Evolution of Complex Hierarchical Societies

Searching for a Proxy of Warfare Intensity

The formal model, thus, confirms the theoretical prediction in this paper: complex multi-level societies controlling large territories are expected to arise in areas where warfare is particularly intense. How can we test this prediction empirically? Ideally, we would wish to determine if there is a statistical relationship between the intensity/frequency of warfare (the independent variable) and the territorial size of societies experiencing such warfare levels (the dependent variable). Such a direct test, unfortunately, is impossible, because we lack systematic data on warfare intensity across the globe throughout history. However, anthropological and historical research identified a number of factors that are correlated with war intensity and frequency. We can use such war correlates as proxies for the independent variable.

Empirical evidence, reviewed in Turchin (2009a), suggests that the intensity of warfare rises dramatically with the cultural distance between the antagonists. Internal warfare, that is warfare within an ethnographic unit – usually, a group of people speaking a language not normally understood by people in neighboring societies (Ember et al. 1992) – tends to be ritualized and relatively bloodless. For example, internal warfare among horticulturalists usually involves set-piece battles that frequently end after the first death or injury. There are typically institutions that mediate conflict resolution and truces. By contrast, external warfare (between the ethnographic unit as a whole and another society) tends to be much more lethal. Instead of pre-arranged battles it usually involves ambushes and raiding, and may result in genocide (whole villages wiped out). Among the pastoralists, similarly, internal conflict is often limited to livestock stealing, whereas external warfare explicitly targets people.

If warfare between ethnic communities tends to be more intense than within them, conflict intensity is ratcheted yet again when the adversaries belong to different metaethnic communities – largest-scale, supranational groupings of people, which include ‘civilizations’ (Huntington 1996; Toynbee 1956) and also such large-scale groupings of ‘barbarian’ people as Iron Age Celts or Turco-Mongolian steppe nomads (Turchin 2003: ch. 4). Warfare intensity at metaethnic frontiers, zones where two distinct metaethnic communities are in contact and conflict, tends to scale up all the way to culturicide and genocide (Hall 2000; Turchin 2003, 2009a).

The evolutionary reason for the correlation between warfare intensity and cultural distance stems from the joint rise of parochial altruism and war. ‘Parochial altruism’ is the well-known tendency of humans to cooperate preferentially with people like themselves (belonging to the same ethnic group), while expressing hostility to members of other ethnic groups. In an elegant model Choi and Bowles (2007) showed that ‘neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly’.

The basic problem lies in the cognitive dissonance inherent in the ‘cooperate to compete’ logic implied by multilevel selection. One kind of people, those belonging to the same cooperating group, should be trusted and treated in a helpful and nonviolent manner. Another type of people, those not belonging to the group, should be distrusted and treated as enemies, that is, attacked and killed whenever possible. The solution is to define only members of the same ethnic group as fully human, while treating everybody else as ‘subhuman’ – not deserving of sympathy, trust, or cooperation.

As a result, the greater the cultural distance, the more likely for the opposing group to be denied its essential humanity. The most commonly used kind of symbolic marker to delineate metaethnic communities is religion – particularly, the exclusive, proselytizing kinds such as Christianity or Islam (Turchin 2006: 84). Thus, it is not surprising that religious wars – Crusades, Jihads, and the like – tend to be among the most intense kinds of warfare. For example, according to the early Islamic doctrine, Muslims had a duty to spread Islam, by sword if necessary. The Islamic metaethnic community, Dar al-Islam, was in an irreconcilable opposition to the non-Muslims, Dar al-Harb (literally, ‘the House of War’). Furthermore, Muslims were strictly forbidden to enslave each other, whereas enslaving a non-Muslim was allowed.

In previous publications (Turchin 2003, 2006, 2009b) one of us has argued that the most intense metaethnic frontiers tend to be the steppe frontiers between ‘the desert and the sown’, between sedentary farmers and nomadic pastoralists (reflected, for example, in the Book of Genesis account of the conflict between the farmer Cain and the herder Abel). There is abundant literature in Chinese, Persian, and Russian characterizing the nomads as the devil horsemen from the steppes (Beckwith 2009). From the point of view of many nomads, on the other hand, farmers were ‘grass-eating people’ not too far removed from livestock (Weatherford 2004). The famous steppe conquerors, such as Chinggis Khan and Timur (Tamerlane), are justly categorized as worst mass murderers in history before the twentieth century. Our sources are unanimous that, for example, the invasion of Khwarizm by Chinggis Khan's army was a calamity on an unprecedented scale (Wink 1997: 13). Populations of entire cities (Samarkand, Balkh, Nishapur, and a number of others) were virtually exterminated. Similar disasters resulted from the invasions of Chinggis Khan's grandson Batu in Russia, Timur in northern India, or Hunnu (Hsiung-Nu) in China.

The examples cited above are anecdotal, but a systematic review of available evidence (Turchin 2009a) comes to the same conclusion, that location on a metaethnic frontier serves as an excellent proxy of warfare intensity. The theoretical prediction with which this section started, then, can be reformulated as follows: the largest-scale societies are expected to arise on metaethnic frontiers.

A Strong Macrohistorical Pattern: Huge Empires Tend to Rise on Steppe Frontiers

Turchin (2009b) tested this proposition empirically, using territorial extent achieved by historical polities at the peak of their power as a proxy of social scale. Maximum territory is a better proxy for the social scale than most others, because the areas of historical states are known with much greater accuracy than, for example, population numbers.

The empirical test focused on the largest territorial states, those whose peak territories exceeded 1 million squared kilometers, and on the most intense frontiers, those between nomadic pastoralists and sedentary farmers (Ibid.). Because the Industrial Revolution dramatically changed the balance of power between nomads and settled societies, the database excludes modern maritime empires of European powers, and focuses on states that peaked before 1800. The empirical database includes 65 of such preindustrial ‘megaempires’. Over 90 % of these empires were situated in, or next to the arid belt that runs through Afroeurasia, from the Sahara in the West to the Gobi in the East (Turchin 2009b: Fig. 1). The exceptions included one empire in Southeast Asia (Khmer), and the only empire in the Americas (Inca). There were also three European exceptions, the Roman and Carolingian empires, and perhaps Lithuania-Poland, although the latter expanded during the fourteenth century into steppe lands. Thus, there is a strong statistical association between proximity to steppe and the rise of megaempires.

A more detailed investigation of three world regions, East Asia, South Asia, and North Africa confirmed the pattern. First, China has been unified fourteen times between the Shang era and the present (some unifications were partial). All but one of these unifications (the Ming) originated in the North: eight from the Northwest, and three each from the North Central and the Northeast. In other words, with one exception all great unifying dynasties arose in the area on the Inner Asian frontier of China. The other side of the frontier saw a succession of gigantic imperial confederations of such nomadic peoples as the Hunnu, the Turks, and the Mongols.

Second, the Eurasian arid zone intrudes into South Asia from the northwest. Out of nine South Asian unifications (most partial, as they did not include India's far south), five originated in the Northwest, three in the North, and one in the West. Despite the formation of numerous small and medium-sized states in other regions, no megaempires originated in the Northeast, Central, or Southern India.

Finally, Ancient Egypt was unified by native dynasties on four occasions: Early Dynastic (c. 3100 BCE), Old Kingdom (2700 BCE), Middle Kingdom (2040 BCE), and New Kingdom (1570 BCE). In all four cases, unifying dynasties arose in Southern Egypt (in Hierakonpolis or Thebes). Furthermore, 5,000 years ago Southern Egypt was surrounded not by a lifeless desert, but by a grassy steppe inhabited by such pastoralist peoples as Nubians and Medjay. Towards the end of the first millennium BCE the steppe turned into desert, and from that point on Egypt never gave a rise to a native unifying dynasty, instead being ruled by a succession of foreign masters. Thus, again we see a spatial and temporal correlation between a steppe frontier and imperial formation.

Imperial Formation in Western Europe/Mediterranean

Empires of Western Europe are exceptions to the pattern of association between steppe frontiers and imperiogenesis, because Western Europe was largely insulated from steppe influences. However, previous work (Turchin 2003: ch. 4; 2006: Part I), showed that politogenesis in Europe conforms to a broader pattern of states arising on metaethnic frontiers. Metaethnic frontiers in Europe were less intense than steppe frontiers, and we expect that they should be associated with expansionist states of lesser scale. This expectation is supported by the empirical test, focusing on Europe during the first two millennia CE (Turchin 2003: ch. 5). The history of Europe is known much better than the rest of Afroeurasia, and thus it was possible to achieve a much more detailed quantification of metaethnic frontiers. Turchin (2003) also considered a much broader spectrum of polities, than just megaempires, by including in the database all states that had peak territory greater than 100,000 squared kilometers. The conclusion was that there was a strong statistical correlation between the locations of frontiers and regions where expansionist states originated (Turchin 2003: Table 5.1).

The basic pattern of imperiogenesis in Europe can be summarized as follows. By the middle of the first millennium BCE a metaethnic frontier formed in the Mediterranean dividing people sharing the Mediterranean civilization (Greeks, Carthaginians, Etruscans, and Latins) from the ‘barbarian’ Celts (Turchin 2006: 140, Map 5). In many ways this was an Ibn Khaldunian kind of a frontier between umran (‘civilization’ with cities, literacy, and states) and al-badw (literally ‘desert’, but used by Ibn Khaldun more broadly – rural peoples without states and cities). The three great powers of the second half of the first millennium BCE, Macedon, Rome, and Carthage, all formed on this civilizational fault-line. Eventually, one of them, Rome, defeated the others and unified the Mediterranean.

The next round of states arose on the Roman frontiers (Turchin 2006: Map 2 and ch. 3). When the Roman frontier on the Rhine formed at the beginning of the Common Era, people living outside it were organized in small-scale tribes such as the Cherusci, the Chatti, the Bructeri, the Sugambri, and so on. The transformative influence of the Roman frontier resulted in these peoples amalgamating into supratribal confederations, such as the Alamanni, the Franks, and the Burgundi. Finally, one of these conglomerates, the Franks, conquered the others and created an imperial confederation. The first dynasty, the Merovingians, collapsed soon after conquering Gaul from the failing Roman empire. The Carolingians were more successful in creating an enduring state, which at its height in c. 800 united most of Western Europe.

The final set of states arose on the frontiers, or the marches, of the Carolingian empire (Turchin 2006: ch. 7). When the empire weakened and eventually crumbled in the ninth and tenth century, it was assaulted by the Saracens from the South, the Norse from the Northwest, the Wends from the East, and the Magyars from the Southeast. The states that arose on these frontiers, Castile-Spain, France, Brandenburg-Prussia-Germany, and Austria, respectively, all later developed into Great Powers of Europe.

In summary, state formation in Europe occurred by ‘contagion’, with new empires arising, after a time lag, on the frontiers of previous ones. The time lag was quite substantial. Data indicate that three centuries or more on a frontier had to pass before a new aggressive state arose (Turchin 2003: ch. 5), an observation suggesting that some kind of slow evolutionary mechanism had to be involved.

DISCUSSION

The main argument in this paper is that large-scale hierarchically complex societies arose as a result of evolutionary pressures brought on by warfare. As Charles Tilly (1975) famously said, ‘states made war, and war made states’. More broadly, we argue that the evolutionary theory can yield valuable insights into the mechanisms underlying territorial dynamics of states. Take warfare, a puzzling human activity because it involves both selfless sacrifice and coldhearted carnage. The key insight from evolutionary theory (and, specifically, multilevel selection) is that warfare is an extreme form of parochial altruism, driven by the ‘cooperate to compete’ evolutionary logic. Parochialism, warfare, and large-scale societies appear to be connected not only by theoretical arguments, but also empirically. Thus, between c. 3000 BCE and 1800 CE large-scale empires tended to arise on metaethnic frontiers, areas where cultural difference between adversaries was particularly large and warfare especially intense.

Since states first appeared c. 5000 years ago, their maximum size has been gradually increasing (Taagepera 1997). This observation prompted some to predict that, sooner or later, a single state will encompass the whole Earth, perhaps by 2300 CE (Carneiro 2004). However, the growth of the maximum size was not linear. Figure 5 presents the temporal evolution of the largest empire size in the database. During the third and second millennia BCE the maximum empire size fluctuated between 0.3 and 1 million squared kilometers, albeit with a gradual upward trend (these were several Egyptian empires, the Akkad, and the Shang). Between 800 and 200 BCE, however, there was a rapid increase in maximum size (in million squared kilometers), from 0.4 in 900 BCE to 1.4 in 670 BCE (the neo-Assyrian empire), then to 5.5 in 500 BCE (the Achaemenid Persia) and finally to 9.0 in 180 BCE (the Hunnu). It is remarkable that this dramatic upsweep in the maximum area coincided almost precisely with the Axial Age, usually dated to 800–200 BCE (Jaspers 1953). After the upsweep of the Axial Age the maximum imperial size continued to increase, but at a much slower rate (Fig. 5). Karl Jaspers speculated that the great religious and philosophical breakthroughs of the Axial Age were responses to political and social instability brought on by intensifying attacks from the nomadic steppe dwellers. Increased pressure form the steppe, in turn, was due to the new military technology, mounted archery. We know that the Scythians were instrumental in the destruction of the neo-Assyrian empire, and that the Achaemenid struggle against them was in many ways similar to the struggle of the Han Empire against the Hunnu (Christian 1998).

Thus, a military revolution in the steppe, apparently, intensified warfare in and around the arid zone of Afroeurasia, thus giving a powerful impetus to the evolution of increased empire size. However, the interaction between the nomadic and agrarian peoples ceased to be a driving force of social evolution during the eighteenth century, when the nomads lost their military superiority as a result of the agrarian/industrial transition. In a forthcoming book, Victor Lieberman proposes that at the same time the nomadic factor lost its saliency, another source of selective pressures arose – from the Europeans, who became the ‘White Inner Asians’ of the modern era (Lieberman 2010). Unlike the Central Asian nomads, the reach of the European colonizing powers was truly global. As a result of sometimes direct colonization (as in Africa) or indirect pressure (as in East Asia) from the Spanish, Dutch, British, and other European Great Powers, the state system spread across the globe.

But does it mean that the trend to ever larger states will continue and a global state is inevitable? Up until the present the force driving the evolution of increased social scale has always been competition/conflict in opposition to some other societies. If the global state were to arise, where will it find the external threat that would keep it unified? Thus, unless (or until) the humanity experiences a major evolutionary breakthrough that will provide a different basis for large-scale cooperation, the rise of a stable state unifying all humanity is unlikely.

The history of the European Union (EU), a most audacious and innovative experiment in building a supranational community, appears to support this pessimistic conclusion. The founding members of the European Union were France, West Germany, Italy, and the Benelux countries. A glance at the historical map of Europe in 800 CE will show that these six countries together are an almost perfect match for the area controlled by the Carolingian empire at its peak. Clearly, the Carolingian empire is the ‘charter state’ of the European Union (Lieberman 2008). Even the ‘capitals’ of the EU, cities like Brussels and Strasbourg, were located within the former Carolingian heartland.

Despite its auspicious beginnings, in recent years the process of European integration hit a stumbling block. The current economic crisis, for example, showed that the member states have been unable (at least, at the time of this writing) to overcome the ‘collective action’ problem and forge a unified fiscal and economic policy that would address the crisis (Krugman 2009). The theories discussed in this paper suggest at least two reasons for the apparent reversal of the integrative dynamic in Europe. First, adversarial relations with the Soviet block (or the ‘Evil Empire’, in a famous characterization of Ronald Reagan) helped to suppress internal bickering among the member states. When the Iron Curtain crumbled in 1989, the disciplining effect of an outside threat has disappeared. Second, rapid expansion into Central and Eastern Europe, by simply adding new members in a completely unstructured way, was clearly a mistake (at least, in retrospect). Twenty seven constitutive units may be too many for a largely decentralized organization that relies on consensus for all major decisions. As we stressed in this paper, both theoretical and empirical lines of evidence suggest that a lasting increase in social scale can be accomplished only by adding extra layers of hierarchical organization.

The question of whether the scale of social integration can encompass the whole planet is not an academic one. Without an international authority possessing sufficient coercive power to hold individual states in check, great powers will continue their attempts to gain power at each other's expense leading, inevitably, to interstate rivalry and war (Mearscheimer 2001). The message of our paper is somewhat pessimistic. All through the history, and for the foreseeable future, integration among humans required conflict against other humans. Even if a world-wide state were to arise, according to this logic, it would rapidly fission into multiple parts. On the other hand, neither history nor evolution is destiny. Humans have transcended their evolutionary limitations before (our huge brains may have evolved to perform social calculation, but now we use them for much more). We just should not expect this to happen automatically, simply as a result of a 5,000-year trend of increasing state size.

ACKNOWLEDGMENTS

We thank Herbert Barry and David Anderson for very useful comments on the manuscript. PT was supported by the National Science Foundation grant HSD SES-0527720.

REFERENCES

Alexander, R. D.

1990. How did Humans Evolve? Reflections on the Uniquely Unique Species. Ann Arbor: Museum of Zoology, University of Michigan.

Anderson, D. G.

1994. The Savannah River Chiefdoms: Political Change in the Late Prehistoric Southeast. Tuscaloosa, AL: University of Alabama Press.

1996. Fluctuations Between Simple and Complex Chiefdoms: Cycling in the Late Prehistoric Southwest. In Scarry, J. F. (ed.), Political Structures and Change in the Prehistoric Southeastern United States (pp. 231–252). Gainesville, FL: University Press of Florida.

Andreevsky, I. E., Arseniev, K. K., and Petrushevsky, F. F. (eds.)

1890. Brockhaus and Efron Encyclopedic Dictionary. St. Petersburg: Brockhaus and Efron.

Barfield, T. J.

1989. The Perilous Frontier: Nomadic Empires and China. Oxford: Blackwell.

Barraclough, G.

1976. The Crucible of Europe: The Ninth and Tenth Centuries in European History. Berkeley: University of California Press.

Beckwith, C. I.

2009. Empires of the Silk Road: A History of Central Eurasia from the Bronze Age to the Present. Princeton: Princeton University Press.

Bielenstein, H.

1980. The Bureaucracy of Han Times. Cambridge: Cambridge University Press.

Boehm, C.

1993. Egalitarian Behavior and Reverse Dominance Hierarchy. Current Anthropology 34: 227–254.

1997. Impact of Human Egalitarian Syndrome on Darwinian Selection Mechanics. American Naturalist 150: 100­–121.

Braudel, F.

1988. The Identity of France. Vol. 2. People and Production. New York: Harper Collins.

Byrne, R. W., and Whiten, A.

1988. Machiavellian Intelligence: Social Expertise and the Evolution of Intellect in Monkeys, Apes, and Humans. Oxford: Clarendon.

Carneiro, R. L.

1970. A Theory of the Origin of the State. Science 169: 733–738.

1981. The Chiefdom: Precursor of State. In Jones, G. D., and Kautz, R. D. (eds.), The Transition to Statehood in the New World (pp. 37–39). Cambridge: Cambridge University Press.

1998. What Happened at the Flashpoint? Conjectures on Chiefdom Formation at the Very Moment of Conception. In Redmond, E. M. (ed.), Chiefdoms and Chieftaincy in the Americas (pp. 18–42). Gainsville: University of Florida Press.

2004. The Political Unification of the World: Whether, When, and How – Some Speculations. Cross-Сultural Research 38: 162–177.

Choi, J.-K., and Bowles, S.

2007. The Coevolution of Parochial Altruism and War. Science 318: 636–640.

Christian, D.

1998. A History of Russia, Central Asia, and Mongolia. Oxford: Blackwell.

Crespigny, R. de

2007. A Biographical Dictionary of Later Han to the Three Kingdoms (23–220 A.D.). Leiden: Brill.

Dunbar, R. I. M.

1992. Neocortex Size as a Constraint on Group Size in Primates. Journal of Human Evolution 22: 469–493.

Dunbar, R. I. M., and Shultz, S.

2007. Evolution in the Social Brain. Science 317: 1344–1347.

Dupâquier, J., et al.

1988. Histoire de la population française. Tome 1. Des origines à la Renaissance. Paris: Presses universitaires de France.

Earle, T.

1991. The Evolution of Chiefdoms. In Earle, T. (ed.), Chiefdoms: Power, Economy, and Ideology (pp. 1–15). Cambridge: Cambridge University Press.

Ember, C. R., Ember, M., and Russett, B.

1992. Peace between Participatory Polities: A Cross-Сultural Test of the ‘Democracies Rarely Fight Each Other’ Hypothesis. World Politics 44: 573–599.

Epstein, J. M., and Axtell, R.

1996. Growing Artificial Societies: Social Science from the Bottom up. Washington, DC: Brookings Institution Press.

Flannery, K.

1999. Process and Agency in Early State Formation. Cambridge Archaeological Journal 9: 3–21.

Flinn, M. V., Geary, D. C., and Ward, C. V.

2005. Ecological Dominance, Social Competition, and Coalitionary Arms Races: Why Humans Evolved Extraordinary Intelligence? Evolution and Human Behavior 26: 10–46.

Gat, A.

2008. War in Human Civilization. New York: Oxford University Press.

Gavrilets, S., Anderson, D. G., and Turchin, P.

2010. Cycling in the Complexity of Early Societies. Submitted to PNAS. In print.

Gavrilets, S., Duenez-Guzman, E. A., and Vose, M. D.

2008. Dynamics of Alliance Formation and the Egalitarian Revolution. PLoS ONE 3: e3293. doi:10.1371/journal.pone.0003293.

Gavrilets, S., and Vose, A.

2006. The Dynamics of Machiavellian Intelligence. Proceedings of the National Academy of Sciences 103: 16823–16828.

Hall, T. D.

2000. Frontiers, and Ethnogenesis, and World-Systems: Rethinking the Theories. In Hall, T. D. (ed.), A World-Systems Reader (pp. 237–270). Lanham, MD: Rowman and Littlefield.

Hallam, E. M., and Everard, J.

2001. Capetian France: 987–1328. 2^nd ed. Harlow: Longman.

Harding, R. R.

1978. Anatomy of a Power Elite: the Provincial Governors of Early Modern France. New Haven: Yale University Press.

Helmold, R. L.

1993. Osipov: the ‘Russian Lanchester’. European Journal of Operational Research 65: 278–288.

Huntington, S. P.

1996. The Clash of Civilizations and the Remaking of World Order. New York: Simon and Schuster.

Ibn Khaldun

1958. The Muqaddimah: An Introduction to History. Transl. by
F. Rosenthal. New York: Pantheon Books.

Jaspers, K.

1953. The Origin and Goal of History. New York: Routledge & Kegan Paul.

Johnson, A. W., and Earle, T.

2000. The Evolution of Human Societies: From Foraging Group to Agrarian State. 2^nd ed. Stanford, CA: Stanford University Press.

Keely, L. H.

1997. War before Civilization: The Myth of the Peaceful Savage. New York: Oxford University Press.

Kemp, B.

1989. Ancient Egypt: Anatomy of a Civilization. New York: Routledge.

Keyes, R.

2006. The Quote Verifier. New York: Macmillan.

Kingman, J. F. C.

2002. Stochastic Aspects of Lanchester's Theory of Warfare. Journal of Applied Probability 39: 455–465.

Kradin, N. N.

2005. From Tribal Confederation to Empire: The Evolution of the Rouran Society. Acta Orientalia Academiae Scientiarum Hungaricae 58: 149–169.

Krugman, P.

2009. A Continent Adrift. New York Times: March 16.

Lieberman, V.

2008. Protected Rimlands and Exposed Zones: Reconfiguring Premodern Eurasia. Comparative Studies in Society and History 50: 692–723.

2010. Strange Parallels: Southeast Asia in Global Context, c. 800–1830. Vol. 2. Cambridge: Cambridge University Press.

Manley, B.

1996. The Penguin Historical Atlas of Ancient Egypt. New York: Penguin Books.

Mann, M.

1986. The Sources of Social Power. Vol. 1. A History of Power from the Beginning to A.D. 1760. Cambridge: Cambridge University Press.

Marcus, J.

1998. The Peaks and Valleys of Ancient States: An Extension of the Dynamic Model. In Feinman, G. M., and Marcus, J. (eds.), Archaic States (pp. 59–94). Santa Fe, NM: School of American Research Press.

Masters, R. D.

1998. On the Evolution of Political Communities: The Paradox of Eastern and Western Europe in the 1980s. In Eibl-Eibesfeldt, I., and Salter, F. K. (eds.), Ethnic Conflict and Indoctrination (pp. 453–478). Oxford: Berghahn Books.

Mattingly, D. J.

1992. War and Peace in Roman North Africa. InFerguson, R. B., and Whitehead, N. L. (eds.), War in the Tribal Zone: Expanding States and Indigenous Warfare (pp. 31–60). Santa Fe: School of American Research Press.

McEvedy, C.

1967. The Penguin Atlas of Ancient History. London: Pebguin.

Mearscheimer, J. J.

2001. The Tragedy of Great Power Politics. New York: Norton.

Mironov, B. N.

2000. A Social History of Imperial Russia, 1700–1917. Boulder, CO: Westview Press.

Planhol, X. de

1994. An Historical Geography of France. Cambridge: Cambridge University Press.

Richerson, P. J., and Boyd, R.

1998. The Evolution of Human Ultrasociality. In Eibl-Eibesfeldt, I., and Salter, F. K. (eds.), Ethnic Conflict and Indoctrination (pp. 71–95). Oxford: Berghahn Books.

2005. Not by Genes Alone: How Culture Transformed Human Evolution. Chicago: University of Chicago Press.

Sanderson, S. K.

1999. Social Transformations: A General Theory for Historical Development. Lanham, MD: Rowman and Littlefield.

Service, E. R.

1975. Origins of the State and Civilization: The Process of Cultural Evolution. New York: Norton.

Shaw, R. P., and Wong, Y.

1989. Genetic Seeds of Warfare. Boston: Unwin and Hyman.

Sneath, D.

2007. The Headless State: Aristocratic Orders, Kinship Society, and Misrepresentations of Nomadic Inner Asia. New York: Columbia University Press.

Soltis, J., Boyd, R., and Richerson, P. J.

1995. Can Group-Functional Behaviors Evolve by Cultural Group Selection? An Empirical Test. Current Anthropology 36: 473–494.

Steponaitis, V. P.

1981. Settlement Hierarchies and Political Complexity in Nonmarket Societies: The Formative Period of the Valley of Mexico. American Anthropologist 83:320–363.

Taagepera, R.

1997. Expansion and Contraction Patterns of Large Polities: Context for Russia. International Studies Quarterly 41: 475–504.

Tarhov, S. A.

2001. Izmenenie administrativno-territorial'nogo deleniya Rossii za poslednie 300 let [The Change of Administrative-Territorial Division of Russia for the last 300 years]. Geografia 15: 1–20.

Tilly, C.

1975. Reflection on the History of European State-Making. In Tilly, C. (ed.), The Formation of National States in Western Europe (pp. 3–83). Princeton, NJ: Princeton University Press.

Toynbee, A. J.

1956. A Study of History. London: Oxford University Press.

Trigger, B. G.

2003. Understanding Early Civilizations. Cambridge: Cambridge University Press.

Turchin, P.

2003. Historical Dynamics: Why States Rise and Fall. Princeton, NJ: Princeton University Press.

2006. War and Peace and War: The Life Cycles of Imperial Nations. New York: Pi Press.

2009a. Warfare and the Evolution of Social Complexity: A Multilevel Selection Approach. In print.

2009b. A Theory for Formation of Large Empires. Journal of Global History 4: 191–207.

Weatherford, J.

2004. Genghis Khan and the Making of the Modern World. New York: Random House.

Wenke, R. J.

1997. City-States, Nation-States, and Territorial States: The Problem of Egypt. In Nichols, D. L., and Charlton, T. H., (eds.), The Archaeology of City-States: Cross-Cultural Approaches. Washington: Smithsonian Institution Press.

Williamson, O. E.

1967. Hierarchical Control and Optimum Firm Size. Journal of Political Economy 75: 123–138.

Wilson, D. S.

2002. Darwin's Cathedral: Evolution, Religion, and the Nature of Society. Chicago: University of Chicago Press.

Wilson, D. S., and Wilson, E. O.

2007. Rethinking the Theoretical Foundations of Sociobiology. Quarterly Review of Biology 82: 327–348.

Wink, A.

1997. Al Hind: The Making of the Indo-Islamic World. Vol. 2: The Slave Kings and the Islamic Conquest. Leiden: Brill.

Wrangham, R., and Peterson, D.

1996. Demonic Males: Apes and the Origin of Human Violence. Boston: Mariner Books.

Wright, H. T.

1977. Recent Research on the Origin of the State. Annual Review
of Anthropology 6: 379–397.

1984. Prestate Political Formations. In Earle, T. K. (ed)., On the Evolution of Complex Societies: Essays in Honor of Harry Hoijer (pp. 41–78). Malibu, CA: Undena Press.

2006. Early State Dynamics as Political Experiment. Journal of Anthropological Research 62: 305–319.

Fig. 1. From (a) a pairwise relationship between a chiefly and a subordinate village to (b) a simple chiefdom and (c) a complex chiefdom (adapted from Anderson, 1994).

Fig. 2. Relationship between the population size of a political unit and its hierarchical complexity for six historical empires. Sources: France (Harding 1978; Planhol 1994), Roman Empire (McEvedy 1967; Planhol 1994), Hunnu (Sneath 2007), Inka (Trigger 2003), Han China (Bielenstein 1980; de Crespigny 2007), and Russian Empire (Andreevsky et al. 1890; Mironov 2000, Tarhov 2001).

Fig. 3a

Fig. 3b

Fig. 3. An example of polities arising in one of the model's realizations. (a) The spatial view. (b) The hierarchical organization. Numbered hexagons are chief communities of their polities.

Fig. 4. Typical trajectories predicted by the model for ‘high warfare’ (solid curves) and ‘low warfare’ (broken curves) conditions. (a) The territorial extent of the largest polity at any given point of time during the simulation. The units on the y-axis are the fraction of the total model domain. (b) The maximum number of hierarchical levels as a function of time during the simulation.

Fig. 5. The area of the largest empire between 2800 BCE and 1800 CE. Note the log-scale for territorial size.