Climate change and the collapse of the Akkadian empire: Evidence from the deep sea

Mesopotamia is the broad, flat alluvial plain between the Tigris and Euphrates Rivers in what is today Syria and Iraq (Fig. 1). Under the rule of Sargon of Akkad, the world’s first united empire was established in this region, linking the remote agricultural hinterlands of northern Mesopotamia with the complex city-states in the south. This united empire extended from the Persian Gulf to the headwaters of the Tigris and Euphrates Rivers from ca. 4300 to 4200 B.P. Particularly important to the success of the Akkadians was the fertile, rain-fed agricultural production of the wide, northern Mesopotamian plains. Over this broad geographic area, the Akkadians imperialized agricultural production and controlled long-distance trade. After <100 yr of prosperity, the Akkadian empire collapsed abruptly near 4200 B.P. (Weiss et al., 1993). Resettlement by smaller sedentary populations occurred ~300 yr later (3900 B.P.). Archeological investigations from the excavation site at Tell Leilan in northeast Syria (Fig. 1) have suggested that a major environmental change associated with the Akkadian collapse occurred near 4200 B.P. Tell Leilan, one of three major citystates in northeast Syria to be integrated into the Akkadian empire, was a provincial capital and primary provider of imperialized cereal production. Immediately above the collapse horizon at Tell Leilan and the nearby site Abu Hgeira, archeologists noted a thin (0.5 cm) volcanic ash layer overlain by a thick (100 cm) accumulation of wellsorted, wind-blown silts which were barren of artifacts. Weiss et al. (1993) interpreted this soil sequence to reflect the sudden onset of more arid conditions, which may have contributed to the observed collapse. This soil micromorphological evidence, however, is inherently subjective and may reflect localized phenomena unrelated to larger scale regional aridification. The Akkadian collapse had been previously attributed to human factors, including invaders and political disintegration (Yoffee and Cowgill, 1988). Whether the Akkadians were an example of social collapse resulting from climatic degradation (Hodell et al., 1995; Sandweiss et al., 1999) or whether this collapse was related to external or internal social factors may be resolved by an independent record of Holocene paleoclimatic variations in Mesopotamia as preserved in a marine sediment core from the Gulf of Oman.