Ancient Egypt developed over at least three and a half millennia. It began with the incipient unification of Nile Valley polities around 3500 BC and is conventionally thought to have ended in 30 BC when the early Roman Empire conquered and absorbed Ptolemaic Egypt as a province. (Though this last did not represent the first period of foreign domination, the Roman period was to witness a marked, if gradual transformation in the political and religious life of the Nile Valley, effectively marking the termination of independent civilisational development).