The Invisible History of the Human Race (22 page)

The careful sampling was Bodmer’s idea. He began his career in genetics when he studied under R. A. Fisher, a famous founder of two fields of modern science:
population genetics and statistics, and he had long 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 believed.

The team ended up with
more than two thousand genomes, and it fell to Leslie to find a completely new way to comb through them. After applying a method called fine-structure analysis, he took each genome and then compared it, segment by segment, to every other genome in the set. Once he had done this, the genomes were sorted into more than a dozen groups. All the genomes within a particular group were genetically more similar to one another than to any outside the group. No geographic information was used to presort people; the selection criteria were purely genetic.

After Leslie assigned a color to every subject based on his or her DNA group, he placed a pin representing each one on a map of Britain based on the location of his or her grandparents’ birthplace. If there was nothing unique in the genetics of each region, Leslie’s map of Britain would look like the sprinkles on a cupcake, a random mix of colors. If there were large-scale trends, as the researchers 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. Leslie hoped to see a refinement of the three or so British groups that had already been identified from other genetic and historic analyses. But when he ran his analysis, he recalled, “I nearly fell over.”

The data revealed that there were more than seventeen distinct bursts of color across the map. In some cases a particular 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 didn’t overlap: Each represented a genetically distinct segment of the population of England in the 1880s. The people pinned to Cornwall, for example, were, stunningly, all the same color—which no one else on the map was. Their color seemed to signify something that was essentially Cornish in their genetics. The same was true for the Anglesey group and for those from Cumbria and Northumberland.

Leslie had been trained as a mathematician, and when he did his doctoral work under Donnelly, he acquired a solid base in genetics, but he was also a mad history buff—widely read in modern and ancient British history. He now runs his own lab at the Murdoch Childrens Research Institute in Melbourne, Australia, but you might still mistake him for a postdoc. Though the tendency of scientists is to cut their ponytails as they move from postdoctoral work to professorship, Leslie’s only grew longer over the many months we spoke. His feeling for the complexities of analysis, the weighing of evidence, and the sheer amount of information contained in DNA was always jubilant and contagious, but when he dug into the topic, his focus was absolute.

Leslie remembers the day he first ran the analysis. He didn’t see only distinct genetic groups appearing on the screen; the groups represented a set of fine-grained, historical 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 Cornwall 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 colored oval neatly demarcated the exact area where the team thought they might find a trace of the Picts. In the north of Ireland was an unusually mixed group containing two colors. Leslie suspected this was where the English conquered Ulster, sending eighty thousand immigrants to the area from England and Scotland in the seventeenth century to replace the indigenous Catholic Irish. The area became Northern Ireland, and the immigration became known as the Plantation of Ulster. The two groups that were living together but not mixing genetically were the Catholics and the Protestants.

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: Modern genetics had mapped the ancient geography of the kingdom of Dalriada, a sixth-century tribal group that spanned Ulster and the Scottish coast. 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?

“I just sat there and then I reran 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 gave a strangled cry—“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.”

Leslie ran a traditional analysis, known as a principal components analysis, or PCA, on the same data to compare the results to his own. It showed a few of the biggest groups, but after that hardly any differentiation at all.

Leslie showed the new analysis to Peter Donnelly, who recalled, “It was better than my wildest dreams.”

I asked Bodmer about the moment of discovery. “
It was absolutely staggering that you could get that much differentiation,” he said. “I was very surprised, even though I was obviously a person that most expected to find something.”

 • • • 

The archaeologist Mark Robinson works in the Oxford University Museum of Natural History, a neo-Gothic mansion on Parks Road. The windows of his second-floor office once stretched twelve feet high, so that the midnineteenth-century astronomer who used to work there could survey the night sky. Now a mezzanine cuts across the room, dividing the windows in half. When I visited him, paper, in one form or another, was piled on every surface, and except for when Robinson offered me a floral teacup with some water in it or produced a head of wheat to illustrate a point about ancient crops, we sat still for hours staring at maps.

When Leslie shared the genetic analysis with Robinson (“
I had naively expected that there was going to be a Saxon-dominated group and there was going to be a Celtic-dominated group,” Robinson recalled), Robinson began to draw a series of maps of Britain at significant periods of history. We sat before his computer, and he showed me four of them.

The first map was of Britain at the end of the last ice age, between 9,000 and 7,500 years ago, when the first modern humans began to arrive. England wasn’t an island then—a huge landmass called Doggerland connected it to the continent. People talk of Doggerland as an ancient land bridge, said Robinson, but it was only a bridge in the sense that Yorkshire is a land bridge between England and Scotland. There were perhaps about 1,100 people living in Britain at the time. Their ancestors had probably taken one of two routes from what we now know as Europe, either walking across Doggerland or traveling by boat across the channel river estuary and up the west coast into Ireland.

Robinson’s next map showed Britain between 4000 BC, when agriculture arrived, and the early Bronze Age, around 2500 BC, when Beaker pottery was brought in. By this point Doggerland had been submerged under the sea and people had settled throughout Britain. They built Stonehenge in the south around 2600 BC, while up north they constructed an even larger henge known as the Ring of Brodgar on the mainland of Orkney. Near Brodgar they built Maeshowe, a hill tomb you can still enter if you are willing to bend over and walk down a ten-meter-long, one-meter-high passage. (Neolithic life wasn’t all funerary grandeur and mystic architecture. A few miles from Brodgar at Skara Brae, you can see hearths, bedheads, and milk crate–style shelving in a cluster of stone houses that are joined by an internal corridor, like those of an apartment block. The houses are five thousand years old, older than the Egyptian pyramids.) What is known of this latter period has been gleaned mostly from artifacts and, thanks to the Romans, who invaded in AD 43, some rare written records. Roman historians described the tribes they encountered, yet apart from a list of tribal and place names and the few Brittonic words that survived—
brock
meaning badger,
tor
meaning hill—we don’t know a lot about the British of that period.

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. I could see little correlation between them.

The third map was of Britain between AD 43 and 410. By this period 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. For the most part they were heavily concentrated in the southeast. 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—Britain in AD 600—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 two hundred years. I looked from it to the genetic map, back and forth. They were so alike, I could almost hear them click.

On the historical 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. But Robinson pointed at the ancient fringe kingdoms, Rheged, Elmet, and Dumnonia in the north and west on the historical 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.

“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 lasted for only about four hundred years. Throughout this period, and despite the fact that they had conquered most of the country, few Romans actually lived in Britain. Indeed, many Roman soldiers were actually Gauls who had been conscripted into the army. 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 AD 410, when the British population was near 2.5 million, the Roman Empire’s hold on Britain began to disintegrate when Saxons, Angles, Jutes, and Frisians raided the southeast coast of England. The Romans responded with various tactics, even inviting some barbarians to settle down in the frontier zones. Yet eventually Roman rule collapsed, as it did throughout western Europe, and the empire’s leaders withdrew from Britain. “There is an imperial letter,” said Robinson, “that says something to the effect that the Britons will just have to try and defend themselves as best they can.”

The shock was enormous. Roman Britain had been literate; now, suddenly, no records were made. The local languages began to disappear (modern English retains only twenty-five words from ancient British) and most of the Roman, as well as the pre-Roman, settlement names were replaced with Saxon ones. Agriculture changed completely. The Romans had planted a variety of wheat that was completely replaced by the Saxon version. Other key technologies simply vanished. For hundreds of years the British had produced fine Romanesque pots—lovely, durable glazed containers that held water. But when the Saxons arrived, they brought their own leaky, crumbly containers, and despite the fact that family-sized kilns existed throughout the country, the older, better pot technology was lost.

Over the years many theories have been proposed 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 eras than by actual history. “There was the romantic nineteenth-century/early-twentieth-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 twentieth-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 hippie 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. 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 a massive, genetically homogeneous 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. This would rule out the theory that the Saxons had no genetic impact on the locals at all.