Some of the earliest agricultural societies never developed complex societies or "civilization". Take for example the Melanesians.

The Agricultural Revolution theory has been propagated as the reason behind social complexity in NE Africa. It was once believed that an arid phase, circa 6000BCE in the Levant dusted out winter crop (wheat, barley) agriculturalists forcing them to migrate to the Nile Delta. From here it was postulated, these immigrants spread agriculture and civilization to the middle Egyptian Badarians.

This theory did not consider the fact that the Saharan predessors of the Badarians allready practiced a forum of proto-agriculture, if not fullfledged agriculture through cattle pastoralism and the cultivation of morphologically wild sorghum. The Badarians did not practice fullfledge, village based agriculture. Instead, they continued the semi-sedentary, part-time agricultural traditions of their ancestors. It was not until the rapid degradation of the desert ecosystem forced populations to congregate around the Nile and its local drainages, with the reduction in cattle pasturage and hunting supplies did the Egyptians adopt fullfledge agriculture.

So a better model for the development of Egyptian civilization is an ecological one. I believe the same can be said of the Kerma civilization which seems to coincide with the aridification of the southern Sahara.

http://www.uea.ac.uk/sahara/publications/nb_collapse_abs.pdf