Sedimentary ancient DNA and molecular evidence for pre-Norse occupation of the Faroe Islands

Abstract:

The Faroe Islands are a remote archipelago located between Norway and Iceland that was settled by Viking explorers in the mid-9^th century CE. However, several lines of evidence have led archaeologists and anthropologists to argue for earlier occupation of the Faroes by Celtic people from the British Isles. The evidence for pre-Norse occupation is fragmentary and circumstantial, and includes the discovery of charred grains of barley in an anthropogenic ash deposit that date to ~550 CE (Church 2013) and a Celtic document from the early 9^th century that reference a group of islands to the North, inhabited by an isolated group of Celts. However, it is not clear whether this document refers specifically to the Faroes, and the question of early human arrival in the Faroe Islands remains controversial. Here, we present sedimentary ancient DNA (sedaDNA) and molecular fecal biomarker evidence from a lake sediment core from Lake Eiðisvatn on the island of Eysturoy in the Faroe Islands to establish the minimum date for occupation of this watershed. The lake is proximal to the archaeological site Argisbrekka, which was a Viking Age summer farm settlement. Our age model is constrained by 10 radiocarbon samples and 5 cryptotephra horizons in the core. Fecal biomarkers are the degradation products of cholesterol and sitosterol produced by the gut bacteria of humans and livestock and deposited on the landscape in feces. We use sedaDNA to determine the first appearance of sheep on the landscape and to document changes in the plant community. Our results reveal an increase in fecal biomarker concentrations and the first appearance of sheep DNA at 500 CE (95% confidence interval is 370-610 CE), pre-dating Viking occupation of Argisbrekka by at least 300 years. In addition to sedaDNA and molecular evidence for livestock, sedaDNA of plants reveals a shift in the ecosystem at this time, with an increase in graminoids and the disappearance of woody taxa presumably due to livestock grazing. Altogether, our new data provide unequivocal evidence for human arrival to the Faroe Islands centuries before Viking settlement in the 9^th century.