Highland aridification and especially the invention of water management technologies in the fourth millennium BC broke the tropical rain barrier that constrained the southward transfer of Levantine domesticated crops. Summer rainfall (carried by monsoon winds during the more northward extent of the ITCZ or Inter-Tropical Convergence Zone) fell across southern Mesopotamia (Sirocko et al 1993), Arabia (Blanchet et al. 1997, 191, 194; Sanlaville 1992, 8-14), southern Sahara (Panchur and Hoezlmann 1991; Haynes 2001, 121, 138), India (Deotare and Kajale 1996, 25; Wasson et al. 1984, 386), and possibly even the extreme southern tip of Jordan (Frumkin et al. 1991, 199; Henry et al. 2003, 21-22) during the early Holocene. Such rainfall would extend the natural range of tropical crops sown in summer and harvested in autumn-winter, such as sorghum, millets, sesame, and summer pulses (gram). Certainly the moisture balance in many highland regions would
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