Published today in Nature, trace how the Vikings radiated across Europe from their Scandinavian homeland, and how people with roots elsewhere also took up Viking ways.

It was a Viking saga written in genes. In 2008, construction work on an isolated Estonian beach near the town of Salme uncovered the skeletons of more than 40 powerfully built men. They were buried around 750 C.E. in two ships with Viking-style weapons and treasure—apparently the aftermath of a raid gone wrong. DNA from the bones has now added a poignant detail: Four of the men, buried shoulder to shoulder holding their swords, were brothers.

The new data come from a massive effort to sequence the DNA of Vikings across Europe. The results, published today in Nature, trace how the Vikings radiated across Europe from their Scandinavian homeland, and how people with roots elsewhere also took up Viking ways. “The big story is in line with what’s told by archaeologists and historians,” says Erika Hagelberg, an ancient DNA expert at the University of Oslo who was not part of the research team. “It’s the small details of particular sites that are really compelling.” The Estonian site, for example, offers powerful evidence that the crew was a tight-knit group from the same village or town. “Four brothers buried together is new and unique … [and] adds a new dimension,” says Cat Jarman, an archaeologist working for the Museum of Cultural History in Oslo, who was not part of the research team.

Over the course of almost 10 years, a team led by geneticist Eske Willerslev of the University of Cambridge and the University of Copenhagen assembled samples from across Scandinavia dating to the Viking Age, from about 750 C.E. to 1050 C.E., as well as some earlier and later samples. The team also gathered human remains from burials elsewhere in Europe and beyond that had Viking grave goods or burial styles. “We approached every place where we could see there should exist somehow an association with Vikings,” Willerslev says. Ultimately, the team was able to sequence 442 Viking Age genomes from as far afield as Italy, Ukraine, and the doomed Viking settlements of Greenland.

The results tell dramatic stories of individual mobility, such as a pair of cousins buried in Oxford, U.K., and Denmark, separated in death by hundreds of kilometers of open ocean. The genetic details may also rewrite popular perceptions of Vikings, including their looks: Viking Age Scandinavians were more likely to have black hair than people living there today. And comparing DNA and archaeology at individual sites suggests that for some in the Viking bands, “Viking” was a job description, not a matter of heredity.

Age of exploration

Viking ships sailed forth from Scandinavia, traversing the waterways of Europe and reaching across the Atlantic Ocean. Vikings from different homelands preferred certain destinations; for example, men from Norway settled Greenland, DNA data now show.

Viking-style graves excavated on the United Kingdom’s Orkney islands contained individuals with no Scandinavian DNA, whereas some people buried in Scandinavia had Irish and Scottish parents. And several individuals in Norway were buried as Vikings, but their genes identified them as Saami, an Indigenous group genetically closer to East Asians and Siberians than to Europeans. “These identities aren’t genetic or ethnic, they’re social,” Jarman says. “To have backup for that from DNA is powerful.”

The results also settle a centuries-old argument about the geography of raiding. Sagas written down centuries after the first expeditions suggest Vikings from certain regions favored specific destinations, but other scholars suggested the Viking command of the waves made them equal-opportunity raiders and traders.

DNA in hand, researchers for the first time could conclusively trace the origins of people from the far edges of the Viking diaspora back to their roots in Scandinavia. “We can follow the patterns of contact suggested by written sources, but disputed by historians for decades,” says co-author Søren Sindbæk, an archaeologist at Aarhus University.

They found that Vikings from what is now Sweden moved east to the Baltics, Poland, and the rivers of Russia and Ukraine, whereas Danes were more likely to head west to what is today England. Norwegians were most likely to set sail for the North Atlantic Ocean, colonizing Ireland, Iceland, and eventually Greenland (see map, above). “This is detail one couldn’t do based just on archaeology,” Willerslev says.

To the team’s surprise, there was little evidence of genetic mixture within Scandinavia itself. Although a few coastal settlements and island trading hubs were hot spots of genetic diversity, Scandinavian populations farther inland stayed genetically stable—and separate—for centuries. “We can separate a Norwegian person from a Swedish person from a Danish person,” Sindbæk says.

The DNA has raised new questions, too. Study co-author and National Museum of Denmark archaeologist Jette Arneborg says DNA recovered from burials in Greenland shows a mix of Scandinavian men from what is now Norway and women from the British Isles. Yet the artifacts and burials look completely Scandinavian. The women “have British genes but we can’t see them in the archaeology,” she says. “The DNA is going to make us think more about what’s happening here.”

Other mysteries remain. Viking settlements in the Americas have not yielded bones for sequencing, leaving the identity of the first European settlers in the Americas a mystery. And to the east, more samples may help illuminate the role of Vikings in the origins of the early Russian state, a topic that remains “extremely politically charged,” Sindbæk says. “This data has the potential to resolve some of these debates.”

The article is originally published at Science mag