Texts on the history of ancient Egypt span the period from the early prehistoric settlements of the northern Nile valley to the Roman conquest, in 30 BC. The Pharaonic Period dates from the 32nd century BC, when Upper and Lower Egypt were unified, until it fell to Macedonian rule in 332 BC. In 305 BC, Ptolemy, one of Alexander the Great's generals, took the title of Pharaoh, and as Ptolemy I Soter ("Saviour") founded the Ptolemaic dynasty that ruled Egypt for nearly 300 years.