The first achievement which radically altered man's condition was the invention of tools. The second achievement was his learning of primitive agriculture which transformed the hunter into the farmer. The domestication of animals and the planting and cultivating of crops had begun in the Near East, but the practice shortly spread to the Nile Valley in Northeast Africa. At the same time, farming communities sprang up throughout the Sahara which, at that time, was going through one of its wet phases. This made it well-suited to early agriculture. Farming permitted men to live together in communities and to pursue a more sedentary way of life. Actually, some Africans had already adopted a sedentary community life before the arrival of farming. Making hooks from bones led to the development of a few fishing communities near present-day Kenya. As the communities along the Nile grew in size and number, society began to develop a complex urban civilization. By 3,200 B.C. the communities along the Nile had become politically united under the first of a line of great pharaohs. These early Egyptians undoubtedly were comprised of a racial mixture. The ancient Greeks viewed the Egyptians as being dark in complexion, and it has been estimated that the Egyptian population at the beginning was at least one-third Negro. Herodotus says that it was impossible to tell whether the influence of the Egyptians on the Ethiopians was stronger than that of the Ethiopians on the Egyptians. What Herodotus and the Greeks referred to as Ethiopia was, in fact, the kingdom of Kush. It was located up the Nile from Egypt. As the Egyptian empire grew in strength and wealth, it strove to expand its power over its neighbors. Egypt sent several military expeditions south along the Nile to try to conquer the black people of Kush. They failed and the Kushites, in turn, endeavored to extend their power over Egypt. In 751 B.C., Kush invaded Egypt and, shortly thereafter, conquered it. This occupation of Egypt lasted for over a hundred years, until both the Kushites and the Egyptians were defeated by an invading army from Assyria in 666 B.C. At that point, the Kushites returned to the safety of their homeland.