The History of Scotland is known to have begun by the end of the last glacial period (in the paleolithic), roughly 10,000 years ago. Prehistoric Scotland entered the Neolithic Era about 4000 bc, the Bronze Age about 2000 bc, and the Iron Age around 700 bc. Scotland's recorded history began with the arrival of the Roman Empire in the 1st century, when the province of Britannia reached as far north as the line between the firths of Clyde to the Forth. North of this was Caledonia, whose people were known in Latin as "Picti", "the painted ones". Constant risings forced Rome's legions back: Hadrian's Wall attempted to seal off the Roman south and the Antonine Wall attempted to move the Roman border north. The latter was swiftly abandoned and the former overrun, most spectacularly during the Great Conspiracy of the 360s. As Rome finally withdrew from Britain, Gaelic raiders called the Scoti began colonizing Western Scotland and Wales.
According to 9th- and 10th-century sources, the Gaelic kingdom of Dál Riata was founded on the west coast of Scotland in the 6th century. In the following century, the Irish missionary Columba founded a monastery on Iona and introduced the previously pagan Scoti and pagan Picts to Celtic Christianity. Following England's Gregorian mission, the Pictish king Nechtan chose to abolish most Celtic practices in favour of the Roman rite, restricting Gaelic influence on his kingdom and avoiding war with Anglian Northumbria. Towards the end of the 8th century, the Viking invasions began. Successive defeats by the Norse forced the Picts and Gaels to cease their historic hostility to each other and to unite in the 9th century, forming the Kingdom of Scotland.
