Regardless of the aridity of the greater Sahara , migration along the river corridor was halted when , during a desert phase 1.8-0 .8 million years ago , the Nile ceased to flow completely and possibly flowed only temporarily in other periods due to Nubian Swell uplift . Regardless of the aridity of the greater Sahara , migration along the river corridor was halted when , during a desert phase 1.8-0 .8 million years ago ( mya ) , the Nile ceased to flow completely and possibly flowed only temporarily in other periods due to the geologic uplift ( Nubian Swell ) of the Nile River region .