The peoples of predynastic Egypt were the successors of the Paleolithic inhabitants of northeastern Africa, who had spread over much of its area; during wet phases they had left remains in regions as inhospitable as the Great Sand Sea. The final desiccation of the Sahara was not complete until the end of the 3rd millennium bce; over thousands of years people must have migrated from there to the Nile valley, the environment of which improved as the region dried out. In this process the decisive change from the nomadic hunter-gatherer way of life of Paleolithic times to settled agriculture has