A comparative framework for studying the causes of integration

among Bronze and Iron Age polities*

Christopher Chase-Dunn, Kirk Lawrence 
and Hiroko Inoue
Institute for Research on World-Systems (IROWS)


University of California-Riverside
v. 2-28-11, 8234 words
This paper is a proposed spatio-temporal framework for interdisciplinary comparative research on the causes of the expansion 
and deepening of ancient interpolity interaction networks. It proposes a focus on changes in the sizes of largest settlements and
 the territorial sizes of the largest polities in several world regional interpolity networks. 

            To be presented at the New York University Abu Dhabi Institute, Abu Dhabi (UAE), March 6/7, 2011 workshop on beliefs, markets and empires: understanding mechanisms of integration in early societies Organized by Andrew Monson (NYU) and Walter Scheidel (Stanford/NYUAD)

IROWS Working Paper # 66  http://irows.ucr.edu/papers/irows66/irows66.htm

*Thanks to Andrew Jorgenson. David Wilkinson and Thomas Hall for help in

developing the ideas in this paper.

This paper outlines a comparative interdisciplinary framework for studying the causes of growing integration among human communities, as well as the factors that brought about declines in the intensity and extent of interpolity interaction. One main rationale for the proposed spatio-temporal framework is the empirical link between the sizes of the largest polities and settlements in regional interaction networks with the emergence of sociocultural complexity and hierarchy within polities and in systems of interacting polities. Focusing on the population sizes of settlements and the territorial sizes of polities[1] allows us to pinpoint those periods in which the scale of sociocultural systems were significantly changing based on relatively simple and knowable quantitative criteria.  Human interaction networks have expanded over the long run, but in the medium-run there have been cycles and occasional upward sweeps and collapses.  It is the upward sweeps that account for the long-term upward trend toward global integration, and so specifying when and where the upward sweeps occurred and examining their causes will help to explain the long-term trend.  It will also enable us to see how the causality of integration has changed over time, and how it may have been different in different regions.[2]

This project could theoretically include all the local, regional and intercontinental networks, including both nomadic and sedentary world-systems, though in practice we may want to limit ourselves by the availability of quantitative estimates of largest polity and settlements sizes. We focus on the territorial sizes of polities and the population sizes of settlements because these are relatively easily ascertainable quantitative indicators of system size and complexity and they allow us to differentiate between cycles and upsweeps. We need to have an interval scale metric in order to tell the difference between small and large changes.  When human sociocultural systems are studied over long periods of time we usually find cyclical processes of population growth and decline, the rise and fall of large and strong polities, etc.  Our research needs to be able to tell the difference between a “normal” upcycle or downcycle in which a feature of sociocultural organization is fluctuating around an equilibrium level and an event of growth or decline that is greater than the “normal” fluctuations. We focus on the largest settlements and polities in each region rather than on individual settlements or polities.  The size of the largest settlement or polity are understood as characteristics of each regional world-system that vary over time. We identify those instances in which there have been large increases or decreases in these system-wide characteristics.[3]

A very long debate has waxed and waned over how to best bound sociocultural systems in time and space for purposes of explaining the emergence of complexity and hierarchy in human societies (e.g. Chase-Dunn and Hall 1997; Mann 1986; Tilly 1984; Wallerstein 1974). Our theoretical approach is what we call institutional materialism: an interdisciplinary approach that combines focusing on the historical emergence and development 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 spatially and temporally bounding human sociocultural systems.[4] Rather than comparing societies with one another, we compare systems of interacting human polities (or interpolity systems) and these are empirically bounded in space and time as interaction networks—multilateral regularized exchanges of materials, obligations, threats, ideas and information.

World-systems are human interaction networks that display oscillations of expansion and contraction, with occasional large expansions that bring formerly separate regional systems into systemic intercourse with one another. These waves of expanded integration, now called globalization, have, in the last two centuries, created a single linked intercontinental political-economy in which all national societies are strongly connected.  But all earlier regional interaction networks also experienced expansions and contractions of trade. Archaeological studies of obsidian and shell exchange show these oscillations even among very small-scale polities in many regions (e.g. Chase-Dunn and Mann 1998).

As Tilly (1984) has emphasized, societies (defined as 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 societies to one another. The world-systems perspective has argued that societies are subsystems within a larger 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 spatially bounding world-systems that enables the comparison of the modern global system with earlier, smaller regional world-systems. They contend that the world-system rather than single polities is the most important unit of analysis for explaining long-term social change because interpolity conflict and cooperation are very important sources of the selection pressures that cause sociocultural development. In this article we explain this nested network approach to spatially bounding world-systems and we propose a practical research design for studying the emergence of larger and larger interaction networks that uses expanding network as the unit of analysis.

      One problem with regional analysis is the effort to define regions in terms of homogenous sociocultural attributes. Thus, comparative civilizationists have mainly focused on the main cultural characteristics that are embodied in religions or institutionalized world-views and have tended to construct lists of such culturally defined civilizations that then become the “cases” for the study of social change (e.g. Toynbee 1947-57). The problem here is that most interactive sociocultural systems are multicultural, and religious ideologies interact with one another, both diffusing attributes to one another and reactively developing distinctions. So the effort to spatially bound systems based on religious beliefs or other ideological characteristics does not produce regions that are autonomous from one another.

 The “culture area” approach developed by geographer Carl Sauer and used widely by ethnographers and archaeologists tries to define regions as areas with homogenous contiguous characteristics (e.g. Wissler 1927). The culture area project gathered and coded valuable information on all sorts of cultural attributes such as languages, architectural styles, technologies of production, and kinship structures, and used these to designate bounded and adjacent “culture areas.”

A major problem with both the civilizationist and the cultural area approaches is the assumption that homogeneity is a good approach to spatially bounding social systems for purposes of explaining social change. Heterogeneity rather than homogeneity has long been an important aspect of human social systems because different kinds of groups often complement one another and interaction often produces differentiation rather than similarity.  The effort to bound systems as homogeneous regions obscures this important fact. Spatial distributions of homogeneous characteristics do not bound separate social systems. Examples in which social heterogeneity was produced by interaction include core/periphery differentiation, urban/rural, and sedentary/nomadic systems. Owen Lattimore’s (1940) classic, Inner Asian Frontiers of China, shows how Central Asian diversified foragers evolved to become specialized steppe pastoralists because of their interactions with farmers along the ecological boundary between steppe and loess.  The farmer/pastoralist interaction was a powerful source of social change among Bronze and Iron Age societies for millennia (e.g. Barfield 1989). And the interaction between farmers and fishing populations led to the emergence of maritime polities that specialized in naval power and sea-borne trade such as Dilmun (Bahrein) in the Arabian/Persian Gulf (Tosi 1986),  perhaps the first semiperipheral capitalist city-state carrying goods between the Indus Valley civilization and Mesopotamia in the Bronze Age. Bounding regions based on homogenous attributes completely ignores important interactions among different kinds of societies.

Anthropologists and geographers have developed complicated multidimensional  approaches that examine distributions of many spatial characteristics statistically (e.g. Burton 1995)  but these approaches still must make rather arbitrary choices in order to specify regional boundaries and they continue to ignore interactions among different kinds of societies. 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 help to untangle the complicated dynamics of sociocultural development.[5]

Another important point is worth making regarding the relationship between natural ecological regions (biomes) and human interaction networks. Biomes are regions that are defined on the basis of soil type, climate, characteristic plants and animals, etc. The relationship between human social structures and the natural world is obviously important, as stressed by cultural ecologists. Comparative research has demonstrated that empires are more likely to expand into regions that are ecologically similar to the home region, and so they are more likely to be wide than to be tall (to expand in the East/West plane rather than North/South (Turchin, Adams and Hall 2006).  Cultural ecology stresses the important ways in which local ecological factors conditioned sociocultural institutions and modes of living. This has been 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 and to convert biomes into “anthroms” – regions in which the ecology has been radically altered by the intervention of humans (Ellis et al 2010). Some social evolutionists have interpreted this to mean that social institutions have become progressively less ecologically constrained (Lenski, Lenski, and Nolan 1995). But what has happened instead is that the spatial scale of ecological constraints has grown to the point where they are operating globally rather than locally (Chase-Dunn and Hall 2006).

Spatially Bounding World-Systems

The world-systems perspective originally emerged as a theoretical approach for explaining the expansion and deepening of the modern Europe-centered system as it engulfed the globe over the past 500 years (Arrighi 1994; Chase-Dunn 1998; Wallerstein 1974). 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 two decades the world-systems approach has been extended to the analysis of earlier interpolity 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 and cities 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 regional interpolity networks composed of sedentary foragers (Chase-Dunn and Mann 1998), as well as larger regional systems containing chiefdoms, early states, agrarian empires, and the contemporary global political economy.

The comparative world-systems perspective is designed to be general enough to allow comparisons between quite different systems. Chase-Dunn and Hall (1997) defined 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 kinds 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.

Part of Chase-Dunn and Hall’s claim that world-system networks are the most important unit analysis for explaining sociocultural development is based on the hypothesis of semiperipheral development. Chase-Dunn and Hall (1997, Chapter 5) contend that semiperipheral regions within core/periphery hierarchies have been fertile locations for the implementation of new technologies of power,  and that semiperipheral polities have played and continue to play  important roles in the transformation of world-systems. Of course semiperipherality is a relational concept that depends on the nature of the larger system.  Semiperipheral marcher chiefdoms were often the agents of the formation of larger paramount chiefdomships by conquest (Kirch 1984) and semiperipheral marcher states have frequently been the founders of large core-wide empires that accounted for upsweeps in polity size. Semiperipheral capitalist city-states in the interstices between tributary states and empires were agents of commodification that expanded trade networks in the Bronze and Iron Ages, and more recently. The phenomenon of semiperipheral development is the main force behind the movement in space of the cutting edge of complexity and hierarchy in human social change. It has mainly been societies out on the edge of older core regions that rewire the networks and expand the polities.

Spatially bounding world-systems must necessarily 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 always linked polities that were near to one another, have not always been global in the sense that actions in one region had important and relatively quick effects on very distant regions. When transportation and communication occurred only over short distances world-systems were small. Thus the word “world” refers to the network of interactions that impinge on any focal locale.

It is necessary to use the notion of “fall-off” of effects over space (Renfrew 1977) to bound the networks of interaction that importantly impinge upon any point of origin. 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.  

This method of bounding systems is “place-centric.” It is also important to distinguish between endogenous systemic interaction processes and exogenous impacts that may change a system, but are not part of that system. Sweet potatoes somehow got from South America to the Polynesian Islands of the Pacific, but this in itself did not constitute a systemic interaction between the two regions. Maize slowly diffused from Mesoamerica to Eastern North America, but that does not mean that the two areas were part of the same world-system. A virulent pathogen might contact a population with no immunity and ravage that population. But such an event does not necessarily mean that the region from which the pathogen came and the region it penetrated, are parts of a single interactive system. Interactions must be two-way and regularized to be systemic.  Alexander of Macedon conquered part of the South Asian subcontinent, but after the subsequent Greek states were expelled there was little direct or indirect political/military interaction between the Mediterranean state system and the Indic system of states until Muhammad of Ghazni once again linked the two systems a millennium later.

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

         Information Networks (INs)

         Prestige Goods Networks (PGNs)

         Political/Military Networks (PMNs) and

         Bulk Goods Networks (BGNs).

The largest networks are those in which information and ideas travel. Information is light and it travels a long way, even in systems based on down-the-line interaction.[6] 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 systems. 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). [7]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 most world-systems.

            World-systems vary in the degree to which these different kinds of interaction are systemic – have important impacts on local sociocultural reproduction and social change. In all systems the Bulk Goods Network (BGN) and the Political-Military Network (PMN) are systemic. But the Prestige Goods Network varies across systems in both the ways it may be systemic and the extent to which it is important for sociocultural reproduction and social change. And the same may be said of the Information Network (IN).

Immanuel Wallerstein (1974) defined core/periphery relations in the modern world-system  in terms of a hierarchical division of labor in the production of necessities between different polities or regions. This is the BGN. In world-system comparative perspective the BGN may or may not be hierarchical in the sense of unequal exchange in different systems, but it is always systemic because it is important for reproducing local households and communities. Political-military interactions among polities (alliances and warfare) may or may not correspond spatially with the Bulk Goods Network, though the assumption that polities do not trade or intermarry with their traditional enemies is often false.

Anthropologists have long noticed the importance of prestige goods when they are used by elites to reward subalterns and to control marriage (Sahlins 1972 ; Eckholm and Friedman  1982     ; Peregrine 1992 ) And Jane Schneider (1991 ) claimed that, contra Wallerstein, prestige goods flows across the Silk Roads had played an important role in the development of the core regions of Eurasia as well.  Mary Helms (1988) has emphasized the importance of exotic ideas as well as goods in the emergence of theocratic chiefdoms and early states.  A study of a very small world-system in Northern California found that prestige goods were an important source of credit in interpolity trade, reducing the likelihood or raiding in times of scarcity (Chase-Dunn and Mann 1998).  So prestige goods can play different roles in different systems and the question of whether or not and how they are systemic should be empirically determined for every system.


Figure 1: Nested Interaction Networks

The first question for any locale concerns the nature and spatial characteristics of its links with the above four interaction nets. This is prior to any consideration of core/periphery relation because one region must be linked to another by systemic interaction in order for a consideration of whether or not interpolity relations involve exploitation or domination is relevant. The spatial characteristics of these networks clearly depend on the costs of transportation and communications, and whether or not interaction is only with neighbors or there are regularized long-distance trade journeys 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. Fall-off in the PMN generally occurs after two or three indirect links. Suppose polity X is fighting and allying with its immediate neighbors and sometimes 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 polity? The number of indirect links that bound a PMN is usually 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.

Figure 2: Chronograph of the Emergence of the Central PMN (following Wilkinson 1987)

Using this conceptual apparatus, we can construct spatio-temporal chronographs for how the social structures and interaction networks of human populations changed their spatial scales to eventuate in the single global political economy of today. Figure 2 uses PMNs as the unit of analysis to show how what David Wilkinson (1987) calls “Central Civilization,” a PMN that was formed when the Mesopotamian and Egyptian PMNs merged in about 1500 BCE and which eventually incorporated all the other PMNs into itself to become the contemporary global interstate system. The timing of mergers and expansions depicted in Figure 2 are based on Wilkinson’s careful reading of world history to determine when the regions specified began to make war and alliances with one another. This kind of chronograph could be constructed for other regions using the same kinds of historical evidence, and this would be a huge contribution to our knowledge of the expansion of socio-cultural systems.

World-System Cycles: Rise-and-Fall and Oscillations

Comparative research reveals that all world-systems exhibit cyclical processes of change. There are two major cyclical phenomena: the rise and fall of large polities, and oscillations 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 and distribution of power across a set of interacting polities.

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 diversified sedentary foragers of Northern California (Chase-Dunn and Mann 1998) did not display a cycle of rise and fall, they did experience oscillations of trade networks.

Chase-Dunn and Hall (1997) contend 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. [8]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 because the modern hegemons have pursued 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 not as 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 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 on hierarchical kinship relations, control of ritual hierarchies, and control of prestige goods imports than did 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 has made core/periphery relations ever more important for competition among core powers and has altered the way in which the rise-and-fall process works in other respects. Chase-Dunn and Hall (1997, Chapter. 6) argue that population growth, degradation of natural resources, and changes in productive technology and social structure, have generated sociocultural development that is marked by cycles and occasional upsweeps. This is because any world-system varies around an equilibrium as a result of both internal instabilities and environmental fluctuations. Occasionally, on one of the upswings, a system solves its problems in a new way that allows for substantial expansion. The point is to explain expansions, qualitative transformations of systemic logics, and collapses by studying whole world-systems over time and by comparing these to one another.

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 Braudel’s work. Temporal depth, the longue durée, needs to be combined with analyses of short-run and middle-run processes to fully understand social change.

A strong case for the very longue durée is made by Jared Diamond’s (1997) study of the long-term consequences of original differences in zoological and botanical wealth or “natural capital.” The geographical distribution of those species that could be easily and usefully domesticated (combined with the relative ease of latitudinal vs. longitudinal diffusion) explains a huge portion of the variation in which world-systems expanded and incorporated other world-systems.

The diagram in Figure 3 depicts the coming together of the East Asian and the West Asian/Mediterranean systems. Both the PGNs and the PMNs are shown, as are the oscillations and rise and fall sequences. The larger PGNs linked intermittently and then joined. The PMNs were joined briefly by the Mongol conquerors, and then more permanently when the Europeans and Americans established Asian treaty ports. The pink area of Figure 3 depicts the same Central PMN that is shown in Figure 2.  The point here is that the chronograph is different depending on where it starts. Figure 2 and the left half of Figure 3 start in Mesopotamian and Egypt where the first cities and states on Earth emerged. The right half of Figure 3 starts in with the emergence of Shang Civilization in the Yellow River valley of China. The chronographs for South Asia and the Americas would be different.

It should be noted that the depiction in Figure 3 of the spatial boundaries of the PMNs and the PGNs is only an approximation. Another rough depiction of expanding, contracting and eventually merging is contained in Chase-Dunn and Hall’s (1998) study of world-systems in North America. Wilkinson (1987-2007) has also specified the boundaries of many other regional PMNs, and he has coded what he calls the “power polarity”  or “power concentration” trajectories for several world regional PMNs. This latter corresponds to what we have called “rise-and-fall” cycles above.[9]

Figure 3: The Eastern and Western PMNs and PGNs

The following section describes the proposed structure and format for a geo-chronological dataset that focuses on the religious, trade, conquest, demographic, political, climate change and epidemiological aspects of settlements and polities in four world regional PMNs and the Central PMN over the past six millennia.  The main purpose of this dataset is to enable the determination of the main causes of systemic integration and disintegration.

The Polities and Settlements in World Interaction Networks (PSWIN) dataset will be established and maintained by the Settlements and Polities Research Working Group at the Institute for Research on World-Systems (IROWS) at the University of California-Riverside in collaboration with colleagues at other universities. This data set will be made available for public usage.  The dataset will link with the World Historical Dataverse at the University of Pittsburgh http://www.dataverse.pitt.edu/

The proposed data set will use CSV data files that will be stored on the IROWS web site at the University of California-Riverside and mirrored at other locations. Though a relational database that links settlements, polities and regional PMNs with time periods is very useful, this project presents the data in a simple spreadsheet format (Excel) that is more broadly useable by researchers, and can be easily transferred into relational databases if so desired.

The PSWIN data set will include historical quantitative estimates of several demographic, political, climate and epidemiological characteristics of settlements and polities. The characteristics will be grouped into several world regional PMNs.  Additional world regions can be added if quantitative estimates of the main variables are located.  An effort will be made to use the same or similar metrics across world regions, but in some cases this may not be possible.

World Regional PMNs and the Central Political-Military Network

Four world regional PMNs and the expanding Central PMN will be initially studied: Mesopotamia, Egypt, South Asia and East Asia. If there are comparable quantitative estimates of the largest settlements and polity sizes, other regions such as the Americas can be added, but so far these have not been located. Each region’s data will be contained in sets of Excel worksheets, with a row for each year of an observation.  The spatial boundaries of each of the world regional PMNs will be ascertained based on the rule of two indirect interactions from the center of the region’s heartland of settlements.  After these regions become incorporated into the Centrall PMN it may be desireable to continue the data coding for the largest settlements and polities in the region. The Central PMN) will be bounded as conceptually and spatially defined by David Wilkinson (1987) and as depicted in Figure 2 above. The Central System eventually includes Europe, Central Asia, sub-Saharan Africa, Oceania, the Americas and the four world regions delineated above. The characteristics of individual settlements and polities within each of these world regions will be coded. We will focus on the largest settlements and polities in each region and on important smaller settlements and polities, such as city-states.

Each of the  world regional PMNs mentioned is understood in world-systemic terms as including populations that were importantly interacting. So, for example, Mesopotamia includes the Susiana Plain in Iran and the nomadic peoples in surrounding mountains and deserts who were interacting with the Mesopotamian cities and states. East Asia includes what became China, Japan, Korea and the populations that interacted with these urbanized areas. Central Asian empires that conquered the East Asian heartland of cities are included in the East Asian system. 

The main variables around which the PSWIN dataset will be constructed are the population sizes of settlements and the territorial sizes of polities.  Every effort will be made to use the same kinds of measurements of variables across the different world regional PMNs. Each world regional PMN will have a work sheet for settlements and separate work sheets for polities, climate change, landscapes, diet and epidemic diseases. The general framework of the variables for each world regional PMNs and the Central PMN is as follows:

The PSWIN variables

I.       Settlements

(1)         Year (a single year, BCE indicated by negative sign, e.g. -3250 = 3250 BCE)

(2)         Period (period of years, e.g. -3250)

(3)         Region (e.g. Mesopotamia) or PMN (e.g. Central System)

(4)         Settlement Name  (e.g. New York)                         

(5)         Alternative Names (e.g. New Amsterdam)

(6)         Built-up Area of the city (hectares)

(7)         Areal and Population Sizes of residential area (house or hearth counts) 

(8)         Population size estimate of the whole settlement

(9)         Longitude of settlement center

(10)     Latitude of settlement center

(11)     Main religion of the urban population

(12)     Locations of food production for the city

(13)     Long-distance trade partners

(14)     Long-distance trade exports

(15)     Long-distance trade imports

(16)                 Internal conflict

(17)                 Involvement in warfare

(13)         Epidemic disease

(14)   Urban planning: rectangular walls, street grid

(15)   Organized drainage or sewer system

(16)   Organized fresh water system: aqueduct, public and restricted wells, etc.

(17)   Extensive use of fermentation in food processing

II.    Polities

(1)         Year  (a single year, BCE indicated by negative sign, e.g. -3250) 

(2)         Period (period of years, e.g.  -3250 to -3225)

(3)         Region (e.g. Mesopotamia) or PMN (e.g. Central System)

(4)         Name of polity                    

(5)         Alternative names

(6)         Territorial size of polity (square megameters)

(7)         Total population size estimate

(18)     Long-distance trade partners

(19)     Long-distance trade exports

(20)     Long-distance trade imports

(8)         Longitude of center of capital city

(9)         Latitude of center of capital city

(10)     Internal political unrest

(11)     Involvement in warfare with other polities 

(12)     Amount of land under cultivation

(13)     Irrigation

(14)     Episodes of epidemic disease

III. Climate data for world regions (as close to the geographical center as possible)

(1)         Year, period, region

(2)         Temperature (cold-normal-hot)

(3)         Precipitation (rain/snowfall)

(4)         Timing of precipitation (season)

(5)         Incidence of violent storms

(6)         River or lake levels

IV.  Epidemic disease data and population well-being

(1)         Year, period, region

(2)         Settlement name

(3)         Longitude of center

(4)         Latitude of center

(5)         Heights (indicator of well-being)

(6)         Real wages (indicator of well-being)

(7)         Grain prices

(8)         Disease severity (mortality rate)

a.                               Number of deaths per capita

b.                              Epidemic reported in nearby cities

               Most of the data on city sizes has already been coded in connection with related projects. It comes primarily from Chandler (1987) and Modelski (2003) supplemented from other regional sources. The estimates of the territorial sizes of states and empires come from Taagepera (1978a, 1978b, 1979, 1997) also supplemented by newer regional atlases. 


            To summarize, it is proposed that a study of the causes of the expansions and contractions of interpolity integration should focus on largest settlements and polities in world regional PMNs, and that the nested networks of interaction as formulated by the comparative world-systems perspective can serve as a good starting point for such a study.  What is large with regard to settlements and polities is a relative question. A very small settlement can be the largest in a region. The place-centric approach to bounding systemic networks is useful because any location where humans have lived can serve as a starting point for constructing the networks.  Thus for example the Arabian-Persian Gulf might be used as such a starting point. Wilkinson’s method of constructing the boundaries of PMNs can be used for any world region, and indeed he has already done many other regions in addition to the Central PMN (Wilkinson 1987-2007). Trade networks among cities and polities can also be coded using documentary evidence, and the distinction between prestige goods and bulk goods will be useful for this.


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[1] We use the term “polity” to generally denote a spatially-bounded realm of sovereign authority such as a band, tribe, chiefdom, state or empire. The term “settlement” includes camps, hamlets, villages, towns and cities. Settlements are spatially bounded for comparative purposes as the contiguous built-up area.


[2] A data set using the approach outlined here is already being developed by the Polities and Settlements Research Working Group at the Institute of Research on World-Systems at the University of California-Riverside. The project web site is at http://irows.ucr.edu/research/citemp/citemp.html


[3] Our empirical inventory of  quantitatively identified upsweep and collapse “events”  in four world regions and the expanding Central Political/Military Interaction network is described in Alvarez et al ( 2011)


[4] World-systems are defined as being composed of those human settlements and polities within a region that are importantly interacting with one another (Chase-Dunn and Hall 1997).

[5] 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 have developed GIS techniques based on vectors for mapping prevailing winds, but also for studying migration (Tobler 1995; n.d.).


[6] Down-the-line exchange is when goods or ideas are passed from group to group and there are few long-distance trade expeditions.


[7] PMNs are interpolity systems of warfare and alliance. This is the same idea as “:international systems” as it is used by Political Scientists who study international relations.

[8] In the comparative civilizations literature what we call core-wide empires are terms “universal empires.”

[9] Wilkinson (1997) says of his “power polarity” scheme  at the most centralized end, where one state encompasses the whole system, is the universal state (Toynbee) or empire (Quigley); next to it is hegemony (or "unipolarity with hegemony"), where a single great power or superpower, with influence to match its capability, oversees a number of subject states which retain internal autonomy; next to that is the condition of unipolarity (more precisely, unipolarity without hegemony), where a single great power, lacking the influence to match its capability, rests among a collection of non-subject non-tributary states;  nearer the decentralized end come configurations with two, three, or more great powers: bipolarity, tripolarity, multipolarity;  and most decentralized, with many ministates and no great powers, is nonpolarity.