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.