Clement and fertile conditions during the Neolithic Subpluvial supported increased human settlement of the Nile Valley in Egypt, as well as neolithic societies in Sudan and throughout the present-day Sahara.
Cultures producing rock art (notably that at Tassili n'Ajjer in southeastern Algeria) flourished during this period.
The classic account of the riparian lifestyle of this period comes from investigations in Sudan during World War II by British archeologist Anthony Arkell.
This type of economy, so richly depicted in the Tassili n'Ajjer cave paintings, predominated in North Africa until the classical period.
Saharan rock art was produced in the "Green Sahara" during the Neolithic Subpluvial period (about 8000 to 4000 BC).
In the southern Sahara, the drying trend was initially counteracted by the monsoon, which brought rain further north than it does today.
By around 4200 BC, however, the monsoon retreated south to approximately where it is today, These conditions are responsible for what has been called the Sahara pump theory.
Based on common patterns at his site and at French-excavated sites already reported from Chad, Mali and Niger (e.g., bone harpoons and a characteristic "wavy line" pottery), Arkell inferred "a common fishing and hunting culture spread by negroid people right across Africa at about the latitude of Khartoum at a time when the climate was so different that it was not desert." The originators of the wavy line pottery are as yet unidentified.
In the 1960s, the archeologist Gabriel Camps investigated the remains of a hunting and fishing community dating from about 6700 BCE in southern Algeria.
During periods of a wet or "Green Sahara", the Sahara becomes a savanna grassland and various flora and fauna become more common.
Following inter-pluvial arid periods, the Sahara area then reverts to desert conditions and the flora and fauna are forced to retreat northwards to the Atlas Mountains, southwards into West Africa, or eastwards into the Nile Valley.
The physical characteristics derived from skeletal remains suggested that these people were related to modern Nilotic peoples, such as the Nuer and Dinka.
Subsequent radiocarbon dating firmly established Arkell's site to between 70 BCE.
During the last glacial period, the Sahara was much larger than it is today, extending south beyond its current boundaries.