(34th century BC - 33rd century BC - 32nd century BC - other centuries)

(5th millennium BC - 4th millennium BC - 3rd millennium BC)

---

Events

• Major climate shift possibly due to shift in solar activity. Glaciers expand, covering plants. Atmospheric temperatures fall to lowest levels.
• Sahara changes from a habitable region into a barren desert.

Significant persons

• About 250 million people occupied planet

Inventions, discoveries, introductions