At the end of the last glacial period, a major marine transgression inundated the head of the Persian Gulf to a position as much as 400 km inland from the present shoreline. After 6000 BP, the Shatt al-Arab delta prograded southward to its current position. These events had a profound impact on our knowledge of early human occupation and the development of civilization in the Tigris-Euphrates valley. The former settlements of people living on the pre-6000 BP coastal plains are today either under the waters of the Gulf or under sediments of the lower alluvial plain.