AI – ‘Evidence suggests Vikings likely reached and settled in the Azores between 700 and 850 CE, approximately 700 years before Portuguese explorers. Studies of lake sediment cores found charcoal, non-native pollen (rye), and evidence of livestock feces, indicating human activity, along with genetic evidence from mice that likely hitched rides on Viking ships. 

Key Findings Supporting a Viking Presence:

• Sediment Core Analysis: Lakebed samples from several islands (such as Pico and São Miguel) show environmental changes consistent with human arrival, such as deforestation and the introduction of livestock, starting as early as the 8th century.
• Rodent Genetics: A 2015 study indicated that mice in the Azores share a common lineage with mice from Scandinavia, suggesting they arrived via Norse ships.
• Agricultural Evidence: The presence of Secale cereale (rye) pollen, a non-native species associated with human activity, appeared in sediment layers centuries before the Portuguese in the 15th century. 

While Portuguese records described the islands as uninhabited, the earlier settlers (presumably Norse) may have left or died out, leaving behind a “pristine” landscape by the time the Portuguese arrived.’