This book by Guillermo Algaze marks a new step in his study of the phenomenon of Uruk expansion and a resumption of his theories on the “world system” applied to early urban Mesopotamia, but with a reverse approach, in which the main focus is now the “core” of the phenomenon, namely, Lower Mesopotamia. This research has the great merit of implicitly trying to answer the criticisms leveled at his work in recent years. Algaze returns to one of his favorite themes—the central role played by long-distance trade in the development of fourth-millennium urban societies—but this time starts from the internal analysis of the societies (above all, the driving center of the phenomenon, the Mesopotamian alluvium), the weakness of which had been the main target of criticism of his previous studies. Algaze has partially revised his positions on a number of points where recent field research has yielded new and clear evidence; more particularly, he acknowledges the basic autonomy of the Upper Mesopotamian and southeastern Anatolian communities during the formation process of the early centralized societies, which he now views as being less dependent on relations with the south, at least in the initial part of the process, the first half of the fourth millennium. He admits that there is a similar degree of social complexity in the northern and southern areas but then emphasizes the formation of a strong inequality between the two regions in the second half of the fourth millennium, marked by the massive urban development of Lower Mesopotamia—the “Sumerian takeoff”—and it is around the attempt to explain this divergence that the whole book hinges. His praiseworthy aim to “elucidate the economic variables underlying the processes of urban growth and socioeconomic differentiation” (p. 7) leads him to systematically review the most important aspects of a set of interconnected variables that may have created the uniqueness of Lower Mesopotamia in this phase of its history. Algaze examines a wide range of conditions and characteristics of Lower Mesopotamian societies, starting from the unique environmental conditions of the alluvium, with its marked variability in ecological niches and natural resources, already well highlighted in the past by Robert McC. Adams. He attributes enormous importance to the dense system of waterways, marshes, and natural and artificial canals, not so much as the means whereby the extraordinary development of agricultural productivity was achieved but as the condition for creating a highly efficient system of internal transport within the region. He then considers the social and economic consequences of these conditions, which may be summarized as a great need for economic specialization and intense exchange practices between the centers in the plain, high agricultural productivity, the development of sophisticated technologies for controlling human capital as a labor force, and ultimately a high level of urban concentration of the population. This concentration would have generated a high level of competition between the centers, as evidenced from the images of the use of force in glyptics and the initial fortification of some centers. The analysis correctly emphasizes that the distinctive feature of fourth-millennium societies in the alluvium is a high level of urbanization, which Algaze underlines by reexamining the old survey data. I agree that this is the real crucial difference between the southern and northern communities, where high levels of urban development occurred only in certain areas, particularly in the Khabour. But I disagree with Algaze on three fundamental related issues. (1) The northern areas cannot be treated as a single whole, because there were substantial differences between them in terms of their level of urbanization and, consequently, in the final outcomes of the processes, which were quite different, for example, in the Euphrates Valley and in the Khabour. (2) I do not believe that a decline occurred in the northern centers in the latter half of the fourth millennium, when, in the cases with which we are familiar, the highest level of development of economic and political centralization is conversely attested to. The evidence that Algaze cites in the case of Tell Brak is not sufficient to speak of a decline; the apparent decrease in Late Uruk pottery from around the site could, on the contrary, argue in favor of a higher degree of urbanization. We know almost nothing about the other main sites mentioned in the book, but another case also exists that Algaze does not mention, that of Arslantepe, which precisely at the end of the fourth millennium reached its peak of development as an early-state center. (3) The level of administrative complexity of these centers was extremely high and, in my opinion, is comparable to that of the southern centers, even though there were no written tablets; at all events, such tablets existed only in the south in the great Uruk-Warka capital, where their appearance was probably due