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.