Warfare and the Evolution of Social Complexity

Peter TurchinUniversity of Connecticut

talk atUC Riverside, Feb. 2009

Odeon Platz, Munich 2 Aug. 1914

August 1914. 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 100-200 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 (1858-1917)

• Ibn Khaldun (1332-1406)

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 archersMorella 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)

Jivaro 59Yanomamo-Shamatari 37Mae Enga 35Dugum Dani 28Murngin 28Yanomamo-Nanowei 24Huli 20Gebusi 8

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

Empire Period max area

pop.

Achaemenid Persia 550-330 BC

6 Mm2 35·106

Roman Empire 27 BC-476 5 Mm2 60·106

Qing China 1644-1912 15 Mm2 400·106

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 1982-4: 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 Mm2 (=106 km2) at peak

• More than 60 such polities are known– only 1 (Inca) outside Afroeurasia

M

Egypt

Axum

FatimAlmorav

Almohad

Mali

Mam

Hsnu

Juan

Turk

UigTufan

Khazar

Hsi

Khorezm

Kara-Kh

Mongol

GoldenH

ChagataiTimur

ShangHanTang

Liang

Liao

Sung

Jur

Ming

ManchuRom

HunsFrank Kiev

Lith-Pol

Osman

Russia

Khmer

Maur

Kushan

GuptaHarsha

Delhi

Mughal

Mar

AssyrMed

AchSas

SeleParth

CaliphSelj

Sam BuyGhazn

AyyIl-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

Unification Dates, BCE

Unifying Pharaoh

From

Early Dynastic

c.3100–2700

Narmer(Dynasty 0)

South(Hierakonpolis

)Old Kingdom 2700–

2180Khasekhemwy

(end of Dynasty II)

South(Hierakonpolis

)Middle Kingdom

2040–1790

Mentuhotep II(Dynasty XI)

South(Thebes)

New Kingdom

1570–1070

Ahmose I(Dynasty XVIII)

South(Thebes)

The largest empire, 2800 BCE - 1800 CE

-2500 -2000 -1500 -1000 -500 0 500 1000 1500

Ter

ritor

y, m

illio

ns o

f sq

. km

0.3

1

3

10

30AxialAge

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 Philip’s War: 2%• World War I: 0.1%• World War II: 0.3%

“The Whites”: Pennsylvania, c.1740

(Silver, 2008. 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