??How did the Sumerian civilization appear in southern Iraq
Civilizations in ancient Iraq first appeared in the northern parts of Iraq during the Neolithic period, that is, between the years 10,000 BC and 5,000 BC. These civilizations were agricultural and relied mainly on rain for their production, and all they needed for abundant production was Fertility.
As for southern Iraq, it was filled with the waters of the Arabian Gulf. With the occurrence of a large population increase in the early sixth millennium BC, more than those areas could bear, and therefore the surplus number of them was forced to migrate to the areas surrounding and close to the city of Samarra, and as long as the lands of these areas suffered from a lack of rainfall, which caused a severe shortage in water. Food and growth of food production means due to the lack of crop growth.
About 4000 years ago BC, the southern part of Iraq began to appear as an area of cultural influence due to the sediments of the Tigris and Euphrates rivers, the Karun River, and Wadi Hafr al-Batin. The surplus population of the northern sections with variable rainfall began to migrate to the southern part of Iraq, as the southern part of it was modern. The formation and its lands are very fertile, and in addition to that, agriculture in it depends on irrigation and not rain as in the northern part of Iraq, so its food was abundant and exceeded the needs of the people migrating to it. Thus, various civilizations and cultures appeared, such as the Ubaid civilization, the Uruk civilization, the Jemdet Nasr civilization, and then the Sumerian civilization.
Source: websites