Science Interviews


Sat, 11th Apr 2015

Garrett Hellenthal - British Genes

Garrett Hellenthal, UCL

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Kat - Our genes can tell us a lot about where we've come from. Now a major new study published in the journal Nature has used genetic analysis to look at the ancestry of British people, showing that different parts of the UK seem to harbour their own distinctive genetic flavour and revealing where some of these groups might have come from. Study researcher Garrett Hellenthal, from UCL, told me more about the work.

Garrett - The aim of the study was to infer the genetic history of the UK. And so, what we did is we sampled some 2,000 individuals from across the United Kingdom. These individuals were selected in a very particular way. There's a requirement for each individual, all 4 of their grandparents had to be born within 80 km from one another. So, we try to get individuals that have been living in a region for a while so we can get a snapshot of older history and avoid recent migration. The aim of study Ė so, two major things that we did. One was to see if we can cluster individuals based solely on looking at their genetics and seeing if for example, individuals that were sampled from one part of the United Kingdom, are they more similar to each other than they are to individual sampled from another part of the United Kingdom and how does this correlate with kind of known boundaries and history. The second thing was to take the DNA of these same individuals and compare them to some 6,000 individuals from across continental Europe and identified different parts of the UK share matching DNA patterns with different parts of Europe. And if so, do those correlate with known migrations from Europe? Of all the migrations from Europe into the UK, which have kind of had the biggest genetic impact in the people of the UK today?

Kat - Tell me some stories. Tell me some stories about us. What have you found?

Garrett - Just looking at the UK itself, there are some fascinating stories just by comparing the DNA of individuals in the UK to each other. There was kind of a striking correlation that turns out with genetics and geography to the point where we can tell whether an individual came from Cornwall which is in the southwest of England versus whether they were sampled from one county over in Devon. Genetically, we can tell them apart which is quite surprising because geographically, those are quite nearby regions. In fact, the difference between the two, the groups seem to be separated largely among modern-day county borders which is another sort of interesting finding. But then at the same time, while you have this kind of very tight regional clustering across the United Kingdom which hadnít been shown before, there are some parts of the UK for example, central, south and eastern England, individuals sampled from across a very large swath of those areas all were genetically very homogeneous. We couldnít really tell them apart, suggesting that there had been quite a bit of movement and intermixing along those regions. And so then, when we try to take the DNA of these individuals and compare them to Europe to learn about why weíre observing these sorts of pockets of genetics across the United Kingdom, we found that one of the bigger stories in UK history appears to be the Anglo-Saxon migrations. So, UK has a very storied history, lots of migrations. For example, the Romans occupied big parts of England for about 400 years, until about the 5th century. And yet despite that, theyíve built lots of walls, baths and other things that you can see across England today. But in spite of that, there seems to be very little genetic impact at all related to the Roman Empire as far as we can tell.

Kat - They didnít fancy us basically.

Garrett - Yeah, they didnít migrate here in large numbers. It is believed that they didnít really migrate here in large numbers. Perhaps it was difficult to convince people to leave the Mediterranean and come up to the UK. In contrast to that, after the fall of the Roman Empire, that kick started what were known as the Anglo-Saxon migrations around the 5th and 6th centuries. For those migrations, there's large scale migrations from places in modern-day Denmark and northwest Germany who settled into a big area within southeast England. It was unknown amongst archaeologists who debated amongst archaeologists and historians as to whether the Anglo-Saxons completely displaced the people that were there. So that if you looked at Englishmen today, basically, they'd be entirely Anglo-Saxon in heritage or whether they intermixed with the inhabitants that were there. And so, what our studies rule out was that they appear to have intermixed. If you look at an Englishman today on average in these regions this area of te southeast England, they have about 10 to 40 per cent of their DNA that seems to trace to these Anglo-Saxon migrations. The rest seems to be similar to other areas of the UK which we think of as the kind of pre-Saxon inhabitants.

Kat - One of the other peoples we know came to the UK are the Vikings. Tell me if you found any evidence of Viking blood in our history.

Garrett - Yes, we did in some parts. So, there were Norwegian Viking invasions and migrations. They came to Scotland in about the 9th century. Orkney Island, which is an island of the north part of Scotland, individuals there seem to have about 25 per cent of their DNA matches to individuals in modern-day Norway, suggesting a link thatís most likely related to those conquests. In fact, Norway annexed Orkney for about 500 years, about until 1470 or so I think.

Kat - Out of all the parts of the country that you looked at, which are the ones that seem to have been most isolated and kept themselves to themselves over the years?

Garrett - The Welsh appear to be a group that seems to have been less impacted by these recent events, these recent Anglo-Saxon and Norwegian Viking migrations. They perhaps look the most similar to what we might think of as the original inhabitants of the pre-Saxon inhabitants. So, they seem to be quite successful at warding off these different invading factions for whatever reason, probably geographically for one thing.

Kat - And not mating with them.

Garrett - Yes, thatís the key. Not intermixing, as they say, with these invading groups, yes.

Kat - So the differences that you're finding between people from different regions, do they mean anything? Does this mean that people in Cornwall have funny-shaped heads or something like that?

Garrett - So, as far as we know, the vast majority of any of the DNA that we looked at is neutral. I mean, it doesnít encode or affect any sort of physical traits or characteristics. What it most likely reflects is the fact that these two groups, for example, if you consider neighbouring counties that appear to be genetically distinct such as Cornwall and Devon as we see in the study. It seems to reflect that theyíve probably been somewhat isolated from one another, meaning they haven't intermixed relatively recently. What that means is if you're isolated, so this is the signature that youíve been isolated, you might start to develop your own cultural traits. But it doesn't mean in any way that the genetics are driving those cultural differences. If anything, itís just sort of telling us that they appear to be isolated and hence, itís not surprising that they have their own minor cultural differences.

Kat - There's quite a lot in the news about immigration coming into the British Isles. Do you feel that when you look at the genetic history of the people who live here that this has been going on for many, many years?

Garrett - Yeah, thatís right. One of the things that I found in my studies is that every group appears to be mixtures of other groups. So, we basically all descend from this sort of passing or mixing events, human populations clearly once we expanded across the globe, we didnít just stay put. We went back out again and intermixed. And so, you see these signals everywhere. Itís a constant interaction amongst different groups and thatís still continuing today and will for a very long time.

Kat - That was Garrett Hellenthal from UCL.



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