Sumer
Sumer () is the earliest known civilization in the historical region of southern Mesopotamia, modern-day southern Iraq, during the Chalcolithic and Early Bronze ages, and one of the first civilizations in the world along with Ancient Egypt and the Indus Valley. Living along the valleys of the Tigris and Euphrates, Sumerian farmers were able to grow an abundance of grain and other crops, the surplus of which enabled them to settle in one place. Prehistoric proto-writing dates back before 3000 BC. The earliest texts, from c. 3300 BC, come from the cities of Uruk and Jemdet Nasr; early cuneiform script emerged around 3000 BC.
Persian Gulf
Earliest evidence of human presence on Persian Gulf islands dates back to Middle Paleolithic and consist of stone tools discovered at Qeshm Island.The world's oldest known civilization (Sumer) developed along the Persian Gulf and southern Mesopotamia. The shallow basin that now underlies the Gulf was an extensive region of river valley and wetlands during the transition between the end of the Last Glacial Maximum and the start of the Holocene, which, according to University of Birmingham archaeologist Jeffrey Rose, served as an environmental refuge for early humans during periodic hyperarid climate oscillations, laying the foundations for the legend of Dilmun.