229Sprawl, Squatters, and Sustainable CitiesSprawl, Squatters and Sustainable Cities: Can Archaeological Data Shed Light on Modern Urban Issues?Michael E. SmithAncient cities as documented by archaeologists and historians have considerable relevance for a broader understanding of modern cities and general processes of urbanization. This article reviews three themes that illustrate such relevance: sprawl, squatter settlements and urban sustainability. Archaeology’s potential for illuminating these and other topics, however, remains largely unrealized because we have failed to develop the concepts and methods required to analyse such processes in the past. The following aspects are examined for each of the three themes: the modern situation, the potential insights that archaeology could contribute, and what archaeologists would need to do to produce those insights. The author then discusses some of the benefits that would accrue from increased communication between archaeologists and other scholars of urbanism.Do archaeological studies of ancient cities have any relevance for understanding the processes and prob-lems of urbanization today? The media and popular press certainly imply that this is the case. National Geographic News tells us that ‘Sprawling Angkor [was] brought down by overpopulation’ (Brown 2007). The Environmental News Network reports that ‘Researchers [at Tell Brak] rewrite the origins of ancient urban sprawl’ (Environmental News Network 2007), whereas the Planetizen web site says of the same site, ‘Ancient cities were clusters, not sprawl’ (Berg 2007). Scientific American, on the other hand claims that ‘Ancient squatters [at Tell Brak] may have been the world’s first suburbanites’ (Biello 2007). In his bestseller, Collapse, Jared Diamond (2004) warns us about the fates that awaited non-sustainable ancient cities. This kind of facile ancient–modern comparison is a staple of the media (and of university public rela-tions offices), but does it signal any real significance for research on comparative urbanism? It is hard to answer this question because no one has attacked the issue with rigorous data and methods.In this article I argue that archaeological research on ancient cities has considerable potential to increase our understanding of modern urban issues and prob-lems, but it will require that archaeologists undertake conceptual and methodological work before this potential can be realized. This work will not only allow better comparisons of ancient and modern urbanism, but it will also improve our understanding of some of the social dynamics at play in the cities of the past. In order to illustrate the reciprocal relationship between analyses of ancient and modern urbanism, I limit my focus to three topics — sprawl, squatters or informal settlements and urban sustainability. These are the targets of considerable bodies of research for modern cities, but archaeologists for the most part have yet to address them systematically. This is a programmatic article, and I present only limited amounts of data to support my assertion. Although I do briefly explore the analysis of these topics within one ancient urban tradition (Prehispanic central Mexico), that exposition is merely for illustrative purposes; it is not a fully worked-out case study. Archaeologists have not yet analysed our data or conceptualized our findings in ways that can inform research on modern urbanism in a convincing manner.1The first question to consider is whether ancient and modern cities are actually comparable. After all, the modern world is quite different from the ancient world in countless ways, and one could easily argue that cities in the two settings are so radically different that serious comparisons are doomed to fail. But in fact we have surprisingly little empirical evidence for Cambridge Archaeological Journal 20:2, 229–53 © 2010 McDonald Institute for Archaeological Researchdoi:10.1017/S0959774310000259 Received 15 Jan 2009; Revised 22 Jul 2009; Accepted 23 Jul 2009230Michael E. Smiththe nature and extent of differences between modern and ancient cities because the two phenomena have rarely been studied together using common methods and concepts. This situation presents a stark contrast to comparative research on state-level economies, where comparisons between ancient and modern economic systems have been endlessly researched and debated with ample presentation of empirical data and theoretical perspectives (see the review in Smith 2004). In my opinion, considerable comparative research will be needed to evaluate the similarities and differences between ancient and modern cities (Smith 2009a). Urban scholars have suggested some of the factors that have produced transformations in cities and urban processes in the twentieth century, and these provide a starting point for comparative research.Most urban scholars stress advances in transport and communications as major forces that shaped new urban forms and processes in the modern era (e.g. Vance 1990; Jackson 1985). Environmental historian John R. McNeill (2000, 281) notes that ‘twentieth-century urbanization affected almost everything in human affairs and constituted a vast break with past centuries’. He cites the size of cities, the amount of garbage and pollution, and the extent of ecological footprints as the major differences between twentieth-century cities and their predecessors. Political econo-mists Gordon McGranahan and David Satterthwaite (2003) emphasize changes brought by the end of colonialism in the third world (2003, 247) and by the expansion of global capitalism: ‘The most important underpinning of urban change during the twentieth century was the large increase in the size of the global economy’ (2003, 246). On a smaller scale than these grand forces, life in cities today is quite different from the past, in everything from expanded life expectancy, to the prevalence of planning and zoning, to the growth of surveillance practices.On the other hand, some writers acknowledge these differences but still argue that ancient and modern cities can be considered within the same frame of reference for many issues. This view is expressed most frequently by scholars working on the urban built environment. Amos