Birth Spacing, Aggression and Chiefly Cycling: The Evolution of Social Complexity

1. Birth Spacing, Aggression and Chiefly Cycling: The Evolution of Social Complexity Professor Dwight Read Department of Anthropology UCLA

2. Introduction • Three paradigms that have been used by archaeologists to account for the evolution of complex societies • Model 1: Decision Making Mediated by Culture • Model 2: Competition Between Groups • Implications of Patch Size and Seasonality for Group Competition • Cyclical pattern of coalescence, replacement of local groups through aggression, and fission (Yanamamo, Highland New Guinea) • Stable coalescence/new form of social organization and eventual global replacement through competition between groups (Hunter-gatherer social organization) • Chiefly Recycling and State systems

3. Sequence of Societies (1) Solitary society: I = <{single individual}> (2) Group consisting of several individuals: G = <{Ii: 1 < i < m}, SG> (3) Band society/community composed of several groups: B = <{Gi: 1 < i < n},SB> (4) Tribal society/simple chiefdoms composed of several B's: T = <{Bi: 1 < i < p}, ST> and (5) Complex chieftains composed of several T's: C = <{Ti: 1 < i < q},SC>, where SG, SB, ST, SC, stand for the internal organization of the units making up a society at a particular level in the sequence.

4. Three Paradigms for Modeling Evolution of Complex Societies (1) Evolution of a Society as a Totality Band Level Societies  Tribal Level Societies  Chieftain Level Societies  State Level Societies White (1949), Steward (1955), Fried (1967), Service (1962)

5. Three Paradigms for Modeling Evolution of Complex Societies (cont’d) (2)Evolution of the Internal Structure of a Society Viewed as a Hierarchical Control/Information Processing System "… the most striking differences between states and simpler societies lie in the realm of decision-making and its hierarchical organization …"(Flannery 1972, p. 412 )

6. Three Paradigms for Modeling Evolution of Complex Societies (cont’d) (3) Agent and Agency in the Evolution of Societies “… the formal, functional, and dynamic properties of the state are outcomes of the often conflictive interaction of social actors with separate agendas, both within and outside the official structure of the decision-making institution” (Blanton 1998, p. 140, emphasis added) “The organizational forms of Mesopotamian complex societies emerged through the dynamic interaction of partly competing, partly cooperating groups or institutional spheres and different levels of social inclusiveness” (Stein 1994, p.12 )

7. Model 1: Decision Making Mediated by Culture Observation: Among the !Kung san, a hunter-gatherer group in southern Africa, women space their children about every four years. Analytic Goal: (1) Construct an ethnographically based decision rule for child spacing decisions by !Kung San women based on individual circumstances. (2) Implement the decision rule in an agent-based demographic simulation and determine its demographic consequences.

8. Ethnographic Basis for Constructing a Decision Rule "They want children, all the children they can possibly have" (decrease spacing) (1) Concern for spacing of births "to carry a third child and the food she gathers would be practically impossible for those small women" (time/energy conflict between parenting and gathering) (Marshall 1976: 166, 168) "they explained that they cannot feed babies that are born too close together. . . . A mother had not enough milk to sustain completely two infants at the same time" (increase spacing) (2) Means for birth spacing ”they believe a child must have strong legs, and it is mother's milk that makes them strong . . . a child needs milk till he is three or four years old at least" (duration of nursing = mechanism for spacing) (3) Time/energy conflict between parenting and gathering

9. Characterization of Female Activities • Set {A1, A2, …, An} of activities • Subset S = {S1, S2 …, Sm} of subsistence activities • Subset P = {P1, P2…, Pk} of parenting activities • Subset O = {O1, O2 …, Oj} of other tasks • Total (perceived) Cost TC = iAi, where i is a conversion factor relating time/energy per unit of time (e.g., day, week, year, etc.) toperceived cost

10. Criterion for Decisions • Tmax, maximum acceptable value for TC • If TC > Tmax then for at least one activity, Aj, the coefficient j will be set to (or close to) 0 Implication: Modify spacing of births since parenting costs are directly related to spacing of births and parenting costs are high and have more elasticity than subsistence costs and other costs.

11. Decision Rule • If TC < Tmax at time t then set f(t) = r0 , (Desire for as many children as possible) • If TC  Tmax at time t then set f(t) = 0 (Desire for well-being of a family, Tmax a cultural parameter) where: r0is the intrinsic fertility rate (~ 10 births per female per reproductive period) and f(t) is her fertility rate at time t

12. Simulation: Implementation of the Decision Rule • TC = (parenting cost) + (foraging cost) = • = nWt + P/K • where: • Wt is the parenting cost/infant • n = number of infants (age IA) • K is a weighting factor that converts P into a foraging cost per female • IA = I0 * P/K, I0 maximum age for weaning

13. Multi-agent Simulation: Simulation events for each simulation year Demographic Event Cultural Context Decision Rule

14. Decision Rule for Birth Spacing

15. Change in Parameters • Cultural --Wt (Value Placed on Parenting) Effect on: • Stabilized Population Size • Demographic Trajectory Through Time (2) Material-- Resource Density Effect on Relationship of Stabilized Population Size to Carrying Capacity

16. Stabilized Population Size

17. DemographicTrajectory: Three Simulations • Wt = Tmax = 16 (arbitrary units) -- Women respond only to cost of children • Wt = 8, Tmax = 16 -- Women respond to both the cost of children and the cost of foraging • Wt = 0, Tmax = 16 -- Women respond only to the cost of foraging • 1) through 3) represent decreasing cultural value placed on the well-being of a family

18. Demographic Trajectory Through Time

19. Number of Foragers n1 Catchment Area = A n2 Resource Density Effect of Change in Resource Density cost/foragerhigh resource density ~ A/n1 < A/n2 ~ cost/foragerlow resource density

20. Carrying Capacity versus Stabilized Population Size

21. Australian Data

22. Model 2: Competition Between Groups dP1/dt = P1(a1 – b11 P1– b12P2) dP2/dt = P2(a2 – b21P1 – b22P2) Equation 1 states: “Growth of population 1 increases according to its intrinsic growth rate (a1), less the extent to which the size of population 1 inhibits its own further growth (b11), less the extent to which the size of population two inhibits the further growth of population 1 (b12).”

23. Competition Between Two Groups

24. Phase State, Equilibrium Between Two Populations

25. Three Groups, Small Resource Patches

26. Change in population size of group 1 Change in Competition, Coalescence of Groups 1 and 2

27. Fission (No Change in Population Density) • Fission of Groups 1 and 2 is likely due to cost of maintaining larger group and ability to revert back to smaller groups without major demographic consequences. • Expect cycling pattern between coalescence/growth and fissioning when growth in size occurs without change in population density.

28. Yanomamo Cycling • A group (teri) of around 30-40 close kin-related persons is a stable social and subsistence unit (Chagnon 1983) • However, resource scarcity leads to warfare (Johnson and Earle 2000) • Warfare often leads to displacement of one teri by another (Bioca 1971, Smole 1976) • Coalescence: A teri needs to have around 80 - 100 persons to defend itself against raids; a large teri is more likely to be able to mount successful raids (Chagnon 1983) • Coalescence does not appear to increase population density--territory, rather than density, increases • Fission: A teri is increasingly likely to break up when the teri exceeds 100 persons (Chagnon 1983)

29. Highland New Guinea Cycling • Local groups around Mount Hagen may expand their territorial base through warfare but in time fission takes place and new local groups are formed (Strathern 1971) • Similar pattern occurs among the Kuma (Reay 1959) • “a single regional Big Man has not emerged… and transformed [Central Enga] into a chiefdom….the conditions for economic control are absent in the Highlands …” (Johnson and Earle 2000, p. 232-33)

30. Seasonal Variation in Resources, Large Patch Size

31. Seasonal Resource Abundance, Implications for Coalescence

32. Change in population size/density of group 1 Coalescence Leads to Increase in Population Density: Combined Group 1 + Group 2 Wins Out

33. Transition from Troop to Hunter-Gatherer Form of Social Organization

34. Groups of Individuals

35. Band society

36. Implications for Chiefly Cycling

37. Chiefdom (Simple)

38. Chiefdom (Complex)

39. Implications for State Society

40. State Structure(top down structure)

41. That’s All Folks!