The Sahara becomes a desert
The monsoon retreats, the lakes evaporate, and populations are pushed into the Nile valley.
- When
- —
- Duration
- 600 years
- Known to
- ± 300 years
- Era
- Neolithic, Holocene
Orbital precession weakens the African monsoon through the fifth and fourth millennia BCE, and the Sahara dries — in places abruptly, in others over centuries. Herders who had ranged across open grassland concentrate along the Nile and in the remaining oases. The desiccation is one of the leading explanations for the population density that makes Egyptian state formation possible, and it creates the barrier that shapes African history thereafter.