JAC: I asked Matthew—actually, I twisted his arm—to tell us a bit about the new paper in Nature dissecting the genetic composition of inhabitants of the UK, which showed lovely genetic clusters reflecting history and ancestry. Of course, as the “race critics” would assure us, those clusters are only social constructs!
by Matthew Cobb
One of the key issues in British politics for some time has been the level of immigration. Over the last decade, hundreds of thousands of people have come to the UK from Europe, which some people find problematic for cultural and economic reasons. (Even more Brits have gone off to live in Spain and elsewhere in Europe, but that fact never gets mentioned, any more than the fact that those immigrants to the UK appear to be driving the economic recovery…)
A new study in Nature this week [reference below] shows that, in genetic terms at least, all this is nothing new. The land mass that is Great Britain (England, Scotland and Wales – the big island) has been subject to repeated waves of immigration over the last few thousand years. That much we knew from the history books. What we didn’t know is what happened when those immigrants – or invaders – hoved up on our shores. Did they settle, breed with the locals and contribute to today’s British genomes? Or did they simply sit in their castles (or big huts) and exploit the poor natives?
The study is part of a long-term investigation of the genetic structure of the UK population (the United Kingdom is a political entity that comprises Great Britain and Northern Ireland), called People of the British Isles (PoBI), based in Oxford and set up by Sir Walter Bodmer.
As Steve Jones has pointed out, the invention of the bicycle did a great deal to shuffle the genes in the UK, as people started moving around the country. To get over this problem, the PoBI project studies only people whose grandparents were all born within 80 km of each other. They were therefore effectively able to study the DNA of those grandparents, most of whom were born in the late 19th century. They recruited 2039 people who met these stringent criteria and then studied the variability in their DNA. They also looked at the DNA from 6,209 people from continental Europe to find matches.
The big picture results are quite astonishing. Firstly, they found groupings of people that basically fit with the key geographical areas of the UK, suggesting that prior to the end of the 19th century, many people did not move around very much. This is true even down to very small regions – look at Devon and Cornwall (bottom left hand corner) – there is a very clear division between the two areas, even though they are right next to each other. Similarly, people from north Wales and from the England/Wales border seem quite distinct. (Note that this is a very fine-grain analysis of small differences – overall, everyone was pretty similar, as you would expect.)
It’s important to note that these different genetic groups were identified without knowing where people came from. When they plotted the data onto the map, it fell out in this dramatic way. Isn’t that cool? The researchers must have been so excited!
So where do these genes come from? They compared the 17 groups they identified in the UK with the data from continental Europe, and you can see that that – despite what some in the UK might like to think, Britain is indeed part of Europe:
The height of the bars shows the proportion of each of the 17 UK groups that can be traced to that particular European group. So, for example, you can see folk from North Wales have a very high proportion of their genes from the light blue French group FRA14, but none at all from the dark blue FRA17 type. [JAC: note that the inhabitants of the northern islands, like the Orkneys, have a substantial genetic component from Scandinavia.]
All this can be explained in terms of the successive waves of migration/invasion over the last 10,000 years, as the authors show in this handy cut-out-and-keep summary of British history:
The data suggest that there was no ‘Celtic’ population in Britain before the Romans arrived – the various groups were already differentiated according to different origins before we were told to stop painting ourselves blue and to start wearing togas.
As the bottom right hand map shows, Britain experienced two waves of Viking invasions, the first from Norwegian Vikings, the second from Danish Vikings, who also ran a protection racket for quite some time, forcing the locals to pay up or be ravaged (this was called the Danegeld). Strikingly, there is no evidence of this long period of Danish occupation in the DNA sampled in this study – although a lot of the people sampled had Danish DNA, it is not localised to any region (you can see this by the relatively even spread of DAN14 across all 17 types, in the second figure).
In other words, the Danish Vikings kept themselves to themselves and did not intermingle with the locals. When they eventually left, they did not leave any DNA behind them.
If you want to know more about this study, I heartily recommend listening to Adam Rutherford’s excellent Inside Science programme* about it (this is available anywhere in the world), in which he interviewed the man who did the statistics, Peter Donnelly [JAC: Peter Donnelly used to be in my department at Chicago, as well as in Statistics here]. There is also this nice summary from Nature news.
* I shamelessly stole the title of this post from Adam’s celebration of the UK’s mongrel nature.
Leslie, S et al (2015) The fine-scale genetic structure of the British population. Nature 519: 309–314. Here (£££).