Researchers found evidence of an ancient river system below the hot, dry sands of the Sahara, indicating the area may have once been lush with water, greenery, and food resources.

Experts have long wondered how early humans were able to survive the migratory trek through the inhospitable Sahara desert, but a new discovery could hold an answer. 
According to a study published in Nature Communications, researchers found evidence of an ancient river system below the hot, dry sands of Mauritania, indicating the area may have once been lush with water, greenery, and food resources. 
They believe the waterways flowed there about 5,000 years ago