I’m thinking neolithic farmers also migrated southwest, finally arriving at the fertile Nile, displacing whatever hunter-gatherers might have been there, and starting Egyptian civilization.
Farming as it developed in the Nile valley was flood-dependent; they were probably doing that for a very long while, and were enjoying gathering a pretty rich bounty before that. Remains of a large Neolithic town in the Nile basin somewhere (I forget) were discovered and excavated some years ago. The remains consisted of postholes for the structures and a layer of ash from the incineration of the town in a single final event. Found throughout the ash? Stone arrowheads and spearheads (y'know, for some unknown reason ;^).