With regard to the Research News article “Sea-floor dust shows drought felled Akkadian empire” by Richard A. Kerr (16 Jan., [p. 325][1]), the sediment core described by Heidi Cullen and Peter deMenocal provides compelling data for the idea of atmospheric drying and an increasingly dust-laden atmosphere for the period 2200 to 1900 B.C. For the Gulf of Oman, this amplifies the data presented by Sirocko ([1][2]), which demonstrates increased arrival of dust in sea floor sediments during periods of decreased strength of the southwest monsoon. However, to explain this dust, rather than look at northern Syria, where trends in atmospheric moisture change may have been opposite to those of the monsoonal area ([2][3]), we should first look at Arabia, where a well-attested moist period terminated around 5000 years ago, or after. The Yemen highlands and the Arabian desert both show significant drying toward the end of the mid-Holocene and could have contributed increased atmospheric dust to the atmosphere. In the later third millennium B.C., abandonment of settlements and terraced fields ([3][4]) may have been related to atmospheric drying resulting from increased southerly penetration of summer northwesterly winds during a period of decreased ocean upwelling and reduced monsoonal strength. In the north, although there was a dramatic decline in settlement in the Rhabur basin in Syria, climatically marginal towns like Tell Brak continued to be occupied in the post-Akkadian period, albeit perhaps with reduced populations. Further west in the Lake Tabqa area, where probably 250 to 300 millimeters of rainfall supported primarily rain-fed agriculture, we see in the final quarter of the third millennium B.C. an increase in settlement numbers and the growth of a town at Tell Sweyhat. In moister areas near Kurban Hoyuk in southern Turkey, growth in rural sedentary settlements was at the expense of towns. As Frank Hole states (“Wheat domestication,” Letters, 16 Jan., [p. 303][5]), something was going on at this time, but whether it was culturally or climatically driven, or a combination of both, is unclear ([4][6]). A case for increased atmospheric moisture in the mid-Holocene can be made from lake sediments and alluvial sediments ([5][7]). The former record suggests that there was dwindling but fluctuating moisture toward the end of the third millennium B.C., followed by greater drying in the later second millennium B.C., when settlement in northern Mesopotamia did indeed decline, but did not disappear. Although I, too, accept a role for climate, especially in these fragile, highly stressed semiarid agricultural systems, archaeological evidence suggests that not only was settlement decline in one part of this zone counteracted by increases in other areas, but also that there were adjustments within both pastoral and sedentary communities that could absorb some of the stress of climatic shocks. 1. [↵][8]1. F. Sirocko , Paleoecol. Africa 24, 65 (1996). [OpenUrl][9] 2. [↵][10]1. H. E. Wright 2. et al. 1. N. Roberts, 2. H. E. Wright , in Global Climates Since the Last Glacial Maximum, H. E. Wright et al., Ed. (Univ. of Minnesota Press, Minneapolis, MN, 1993), pp. 194-220. 3. [↵][11]1. T. J. Wilkinson , Geoarchaeology 12, 853 (1997). [OpenUrl][12] 4. [↵][13]1. H. N. Dalfes, 2. G. Kukla, 3. H. Weiss 1. K. Butzer , in Third Millennium B.C. Climate Change and Old World Collapse, H. N. Dalfes, G. Kukla, H. Weiss, Eds. (NATO ASI Series, Springer, Berlin, 1997), pp. 245-296. 5. [↵][14]1. G. Lemcke, 2. M. Sturm , ibid. 653-678; 1. A. M. Rosen , Geoarchaeology 12, 395 (1997). 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