A DNA study of the Vikings showed that they were more genetically diverse than modern Scandinavians

A DNA study of the Vikings showed that they were more genetically diverse than modern Scandinavians

A DNA study of the Vikings showed that they were more genetically diverse than modern Scandinavians

Modern people like it think a lot about yourself – take globalization for example. Modern people would be forgiven for believing that, thanks to the ease of travel and the historical migration of peoples around the world, most populations have a more diverse genetic record than in their supposedly more isolated past. But a new study that traces Viking DNA all the way to modern-day Scandinavia suggests otherwise.

Some interactions between different groups of people leave a permanent mark on the genes of their descendants, for example, people of European descent tend to carry tiny bits of Neanderthal DNA in their genomes.

Other times, however, the genetic record of ancient interactions fades over time. This appears to have happened after the Viking Age in Scandinavia, which now includes Denmark, Norway and Sweden, according to a recent study. Paleogeneticist Ricardo Rodrı́guez-Varelal and his colleagues at Stockholm University and the Center for Paleogenetics studied ancient DNA collected from people buried at sites in Scandinavia dating back 2,000 years. The researchers tracked how the Scandinavian genome changed over time and how immigrants to northern Europe affected the gene pool.

The results were published Thursday in the journal Cell.

What’s new – Rodrı́guez-Varela and his colleagues compared about 300 genomes of people buried in Scandinavia over the past 2,000 years with those of more than 16,000 modern Scandinavians, as well as more than 9,000 people whose ancestors came from elsewhere in Europe and western Asia. They found that Viking Age Scandinavia was much more genetically diverse than modern Scandinavia.

This person, who died in the wreck of the Swedish warship Kronan in 1676, unwittingly made a posthumous contribution to research. LARS EINARSON

Rodrı́guez-Varela and his colleagues discovered threads of origin from the eastern coast of the Baltic Sea, the far southern tip of Europe, and Britain and Ireland, running through the genomes of people from the Viking Age and early medieval Scandinavia.

The fact that the Viking Age was diverse is not too surprising; a previous study found similar results, suggesting that the ancient Scandinavian peoples exchanged DNA quite freely with other people they met—sometimes with the consent of all parties involved, and sometimes not. As a result, Viking society was far from homogeneous and surprisingly cosmopolitan, especially in the big cities.

The Viking Age was defined by sea travel and trade. But the DNA of people who lived that age suggests that the Vikings were not alone in sowing wild oats across the ocean. People from abroad also came to Scandinavia, and in such large numbers that they appeared in the gene pool of the region.

plot twist – More surprisingly, several centuries after the end of the Viking Age, the genetic traces of these interactions have mostly disappeared. People who came to Scandinavia during the heyday of Viking raiding and trade – whether they were traders, missionaries or enslaved captives – have all but disappeared from the gene pool of modern Scandinavia.

“The decrease in the current level of external ancestry suggests that Viking Age migrants either had fewer children or somehow contributed proportionately less to the gene pool than people who were already in Scandinavia,” says paper co-author and Stockholm University geneticist Anders Götherström Reciprocal.

Here is the background – Shortly after the fall of the Roman Empire, small kingdoms began to appear in Scandinavia. The fledgling ruling class needed money, and that need – along with many other factors, including climate change – fueled what became known as the Viking Age.

Ancient DNA samples have made a thrilling journey from muddy archaeological sites to pristine genetic laboratories.David Díaz del Molino

Even before the 793 CE raids on Lindisfarne in Ireland ushered in a new period of expansion, the Scandinavian kingdoms had established trade networks reaching as far as the Middle East and made mercenary contracts as far away as Constantinople.

Archaeologists have discovered Arabic writing woven into the fabric of clothing in Viking boat burials, making it clear that cultural exchanges took place on a regular basis – and human nature means that sometimes the exchange must have been personal as well. But most of these individual stories of how people met, mixed and interacted do not end up in the genome several generations later; the signal is not strong enough and eventually fades into the background and gets lost. Rather, the gene pool of a population reveals major large-scale trends over a long period of time, rather than individual relationships.

Perhaps not surprisingly, the populations that most influenced the Viking gene pool came from all over Europe, within reach of trade networks, and not even from distant places.

It is also not surprising that traces of the origin of immigrants from the Baltic and southern European countries disappeared from circulation in Scandinavia during several centuries of the Viking Age. These migrants left their mark on the Scandinavian gene pool for several centuries, but no longer. However, British and Irish ancestry still appear in modern Scandinavian genomes, albeit in small numbers.

“Perhaps this is not surprising, given the extent of Norse activity in the British Isles beginning in the 8th century … and culminating in the 11th-century North Sea Empire,” Rodriguez-Varela and colleagues write in the paper. Interactions with other people in other places were less intense and did not last as long.

Why is it important – If you take nothing else from this study, take this: Genomes usually only reveal the biggest, broadest strokes of human interaction. Even important events from the past are lost. The nuance is lost.

DNA tells one part of the story, and archeology and written history tell other parts. The best way to understand the past is to combine these lines of evidence. For example, Rodrı́guez-Varela and colleagues found that the rise of eastern Baltic ancestors in Gotland and central Sweden was consistent with the time of treaty making and other events. Without recorded history, we would not know what factors attracted people from the Baltic to Sweden. Without genetic history, we would not know the important effects of these treaties and trade relations on humans.

Genetic ancestry testing with a homemade kit is fun, and many people are happy to brag about being Viking descendants for whatever reason. But studies like this suggest that this ancestral picture is more complicated than most people realize.

First, ancient genomes challenge the idea that the Vikings were a force acting on the rest of the world with no influence in return. People migrating to Scandinavia left a mark, suggesting that we should not see the Vikings as actors, and everyone in their path as passive. Scandinavia was also influenced by these Viking Age interactions.

It is also clear that many people in modern Scandinavia are descended from people who originally came from elsewhere, even if these genetic clues have been lost. This means that regardless of what your home DNA ancestry kit tells you (and there are plenty of reasons to take these results with a grain of salt), your real ancestral history is probably more complicated – and more varied – than it looks paper.

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