Societies in many regions all over the world started down the path toward large-scale social formations, so the number of trajectories available for comparative study is large. Although most of these regional trajectories are not well known, the few that are well enough documented for comparative study are more than comparisons can easily handle. A focus on early civilizations leads to comparing large world areas (Mesopotamia, Nile Valley, North China, Mesoamerica, Central Andes, etc.) because early civilizations are very large-scale social formations – finally, each of these world areas contained only one civilization. The beginnings of large social formations, which is the subject of this chapter, however, can be found in multiple separate regions within any of these areas. It is the specific trajectories of societal change within these smaller regions that we seek to compare, not culture-historical constructs like archaeological cultures, horizons, or traditions. For comparing trajectories, attention must be focused on human activities and the organization of social relationships in a place, and culture history is not the most effective or direct approach to these subjects. We treat each regional trajectory as a separate instance to be compared with others.

This chapter lays aside the data threads spun around differentiation in Chapter 5 in order to focus on those most directly connected to the emergence and growth of supra-local communities: local community structure, supra-local community scale, supra-local community centralization, demographic density, public works investment, tax rate, and conflict. Estimation of ancient populations and labor investment in public works lies at the core of the comparisons presented here. At least some archaeologists have long been willing to make such estimates, but the task should only be attempted by archaeologists willing to “dare to be inaccurate” (cf. Martens 2008:1160). Although the empirical basis for archaeological population and labor investment estimates is far better than it was twenty years ago, both still come with very wide error ranges. They can be put to effective use, but only if we adopt the attitude required for solving what have come to be called Fermi problems in the natural sciences, where the vital role played by quick calculations on cocktail napkins is thoroughly appreciated (Morrison 1963; Weinstein and Adam 2008). The comparisons we offer here are based on more rigorous use of empirical data than the solutions to Fermi problems often are, but the reader is forewarned that we have not let the imprecision of archaeological population or labor investment estimates stop us. We have been willing to work with sometimes uncomfortably large error ranges in order to see what kind of conclusions the best information now available leads toward. We offer them as cocktail napkin calculations; readers more interested in data precision than in the heuristic value of seeing where even imprecise data might lead should probably stop here. Those willing to join us in being as careful as possible with the data but riding roughshod when necessary, should read on. The sources of the empirical information we have used and the nature of our analyses are discussed in the appendix.

As archaeologists, we seek to understand variation and change in past human societies. This goal necessitates a comparative approach, and comparisons justify the broad cross-cultural and diachronic scope of our work. Without comparisons we sink into the culture-bound theorizing against which anthropology and archaeology have long sought to broaden social science research. By undertaking comparisons that incorporate long-term social variability, archaeologists not only improve our understanding of the past, but also open the door to meaningful transdisciplinary research. Archaeologists have unique and comprehensive data sets whose analysis can contribute to dialogues surrounding contemporary issues and the myriad challenges of our era.

In the past two decades, the pendulum seems to have swung away from comparative research in archaeology. Many archaeologists focus on detailed contextual descriptions of individual cases, and only a few have dedicated themselves to explicit comparative work. Yet in that same time span, fieldwork has expanded tremendously throughout the world, leading to an explosion of well-documented diachronic data on sites and regions. We now have substantial detail on the variation inherent in phenomena such as cultural assemblages, settlement patterns, and economic activity. New methods, from dating techniques to digital data processing, promote comparative analysis and greatly advance our understanding of human societies and change. The time is ripe for a renewed commitment to comparative research in archaeology.

Early complex society studies, like anthropology in general, are strongly rooted in comparative analysis. Cultural evolutionists of the mid-nineteenth century (Tylor 1865; Morgan 1877; Spencer 1880–97) relied entirely on comparative ethnography to create speculative accounts of the antecedents of contemporary societies. A century later, Sahlins (Sahlins and Service 1960), Service (1962), Fried (1967), and other scholars did the same without assuming that “savages” would naturally aspire to better things, and slowly work their way through “barbarism” toward the “civilized” condition of Victorian Britain. Value-neutral vocabulary was sought and forces driving social change were considered, but the entire comparative enterprise still depended on imagining that some contemporary societies were like the unknown ancestors of other more complex contemporary societies. There was virtually no direct information about human societies before those that could be observed in the ethnographic present or through historical sources.

By the beginning of the twenty-first century, that situation has changed dramatically. It is no longer necessary to speculate about diachronic processes from synchronic snapshots of societies not historically related to each other, because of a flood of direct archaeological evidence about long-term trajectories of social change. We still do not know as much about the past of any region as we would like to, but we do now know more about many regions than we are fully able to make sense of. Comparative study is important to this task of, quite literally, making sense of abundant detailed information. It was exactly this that the early cultural evolutionists were doing with their comparative ethnography: making sense of a welter of ethnographic detail. Scholars from Morgan to Service and Fried offered understanding by placing ethnographically known contemporary societies in an imaginary developmental sequence. Since the sequence was based on nothing more than ethnographic information about contemporary ⁠unrelated societies, it is remarkable how much the cultural evolutionists got right about the past ten thousand years of human history.