Who were the first Faroese? Genetics complicates the story of who came first

The Faroe Islands, a remote archipelago in the North Atlantic, are home to more than 54,000 people. But exactly who first settled the islands – and when – has remained uncertain for centuries.

Researchers sequencing Faroese genomes in search of genetic variants linked to disease have now uncovered clues to that earlier history. Their findings, presented in eLife, reveal ancestry connected to both Scandinavia and northwestern Europe – but suggest that the familiar story of who arrived first may be too simple.

These results are “just the very beginning of this project,” says co-author Fernando Racimo, associate professor at the University of Copenhagen who studies evolutionary and ecological genetics. “With just 40 genomes, we could already do quite a lot. But there are thousands of genomes in the works.”

The clues disagree by centuries

The Faroese experience higher rates of several conditions than people in much of mainland Europe, including multiple sclerosis, type 2 diabetes and inflammatory bowel disease. FarGen’s recruitment data also suggest that ankylosing spondylitis, a chronic inflammatory disease that mainly affects the spine, may be more common, although that has not yet been confirmed by formal epidemiological studies. Lifestyle may contribute, Racimo says, but genetic variants that became common in this historically small population could also play a role.

For centuries, the Faroe Islands were relatively isolated, with the population numbering only around 4,000 in the 1700s. In small populations, chance can make some genetic variants unusually common – one reason the researchers began sequencing Faroese genomes.

But the same genomes could also address a much older mystery: where did the first Faroese come from, and when did they arrive?

In the 9th century, the Irish astronomer and monk Dicuil wrote that Irish hermits had lived on the islands for about a century before being driven away by Norwegian pirates. Dicuil’s source? A “man worthy of trust” who had heard the story from his master. Three hundred years later, the Færeyinga Saga, or the Faroe-Islander Saga, told of Grímr Kamban – a man with a Norse first name and a Gaelic surname – settling there around the time of Harald Hårfagre, king of Norway around the turn of the 10th century.

Sheep DNA pushes the story further back

Burnt barley and ancient sheep DNA preserved in pond sediments suggest that people had brought agriculture to the islands as early as the 5th century – centuries before the settlement described in the saga.

To see where modern Faroese ancestry fits into this history, the researchers fully sequenced the genomes of 40 volunteers from across the islands, chosen with the help of genealogical records stretching back to around 1650. They then compared their roughly 3 billion DNA letters with genomes from present-day populations around the world.

They also compared the Faroese genomes with 616 ancient European genomes from the past 3,000 years, focusing on northern and western Europe. Because ancient DNA is often incomplete, the researchers used imputation – a technique that uses probability to fill in the gaps.

“This allowed us to draw connections between ancient populations and present-day Faroese,” Racimo says. “We find that present-day Faroese people have strong affinities both to northern European Viking-like populations, but also northwestern European Celtic-like populations.”

The genomes point both north and west

Present-day Faroese carried roughly similar amounts of ancestry linked to Iron Age and Viking Age Scandinavia and to ancient western European populations, including Britain.

The genomes therefore support traces of both sides of the old story – Scandinavian and Gaelic – without settling who reached the islands first.

“Now, this does not mean that the Faroese descended directly from Vikings or Celtic people,” Racimo emphasises. “It is still unclear at what point the people arrived on the island.”

Faroese remains from the 17th and 18th centuries already have almost the same ancestry mixture as people living on the islands today. One older genome, however, looks very different.

“There is one ancient Faroese genome - the oldest one we have - that looks quite different,” Racimo says. “It is 800 years old from a church site in Suðuroy, the southernmost Faroe Island. That genome has much stronger affinities to northwestern Europeans than Scandinavian populations.”

An 800-year-old genome complicates the picture

In the analysis, that individual was almost entirely linked to western European ancestry. But one person cannot reveal an entire population – he may simply have arrived from elsewhere.

One possibility is that people related to northwestern European populations arrived before later Scandinavian settlers. But there is another possibility that changes the settlement story more fundamentally: the two ancestries may already have mixed before people reached the Faroe Islands.

“We also find that these two populations might not have met on the islands – that individuals of mixed ancestry were coming in,” Racimo says.

When the researchers tried to date that mixing, the genomes pointed surprisingly far back – to before the historically documented settlement of the Faroe Islands. The estimates are uncertain, Racimo stresses, but they fit the possibility that people arriving on the islands were already of mixed ancestry.

“Another possibility is that the settlement happened much earlier than has been thought.”

What isolation left in the Faroese genome

The first 40 genomes did not reveal a single genetic variant that could explain the higher rates of inflammatory bowel disease or diabetes – or the possible excess of ankylosing spondylitis suggested by FarGen’s recruitment data. One of the strongest known genetic risk factors for ankylosing spondylitis, HLA-B27, was no more common than in the European populations used for comparison.

So if the disease really is more common in the Faroes, the explanation appears to lie elsewhere.

The disease search may not yet have yielded an answer, but other parts of the genome carried traces of a different history: how generations of Faroese may have adapted to life on the islands.

Many of the strongest genetic signatures of natural selection were shared with British genomes and probably predate settlement of the Faroe Islands. But one signal looked particularly distinctive in the Faroese: a region around the SLC10A1 gene.

“We found a signature specific to the Faroese population on SLC10A1, which is involved in fat and vitamin D absorption,” Racimo explains.

Clues from dark winters and a different diet

That makes the gene intriguing in a population that historically endured dark northern winters on a diet rich in marine foods and animal fat. But the genetic signal alone cannot tell the researchers what drove the change.

“In the history of the islands, much of the diet is based on sheep tallow, whale blubber and cod liver,” he says.

The researchers also found more genetic diversity around lactase persistence – the ability to continue digesting milk after childhood – than in the British comparison group.

One possibility is that milk and dairy products played a smaller role after the ancestors of the Faroese settled the islands, reducing the advantage of being able to digest milk throughout life. But chance alone in a small population could produce a similar pattern.

The 40 genomes are only the first phase of a collaboration between researchers at the University of Copenhagen, the FarGen initiative at the University of the Faroe Islands and the biotechnology company VariantBio.

“Usually, when one tries to relate the particular prevalence of disease to a particular genomic variant, one relies on tens of thousands of genomes,” Racimo says.

More than 3,500 Faroese – roughly 6.5% of the population – have now donated samples for the next phase. That should give the researchers far more power to find genetic variants linked to disease – and perhaps reconstruct the islands’ past in greater detail.

Because these first genomes have made one thing clear: the story of who reached the Faroe Islands first may be more complicated than the sagas and archaeological clues suggest.