00:006,000 years ago, while humans were inventing farming and building the first cities, the Sahara Desert was green.
00:08Not a desert at all. It was a vast savanna, full of grass, trees, and huge lakes.
00:16There were hippos swimming in what is now Egypt.
00:19Elephants, giraffes, and crocodiles lived there, and people herded cattle across it for thousands of miles.
00:26We know because they carved pictures of them into rocks that are now in the middle of the driest place
00:32on Earth.
00:33So what happened?
00:35The Earth wobbles, very slowly.
00:39That tiny wobble changed where sunlight hits and shifted the African monsoon.
00:44The rains stopped coming, and the green died.
00:48It wasn't humans. It was orbital mechanics.
00:51And here's the wildest part.
00:53In about 15,000 years, that wobble will shift back.
00:58The rains will return, and the Sahara will be green again.
