Abstract:

            This paper discusses methodological and conceptual issues in bounding human social systems and their interactions with the natural environment. We contend that interaction networks are far superior to cultural area and regional approaches for bounding human social systems. And we review several new approaches for studying the interactions between human systems and the natural environment.

            An ancient debate has waxed and waned over how to bounding social systems in time and space for the purposes of telling human histories for explaining social change. Sociospheres have long interacted with biospheres and the geosphere, and humans have long painted their stories with attention to the significance of place and the natural world.  Theorists of the emergence of complex and hierarchical social systems have treated or ignored geographical and biological context depending on their mix of material determinism on the one hand and social and cultural constructionism on the other.

            Our theoretical approach can be characterized as institutional materialism, a combination of focusing on the historical evolution of humanly constructed institutions (language, kinship, production technology, states, money, markets, etc) and the changing ways that humans interact with their biological and physical environment. This theoretical framework deploys what has been called the comparative world-systems approach to bounding social systems. Rather than comparing societies with one another we compare systems of human societies (or intersocietal systems) and these are empirically bounded in space as interaction networks À bilateral or multilateral regularized exchanges of materials, obligations, threats or information.

            As Charles Tilly (1984) has emphasized, societies (defined as national communities that share a common language and culture) are messy entities when we consider interaction networks. Many of the networks in which households are deeply involved are local, while many other important interactions strongly link the inhabitants of many different national societies to one another. The world-systems perspective has argued that societies are subsystems within a larger single system, and that in order to understand historical development we must focus on the larger system as a whole. Chase-Dunn and Hall (1997) have developed a nested network approach for bounding world-systems that enables the comparison of the modern global system with earlier, smaller regional world-systems (see below). They contend that it is world-systems rather than societies that constitute the most important unit of analysis for explaining social evolution. In this paper we will explain this  nested network approach to spatially bounding world-systems and then consider how new developments in "Hierarchical Linear Modeling" (HLM) Geographical Information Systems (GIS) may allow the questions of causally most powerful units of analysis to be subjected to testing against historical (and prehistoric) data.

            New developments in our abilities to empirically examine and model spatial characteristics, especially dynamic spatio-temporal GIS, are combining with new theoretical perspectives, especially the comparative world-systems approach, to promise a new dawn for our understanding and explanation of social change. This involves a new way of combining the study of geographical regions with the examination of human interaction networks.

            Regions are often defined geographically in terms of distributions of natural attributes such as climate, soil types, elevation, temperature, and related botanical and zoological habitation. Geographers conceptualize regions and space at varying and interacting scales, and regional definitions are necessarily multiscalar À it is recognized that smaller regions are nested within larger ones. Regions are also defined in terms of the scale of variation of attributes. So that fine-grained ecologies have rather different adjacent microclimates, whereas coarse-grained ecologies have large homogenous subregions.

            One limitation of some regional analysis has been the tendency to define regions in terms of homogenous attributes, either natural or social. Thus comparative civilizationists have tended to focus on the core cultural characteristics that are embodied in religions or world-views and to construct lists of such culturally defined civilizations that then become the "cases" for the study of social change. Another approach that defined regions as areas with homogenous characteristics was the "culture area" approach developed by Carl Sauer and his colleagues (Wissler 1927). This project gathered information on all sorts of cultural attributes  —languages, architectural styles, technologies of production, kinship structures, etc. — and used these to designate bounded and adjacent "culture areas." A major problem with both the civilizationist and cultural area approaches is the assumption that homogeneity is a good approach to bounding social systems that are evolving. The world-systems approach focuses instead on human interaction networks, and so it is able to define its units of analysis as systemic combinations of very different kinds of societies. This makes it possible to study multicultural systems and core/periphery relations as cases that can display dynamics of social evolution. Heterogeneity rather than homogeneity has long been an important aspect of human social systems. The effort to bound systems as homogeneous regions obscures this important fact.¹

            Some social scientists erroneously assume that GIS data structures are restricted to the mapping of attributes that are stationary in space and that GIS is useless for studying things that move. Geographers are now developing GIS techniques based on vectors for mapping prevailing winds, but also for studying migration (Tobler 1995; n.d.).

            Another important point is worth making regarding the relationship between natural regions and human interaction networks.  Cultural ecology stressed the important ways in which local ecological factors conditioned sociocultural institutions and modes of living. This was an especially compelling perspective for understanding small-scale systems in which people were mainly interacting with adjacent neighbors not very far away. But this kind of local ecological determinism is much less compelling when world-systems get larger because long-distance interaction networks and the development of larger scale technologies enable people to impose socially constructed logics on local ecologies. Some social evolutionists have interpreted this to mean that social institutions have become progressively less ecologically determined (Lenski, Lenski and Nolan 1995). But what has happened instead is that the spatial scale of ecological determinism has grown to the point where it is operating globally rather than locally (Chase-Dunn and Hall 1997).

Spatially Bounding World-Systems

            The world-systems perspective emerged as a theoretical approach for modeling and interpreting the expansion and deepening of the European system as it engulfed the globe over the past 500 years (Wallerstein 1974; Arrighi 1994;Chase-Dunn 1998;). The idea of a core/periphery hierarchy composed of "advanced" economically developed and powerful states dominating and exploiting "less developed" peripheral regions has been a central concept in the world-systems perspective. In the last decade the world-systems approach has been extended to the analysis of earlier and smaller intersocietal systems. Andre Gunder Frank and Barry Gills (1993) have argued that the contemporary world system is a continuation of a 5000-year old system that emerged with the first states in Mesopotamia. Chase-Dunn and Hall (1997) have modified the basic world-systems concepts to make them useful for a comparative study of very different kinds of systems. They include very small intergroup networks composed of sedentary foragers, as well as larger regional systems containing chiefdoms, early states, agrarian empires and the contemporary global political economy in their scope of comparison.

            The comparative world-systems perspective is designed to be general enough to allow comparisons between quite different systems. Chase-Dunn and Hall (1997) define world-systems as important networks of interaction that impinge upon a local society and condition social reproduction and social change. They note that different kinds of interaction often have distinct spatial characteristics and degrees of importance in different sorts of systems. And they hold that the question of the nature and degree of systemic interaction between two locales is prior to the question of core/periphery relations. Indeed they make the existence of core/periphery relations an empirical question in each case, rather than an assumed characteristic of all world-systems.

            Spatially bounding world-systems necessarily must proceed from a locale-centric beginning rather than from a whole-system focus. This is because all human societies, even nomadic hunter-gatherers, interact importantly with neighboring societies. Thus if we consider all indirect interactions to be of systemic importance (even very indirect ones) then there has been a single global world-system since humankind spread to all the continents. But interaction networks, while they were always intersocietal, have not always been global in the sense that actions in one region had major and relatively quick effects on distant regions. When transportation and communications were over short distances the world-systems that affected people were small.

            Thus it is necessary to use the notion of "fall-off" of effects over space to bound the networks of interaction that importantly impinge upon any focal locale. The world-system of which any locality is a part includes those peoples whose actions in production, communication, warfare, alliance and trade have a large and interactive impact on that locality. It is also important to distinguish between endogenous systemic interaction processes and exogenous impacts that may importantly change a system but are not part of that system. So maize diffused from Mesoamerica to Eastern North America, but that need not mean that the two areas were part of the same world-system. Or a virulent micro parasite might contact a population with no developed immunity and ravage that population. But such an event does not necessarily mean that the region from which the microparasite came and the region it penetrated are parts of a single interactive system. Interactions must be two-way and regularized to be systemic. One-shot deals do not a system make.

            Chase-Dunn and Hall (1997) note that in most intersocietal systems there are several important networks of different spatial scales that impinge upon any particular locale:

            The largest networks are those in which information travels. Information is light and it travels a long way, even in systems based on down-the-line interaction. These are termed Information Networks (INs). A usually somewhat smaller interaction network is based on the exchange of prestige goods or luxuries that have a high value/weight ratio. Such goods travel far, even in down-the-line systems². These are called Prestige Goods Networks (PGNs). The next largest interaction net is composed of polities that are allying or making war with one another. These are called Political/Military Networks (PMNs). And the smallest networks are those based on a division of labor in the production of basic everyday necessities such a food and raw materials. These are Bulk Goods Networks (BGNs). Figure 1 illustrates how these interaction networks are spatially related in many world-systems.

	Figure 1 : Nested Interaction Networks

            The first question for any focal locale is about the nature and spatial characteristics of its links with the above four interaction nets. This is prior to any consideration of core/periphery position because one region must be linked to another by systemic interaction in order for consideration of core/periphery relations to be relevant.

            The spatial characteristics of these networks clearly depend on many things - the costs of transportation and communications, and whether or not interaction is only with neighbors or there are regularized long-distance trips being made. But these factors affect all kinds of interaction and so the relative size of networks is expected to approximate what is shown in Figure 1. As an educated guess we would suppose that fall-off in the PMN generally occurs after two or three indirect links. Suppose group A is fighting and allying with its immediate neighbors and with the immediate neighbors of its neighbors. So its direct links extend to the neighbors of the neighbors. But how many indirect links will involve actions that will importantly affect this original group? The number of indirect links that bound a PMN are probably either two or three. As polities get larger and interactions occur over greater distances each indirect link extends much farther across space. But the point of important fall-off will usually be after either two or three indirect links.

            Chase-Dunn and Hall (1997) divide the conceptualization of core/periphery relations into two analytically separate aspects:

            Core/periphery differentiation exists when two societies are in systemic interaction with one another and one of these has higher population density and/or greater complexity than the other. The second aspect, core/periphery hierarchy, exists when one society dominates or exploits another. These two aspects often go together because a society with greater population density/complexity usually has more power than a society with less of these, and so can effectively dominate/exploit the less powerful neighbor. But there are important instances of reversal (e.g. the less dense, less complex Central Asian steppe nomads exploited agrarian China) and so this analytical separation is necessary so that the actual relations can be determined in each case. The question of core/periphery relations needs to be asked at each level of interaction designated above. It is more difficult to project power over long distances and so one would not expect to find strong core/periphery hierarchies at the level of Information or Prestige Goods Networks.  Figure 2 illustrates a core/periphery hierarchy.

	Figure 2 : Core/Periphery Hierarchy

            Using this conceptual apparatus we can construct spatio-temporal chronographs for how the social structures and interaction nets of the human population changed their spatial scales to eventuate in the single global political economy of today. Figure 3 uses PMNs as the unit of analysis to show how a "Central" PMN composed of the merging of the Mesopotamian and Egyptian PMNs in about 1500 BCE eventually incorporated all the other PMNs into itself.

	Figure 3 : Chronograph of PMNs

World-system Cycles: Rise-and-Fall and Pulsations

            Comparative study reveals that all world-systems exhibit cyclical processes of change. There are two major cyclical phenomena: the rise and fall of large polities, and pulsations in the spatial extent and intensity of trade networks. "Rise and fall" corresponds to changes in the centralization of political/military power in a set of polities. It is a question of the relative size of and distribution of power across a set of interacting polities. The term "cycling" has been used to describe this phenomenon as it operates among chiefdoms (Anderson 1994).

            All world-systems in which there are hierarchical polities experience a cycle in which relatively larger polities grow in power and size and then decline. This applies to interchiefdom systems as well as interstate systems, to systems composed of empires, and to the modern rise and fall of hegemonic core powers (e.g. Britain and the United States). Though very egalitarian and small scale systems such as the sedentary foragers of Northern California (Chase-Dunn and Mann, 1998) do not display a cycle of rise and fall, they do experience pulsations.

            All systems, including even very small and egalitarian ones, exhibit cyclical expansions and contractions in the spatial extent and intensity of exchange networks. We call this sequence of trade expansion and contraction pulsation. Different kinds of trade (especially bulk goods trade vs. prestige goods trade) usually have different spatial characteristics. It is also possible that different sorts of trade exhibit different temporal sequences of expansion and contraction. It should be an empirical question in each case as to whether or not changes in the volume of exchange correspond to changes in its spatial extent. In the modern global system large trade networks cannot get larger because they are already global in extent. But they can get denser and more intense relative to smaller networks of exchange. A good part of what has been called globalization is simply the intensification of larger interaction networks relative to the intensity of smaller ones. This kind of integration is often understood to be an upward trend that has attained its greatest peak in recent decades of so-called global capitalism. But research on trade and investment shows that there have been two recent waves of integration, one in the last half of the nineteenth century and the most recent since World War II (Chase-Dunn, Kawano and Brewer 2000).

            The simplest hypothesis regarding the temporal relationships between rise-and-fall and pulsation is that they occur in tandem. Whether or not this is so, and how it might differ in distinct types of world-systems, is a set of problems that are amenable to empirical research.

            Chase-Dunn and Hall (1997) have contended that the causal processes of rise and fall differ depending on the predominant mode of accumulation. One big difference between the rise and fall of empires and the rise and fall of modern hegemons is in the degree of centralization achieved within the core. Tributary systems alternate back and forth between a structure of multiple and competing core states on the one hand and core-wide (or nearly core-wide) empires on the other. The modern interstate system experiences the rise and fall of hegemons, but these never take over the other core states to form a core-wide empire. This is the case because modern hegemons are pursuing a capitalist, rather than a tributary form of accumulation.

            Analogously rise and fall works somewhat differently in interchiefdom systems because the institutions that facilitate the extraction of resources from distant groups are less fully developed in chiefdom systems. David G. Anderson's (1994) study of the rise and fall of Mississippian chiefdoms in the Savannah River valley provides an excellent and comprehensive review of the anthropological and sociological literature about what Anderson calls "cycling," the processes by which a chiefly polity extended control over adjacent chiefdoms and erected a two-tiered hierarchy of administration over the tops of local communities. At a later point these regionally centralized chiefly polities disintegrated back toward a system of smaller and less hierarchical polities.

            Chiefs relied more completely on hierarchical kinship relations, control of ritual hierarchies, and control of prestige goods imports than do the rulers of true states. These chiefly techniques of power are all highly dependent on normative integration and ideological consensus. States developed specialized organizations for extracting resources that chiefdoms lacked — standing armies and bureaucracies. And states and empires in the tributary world-systems were more dependent on the projection of armed force over great distances than modern hegemonic core states have been. The development of commodity production and mechanisms of financial control, as well as further development of bureaucratic techniques of power, have allowed modern hegemons to extract resources from far-away places with much less overhead cost.

            The development of techniques of power have made core/periphery relations ever more important for competition among core powers and have altered the way in which the rise-and-fall process works in other respects. Chase-Dunn and Hall (1997) argued that population growth in interaction with the environment, and changes in productive technology and social structure produce social evolution that is marked by cycles and periodic jumps (Chase-Dunn and Hall 1997:Chapter 6). This is because any world-system varies around an equilibrium or mean due both to internal instabilities and environmental fluctuations. Occasionally, on one of the upswings a system solves its problems in a new way that allows substantial expansion. We want to explain expansions, evolutionary changes in system logic, and collapses. That is the point of comparing world-systems.

            The multiscalar regional method of bounding world-systems as nested interaction networks outlined above is complimentary with a multiscalar temporal analysis of the kind suggested by Fernand Braudelês work. Temporal depth, the longue duree, needs to be combined with analyses of short-run and middle-run processes to fully understand social change. Perhaps this is not a point that needs to be hammered for an audience of world historians, but the predominant presentism of most social science and contemporary culture needs to be denounced at every opportunity.

            A strong case for the very longue duree is made by Jared Diamondês (1997) study of original zoological and botanical wealth. Those Mesolithic human groups that had access to species that could be easily and profitably domesticated (combined with the relative ease of latitudinal vs. longitudinal diffusion) explains a huge portion of the variance regarding which world-systems expanded and incorporated other world-systems thousands of years hence.

            As mentioned in the introduction above, we see the emergence of certain new analytic techniques as having important possibilities for improving the comparative world-systems theoretical research program.  GIS has been used mainly as a mapping device for linking and comparing geographical information. In this guise it has important applications for allowing us to think spatially and to imagine causal explanations for patterns and events. Standardized ways of representing Earthly space (e.g. digitalearth.gov) present an opportunity for linking and understanding historical events and relationships as a World History GIS.

            But the potential for GIS as an analytic device for suggesting and testing causal models is as yet in its infancy. Spatial analysts have begun to develop GIS techniques for optimization of location decisions À where to build the firehouse or the McDonalds. The next step is to use GIS for testing models of historical development. This will involve further elaboration of the ability to represent movement and interaction networks with GIS, and the development of modeling techniques that use change over time to test complex causal models. In this connection GIS might be combined with Hierarchical Linear Modeling (HLM), a technique that is used to study causal interactions among different levels of nested interaction networks (e.g. schools, classrooms, and students).  HLM is quite useful because it makes it possible to separate the variance into components explaining the effects of different levels of analysis (Vogt 1999).  With HLM, each of the levels in this structure is formally represented by its own submodel.  These submodels indicate relationships among variables within a given level, and specify how variables at one level influence relations occurring at another (Bryk and Raudenbush 1992).  Using empirical data, this will enable us to address the questions of what relationships at which levels of analysis really are more causally powerful.  The debates about whether national societies or variable characteristics of the world-system as a whole are most powerful for explaining social change may then be able to partially transcend the current shouting and arm waving.

            The general comparative method of non-experimental research design assumes that "cases" (units of analysis) are independent instances of the process under study. When we compare cases, such as national societies, that are clearly not independent in some respects, we model this non-independence by including measures of the international, transnational or world-system level characteristics that are thought to be causes of the dependent variable under study. HLM and its possible combination with GIS may allow us to determine degrees of independence of processes as well as the causal power of variable characteristics of different levels of analysis.

            GIS also could profitably be combined with network analysis as it has developed among mathematical sociologists of interaction. Network analysis is a quantitative approach to interaction networks that produces measurements of network structures and of positions (nodes) within networks. It is a rather sophisticated analytic technique that is little known outside of mathematical sociology. Linking with GIS-organized data could enhance this analytic approach to spatial relations.  GIS has been used for geometric networks, a more elementary process that allows for the modeling of different infrastructures including highways, cables, and pipeline (Zeiler 1999).  This suggests the feasibility of combining the two methods.  Network analysis, currently a mainly descriptive tool, might also importantly benefit from new GIS techniques that allow causal analysis.

            To reiterate, we contend the interaction networks, the empirically determinable links among people, are far superior to categorical attributes for solving the problem of the spatial bounding of social systems. These allow us to examine the spatial nature of subgroups within societies as well as the important ways in which the members and organizations in different societies are connected with one another. We also see new techniques for organizing spatial data and for analyzing nested systems as promising tools that will help us to crack the codes of historical development and social evolution. GIS also enables us to present spatial illustrations that are extremely useful for education and for conveying the results of historical science to a larger public.

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