Although direct evidence for agriculture and animal herding has not yet been found for this early period controversy exists.
Grinding stones, usually associated with grain production, and hence farming, were discovered.
With the onset of the last great ice age about 30,000 years ago huge glaciers formed on the high African mountains of Ethiopia, Kenya and Uganda.
Then, as the glacial melting slowed the valley became suitable to human settlement once again.
The glaciers continued to melt through the millennia, until today very little is left of them.
The final desiccation of the Sahara was not complete until the end of the 3rd millennium BC.
Many archaeologists believe those people migrated south to sub-Saharan Africa, or to the Nile valley, the environment of which greatly improved as it dried out from the previous heavy flooding.
However, melting of the world ice sheets caused a northward shift of the monsoon belt, creating increasingly arid conditions in the once verdant Sahara regions.
The peak of human occupation in the Western Desert took place between 6,500 and 4,700 BC, when weather conditions forced abandonment of those areas.
Some favor the Levant, and countries along the eastern Mediterranean shores. The first possibility is preferred by many archaeologists because they believe the earliest known Neolithic cultures in Egypt were found at Marimda Bani Salama, on the southwest edge of the Delta, and farther to the southwest, in the Fayyum lake region.
The site at Marimda, which dates to the 6th-5th millennia BC, gives evidence of settlement and shows that cereals were grown.
A hiatus in radiocarbon dates suggests the valley was barren of settlements during that period. Still others were Andite, coming from Mesopotamian regions and overland from the Red Sea. The Nile valley did not exist in grand isolation from the rest of the world, even though many Egyptologists are oriented to that frame of mind.