Akkad and Shu-turul. The named kings of Uruk may have been contemporaries of the last kings of Akkad, but in any event could not have been very prominent. The period between BC and 2004 BC is known as the Ur III period. Documents again began to be written in Sumerian, although Sumerian was becoming a purely literary or liturgical language, much as Latin later would be in Medieval Europe. One explanation for the end of the Akkadian empire is simply that the Akkadian dynasty could not maintain its political supremacy over other independently powerful city-states. Drought One theory associates regional decline at the end of the Akkadian period (and of the First Intermediary Period following the Old Kingdom in Ancient Egypt) with rapidly increasing aridity, and failing rainfall in the region of the Ancient Near East, caused by a global centennial-scale drought. Harvey Weiss has shown that Peter B. de Menocal has shown "there was an influence of the North Atlantic Oscillation on the streamflow of the Tigris and Euphrates at this time, which led to the collapse of the Akkadian Empire". More recent analysis of simulations from the HadCM3 climate model indicate that there was a shift to a more arid climate on a timescale that is consistent with the collapse of the empire. Excavation at Tell Leilan suggests that this site was abandoned soon after the city's massive walls were constructed, its temple rebuilt and its grain production reorganized. The debris, dust, and sand that followed show no trace of human activity. Soil samples show fine wind-blown sand, no trace of earthworm activity, reduced rainfall and indications of a drier and windier climate. Evidence shows that skeleton-thin sheep and cattle died of drought, and up to 28,000 people abandoned the site, presumably seeking wetter areas elsewhere. Tell Brak shrank in size by 75%. Trade collapsed. Nomadic herders such as the Amorites moved herds closer to reliable water suppliers, bringing them into conflict with Akkadian populations. This climate-induced collapse seems to have affected the whole of the Middle East, and to have coincided with the collapse of the Egyptian Old Kingdom. This collapse of rain-fed agriculture in the Upper Country meant the loss to southern Mesopotamia of the agrarian subsidies which had kept the Akkadian Empire solvent. Water levels within the Tigris and Euphrates fell 1.5 meters beneath the level of 2600 BC, and although they stabilized for a