Biochemical evidence from environmental DNA suggests Norse people arrived in Iceland around AD 810, nearly 70 years before the traditionally accepted date of the 870s. This challenges the view of early settlement as an immediate ecological disaster. Researchers found signs of human activity predating a key volcanic ash layer, alongside indications of managed forests rather than rapid deforestation.
Historical records place the first Norse settlements in Iceland in the 870s, often blamed for clearing the island's birch and willow forests for fuel and agriculture, leaving only 2 percent tree cover today. However, new research led by Eske Willerslev at the University of Copenhagen challenges this timeline and narrative.
The team analyzed environmental DNA (eDNA) from sediment cores at Lake Tjörnin in central Reykjavík, one of Iceland's oldest settlements. Using volcanic ash layers, radiocarbon dating, and plutonium isotopes, they constructed a timeline from AD 200 to the present. A pivotal marker is the Landnám tephra from an AD 877 eruption, above which most human evidence appears.
Below this layer, around AD 810, the researchers detected elevated levoglucosan—a biomass burning indicator—and viruses linked to sewage, suggesting early human presence. "Signs below the tephra are like the smoking gun that there was earlier human activity," says Chris Callow at the University of Birmingham, who was not involved in the study.
Skeptics note limitations. Callow calls the 810 date controversial, as it predates typical Viking North Atlantic expansion. Kathryn Catlin at Jacksonville State University questions the evidence's conclusiveness, pointing to a brief sewage biomarker spike around 800 with no follow-up until 1900, and noting natural causes for fires like lightning.
The eDNA also reveals positive environmental impacts. Pollen shows birch expanding fivefold between AD 900 and 1200, possibly from settlers protecting trees while introducing livestock, hay meadows, and barley cultivation. Major biodiversity loss, including trees, occurred after 1200, linked to the Little Ice Age (1250-1860), volcanic activity, and storms—not initial settlement.
Callow proposes the earliest visitors might have been seasonal walrus hunters. Sheep, cattle, pigs, and horses appear decades later, aligning with herd growth over about 20 years.
"This is the nail in the coffin for that old just-so story of the Vikings getting to Iceland and then, suddenly, ‘oh no, the environment is destroyed’," says Catlin.
The findings are detailed in a bioRxiv preprint (DOI: 10.1101/2025.10.08.681091). An older longhouse from the 800s near Stöðvarfjörður supports early activity but remains unpublished in a peer-reviewed journal.