The Dynastic period begins ca. 2900 BC and includes such legendary figures as Enmerkar and Gilgamesh—who are supposed to have reigned shortly before the historic record opens ca. 2700 BC, when the now deciphered syllabic writing started to develop from the early pictograms. The center of Sumerian culture remained in southern Mesopotamia, even though rulers soon began expanding into neighboring areas, and neighboring Semitic groups adopted much of Sumerian culture for their own.
The earliest Dynastic king on the Sumerian king list whose name is known from any other legendary source is Etana, 13th king of the first Dynasty of Kish. The earliest king authenticated through archaeological evidence is Enmebaragesi of Kish (ca. 26th century BC), whose name is also mentioned in the Gilgamesh epic—leading to the suggestion that Gilgamesh himself might have been a historical king of Uruk. As the Epic of Gilgamesh shows, this period was associated with increased violence. Cities became walled, and increased in size as undefended villages in southern Mesopotamia disappeared. (Gilgamesh is credited with having built the walls of Uruk).
The dynasty of Lagash, though omitted from the king list, is well attested through several important monuments and many archaeological finds.
Although short-lived, one of the first empires known to history was that of Eannatum of Lagash, who annexed practically all of Sumer, including Kish, Uruk,Ur, and Larsa, and reduced to tribute the city-state of Umma, arch-rival of Lagash. In addition, his realm extended to parts of Elam and along the Persian Gulf. He seems to have used terror as a matter of policy—his Stele of the Vultures has been found, showing violent treatment of enemies. His empire collapsed shortly after his death. He is notable for the policy of having deliberately introduced the use of "terror" as a weapon against his enemies.
Later, Lugal-Zage-Si, the priest-king of Umma, overthrew the primacy of the Lagash dynasty in the area, then conquered Uruk, making it his capital, and claimed an empire extending from the Persian Gulf to the Mediterranean. He was the last ethnically Sumerian king before the arrival of the Semitic king, Sargon of Akkad.
The Semitic Akkadian language is first attested in proper names of the kings of Kish ca. 2800 BC, preserved in later king lists. There are texts written entirely in Old Akkadian dating from ca. 2500 BC. Use of Old Akkadian was at its peak during the rule of Sargon the Great (ca. 2270–2215 BC), but even then most administrative tablets continued to be written in Sumerian, the language used by the scribes. Gelb and Westenholz differentiate three stages of Old Akkadian: that of the pre-Sargonic era, that of the Akkadian empire, and that of the "Neo-Sumerian Renaissance" that followed it. Speakers of Akkadian and Sumerian coexisted for about one thousand years, until ca. 1800 BC, when Sumerian ceased to be spoken. Thorkild Jacobsen has argued that there is little break in historical continuity between the pre- and post-Sargon periods, and that too much emphasis has been placed on the perception of a "Semitic vs. Sumerian" conflict. However, it is certain that Akkadian was also briefly imposed on neighboring parts of Elam that were conquered by Sargon.
The Gutians practiced hit-and-run tactics, and would be long gone by the time regular troops could arrive to deal with the situation. Their raids crippled the economy of Sumer. Travel became unsafe, as did work in the fields, resulting in famine.
The Sumerian king list indicates that king Ur-Utu of Uruk was defeated by the barbarian Guti, perhaps around 2150 BC. The Guti swept down, defeated the demoralized Akkadian army, took Akkad, and destroyed it around 2115 BC. However, they did not supplant all of Akkad, as several independent city states remained alongside them, including Lagash, where a local dynasty still thrived and left numerous textual and archaeological remains.
Ultimately Akkad was so thoroughly destroyed that its site is still not known. The Guti proved to be poor rulers. Under their crude rule, prosperity declined. They were too unaccustomed to the complexities of civilization to organize matters properly, particularly in connection with the canal network. This was allowed to sink into disrepair, with famine and death resulting. Thus, a short "dark age" swept over Mesopotamia.
Akkad bore the brunt of this as the center of the Empire, so that it was in Akkad that the Guti established their own center in place of the destroyed Akkad. Some of the Sumerian cities in the south took advantage of the distance and purchased a certain amount of self-government by paying tribute to the new rulers.
Uruk was thus able to develop a 5th dynasty. Even in the city of Akkad itself, a local dynasty was said to have ruled. The best known Sumerian ruler of the Gutian period was the ensi of Lagash, Gudea. Under him, ca. 2075 BC, Lagash had a golden age.
After a few kings, the Gutian rulers became more cultured. Guti rule lasted only about a century - around 2050 BC, they were expelled from Mesopotamia by the rulers of Uruk and Ur, when Utu-hengal of Uruk defeated Gutian king Tirigan. Utu-hengal's victory revived the political and economic life of southern Sumer.
2nd Dynasty of Lagash
Following the downfall of the Akkadian Empire at the hands of Gutians, another native Sumerian ruler, Gudea of Lagash, rose to local prominence and continued the practices of the Sargonid kings' claims to divinity. Like the previous Lagash dynasty, Gudea and his descendents also promoted artistic development and left a large number of archaeological artifacts. After the fall of their empire, the Akkadians themselves essentially coalesced into two states; Babylon in the south and Assyria in the north of Mesopotamia.
Later, the 3rd dynasty of Ur under Ur-Nammu and Shulgi, whose power extended as far as northern Mesopotamia, was the last great "Sumerian renaissance", but already the region was becoming more Semitic than Sumerian, with the rise in power of the Akkadian speaking Semites and the influx of waves of Semitic Martu (Amorites) who were later to found the Babylonian Empire. The Sumerian language, however, remained a sacerdotal language taught in schools in Babylon and Assyria, in the same way that Latin was used in the Medieval period, for as long as cuneiform was utilised.
This period is generally taken to coincide with a major shift in population from southern Mesopotamia toward the north. Ecologically, the agricultural productivity of the Sumerian lands was being compromised as a result of rising salinity. Soil salinity in this region had been long recognized as a major problem. Poorly drained irrigated soils, in an arid climate with high levels of evaporation, led to the buildup of dissolved salts in the soil, eventually reducing agricultural yields severely. During the Akkadian and Ur III phases, there was a shift from the cultivation of wheat to the more salt-tolerant barley, but this was insufficient, and during the period from 2100 BC to 1700 BC, it is estimated that the population in this area declined by nearly three fifths. This greatly weakened the balance of power within the region, weakening the areas where Sumerian was spoken, and comparatively strengthening those where Akkadian was the major language. Henceforth Sumerian would remain only a literary and liturgical language, similar to the position occupied by Latin in medieval Europe.
Following an Elamite invasion and sack of Ur during the rule of Ibbi-Sin (ca. 1940 BC), Sumer came under Amorite rule (taken to introduce the Middle Bronze Age). The independent Amorite states of the 20th to 18th centuries are summarized as the "Dynasty of Isin" in the Sumerian king list, ending with the rise of Babylonia under Hammurabi ca. 1700 BC.
During the third millennium BC, there developed a very intimate cultural symbiosis between the Sumerians and the Akkadians, which included widespread bilingualism. The influence of Sumerian on Akkadian (and vice versa) is evident in all areas, from lexical borrowing on a massive scale, to syntactic, morphological, and phonological convergence. This has prompted scholars to refer to Sumerian and Akkadian in the third millennium as a sprachbund.
Akkadian gradually replaced Sumerian as a spoken language somewhere around the turn of the 3rd and the 2nd millennium BC (the exact dating being a matter of debate), but Sumerian continued to be used as a sacred, ceremonial, literary and scientific language in Mesopotamia (Babylonia and Assyria) until the 1st century CE.