter German from earlier migrants from what is now Germany. Likewise the 45 per cent French contribution to our genes came much earlier than the Norman Conquest in 1066. Some is from the earliest modern Britons who arrived after the last Ice Age and more came from a mystery set of migrants who settled before the Romans invaded. Other countries to contribute genes to English DNA include Belgium, Denmark and Spain.
• The Welsh have the most DNA from the original settlers of the British Isles but within Wales there are two distinct groups. People in North and South Wales are less similar genetically to each other than the Scots are to people from Kent.
• There are two genetic groupings in Northern Ireland. One of these also contains individuals in western Scotland and the Highlands, which appears to reflect the kingdom of Dalriada 1,500 years ago. The other grouping also contains individuals in southern Scotland and southern England, and probably represents the settlers of the Ulster Plantations.

The results also shed light on what happened during Britain's Dark Ages, in the years between AD 400 and AD 600, after the Romans left (the ancient Romans left little of their DNA behind after their conquest). Towns were abandoned; the language over much of what became England changed (to Anglo Saxon, which became English); pottery styles altered; so too even the cereals that were grown, following the arrival of people from the base of the southwest Danish peninsula and northwestern Germany (the Anglo Saxons).

Earlier theories suggested that this was the result of (a) the Saxons entirely replacing the existing population as they moved westwards (possibly through Saxon introduced disease, for example) or (b) that the existing population simply dropped their old ways and adopted the Saxon way of life. The new analysis shows a modest level of Saxon DNA, suggesting that the native British populations lived alongside each other and intermingled with the Anglo Saxons to become the English.

The study seems to confirm the view that Celts retained their identity in western and northern areas of England where the regions were incorporated into Anglo Saxon territory by conquest.

The variation in the DNA of those of Celtic ancestry in Cornwall, Wales and Scotland might be the result of groups having been separated for a period of time, so they will diverge genetically.

The Viking armies that laid waste to parts of England, and for a while ruled what became known as the Danelaw, left little if any genetic trace, confirming that their success was due to their military prowess rather than large-scale population movement.

Sources

DNA study shows Celts are not a unique genetic group: by Pallab Ghosh Science correspondent, BBC News http://www.bbc.co.uk/news/science-environment-31905764

Fiona Macrae, Science Correspondent for the Daily Mail. http://www.dailymail.co.uk/sciencetech/article-3000998/Are-Welsh-truest-Brits-English-genomes-contain-German-French-DNA-Romans-left-no-trace.html#ixzz3UovhcRmc

THEVERGE.com http://www.theverge.com/2015/3/18/8252797/uk-genetic-map-reveals-invasions-regional-identity