<P> It is in this region where the first libraries appeared, some 5,000 years ago . The oldest known library was found in northern Syria, in the ruins of Ebla, a major commercial center that was destroyed around 1650 BCE . </P> <P> Both the Tigris and Euphrates start in the Taurus Mountains of what is modern - day Turkey . Farmers in southern Mesopotamia had to protect their fields from flooding each year, except northern Mesopotamia which had just enough rain to make some farming possible . To protect against flooding, they made levees . </P> <P> Since the Bronze Age, the region's natural fertility has been greatly extended by irrigation works, upon which much of its agricultural production continues to depend . The last two millennia have seen repeated cycles of decline and recovery as past works have fallen into disrepair through the replacement of states, to be replaced under their successors . Another ongoing problem has been salination--gradual concentration of salt and other minerals in soils with a long history of irrigation . </P> <P> Prehistoric seedless figs were discovered at Gilgal I in the Jordan Valley, suggesting that fig trees were being planted some 11,400 years ago . Cereals were already grown in Syria as long as 9,000 years ago . Small cats (Felis silvestris) also were domesticated in this region . </P>

What is the importance of the fertile crescent in the development of religions