TheChacoAnasazi

InthetenthcenturyAD,aremarkableculturaldevelopmenttookplaceintheharshandforbiddingSanJuanBasinofnorthwesternNewMexico.Fromsmall-scale,simplyorganised,prehistoricPueblosocieties,acomplexandsociallydifferentiatedpoliticalsystememergedwhichhasbecomeknownastheChacoPhenomenon.Theorigins,evolution,anddeclineofthissystemhavelongbeenthesubjectofintensearchaeologicaldebate.LynneSebastianexaminesthetransitionoftheChacosystemfromanacephaloussociety,inwhichleadershipwassituationalandmostdecisionmakingcarriedoutwithinkinshipstructures,toahierarchicallyorganisedpoliticalstructurewithinstitutionalrolesofleadership.Shearguesthatharshenvironmentalfactorswerenotthecatalystforthetransition,ashaspreviouslybeenthought.Rather,theincreasingpoliticalcomplexitywasaconsequenceofimprovedrainfallintheregionwhichpermittedsurplusproduction,thusallowingthosefarmingthebestlandtocapitaliseonthematerialsuccess.Bycombininginformationonpoliticalevolutionwitharchaeologicaldataandtheresultsofacomputersimulation,sheisabletoproduceasociopoliticallybasedmodeloftherise,florescence,anddeclineoftheChacoPhenomenon.