20 April 2015
ByAppeared in BioNews 798
Guardian Science Weekly, Friday 20 March 2015
Presented by Dr Hannah Devlin
What does it mean to be British? These are not philosophical ruminations about the nature of national identity, but a question a new genetic study purports to have cracked wide open.
This podcast by the Guardian's Science Weekly brought in the study's lead author, Professor Peter Donnelly from the University of Oxford. As a part of the People of the British Isles project, his team has just mapped the DNA of 2,039 Caucasian Britons from all over rural UK. By selecting only participants whose four grandparents were born within close proximity of each other, they were able to effectively analyse the genetic make-up of the population before the mass population movements of the 20th century.
Their results, published in Nature, say that the British are pretty similar genetically. But, through statistical wizardry - which Professor Donnelly did well to give us a flavour of - they were able to figure out the subtle differences within the population. According to him, the UK is a patchwork of 17 distinct genetic clusters, which neatly match the volunteers' geographical location, and tell the story of Britain.
I was impressed by how his team performed its analysis blindfolded – having anonymised the identities of all individuals and let the pins fall on the map based solely on genetics.
The largest cluster - with almost half of the participants - was that of central and southern England. Perhaps to their delight, West Yorkshiremen and Cumbrians formed distinct clusters of their own.
What followed next was a crash-course in British history (for non-Brits like me) with a dash of genetics. Professor Donnelly presented a case for how this section's unique history has left an indelible mark on its inhabitants' DNA.
Following the collapse of the Roman Empire, there was a large influx of Anglo-Saxons. This led to an intermingling of the incomers with the natives, and not a mass extermination of the latter, as suggested by some.
The researchers then compared these results with the DNA of about 6,000 Europeans. It emerged that about 40 percent of the ancestry of this cluster matches that of modern France, another 25 percent matching that of Germany, with some input from Belgium and Denmark.
Similarly, the Isles of Orkney had a very distinct genetic identity with a strong Norwegian Viking signature, not unexpected when one considers that it was a part of Norway for 600 years.
Barring a few novelties, I did not find these figures terribly surprising, given the swathes of historical evidence towards these trends. Nonetheless, it was exciting to see how genetics can indeed back up what other disciplines point towards.
Professor Donnelly's most intriguing message was that genetics is the great equaliser - something that rings true with me. 'There's a saying that history is written by the victors and to some extent, that's true,' he said. Historical records are disproportionately biased towards the lives of the rich and the powerful, providing little insight into the masses - a shortcoming genetics does not face.
So should genetic studies become a routine part of historical explorations? I would argue that, whilst there is a case to be made for it, it only presents a part of the story. The Romans for example, are virtually invisible from the genetic landscape of Britain. However, they have left a deep cultural, social and architectural imprint with signs of their presence dotted all about modern Britain.
Finally, one might ask what tangible benefits this study might have towards public health. I am certain that it will prove to be an invaluable source for other population genetics studies, but I find it less convincing that it is a step towards the nebulous promise of 'precision medicine', as the presenter asked.
Overall, the podcast was an enjoyable ride through the history of the British Isles with a few bumps along the way. It nonetheless presented a complex set of research in an engaging and accessible manner.
So, Brits are a mosaic population forged by enduring waves of immigration and invasion, with constant intermixing of populations. Or, to put it in Professor Donnelly's words to Sky News: 'One of the nice things about our study is that it reminds us that everyone in Britain is an immigrant. There was no one in Britain 10-11,000 years ago. It is only a question of when people arrived.'