What evidence shows that the Sahara Desert once contained lakes and rivers?

Evidence confirming that the Sahara once contained lakes and rivers—a period known as the African Humid Period—is derived from several geological and archaeological sources:

• Landscape Features: The presence of depressions and basins across the modern desert landscape serves as a primary indicator of ancient, dried-up lake beds.12
• Sedimentary Records: Layers of sedimentary rock found in marine environments near the North African coast contain varying amounts of wind-driven dust. These layers reveal alternating phases of arid and humid conditions.12
• Biological Clues: Scientists have analyzed fossilized waxy leaf parts found in Lake Tanganyika and marine sediments. Because plants produce waxy leaves to prevent water loss in dry environments, the concentration of hydrogen isotopes within these sediments helps track historical moisture levels.12
• Archaeological Findings: Excavations of prehistoric settlements have uncovered bone harpoons, fish remains, and the bones of crocodiles and hippopotamuses, alongside shell accumulations, all of which indicate the former presence of permanent water bodies and diverse aquatic life in regions that are now arid.3