Legend has it that, in 1588, a Spanish galleon sank off the coast of Westray, one of Scotland's Orkney islands, and that the sailors who weren't dashed on the rocky spires were welcomed by the locals. Today Westrayans with dark hair or olive skin are said to be descendants of these lucky sailors. It is a romantic origin story, and it's not implausible, but in the absence of solid records it's hard to test. When I caught the ferry from Orkney's Mainland and drove to the village of Pierowall's tranquil bay, I saw a lot of lovely blue eyes but no dark-haired beauties. In the town archives, I read about the sailors and leafed through old photos. Here and there were pictures of olive-skinned boys, looking reasonably Spanish. But the records didn't reveal much about who they actually were or even if they were native to the island.
Still, behind their eyes, beneath their skin, below the membranes of their cells, there is something in the DNA of Westrayans that marks them and no one else. The origin of that distinction is not yet clear, but whatever it is, is not shared even by the Orkney Mainlanders. Is it a legacy of the shipwreck? Or something much older and weirder?
It's not just the Westrayans who are different from everyone else. If you examine all the longtime residents of all the Orkney Islands together, they, too, have something inside their cells that distinguishes them from everyone else in Britain. In fact, a team of scientists from Oxford, England, and Melbourne, Australia, published a groundbreaking paper today in Nature that shows all throughout the British Isles, clusters of people carry distinctive traces of ancient events and decisions within them. Celtic kingdoms, barbarian invasions, Norse raids from more than 1,000 years ago — traces of these distant, almost mythical moments in time are written in the bodies of the good and ordinary people of Devon, Anglesea, Westray, and many other places.
The Nature paper describes a way to read the book of history in human DNA to a level of detail that is completely unprecedented. In fact, the new technique is the closest thing we have to a time machine.
If we consider the entirety of human history, it is quite obvious that if people live near one another long enough, their DNA will eventually become blended. So inclined are people to mix it up with everyone around them that there is always a good reason when they don't, which is to say that barriers to reproduction must be high. They might be physical factors like mountains or oceans, or strongly enforced beliefs. The Orthodox Jewish community in Brooklyn, New York, lives in close proximity to other ethnic groups but marry only one another; genetically, it's as if they live on an island.
Even when people marry only within their own group, or on an actual island, their DNA is never static. As time passes, and DNA is passed from one generation to the next, changes naturally arise in the genome. While some are not passed on, others diffuse through the gene pool. And if the group does not mix with others, the changes may become characteristic of that particular group.
In order to have the best shot at finding the characteristic genetic traces of British ancestry, the British project focused on areas with rich archeology and looked only at people whose four grandparents were born in rural areas within 80 kilometers of one another. Sampling anyone's genome is essentially the same as taking a smaller sample of their parents' genomes, and an even smaller sample of their grandparents' genomes.
"Effectively we're looking back in time to what the genetics of that area looked like when those grandparents were born," Stephen Leslie, a statistician at the Murdoch Children's Research Institute in Melbourne, Australia, and an author of the new Nature study, told me. "The hope is that if the four grandparents were born in Cornwall, then their parents were born in Cornwall, and so on. We were hoping to get right back to when people didn't move a lot and lived in their own little communities for generation after generation." Many of those who responded to the team's call for subjects were of retirement age, which meant the average year of birth of their grandparents was around 1885.
The careful sampling was the idea of geneticist Walter Bodmer, now a professor emeritus at Oxford. For his entire professional life Bodmer had been interested in the ways that history shaped populations. It was he more than anyone who believed there was much more to the genetic history of the British Isles than was previously thought.
The team ended up with more than 2,000 genomes, and it fell to Leslie to find a completely new way to comb through them. He began by taking each genome and then comparing it, segment by segment, to every other genome in the set. Then he sorted the genomes into more than a dozen groups. Everyone within a particular group was genetically more similar than anyone outside the group. Crucially, no geographic information was used to pre-sort people; the selection criteria was purely genetic.
After Leslie assigned a small marker — such as white squares, yellow triangles, and pink circles — to every subject based on their DNA group, he placed each marker onto a map of Britain based on the location of their grandparents' birthplace. If there was nothing unique in the genetics of each region, Leslie's map of Britain would have looked like the sprinkles on a cupcake, a random mix of colors. But if there were large-scale trends, as was expected, the map would display a messy but suggestive pattern, with perhaps one group of colors clustering toward the east of the country and another skewing toward the west. At least three different British groups had already identified by other genetic and historical analyses, and Leslie hoped to see a refinement of them. But when he ran his analysis, he recalled, "I nearly fell over."
The analysis revealed more than 17 distinct bursts of color across the map. In some cases a group's borders aligned with modern county boundaries or with natural features, like the Tamar Estuary and Bodmin Moor. In most cases the individual groups did not overlap: Each represented a genetically distinct segment of the population of England in the 1880s. For example, the people pinned to Cornwall because that's where their grandparents were from were also stunningly all pink crosses — which appeared nowhere else on the map. The marker signified something that was essentially Cornish in their genetics. The same was true for the Anglesea group, and for those from Cumbria and Northumberland and others.
Leslie, who was trained as a mathematician, had acquired a solid base in genetics for his doctoral work. But he was also a mad history buff — widely read in modern and ancient British history. He told me about the day he first ran the analysis: He saw not only distinct genetic groups appearing on the screen, but a set of fine-grained, historic details mapping themselves out of the genetics of Britain.
First he saw Orkney break away from the rest of Britain. The order of a group's appearance, Leslie explained, reflected its degree of difference, which meant the Orcadians were the most different from the rest of the British population. Next came the Welsh. Then north and south Wales split apart. Then the south of England broke away from the rest. Then Cornwell appeared as distinct group. "Being able to see that so soon was just astonishing to me," Leslie said. Other groups broke away, like the north of England and Scotland, then came Westray, which turned another color, distinguishing itself even from the rest of the Orkneys.
A pink oval neatly demarcated the exact area where the team thought they might find a trace of the Picts. One of Leslie's favorite discoveries showed up next. This cluster lay over the Irish Sea, joining the northeast coast of Ireland with parts of southwestern Scotland. Leslie recognized the digital apparition as soon as he saw it: The modern genetics mapped the ancient geography of the Kingdom of Dalriada, a sixth-century tribal group that spanned Ulster and the Scottish coast.
"I just sat there and then I re-ran it, just in case I'd got it wrong. I ran it over and over again and just went" — Leslie threw up his hands and with a strangled cry said — "Ah, this is amazing! I knew that you could pull apart continents and potentially countries but to get something at this fine grain, I couldn't believe it was true."
A final group remained. Unlike the other small clusters, this was a massive area of red that covered most of central and southern England. Almost half of the genomes in the study were sorted into it. All those people had something in common. But who were they?
Leslie shared the genetic analysis with archeologist Mark Robinson, who works in the Oxford University Museum of Natural History. I visited Robinson in his second-floor office in the museum's neo-Gothic mansion. The windows there once stretched 12 feet high, so that the mid-19th-century astronomer who used to work there could survey the night sky. Now a mezzanine cut across the room, dividing the windows in half. Paper, in one form or another, appeared to be piled on every surface, except for when Robinson offered me a floral teacup with some water in it or, say, produced a head of wheat to illustrate a point about ancient crops.
In order to understand the analysis, Robinson began to draw a series of maps of Britain at significant periods of history to see if the genetic patterns might match up. We sat before his computer, and he showed me four of them.
The first map was of Britain after the last Ice Age, between 9,000 and 7,500 years ago, when modern human settlers began to arrive. England wasn't an island then; instead it was connected to the continent by a huge land mass called Doggerland. There were perhaps about 1,100 people living in Britain at the time.
Robinson's next map showed Britain between 4000 B.C., when agriculture arrived, and the early Bronze Age, roughly 2500 B.C., when Beaker pottery was brought in. By this point Doggerland was submerged under the sea and people had settled throughout Britain. What is known of this latter period has been gleaned mostly from artifacts and, thanks to the Romans who invaded in 43 A.D., some rare written records. Roman historians described the tribes they encountered, but little has survived apart from a list of tribal and place names and a few Brittonic words — brock meaning "badger," tor meaning "hill."
Robinson also set up a second screen next to his computer, so he could put the team's modern genetic map beside the first two maps of ancient Britain. l could see little correlation between them.
The third map was of Britain between 43 and 410 A.D. By this point the Picts were in Scotland, the people we think of as the Irish were in Ireland, and the Romans had established a presence throughout England extending as far north as Hadrian's Wall and sometimes beyond. This map looked more like the modern genetic map, because the area dominated by the Romans looked a lot like the large red area on Leslie's genetic map. But it was the fourth map that Robinson showed me — Britain in 600 A.D. — that suddenly looked familiar. By this time the Romans had left, and as if they hit the light switch on the way out, the written records went quiet for about 200 years. I looked from it to the genetic map, back and forth. They were so alike, I could almost hear them click.
On the historic map, the region representing the area of the major Anglo-Saxon invasion was shaded one color. On the genetic map, the same region was also a single color. Robinson pointed at the ancient fringe kingdoms, Rheged, Elmet, and Dumnonia in the north and west on the historic map, regions that were home to small Celtic groups that had hung on to their identity. Rheged, Elmet, and Dumnonia were also clearly delineated on the genetic map: Rheged is in modern Cumbria, Elmet is north-central England, and Dumnonia spans Devon and Cornwall.
It was incredible that the three kingdoms had left such strong traces, and it was also significant that the three groups were different from one another. Today we tend to think of the Celts as a wild, creative, and singular group of ancient people. But there was no one group of Celts, just like there is no one group of Europeans — there were many, and each was as different from the other as from the Saxon invaders.
"This is the major achievement of the project," Robinson explained. "It gives us a plausible answer, backed up with a lot of data, about what happens at the end of Roman Britain." Which is to say, the team has essentially turned the light back on in the Dark Ages.
Roman Britain only lasted for around 400 years. But despite the fact that they had conquered most of the country, few Romans actually lived in Britain. Their army was so well organized they didn't need many soldiers, and indeed, most Roman soldiers were actually Gauls, who had been conscripted. Although the Roman-ruled southeast was still largely populated by ancient Britons, they had become culturally Roman. Their leaders lived in Roman villas, some of them spoke Latin, their artisans created Roman goods, and unlike their own pre-Roman culture, they had a sophisticated monetary system.
Around 410 A.D., as the British population neared 2.5 million, the Roman Empire began to disintegrate when Saxons (including Angles, Jutes, and Frisians) raided the southeast coast of England. The Romans responded with various tactics, yet eventually Roman rule collapsed, as it did all through Western Europe, and its leaders withdrew from Britain.
The shock was enormous. Roman Britain was literate, but now, suddenly, no records were made. The local languages began to disappear, and most of the Roman and pre-Roman settlement names were replaced with Saxon ones. Agriculture changed completely, and key technologies, like lovely, durable Romanesque pots, simply vanished.
Over the years many theories have attempted to explain what happened to the Britons themselves but, as Robinson observed, "an awful lot of them are complete rubbish," shaped more by the politics of their era than by actual history. "There was the romantic 19th-century, early 20th-century view of Saxons coming in with heavy plows, and the Romano-British, who just farmed the light soils of the hilltops, were forced into Wales," he said. "But the Romans had heavy plows and were certainly farming a far larger area than the Saxons.
"You then had the 20th-century view of complete military conquest by Saxons. The British were supposedly wiped out or fled to Brittany or Wales," Robinson continued.
"Then in the 1970s you have the idea that it's all acculturation, and that the freedom-loving Saxons liberated the Romano-British from the imperial system. So they gave up on material culture, and things you could buy in towns, and switched over to self-sufficiency and the hippy lifestyle.
"Then, around the time of the genocides in former Yugoslavia, and the idea that one ethnic group will slaughter another entered public awareness, you had the theory of Saxon genocide of the Britons."
The prevailing view has been that the catastrophic cultural collapse of post-Roman England is evidence of either a complete massacre, or a flight to the west, leaving the population purely Saxon in culture and genes. But now, with the new genetic evidence, one version of what actually happened in the Dark Ages rings much truer than the rest.
The big red group in Leslie's analysis showed that there was a massive, genetically homogenous area in the southeast of England. History tells us that this DNA would not have been significantly influenced by the DNA of the Roman (genetically Gallic) army. Indeed, the biggest influx of people in the period were Saxons, so it's most likely that the group originated with the Saxon onslaught. But how much of the region's genetic profile is ancient-Briton DNA, and how much is Saxon-marauder DNA? If a huge number of Saxons raced in and killed almost everyone, the proportion might be 10% Briton. If instead only small groups of adventurous Saxons came to Britain, the population could be as much as 90% Briton. The only way to know for certain would be to match the DNA against that of the marauders themselves, or against a modern group descended from them. In the absence of a handy source of ancient DNA, the team looked to continental Europe for genomes.
With access to more than 6,000 European genomes from a medical study, the team ran the same kind of analysis and found 51 distinct groups, most of whom had contributed nothing to Britain. (Ancient Italy, for example, was not represented in the modern British gene pool, confirming what historians have long said about the absence of actual Romans in Roman-occupied Britain.)
As far as the big red group in England's southeast was concerned, the analysis showed that the genome that emerged from the cataclysm of 410 A.D. was probably 10 to 40% Saxon and at least 50% ancient British, meaning that the DNA of the natives in England's southeast was not replaced, but became strongly Saxon-flavored during the Dark Ages.
The likeliest explanation for this genetic state of affairs, said Robinson, is that in the absence of the Romans, the state — and the local population — fell apart. Others have suggested that as many as 1.5 million of the 2.5 million Britons died, but Robinson believes that only one-quarter million may have survived, and that for a long period there was complete chaos.
By contrast, these terrible conditions were just the sort to which Saxon settlers were accustomed. "Saxons were coming in, who although they looked more primitive on the face of it, had societies that worked at the small scale. Every man would have had to bear arms since he was young," Robinson said.
"My view is it only takes about 400 Saxons arriving each year for a period of 75 years and good reproductive success to have them contributing 25% of the DNA," Robinson said. "Effectively the Britons still enjoyed a high reproductive success, as their genes were in people who culturally were Saxon."
What of the Celtic kingdoms — Rheged, Elmet, and Dumnonia? Robinson already knew from the written record that these kingdoms hadn't disappeared into the post-Roman vacuum, but no one had ever imagined that they might once more be visible. How did they survive both Roman rule and the Saxon onslaught? According to Robinson, it was because they had never been fully controlled by the Romans in the first place.
"There was a Roman military presence," Robinson said, "but the ordinary Iron Age peasants were left to get on with things. If they misbehaved they would be slaughtered. It was like native states in British colonial India. Provided the local maharajah wasn't anti-British, he was allowed to get on administering his society by his own laws." The different Celtic groups still had their own leaders and weapons and were able to organize themselves. They knew how to barter and exchange goods and services. Enough of them survived to have children, who in turn had children, whose descendants today walk the streets of Cumbria and Cornwall, 21st-century ghosts shaped by great socioeconomics and good-enough DNA.
The key to the project's success is that the researchers didn't go looking for a Celtic gene or a Saxon allele. They looked instead at patterns across the genome, which most analyses ignore. As a result they discovered very small but significant differences between people who are otherwise overwhelmingly the same. "It's a collection of very slight differences but across lots and lots and lots of bits of the genome," Peter Donnelly, one of the team's leaders and the director of Wellcome Trust Centre for Human Genetics, told me. "You need to integrate all of this information in order to see the whole pattern of subtle difference."
Essentially the British genetic groups look like different blends of very similar material, like Arabica and Robusta coffees. Or like different hues on a color wheel. The Cornish are, say, genetically royal blue while the Devonians are light blue — fundamentally the same, but still categorically different. Which means that one of the big stories of ancient British genetics is a tale of people staying put. The history would not be detectable in the biology if many people hadn't lived in the same place and married someone from their own neighborhood generation after generation. In the case of Saxon Britain, that meant local boys partnering up with local girls from the 400s until at least the early 1800s — about 50 generations who married their high school sweetheart (or her peasant equivalent).
By contrast, the backstory of the big red genetic group is not so much one of a large homogenous community as an area that lacked significant geographic or historic barriers, a place where DNA has washed freely back and forth since Roman times.
For all the extraordinary insight that the project provides about Britain a millenia and a half ago, its value goes way beyond what it tells us about the Dark Ages. This kind of genome reading will allow us to reverse-engineer a great deal of history.
The study demonstrates "how much information is present in genomic data," said Graham Coop, a population geneticist at the University of California at Davis. It adds a "whole new layer of information on top of the information provided by historical records."
A lot of people might think that because, for example, the Vikings had a big impact on history that they are descended from Vikings, Coop added. But this work helps us distinguish "small groups of people coming in and having a large historical impact but not necessarily a big impact on people's ancestry."
Carlos Bustamante, a geneticist at Stanford, called the new technique a "powerful lens, a microscope for reconstructing aspects of historical migration." Its value may not just be in unearthing history but in predicting possible futures as well.
"We have been unwittingly limited by geopolitical borders," Bustamante said. "Most modern states were invented in the 19th century. But if you think about actual historical settlements and centers of large population density, they don't necessarily correspond today with where we've drawn either national boundaries or within country boundaries.
"This is something that we're facing more and more in the globalized world. Think about the Ebola outbreak — Ebola doesn't care where Sierra Leone ends, right? So understanding those clusters on real ancient historical and now modern migratory routes is critical. It is just so fundamental for public health in lots of different settings, genetics being one of them."
The number of questions the project raises for Britain alone is impressive. Why, for example, did the Danish Vikings who invaded England leave almost no genetic trace while the Norwegians reshaped the population of the Orkneys? What about the Orkneys' DNA? The team discovered that it's 25% Norwegian, but where does the rest come from? People have debated the degree to which the Norwegians slaughtered the Picts, Robinson said. But the genetics suggests the Picts live on in Orkney still. What about Westray? As far as the genetic analysis goes, says Leslie, it's unlikely to have been the result of a single shipwreck. What then were the social forces that laid down these archaic patterns still visible in the modern genome? And why hasn't there been enough intermarriage across Orkney to subsume the ancient legacy? It's not as if the Westrayans don't have boats.
The method may be applied in other countries as well. Adding the multidimensional genetic record to the historic and material record of any population can confirm existing knowledge, contribute completely new insights, and resolve old debates. Today, individuals can access their own, more coarse-grained genetic history through companies like 23andMe and Ancestry, but this new method could give them a finer-grained ancestry — not so much tracking one's ancestors to Britain as tracking them to the northern tip of southern Wales. A good chunk of the population of the United States could be painted by the European palette in the same way that Britain was. Likewise, there's a massive group of U.S. citizens whose genomes would be strongly flavored by different groups from South America. Many Americans could gain unprecedented insight into their history if the genomics of Africa were analyzed in the same way too. Almost no one in the U.S. with slaves in their ancestry has access to information about where exactly in Africa their ancestors came from. This technique could change that.
There are also many small populations throughout the States whose origins are perplexing. In Tennessee and neighbouring states, a group of interconnected families known as Melungeons long puzzled their neighbours. They were said to be dark-skinned but to have Caucasian features. Were they descended from Portuguese sailors? Runaway slaves? The most popular theory is that they are a mix of European, African, and Native American genes. While preliminary DNA studies have shown European and African ancestry, they only measured a small part of the genome. The British technique could finally solve the mystery.
The even smaller but equally intense questions that chase many families through history, wherever they live, might now be answerable too. When I spoke to Robinson, he said, "The bits that are documented in my family are lowland Scots, Welsh, southern Irish, and English … It's very, very mixed." But Robinson had always wondered about the background of his maternal grandfather, who'd had racist abuse hurled at him as a young man.
"They shouted 'Where's your monkey?' because he was a dark person with curly hair. His hair was white by the time I knew him in the 1960s, but whether he was very dark and Neapolitan in ancestry, or whether he was descended from a Lasker on the coal boats to Cardiff or something, I don't know. His name was Jones. I just have no idea."
This story is adapted from Christine Kenneally's The Invisible History of the Human Race, published in 2014 by Viking.
Contact Christine Kenneally at email@example.com.
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