JWSR v12n2 - Complete Issue  East-West Orientation of Historical Empires and Modern States journal of world-systems research, xii, , december , – http://www.jwsr.org/ issn 1076–156x © 2006 Peter Turchin, Jonathan M. Adams, & Thomas D. Hall introduction In a chapter entitled “Spacious Skies and Tilted Axes” Jared Diamond (1997) argues that crops and domestic animals are spread more easily along lines of latitude (along an East-West axis) rather than along lines of longitude (along a North-South axis). Diamond suggests that East-West spread is easier because similar climates and soil types tend to be arranged in east-west oriented bands. Th is geographic pattern is fundamental to natural vegetation types and wild animal distributions, and is best illustrated by a map of the global distribution of biomes (Figure 1). A biome is a major type of ecological community such as the grassland, desert, or temperate seasonal forest (Ricklefs 2001). Although Diamond focused primarily on the spread of crop cultivars and domesticated animals, the same principle should infl uence the military/politi- cal, demographic, and cultural dynamics of societies. An obvious example which seems to fi t this pattern is the Mongol empire under Chinggis Khan and his Jared Diamond (1997) hypothesized that if environment is important in limiting the spread of cultures, cultural units would also tend to extend more broadly along lines of latitude than along lines of longitude. We test this hypothesis by studying the range shapes of (a) historical empires and (b) modern states. Our analysis of the 62 largest empires in his- tory supports this conjecture: there is a sta- tistically significant tendency to expand more east-west than north-south. Modern states also show this trend, although the results are not statistically significant. abstract: Peter Turchin Department of Ecology and Evolutionary Biology University of Connecticut 75 N. Eagleville Road, U-43 Storrs, CT 06269-3043 Peter.Turchin@uconn.edu Thomas D. Hall Department of Sociology and Anthropology DePauw University 106 Asbury Hall Greencastle, IN 46135 thall@depauw.edu Jonathan M. Adams Biological Sciences Department Boyden Hall 195 University Avenue Rutgers University Newark, NJ 07102 jonadams@andromeda.rutgers.edu Peter Turchin Jonathan M. Adams Th omas D. Hall http://www.jwsr.org mailto:Peter.Turchin@uconn.edu mailto:thall@depauw.edu mailto:jonadams@andromeda.rutgers.edu Turchin, Adams, & Hall220 East-West Orientation of Historical Empires and Modern States  immediate successors; the largest historical empire in terms of contiguous terri- tory. Th e core of the Mongolian Empire was the Eurasian Steppe that stretches for many thousands of kilometers from the Khingan Mountains in the east to the Carpathians in the west (McNeill 1964). Th e Mongols were steppe war- riors, and they were able to extend rapidly their infl uence over this whole region (Barfi eld 1994). Th e regions inhabited by settled agriculturalists adjacent to the steppe were incorporated more slowly and to a lesser degree than the steppe. For example, the Russian principalities of the forest zone were not occupied by the steppe-dwellers, and were instead subjected to tribute. As a result, the Mongol Empire, based on the steppe, was much wider in the latitudinal rather than longitudinal direction. Th e ease of conquest was not the only factor promoting the latitudinal spread of large empires. Societies inhabiting similar ecological zones tend to be more similar to each other than societies located in very diff erent zones. Techniques developed for integrating and controlling a certain type of society should, therefore, be easier to extend latitudinally. Th ere is also a scale aspect to this “ecological factor.” It will be detectable primarily at large geographic scales. Small states or empires, as long as they stay within the same biome, should fi nd it equally easy (or equally hard) to expand in any direction because the climatic diff erences in any direction will be minor. A major exception here might be those states which encompass highly varied terrain. Finally, we note that the latitudinal eff ect should be much stronger for land- based, contiguous empires than for sea-borne empires. Th us, we would expect stronger latitudinal eff ect for historical empires than for modern empires. Also as we note below we omit modern colonial empires from the analysis. However we revisit this issue in the conclusion. analysis of the shapes of historical empires Territorial expansion by states is, of course, a complex process, infl uenced by many factors other than the environment. Th e question of interest here is whether this ecological factor has a detectable eff ect on the projection of mili- tary/political power, or if its infl uence is lost in the “noise” of complex interac- tions. To answer this question we compiled a list of all large historical empires with peak territories exceeding 1 Mm² (= 1,000,000 km²), and measured the distances from their eastern to western extremes, as well as from the northern to southern extremes.¹ Many of the historical empires in our analysis rose and fell starting from the same territory, for instance the diff erent Chinese dynasties. However, this does not invalidate the analysis because each dynastic empire had the opportunity to expand either north-south or east-west (omitting repeat empires from the analysis produced substantially the same result). Figure 1 – Distribution of World Biomes (Ricklefs 2001) ¹. Our list of large historical states was based on the compilation by Taagepera (a, b, , ), which has been systematized and posted on the web by Chase-Dunn and coworkers http://irows.ucr.edu/. We checked the Taagepera list with all major historical atlases in the library of the University of Connecticut and found eight additional empires that fi t our criteria (Axum, Hsi-Hsia, Kara-Khitai, Srivijaya, Maurian, Kushan, Gupta, and Maratha). For historical empires, we used states that peaked before . We excluded the maritime empires of the European Great Powers, because these empires were not contiguous (widely distributed collections of terri- tories). One diffi culty in constructing the list was presented by the repeated rise of empires in the same location, such as in China. We adopted the middle road of count- ing each major dynasty (Han, Tang, Ming, etc.) as a separate empire, but did not distin- guish between cycles within any one dynasty (e.g., Early versus Late Han). Analysis of a reduced dataset, which included only the largest empire for each geographic location, yielded qualitatively the same result. Th is lends support to our argument that succes- sive dynasties had signifi cantly independent opportunities to expand in any direction. See Table  for the list of empires. http://irows.ucr.edu Turchin, Adams, & Hall222 East-West Orientation of Historical Empires and Modern States  Our measure of the tendency to expand in the latitudinal direction is the log-transformed ratio of the east-west distance to north-south distance.² Date (peak) Empire Name World Region Area (Mm2 ) Latitude Index -1300 Egypt (New Kingdom) Africa 1.00 -1.292 350 Axum Africa 1.25 0.241 969 Fatimid Africa 4.10 0.782 1120 Almoravid Africa 1.00 0.561 1200 Almohad Africa 2.00 0.864 1380 Mali Africa 1.10 0.512 1400 Mameluk Africa 2.10 -0.225 1527 Inca America 2.00 -1.139 -176 Hsiung-Nu (Hunnu) Central Asia 9.00 0.818 405 Juan-Juan Central Asia 2.80 0.740 557 Turks Central Asia 6.00 1.026 800 Uigur Central Asia 3.10 0.213 800 Tufan (Tibet) Central Asia 4.60 0.605 850 Khazar Central Asia 3.00 0.139 1100 Hsi-Hsia Central Asia 1.00 0.655 1210 Khorezm Central Asia 2.30 0.054 1210 Kara-Khitai Central Asia 1.50 0.362 1270 Mongol Central Asia 24.00 0.737 1310 Golden Horde Central Asia 6.00 0.153 1350 Chagatai Central Asia 3.50 0.383 1405 Timur’s Central Asia 4.40 0.426 -50 China-Early Han East Asia 6.00 0.661 579 Liang East Asia 1.30 0.137 715 China-Tang East Asia 5.40 0.375 947 Liao (Kitan) East Asia 2.60 0.606 980 China-Sung East Asia 3.10 -0.164 1126 Jurchen (Chin) East Asia 2.30 -0.147 1450 China-Ming East Asia 6.50 -0.138 1790 China-Manchu East Asia 14.70 0.246 117 Rome Europe 5.00 0.204 441 Huns (Atilla’s) Europe 4.00 1.003 555 East Roman Europe 2.70 0.516 814 Frankish Europe 1.20 0.092 1000 Kiev Europe 2.10 -0.132 1025 Byzantine Europe 1.35 0.806 Table 1 – The Large Historical States Used in the Analysis Shang East Asia 1.25 0.050-1122 1480 Lithuania-Poland Europe 1.10 0.079 1683 Ottoman Europe 5.20 0.320 1895 Russia Europe 22.80 0.303 1200 Srivijaya Southeast Asia 1.20 0.272 1290 Khmer Southeast Asia 1.00 -0.665 -250 Mauryan South Asia 5.00 0.191 200 Kushan South Asia 2.00 0.095 400 Gupta South Asia 3.50 -0.031 648 Harsha (Kanyakubia) South Asia 1.00 0.668 1312 Delhi South Asia 3.20 -0.082 1690 Mughal South Asia 4.00 0.435 1760 Maratha South Asia 2.50 -0.280 -670 Assyria Southwest Asia 1.40 1.845 -585 Media Southwest Asia 2.80 0.141 -500 Achaemenid Persia Southwest Asia 5.50 0.200 -323 Alexander’s Southwest Asia 5.20 0.478 -301 Seleucid Southwest Asia 3.90 0.882 0 Parthia Southwest Asia 2.80 1.374 550 Sassanian Persia Southwest Asia 3.50 0.292 750 Caliphate Southwest Asia 11.10 0.730 928 Samanid Southwest Asia 2.85 -0.194 980 Buyid (Buwahid) Southwest Asia 1.60 0.142 1029 Ghaznavid Southwest Asia 3.40 0.689 1080 Seljuk Southwest Asia 3.90 0.409 1190 Ayyubids Southwest Asia 2.00 -0.300 1310 Il-Khan Southwest Asia 3.75 0.664 Date (peak) Empire Name World Region Area (Mm2 ) Latitude Index Table 1 (Continued) ². Log-transformation of the ratio of distances was necessary to make the dis- tribution of the index normal, because the ratio cannot be less than zero. Logically, the metric chosen to quantify the East-West versus North-South spread should give the same magnitude to ratios of : and : (but with the opposite sign), and log- transformation accomplishes this. Positive values of the log-transformed ratio, thus, indicate east-west orientation, and negative values north-south orientation. Turchin, Adams, & Hall224 East-West Orientation of Historical Empires and Modern States  Th e frequency distribution of the latitudinal index in our sample of 62 his- toric empires is strongly skewed to the right (Figure 2), and the mean index is signifi cantly greater than zero (t = 4.83, P < 0.001). Th e great majority of empires, nearly 80, have a positive latitudinal index—that is, they are wider in the east-west compared to the north-south direction. Th ere are only three empires that have a strong north-south orientation, and these are the proverbial exceptions that prove the rule. Th e New Kingdom of Egypt had at its core the valley of a major river running south-north, the Nile. Th e Inca empire is located on the west coast of South America where ecological zones are longitudinal (see Figure 1) along the Andean mountain chain. We do note, however, that Andean empires, especially the Inca, did transcend ecological zones from the altiplano to the coast, but these are over very short distances. Indeed, many empires, if examined more locally, would also exhibit short range biome diversity. Finally, the Khmer empire was located entirely within the wet tropical forest biome. Th us, even though these three cases do not conform to the rule of latitudinal spread, they obey a more general rule of expansion within an ecological zone. All of the largest empires (with territory over 10 Mm²) were oriented in the east-west direction. We have already discussed the case of the Mongol empire. Th e Islamic Caliphate is a variation on the same pattern, except that the “native biome” of the Arabs was the subtropical desert, rather than the temper- ate grassland/desert of the Mongols. Th e next largest state in history after the Mongols, the Russian empire (peak area of 22.8 Mm² in 1895), originated in the transitional zone between the steppe and the forest (ecologists call such tran- sitional zones ecotones). When the Muscovite state began to expand in the six- teenth century, it spread fastest precisely within the same ecotone—eastward along the boundary between the Eurasian steppe and northern taiga. Eastward expansion was extremely rapid, so that the Pacifi c was reached by the mid-sev- enteenth century. In contrast, the southern advance into the steppes and deserts of Central Asia took a much longer time, and they were conquered only by the late nineteenth century. In addition to ecological considerations the presence of strong pastoral confederacies abetted this slowing (Khodarkovsky 2002). But this is also indirectly ecological since these confederacies, many remnants of the Mongol Empire, depended on a steppe environment to make their living. Another example of the same dynamic is the early expansion of Rome. Th e territory of the Roman Empire in the fi rst century b.c.e. coincides almost pre- cisely with the woodland/shrubland biome (also known as the Mediterranean zone). Subsequent expansion took the Romans into the forests of northern Europe. However, severe reverses, such as the battle of Teutoburg Forest in 9 c.e., in which 20,000 legionnaires were obliterated by the tribal Germans (Wells 2003), persuaded the Romans to abandon plans of further conquest. Th e general rule, thus, seems to be that expansion is easiest and most lasting when occurring within the same ecological zone. Expansion into other biomes is possible, but more diffi cult, slow, and requires greater state resources. China is probably the best illustration of this principle. Th e native biome for China is the temperate seasonal forest,³ and this was precisely the area that was fi rst unifi ed by each of a long succession of Chinese empires. Th e strength of the Chinese state, however, allowed it to expand into alien biomes. At their peaks the Chinese empires intruded into the steppe (Inner Mongolia, Chinese Turkestan), the alpine biome (Tibet), and the tropical rain forest (Vietnam). Latitude Index -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Fr eq u en cy 0 2 4 6 8 10 12 14 16 18 Egypt Inca Khmer Figure 2 – Frequency Distribution of the Latitude Index in the Sample of Large Empires ³. It may seem strange to call the Chinese home biome a “forest,” because in pres- ent-day China, of course, very few forests are left. Remember, however, that the biome names refl ect the types of ecological communities that would be present before sub- stantial human impact. Th e names are simply a short-hand reference to particular com- binations of the climate and soil types. Th e same principle applies to the “subtropical desert.” Some examples of this biome (e.g. Sahara) extend well beyond the subtropics in the strictly geographic sense of the word. Turchin, Adams, & Hall226 East-West Orientation of Historical Empires and Modern States  analysis of the shapes of modern political states Is the infl uence of ecology detectable in the shapes of modern states? At fi rst glance, no. Th e average latitude index for the 29 modern states whose territory exceeds 1 Mm² is positive, but not signifi cantly diff erent from 0. However, if we exclude South American countries, where biomes extend in the longitudinal direction, the statistical test indicates that the pattern is detectable even today (t = 2.66, P = 0.014). Th e tendency to east-west orientation in modern coun- tries, nevertheless, is much weaker than for historical empires. Th ere are mul- tiple reasons for this. First, most modern colonial states were sea-borne and not land based. Second, modern transportation technology made and continues to make long-distance travel much cheaper (Ciccantell and Bunker 1998; Bunker and Ciccantell 2005a, 2005b). Th ird there has been a propensity among colonial states to claim territory that is either not inhabited by the home populations, or little used, or being held in reserve for future use. A striking example of this tendency is Canada, whose population is squeezed into a narrow band running east-west along its southern border with the us, but which nevertheless claims extensive territories in the Arctic. Because of the addition of these lands, which are very sparsely populated, the latitudinal index of Canada is slightly negative. Algeria and Lybia provide other examples of the same tendency—their popula- tions are largely confi ned to the east-west band along the Mediterranean lit- toral, but their latitudinal indices are essentially zero, because they claim huge territories to the south, in the Saharan desert. Fourth, and probably the most important in world-system terms, with advent of industrial technology and the rise of modern capitalism, states inten- tionally sought new resources (Bunker and Ciccantell 2005a, 2005b). Where those resources were ecologically based, increased biological and ecological diversity became a disiderata if not an explicit goal. Th is marked a signifi cant change in world-system logic as argued by Chase-Dunn and Hall (1997). conclusions Our results indicate that the physical and biological environment has a detectable eff ect on the shapes of historic states and to a lesser extent on modern states. It appears that projection of military/political power is easier within the same ecological zone (biome). Th is, however, does not support “ecological determinism.” Although ecology is important, its infl uence on state expansion patterns is transmitted by social mechanisms which can either abate, or some- times overturn these ecological eff ects. Despite the complexities of the human world, certain techniques and ideas from ecological sciences have proven to be fruitful in suggesting novel approaches to the study of social systems (Turchin and Hall 2003; Hall and Turchin 2007). Diamond’s original insight, which motivated our study, is one example. Another is the recent demonstration that cultural variability exhibits a latitudinal gradient (Pagel and Mace 2004). Our results also have interesting implications for the study of historical dynamics (Turchin 2003). Researchers working within the world-system paradigm have noted that the rise and fall of populations, cities, and empires is characterized by a broad-scale synchronicity (Chase-Dunn and Hall 1997, Chase-Dunn et al. 2000; Chase- Dunn, Hall, and Turchin 2007). For example, there is a substantial correla- tion between the dynamics of Western Europe and China. On the other hand, South Asian dynamics are completely uncorrelated with the rest of Eurasia. Our fi nding that the propagation of “signals” within military-political networks is facilitated in the latitudinal, but not longitudinal, directions suggests another possible explanation for this pattern. Finally, these results support the arguments originally advanced by Wallerstein (1974, 2004) and elaborated by Chase-Dunn and Hall (1997). Contra Frank and Gills (1993), there was signifi cant break in world-system logic with rise of modern capitalism. It is here evidenced in an attenuation of the latitudinal, or ecological, eff ects on shapes of states and empires with the rise of industrial capitalism. Th e logic of capitalist accumulation of capital⁴ emphasizes ecological diversity over contiguity, shored up by radical decreases in transportation costs and regimes. It remains fascinating, yet problematic, that even in modern states there is still some residual ecological eff ect. Th is is a topic that warrants further, and more nuanced, research than the broad-brush analysis presented here. ⁴. Th e phrase “capitalist accumulation of capital,” which comes from Chase-Dunn and Hall (), serves to distinguish capitalist modes of accumulation from tributary or kin modes of accumulation. Our point is that the logic of capitalist accumulation emphasizes ecological diversity much more than any other mode of accumulation, thus overcoming much of the latitude eff ect. Turchin, Adams, & Hall228 East-West Orientation of Historical Empires and Modern States  _________. . “Size and Duration of Empires: Growth Decline Curves,  b.c. to  a.d.” Social Science History :–. _________. . “Expansion and Contraction Patterns of Large Polities: Context for Russia.” International Studies Quarterly :–. Turchin, Peter. . Historical Dynamics: Why States Rise and Fall. Princeton: Princeton University Press. Turchin, Peter, and Thomas D. Hall. . “Spatial Synchrony Among and Within World-Systems: Insights from Theoretical Ecology.” Journal of World-Systems Research ():–. http://www.jwsr.org Wallerstein, Immanuel. . The Modern World-System: Capitalist Agriculture and the Origins of European World-Economy in the Sixteenth Century. New York: Academic Press. _________. . World-Systems Analysis: An Introduction. Durham, NC: Duke University Press. Wells, Peter S. . The Battle that Stopped Rome: Emperor Augustus, Arminius, and the Slaughter of Legions in the Teutoburg Forest. New York: W. W. Norton. references Barfield, Thomas J. . “The Devil’s Horsemen.” pp. – in Studying War: Anthropological Perspectives, edited by Stephen P. Reyna and R. E. Downs. Langhorn, PA: Gordon and Breach. Bunker, Stephen G. and Paul S. Ciccantell. a. “Space, Matter, and Technology in Globalization of the Past and Future. pp. – in The Historical Evolution of World-Systems, edited by Christopher Chase-Dunn and E. N. Anderson. New York and London: Palgrave. Bunker, Stephen G. and Paul S. Ciccantell. b. Globalization and the Race for Resources. Baltimore: Johns Hopkins University Press. Chase-Dunn, Christopher, Susan Manning, and Thomas D. Hall. . “Rise and Fall: East-West Synchronicity and Indic Exceptionalism Reexamined.” Social Science History :–. Chase-Dunn, Christopher K., and Thomas D. Hall. . Rise and Demise: Comparing World-Systems. Westview Press, Boulder, CO. Chase-Dunn Christopher, Thomas Hall, & Peter Turchin. . “World-Systems in the Biogeosphere: Urbanization, State Formation, and Climate Change Since the Iron Age.” pp.– in The World System and the Earth System: Global Socioenvironmental Change and Sustainability Since the Neolithic, edited by Alf Hornborg and Carole L. Crumley. Walnut Creek, CA: Left Coast Books. Ciccantell, Paul S. and Stepehn G. Bunker, eds. . Space and Transport in the World-System. Westport, CT: Greenwood Press. Diamond, Jared. . Guns, Germs, and Steel: The Fates of Human Societies. New York: W. W. Norton. Frank, Andre Gunder and Barry K. Gills, eds. . The World System: Five Hundred Years or Five Thousand? London: Routledge. Hall, Thomas & Peter Turchin. . “Lessons from Population Ecology for World- Systems Analyses of Long-Distance Synchrony.” pp. – in The World System and the Earth System: Global Socioenvironmental Change and Sustainability Since the Neolithic, edited by Alf Hornborg and Carole L. Crumley. Walnut Creek, CA: Left Coast Books. Khodarkovsky, Michael. . Russia’s Steppe Frontier: The Making of a Colonial Empire, –. Bloomington, IN: Indiana University Press. McNeill, William. H. . Europe’s Steppe Frontier. Chicago: University of Chicago Press. Pagel, Mark and Ruth Mace. . “The Cultural Wealth of Nations.” Nature :–. Ricklefs, Robert E. . The Economy of Nature, th edition. New York: W. H. Freeman. Taagepera , Rein. a. “Size and Duration of Empires: Systematics of Size.” Social Science Research :–. _________. b. “Size and Duration of Empires: Growth-decline Curves,  to  b.c.” Social Science Research :–. http://www.jwsr.org Turchin, Adams, & Hall