The Sahara Desert was a green forest with lakes and rivers between 5,000 and 11,000 years ago.

The Earth wobbles on its axis as it spins. This wobble is called orbital precession and happens every 23,000 years. Thousands of years ago, this wobble changed how much sunlight hit the Northern Hemisphere. The extra heat created stronger wind patterns called monsoons.These monsoons carried moisture from the ocean deep into Africa. This rain turned the desert into a savanna filled with plants. Scientists like Peter deMenocal studied dust in the ocean to prove this. They found much less dust from this time because plants held the soil in place.Satellites have found hidden riverbeds under the sand today. One ancient river called the Tamanrasset once flowed through Algeria. Rock art in Chad shows that humans lived there among elephants and giraffes. When the Earth's tilt shifted back, the rain stopped and the lakes dried up. People moved toward the Nile River, which helped start the Ancient Egyptian civilization.