Why is the continent of Africa known as the “cradle of civilization”?

In Mesopotamia, the convergence of the Tigris and Euphrates rivers produced rich fertile soil and a supply of water for irrigation. ... It is because of this that the Fertile Crescent region, and Mesopotamia in particular, are often referred to as the cradle of civilization.

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necessary and proper clause. the congress shall have power to all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states, or in any department or officer thereof.

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.