Warfare and the Evolution of Social Complexity Peter Turchin University of Connecticut talk at UC Riverside, Feb. 2009

Odeon Platz, Munich 2 Aug August Outbreak of World War I. All over Europe patriotic crowds demonstrate in support of war 750,000 British men volunteer in August and September Total war deaths: 8.5 million

Why are humans willing to sacrifice for the sake of whole societies? Ultrasociality – extensive cooperation among very large numbers of genetically unrelated individuals –a unique feature of humans –a challenge to the evolutionary theory –cannot be explained by kin selection reciprocal altruism The Theory of Multilevel Selection D.S. Wilson, Boyd & Richerson, Bowles

Evolution of human sociality by multilevel selection A rapidly maturing theory for the evolution of small-scale sociality –groups of up to people Ultimate mechanism: multilevel selection –Selfishness beats altruism within groups. Altruistic groups beat selfish groups (Wilson and Wilson 2007) Proximate factors –egalitarianism, levelling mechanisms, inequity aversion: reduce intragroup variance in fitness –moralistic punishment stabilizes cooperation –intergroup competition/conflict: warfare

Cooperation as a glue of society The nonobvious sociological insight –(Collins 1992) Emile Durkheim ( ) Ibn Khaldun ( ) Asabiya: capacity of a group for collective action need a theory for the dynamics of asabiya –why it increases and why decreases

Warfare: the Selective Force A Human Universal –apes do it –small-scale societies do it –states do it Neolithic cave painting of battle between two groups of archers Morella la Villa, Spain

Why War? Ultimate causation –pacifist groups are eliminated by warlike groups Proximate mechanisms –Competition for scarce resources territory (hunting grounds, cropland) females, slaves, livestock booty (portable wealth) –Strategic calculations Revenge: retaliation to eliminate/deter enemies The security dilemma: expectation of an impending conflict leads to a preemptive attack

Percentage of male deaths due to warfare (Keeley 1996) Jivaro59 Yanomamo-Shamatari37 Mae Enga35 Dugum Dani28 Murngin28 Yanomamo-Nanowei24 Huli20 Gebusi8

Evolutionary responses to warfare Increasing group solidarity/cohesion Development of new technologies –military –administrative –ideological (religion, social prestige) Increasing the size of the cooperating group –God favors the big battalions The Social Brain hypothesis

Summary so far We have good beginnings of a theory for the evolution of small- scale sociality But how did large-scale societies evolve? How did evolution break through the limits imposed by face-to-face sociality?

The Plan A theory for the evolution of large- scale societies on metaethnic frontiers An empirical test: the association between nomadic/farmer frontiers and empire size in historical record The European/Native frontier in North America

Large-scale human societies –size: up to tens/hundreds of million people –stratified (inegalitarian) –complex: many hierarchical (nested) levels –organized: as states EmpirePeriodmax areapop. Achaemenid Persia BC6 Mm 2 35·10 6 Roman Empire27 BC-4765 Mm 2 60·10 6 Qing China Mm 2 400·10 6

A mechanism for the social scaling-up process A binary relationship: lord-vassal –chiefly village/subordinate village An elementary building block for constructing hierarchical social nets

Adding hierarchical levels allows building social networks of practically unlimited size

Hierarchical social organization allows to increase group size without increasing social channel capacity but there is a downside: it inevitably leads to inegalitarian societies there must be a compelling reason for this innovation to be adopted A hypothesis: evolution of social complexity should be favored where (when) warfare is particularly intense

Metaethnic frontiers A metaethnic community: the largest- scale (supranational) grouping of peoples Latin Christendom Dar al Islam Turco-Mongolian nomadic pastoralists Metaethnic frontiers: where warfare tends to be particularly intense Sharp cultural boundaries demarcated with symbolic markers Large cultural distance makes it easier to dehumanize the adversary

Darfur: Genesis of a Genocide Failure of the state to impose peace/order From : a severe drought Plains used by the nomads were worst hit The nomads migrated towards the hill region, inhabited by farmers (greater rainfall) Conflict between farmers and nomads Nomads created an alliance against the farmers (Janjaweed), raided villages Farmers created their own defensive alliance and allied with the SPLA The government began supporting Janjaweed

Metaethnic Frontiers civilizational faultlines (a la Huntington) –example: Iberian Muslim/Christian frontier civilization/barbarism frontier –example: Mediterranean civilization/barbarian Celts steppe frontiers between nomadic pastoralists and settled agriculturalists –tend to be the most intense kind

Steppe Frontiers anisotropy in military power –especially since the invention of mounted archery (~IX c. BC) carbohydrate deficiency of pastoralist economy huge difference in the way of life and culture –demonization of the other

A prediction: largest states should be found at interfaces between settled and nomadic societies Database: largest territorial polities –excluding modern sea-based empires Source: Taagepera, Chase-Dunn, et al Cut-off point: territory 1 Mm 2 (= 10 6 km 2 ) at peak More than 60 such polities are known –only 1 (Inca) outside Afroeurasia

M Egypt Axum Fatim Almorav Almohad Mali Mam Hsnu Juan Turk Uig Tufan Khazar Hsi Khorezm Kara-Kh Mongol GoldenH Chagatai Timur Shang Han Tang Liang Liao Sung Jur Ming Manchu Rom Huns Frank Kiev Lith-Pol Osman Russia Khmer Maur Kushan Gupta Harsha Delhi Mughal Mar Assyr Med Ach Sas Sele Parth Caliph Selj Sam Buy Ghazn Ayy Il-Kh Byz

The East Asian Imperiogenesis Hotspot: Empirical Patterns 14 unifications of China from the Shang to Communist eras (some partial) –(E.N. Anderson, supplemented) Summary: –8 unifications from NW (usually, Wei RV) –3 unifications from NE (Liao, Manchuria) –2 unifications from NC (Huang He) –1 unification from SC (Nanjing)

Imperiogenesis in South Asia: Empirical Patterns Northwest (Afghanistan) 5 North (the Gangetic plain)3 West (western Deccan)1 Northeast (Bengal and Assam) Central India Southern India

Unifications of Egypt by Native Dynasties UnificationDates, BCE Unifying Pharaoh From Early Dynasticc.3100– 2700 Narmer (Dynasty 0) South (Hierakonpolis) Old Kingdom2700– 2180 Khasekhemwy (end of Dynasty II) South (Hierakonpolis) Middle Kingdom 2040– 1790 Mentuhotep II (Dynasty XI) South (Thebes) New Kingdom1570– 1070 Ahmose I (Dynasty XVIII) South (Thebes)

Religion as an integrative ideology Axial age ideologies enabled cooperation at a very large scale, beyond ethnic communities –Monotheism –Buddhism –Confucianism –Stoicism The key is not the supernatural, but the integrative aspect Latin religio = bond

Another example: the United States A highly cooperative society –exceptional ability for voluntary association (de Tocqueville) –abundance of social capital (Putnam) The melting pot –e pluribus unum

European Settlers and Indians A civilization-barbarism frontier –almost three centuries long Very intense, sometimes genocidal intensity of conflict –torture, mutual atrocities (16,000 recorded) Casualties in some American wars First Powhatan War: 30% Second Powhatan War: 6% King Philips War: 2% World War I: 0.1% World War II: 0.3%

The Whites: Pennsylvania, c.1740 (Silver, Our Savage Neighbors) Quakers Anglicans Irish Presbyterians Scottish Covenanters German Lutherans Moravians Mennonites, Schwenkfelders, etc –Pennsylvania is a compleat Babel

Civic Organizations and Indian Wars 1740s: Appearance of ethnically and denominationally based clubs –St. Andrews Society –Deutsche Gesellschaft 1760s: focus shifts to charity for the victims of Indian attacks –first, directed at the narrow group –later, the definition of us expanded –eventually included all white people

Conclusions Warfare is ubiquitous but not constant It is particularly intense where culturally very different groups are in contact and conflict –metaethnic (esp., steppe) frontiers Empirical evidence: a strong association between metaethnic frontiers and formation of the largest empires