Ancient Egyptian civilization was certainly one of the most longlived and durable in all of world history. Among the factors contributing to its longevity are the Nile River, its naturally protected valley, and the stable weather conditions. The Nile valley is enclosed by the Mediterranean Sea on the north; the Arabian Desert and Red Sea on the east; the Libyan Desert on the west, and in ancient times danger seldom came from the south. By the Neolithic Period (CA. 5000 B.C.), the Egyptians already enjoyed a sedentary and stable existence. The annual inundation of the Nile induced them to construct dykes and dams to protect their settlements, and to dig canals to better irrigate and cultivate their fields. They began to store harvest crops against times of famine, and they learned how to gauge the rise and fall of the inundation waters. One might even say that the regular annual rhythm of the river was the primary catalyst underlying the organization and political unification of the country! In this sense, then, Herodotus, the "father of history*, was surely correct when he wrote in 449 B.C. that “Egypt is the gift of the Nile".