(CNN)The isolated Faroe Islands were once home to an unknown population in 500 AD, about 350 years before Vikings ever arrived, according to new research. And the evidence comes from an unusual source: ancient sheep poop.
Ancient sheep poop reveals an unknown population on Faroe Islands before Vikings
Sign up for CNN's Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
The striking Faroes are a small archipelago located in the North Atlantic halfway between Norway and Iceland. Vikings reached the islands once they developed ships for long-distance sailing, about 850 AD, before they moved on to Iceland in 874. For a long time, researchers believed they were the first human inhabitants of the rugged Faroes.
Until this century, the only evidence for the first people to set foot on the Faroes ahead of the Vikings came from mentions in medieval texts. There is no current evidence to suggest that Indigenous people ever lived there.
In 2013, researchers found ancient burnt barley grains beneath the floor of a Viking longhouse on the Faroese island of Sandoy.
The grains were dated between 300 and 500 years before the Norse occupation of the Faroes. Barley was not native to the islands ahead of humans living there.
In order to find more evidence of this group of humans, a research team formed to conduct an investigation of a lake on the Faroese island of Eysturoy. While no homes or archaeological evidence have been found from this early group of explorers, this team decided to take a different approach to determine when humans arrived on the Faroe Islands.
Specifically, the scientists wanted to collect lake sediment cores.
"Lakes are amazing archives of environmental information, because they accumulate material from the surrounding landscape in sequential layers in their sediments," said lead study author Lorelei Curtin, a postdoctoral research associate in the University of Wyoming's department of geology and geophysics.
"Each member of our team uses different tools to analyze the lake sediments, and by working together, we gain a holistic understanding of changes in the environment, including human impacts on the landscape," she said.
When they reached Eysturoy, the team members set out in a small boat on a lake near the village of Eiði, which once hosted a Viking settlement. They dropped weighted tubes into the lake bottom and collected cores that were 9 feet (2.7 meters) in length -- collecting 10,000 years of environmental history.
The analysis of the lake sediments revealed the sudden presence of domesticated sheep in large numbers, arriving between 492 and 512. Sheep leave distinctive biomarkers in their fecal matter that were traceable as DNA in the sediments. The researchers were able to use a layer of ash, from the known eruption of an Icelandic volcano in 877, to help them establish dates.
Before the arrival of these sheep, there is no evidence of mammals on the island, so the sheep must have been brought by people arriving on the Faroes. Today, sheep are a staple of the Faroese diet.
The appearance of the sheep also aligned with the disappearance of woody plants, like willow, juniper and birch.
"After humans arrived and brought sheep with them, the vegetation changed," Curtin said. "We see more grass-type vegetation, which is consistent with landscape modification from animal grazing. This what we see on the Faroes today."
The study published Thursday in the journal Communications Earth & Environment.
Archaeologist Kevin Edwards, an environment researcher and professor emeritus at the University of Aberdeen and coauthor of the 2013 barley study, said this new research "has produced convincing and exciting evidence from another island within the archipelago."
In addition to receiving support from the Faroese, the researchers were assisted by Símun Arge, an archaeologist at the National Museum of the Faroe Islands.
"Símun sadly passed away in February of 2021, and we've dedicated this study to him," Curtin said.
Located 200 miles (322 kilometers) northwest of Scotland, the Faroes showcase signature towering cliffs as their coastlines. They endure often cloudy weather and are constantly hit by strong winds. Few places would have been enticing for settlement to early explorers because the landscape is largely tundra.
There are some flat places near protected bays where Vikings set up camp. The Faroes likely allowed the Vikings to reach places like Iceland and Greenland later on.
Medieval writings support the idea that Irish monks were on the Faroes by 500, including Irish navigator St. Brendan who was famed for sailing the Atlantic.
Now, the sheep DNA, biomarkers and writings all align, said study coauthor William D'Andrea, a paleoclimatologist at Columbia University's Lamont-Doherty Earth Observatory.
But who, exactly, were the first people to land on the Faroes?
The researchers believe they were Celts crossing the sea from Scotland or Ireland, based on clues that, pieced together, hint at the distant past of the current-day island inhabitants.
For example, there are many names on the Faroe Islands that come from Celtic words, and there are undated Celtic grave markings on the islands. Studies of DNA from Faroese people have maternal Celtic lineage. While it's possible that Vikings brought Celtic brides with them, the maternal Celtic ancestry level is so high that the researchers think Celts were present on the islands ahead of the Vikings.
"Our data can't really speak to who the people were who arrived before the Vikings with their livestock, however there is some evidence to suggest that the Vikings did not use sailing technology at that time," Curtin said. "I think this is motivation for further archaeological exploration in the Faroe Islands."
Whoever the first inhabitants of the Faroe Islands were, the fact that they crossed the ocean with livestock reveals their advances -- and spirit.
"I think we often underestimate early human explorers and their ability to reach new, unknown lands," Curtin said. "I can't imagine the courage and skill it takes to set sail across the North Atlantic ocean. It really is a testament to the human spirit of exploration."