The history of Norway has been influenced to an extraordinary degree by the terrain and the climate of the region. About 10,000 BC, following the retreat of the great inland ice sheets, the earliest inhabitants migrated north into the territory which is now Norway. They traveled steadily northwards along the coastal areas, warmed by the Gulf Stream, where life was more bearable. To survive they fished and hunted reindeer (and other prey). Between 5,000 BC and 4,000 BC the earliest agricultural settlements appeared around the Oslofjord. Gradually, between 1500 BC and 500 BC, these agricultural settlements spread into the southern areas of Norway – whilst the inhabitants of the northern regions continued to hunt and fish.