All of the following factors have contributed to the desertification of the Sahel except: Deforestation

Overgrazing

Desalination

Poor soil management

The river valleys (the Nile,Tigris,and Eupharites valleys) provision of aquatic bodies enabled fishing, hunting.The constant flooding of these valleys provided natural irrigation, which made the soil to be fertile for crop production.

These civilization aids agricultural growth, and with continuous practices  resulted in the emergence of social organization that promoted the formation of large group in the society, which necessitated the introduction of a sophisticated mode of administration for organization.

The improvements and expansion   in agricultural growth leads to the  establishments of  well organised  Complex  society of villages ,towns, cities.

Finally  specialize Labours  to manage the agricultural growth and developments leads to the formation of distinct social classes which resulting  in different innovations.

Explanation: