Sumer) and Ebla (in Syria), both from c. 2500 BCE. 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. Northern Mesopotamia had sufficient rain to make some farming possible. To protect against flooding they made levees. 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. Early domestications 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. Also, legumes including peas, lentils and chickpea were domesticated in this region. Domesticated animals include the cattle, sheep, goat, domestic pig, cat, and domestic goose. Cosmopolitan diffusion Modern analyses comparing 24 craniofacial measurements reveal a relatively diverse population within the pre-Neolithic, Neolithic and Bronze Age Fertile Crescent, supporting the view that several populations occupied this region during these time periods. Similar arguments do not hold true for the Basques and Canary Islanders of the same time period, as the studies demonstrate those ancient peoples to be "clearly associated with modern Europeans". Additionally, no evidence from the studies demonstrates Cro-Magnon influence, contrary to former suggestions. The studies further suggest a diffusion of this diverse population away from the Fertile Crescent, with the early migrants moving away from the Near East—westward into Europe and North Africa, northward to Crimea, and northeastward to Mongolia. They took their agricultural practices with them and interbred with the hunter-gatherers whom they subsequently came in contact with while perpetuating their farming practices. This supports prior genetic and archaeological studies which have all arrived at the same conclusion. Consequently, contemporary in situ peoples absorbed the agricultural way of life of those early migrants who ventured out of the Fertile Crescent. This is contrary to the suggestion that the spread of agriculture disseminated out of the Fertile Crescent by way of sharing