Sumer is the earliest known civilization in the historical region of southern Mesopotamia (now southern Iraq), emerging during the Chalcolithic and early Bronze Ages between the sixth and fifth millennium BC. It is also one of the first civilizations in the world, along with Ancient Egypt, Norte Chico, Minoan civilization, Ancient China, Mesoamerica and the Indus Valley. Living along the valleys of the Tigris and Euphrates, Sumerian farmers grew an abundance of grain and other crops, the surplus from which enabled them to form urban settlements. Prehistoric proto-writing dates back before 3000 BC. The earliest texts come from the cities of Uruk and Jemdet Nasr, and date to between c. 3500 and c. 3000 BC.
Most historians have suggested that Sumer was first permanently settled between c. 5500 and 4000 BC by a West Asian people who spoke the Sumerian language (pointing to the names of cities, rivers, basic occupations, etc., as evidence), a non-Semitic and non-Indo-European agglutinative language isolate. In contrast to its Semitic neighbours, it was not an inflected language.
Others have suggested that the Sumerians were a North African people who migrated from the Green Sahara into the Middle East and were responsible for the spread of farming in the Middle East. Although not specifically discussing Sumerians, Lazaridis et al. 2016 have suggested a partial North African origin for some pre-Semitic cultures of the Middle East, particularly Natufians, after testing the genomes of Natufian and Pre-Pottery Neolithic culture-bearers. Alternatively, recent genetic analysis of four ancient Mesopotamian skeletal DNA suggest an association of the Sumerians with Indus Valley Civilization, possibly as a result of ancient Indus-Mesopotamia relations: Sumerians, or at least some of them, may have been related to the original Dravidian population of India.
These prehistoric people before the Sumerians are now called "proto-Euphrateans" or "Ubaidians", and are theorized to have evolved from the Samarra culture of northern Mesopotamia. The Ubaidians, though never mentioned by the Sumerians themselves, are assumed by modern-day scholars to have been the first civilizing force in Sumer. They drained the marshes for agriculture, developed trade, and established industries, including weaving, leatherwork, metalwork, masonry, and pottery.
Some scholars contest the idea of a Proto-Euphratean language or one substrate language; they think the Sumerian language may originally have been that of the hunting and fishing peoples who lived in the marshland and the Eastern Arabia littoral region and were part of the Arabian bifacial culture. Reliable historical records begin much later; there are none in Sumer of any kind that have been dated before Enmebaragesi (c. 26th century BC). Juris Zarins believes the Sumerians lived along the coast of Eastern Arabia, today's Persian Gulf region, before it was flooded at the end of the Ice Age. More details
