Wadi Howar is the remnant of the ancient Yellow Nile, a tributary of the Nile during the African humid period from about 9500 to 4500 years ago. At that time, savanna fauna and cattle herders occupied this region and the southern edge of the Sahara was some further north than it is today. When the Sahara underwent desertification between 6000 and 4000 years ago, the wadi first became a chain of freshwater lakes and marshes, as shown by Ptolemy's world map, then it became extinct about 2000 years ago.