The pinnacle of ancient Egyptian power was achieved during the New Kingdom, which extended its rule to much of Nubia and a considerable portion of the Levant. After this period, Egypt entered an era of slow decline. Over the course of its history, it was invaded or conquered by a number of foreign civilizations, including the Hyksos, the Kushites, the Assyrians, the Persians, and, most notably, the Greeks and then the Romans. The end of ancient Egypt is variously defined as occurring with the end of the Late Period during the Wars of Alexander the Great in 332 BC or with the end of the Greek-ruled Ptolemaic Kingdom during the Roman conquest of Egypt in 30 BC.[3] In AD 642, the Arab conquest of Egypt brought an end to the region's millennium-long Greco-Roman period. The success of ancient Egyptian civilization came partly from its ability to adapt to the Nile's conditions for agriculture. The predictable flooding of the Nile and controlled irrigation of its fertile valley produced surplus crops, which supported a more dense population, and thereby substantial social and cultural development. With resources to spare, the administration sponsored the mineral exploitation of the valley and its surrounding desert regions, the early development of an independent writing system, the organization of collective construction and agricultural projects, trade with other civilizations, and a military to assert Egyptian dominance throughout the Near East. Motivating and organizing these activities was a bureaucracy of elite scribes, religious leaders, and administrators under the control of the reigning pharaoh, who ensured the cooperation and unity of the Egyptian people in the context of an elaborate system of religious beliefs.[4] The Nile has been the lifeline of its region for much of human history. The fertile floodplain of the Nile gave humans the opportunity to develop a settled agricultural economy and a more sophisticated, centralized society that became a cornerstone in the history of human civilization.[8]In Predynastic and Early Dynastic times, the Egyptian climate was much less arid than it is today. Large regions of Egypt were savanna and traversed by herds of grazing ungulates. Foliage and fauna were far more prolific in all environs, and the Nile region supported large populations of waterfowl. Hunting would have been common for Egyptians, and this is also the period when many animals were first domesticated.[9] By about 5500 BC, small tribes living in the Nile valley had developed into a series of cultures demonstrating firm control of agriculture and animal husbandry, and identifiable by their pottery and personal items, such as combs, bracelets, and beads. The largest of these early cultures in upper (Southern) Egypt was the Badarian culture, which probably originated in the Western Desert; it was known for its high-quality ceramics, stone tools, and its use of copper.[10] The Badari was followed by the Naqada culture: the Naqada I (Amratian), the Naqada II (Gerzeh), and Naqada III (Semainean).[11] These brought a number of technological improvements. As early as the Naqada I Period, predynastic Egyptians imported obsidian from Ethiopia, used to shape blades and other objects from flakes.[12][13] Mutual trade with the Levant was established during Naqada II (c. 3600–3350 BC); this period was also the beginning of trade with Mesopotamia, which continued into the early dynastic period and beyond.[14] Over a period of about 1,000 years, the Naqada culture developed from a few small farming communities into a powerful civilization whose leaders were in complete control of the people and resources of the Nile valley.[15] Establishing a power center at Nekhen, and later at Abydos, Naqada III leaders expanded their control of Egypt northwards along the Nile.[16] They also traded with Nubia to the south, the oases of the western desert to the west, and the cultures of the eastern Mediterranean and Near East to the east.[17]  In the Early Dynastic Period, which began about 3000 BC, the first of the Dynastic kings solidified control over Lower Egypt by establishing a capital at Memphis, from which he could control the labor force and agriculture of the fertile delta region, as well as the lucrative and