Ancient Egypt was a cradle of civilization concentrated along the lower reaches of the Nile River in the eastern corner of North Africa. It emerged from prehistoric Egypt around 3150 BC, when Upper and Lower Egypt were united by Menes, who is believed by the majority of Egyptologists to have been the same person as Narmer. The history of ancient Egypt unfolded as a series of stable kingdoms interspersed by the "Intermediate Periods" of relative instability. These stable kingdoms existed in one of three periods: the Old Kingdom of the Early Bronze Age; the Middle Kingdom of the Middle Bronze Age; or the New Kingdom of the Late Bronze Age.