please answer the question based on the documents I provided down below.

User Generated

ovovov

Writing

University of Florida

Description

The questions of this week draw on these readings:

Natalie Angier’s ‘‘Furs for Evening, But Cloth was the Stone Age Standby’’

Clive Ponting’s ‘‘Crops and Animals’’

David Rindos’s ‘‘Symbiosis, Instability, and the Origins and Spread of Agriculture: A New Model’’

Respond to one question from part 1 and one question from Part 2. Your total answer should be at least 250 words. Please use the readings carefully to answer your questions. Whenever you quote, please use this citation format: (the last name of the author, page number), for example; (Angier, 7).

Part 1:

What are the differences between primary sources and secondary sources? Please provide some examples of primary and secondary sources from this week’s readings.

Part 2:

How do historians organize the past in stages? If we consider ‘‘the string revolution,’’ how might our understanding of history changes according to Angier?

Why did humans abandon a life of hunting and gathering for agriculture? How did the adoption of farming transform human society?

What does Rindos argue in his article about the origins and spread of agriculture?

Unformatted Attachment Preview

Symbiosis, Instability, and the Origins and Spread of Agriculture: A New Model [and Comments and Reply] Author(s): David Rindos, Homer Aschmann, Peter Bellwood, Lynn Ceci, Mark N. Cohen, Joseph Hutchinson, Robert S. Santley, Jim G. Shaffer and Thurstan Shaw Reviewed work(s): Source: Current Anthropology, Vol. 21, No. 6 (Dec., 1980), pp. 751-772 Published by: The University of Chicago Press on behalf of Wenner-Gren Foundation for Anthropological Research Stable URL: http://www.jstor.org/stable/2742515 . Accessed: 28/09/2012 11:48 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . The University of Chicago Press and Wenner-Gren Foundation for Anthropological Research are collaborating with JSTOR to digitize, preserve and extend access to Current Anthropology. http://www.jstor.org CURRENT ANTHROPOLOGY ? Vol. 21, No. 6, December 1980 1980 by The Wenner-GrenFoundation for Anthropological Research 0011-3204/80/2106-0002$02.55 and the Originsand Symbiosis,Instability, A New Model Spread of Agriculture: by David Rindos INTRODUCTION The originsofagriculture and its subsequentspreadhave been of concernto both naturaland social scientistsforover 100 years.The studyofagricultural originsis farmorethanmerely the investigationof a particularshiftin man's subsistence. is seenby mostpeopleas thefoundation Agriculture ofmodern civilization.It is frequently heldthatonlyagriculture permitsa societytheluxuryofexcessproductionand thatalongwiththis excessproductioncomes the developmentof the hallmarksof civilization:writing,metalworking, and the establishmentof well-defined economicclasses. Despite the significance of agriculturalorigins,our understanding of thisphenomenonis far fromsatisfactory. We lack any unifiedtheoryto explainboth howagriculture aroseand whyit shouldhave arisenat all. Variousapproacheshave been takentowardstheexplanation of the initial appearance of agriculturalsubsistence.Most workersin thesocial scienceshave begunby lookingintoman's cultureforthe factorswhichcould explainthe developmentof pristineagriculturalsocieties. Bachofen (1967 [1861]) and Frazer (1912) believedthatagriculturedevelopedout of traditionalsexual rolesand the divisionsoflabor that theycreated. Allen (1897) and Hahn (1909) presentedargumentsseekingto understandagricultureas an outgrowthof ritualisticand religiouspractices.This approachhas been recentlydevelopedin greatdetail by Isaac (1970). Otherworkershave ascribedthe originof agricultureto the influenceof climaticevents (Pumpelly 1908,Childe 1951,Wright1968). Finally,certainauthors have alwaystakenwhatmaybe describedas a "commonsense" view of the originof agriculture:that agriculture,like other is theresultofan "invention."Carter technological innovation, (1 977) is a contemporary authoradheringto thisviewpoint. Recently,ecologicalparadigmshave cometo dominateagriculturaloriginstheories.Ecological theoristshave developed thepioneeringworkofthebiologistsDe Candolle(1959 [1886]) and Vavilov (1926) and thegeographerSauer (1936, 1969).The is a graduatestudentat CornellUniversity and teaching and research assistantat theUniversity's L. H. Bailey Hortorium (467MannLibrary, CornellUniversity, Ithaca,N.Y. 14853,U.S.A.).Bornin 1947,hereceived hisB.S. inruralsociology from Cornell in 1969andhisM.S. inplanttaxonomy, witha minor in anthropology, in 1980.He has beenpalaeoethnobotanist with theCornellArchaeological Projectin Cyprusand in Honduras. His research interests are thesystematics oftheCompositae and theinteraction ofplantsand man.His Master'sthesisis entitled " GenericDelimitation in theVerbesinoid Heliantheae(Compositae).I. The GenusZexmenia." The present paperwas submitted in finalform8 I 79. DAVID RINDOS Vol. 21 * No. 6 * December1980 hallmarkof the ecologicaltheoristis thathe places major emphasis on the interactionbetween man and his immediate comworkersstressdifferent environment. Of course,different Workersplacinggreatemphasison ponentsofthisrelationship. a theoretical"equilibrium"betweenpopulationand the environment includeBinford(1968),Meyers(1971), Cohen(1975, 1977),and Flannery(1965,1973).Most oftheseworkersexplain the originor adoptionof agricultureas the resultof attempts to correcta disturbedequilibriumbetweenpopulationand the environment. Others,such as Lewis (1972) and Harris (1969, 1972), along with Flanneryin a paper otherthan those just cited (1969), stressthe importanceof the developmentof new techniquesand culturalpatternsto the originof agricultural systems. Most of thistheorizing on the subjectofagriculturalorigins has been permeatedby two fundamentalconcepts:that agriin originand that its adoptionand culturewas revolutionary subsequentdevelopmentweredue to intentionalpractices.As notedby Harlan, de Wet,and Stempler(1976:3), "the idea of an agriculturalrevolutionas elaboratedby V. GordonChilde fortheNear East was basicallyappliedto thesocialand cultural economies."Onlyrecentlyhas consequencesof food-producing thisidea begunto be challenged.The agricultural way oflifeis now beginningto be seen as the resultof a seriesof gradual changes(cf. MacNeish 1964,Bray 1974,Higgs 1976, Pfeiffer 1976). Even today,most modelsforthe originof agriculture containat least some elementsof culturalor individualintention-eitherto explaintheinitialappearanceof thetechniques and plants of agriculturalsystemsor to elucidatethe survival and dispersalofagricultural systems.Corollaryto,and perhaps underlying, theseconceptsis the beliefthat agriculturefacilitatesthedevelopment ofa "superior"economy-onewithclear and substantialadaptivebenefitsto thesociety.This adaptiveinvokedto explainthe maintenanceand nessis also frequently it is held,is maineconomies.Agriculture, spreadofagricultural meansto feedlargenumtainedbecauseit is themosteffective bersofpeople;agriculture spreadsbecauseits greateradaptiveness allows it to spread at the expenseof more "primitive" meansofproduction. I shallhereintroducea newmodelfortheoriginand developmentof domesticatedplantsand agriculturalsystems.Rather thanrelyingupon the assumptionsjust mentioned,thismodel views agricultureas the outgrowthof evolutionarypotentials feedsupon whichmaydevelopwheneveran animalconsistently any set offoodplants.Intentand inventionare notdenied,but they are regardedas unnecessaryto the model. Parsimony would suggestthat if agriculturaloriginsmay be explained 751 withoutuse ofintentor invention, thentheseconceptsmay,for thepurposesofthismodel,be set aside.' Given the evolutionary means by whichagriculturalplants and systemsdevelop,the originof agricultureis anythingbut theultimateeffects revolutionary-although oftheprocessmay be describedas a revolutionofthefirstorder.The adaptiveness of agricultureis not stressedin this model,althoughit is not denied that agriculturepermitsgreaterdensitiesof human populationthan mostotherformsof subsistence.Instead,emphasisis placed upon theinstabilities whichfirstdomestication and then agriculturalproductionintroduceinto subsistence strategiesand whichare the basis foragriculture's"success." Finally,the relationship betweenthe originof agricultureand the riseof moderncivilization,whileaddinga certainurgency to the study of the problem,is not addresseddirectlyhere. Discussionof thisdifficult problemwouldof necessitytake us farbeyondthe consideration ofagriculturalorigins.Nevertheless, if thismodelhas any heuristicvalue, implicationsmay be drawnfromit whichgo beyondthe meredescriptionof a new modeoflifeforman. Modernagriculturaldevelopmentschemesare a responseto theshortagesoffoodand resourcesthatplague so muchof the world.Allagricultural systemsappearproneto occasionalcrises in production.Besides their immediateeffectsupon human healthand survival,shortagesoffoodfrequently have deleterious effects uponthestabilityofpoliticaland economicsystems. The importanceof theinteractionofpopulationgrowth,dwindlingnaturalresources,and recurrent shortagesof foodplaces the studyof agriculturalsystemsin the mainstreamof human concern.The prospectof foodshortagesencouragesthe breeding of improvedcrops and the developmentof moreefficient croppingsystems.Success in theseprogramsencouragesreliance upon fewerand fewerspeciesofplantsand upon an ever decreasingnumberof varietiesof a givenspecies.Agricultural productionalso tendsto becomemorelocalized,to take advantageoffavorableenvironmental conditions, and to allowforthe exploitationof economiesof scale. Yet, as is well recognized, monocultures are extremelyvulnerableto catastrophicfailure as a resultofdisease,pests,and climaticextremes. Today, man reliesuponabout 20 speciesofplantsto provide most of his food (National Academyof Sciences 1975). Yet hundredsof species of plants have been domesticatedand thousandsutilized.Remarkably,no majorcrophas beendomesticatedfromthewildsincetheearliestdaysofagriculture. Even our best attemptsat improvement of existingcropshave been less than totallysuccessful.Recentlywe have begunto understand that plant breedingand the successfulintroductionof new,improvedcultivarsmay inadvertently be acceleratingthe loss ofmuchofthevariationin thecropsgrownby man. Attention has come to be directedtowardsthe importanceof the conservationof gene pools forcultivatedplants. We are also to understandthatthebreedingofimprovedvarieties beginning of crop plants is, paradoxically,oftenaccompanied by increased susceptibilityof the crop to previouslyunknownor unimportant pests and diseases. We are finallybeginningto recognizethatagricultureis a dynamicsystem-thatthe agriculturalecologyexistingin any regionis the productof the interactionofnumerousfactorsoverlongperiodsoftime.Only certainparts of the agriculturalecologyare completelyunder humancontrol.As we beginto understandthefunctioning and the evolutionof theagriculturalecology,however,our control over it is likelyto increase.Part of this understanding must come froma considerationof the originand developmentof agriculturalsystemsand an investigation of the factorswhich controland limitthedomestication ofplants. 1 Elsewhere I have given the issues of intent and inventionextendedtreatment(Rindosn.d.). The viewofhuman behaviorpresented here should not be confusedwith "sociobiology"; instinctand geneticsare also set aside. 752 If themodelforagriculturaloriginsand thedomestication of plants presentedhere proves useful,its greatestcontribution maycomefromtherecognition thatwe are notfacinga qualitativelydifferent set ofproblemsfromthosefacedby our distant forebears.The historyof agricultureis a historyof instability inproductionand ofagriculturally inducedcrises.Identification of the factorsresponsibleforthis instabilitymay allow us to takeactionto reduceit. Seen fromtheperspectiveofthemodel, manyof ourbestattemptsat increasingagricultural productivitycan be expectedto increasethevulnerability of thesystem to failureas well;thebestattemptsofourancestorsto improve the productivity of theirsystemshad similareffects.Whilein the past we have survivedagriculturalcrisesand even benefitedfromthem,however,we are no longerin a strictlycomparable situation.The consequenceof agriculturalcrisisis no but thepossibilityof starvation.By apprelongeremigration, ciatingthe historyof agriculturalsystemswe may be better preparedto developourpresentsystemsto satisfythedemands of the future. In the model, domesticationoccurs beforethe originand developmentof agriculturalsystems.Domesticationis thereason agricultural systemsdevelop.Althoughthe importanceof domesticationper se to a societydecreaseswith the rise of agricultural systems,domestication does not cease. It continues withinthe agriculturalcontext,furthermodifying the plants undercultivation.It may also occurwithplantsoutsideof the agriculturalecology.Domesticationis theresultoftheevolution ofa symbiosis between man and plant. The best way to understandthe changesthat have occurred in domesticated plantsis to lookat therelationship betweenthe plantand theanimalwhichfeedson it. Two ofthemostimportant effectsof domestication are (1) intensification of the mutualisticrelationship betweenanimal and plant and (2) exclusion ofotheranimalswhichmightalso be competingforaccess to theplant.These effects are usuallymediatedby morphological change.One of the mostimportantfactorsin the evolution ofthecultivatedplantis theisolationofthepotentialcultivated plant, by eithergeneticor spatial mechanisms,fromthe protakenhere mayalso genitorspecies.The viewofdomestication be used to accountforthe evolutionof weedsand forthe nondomestication ofpotentiallyvaluable crops. The transitionfrommutualisticdomesticationto evolved agriculturalsystemswas mediatedby environmental manipulation.Humanactivitiessuchas thefellingoftreesorthesetting offirescannothelpbut have had effects uponthelocal environment.The major effectof theseactivitieswas the concentration of domesticatedplants in localized areas. This permitted therealizationofa newseriesofevolutionary potentials.I shall presenta dynamicand interactivemodel to account for the originand subsequentspreadofagriculturalsystems. is based on environmental Agriculture manipulation.Ecological limitsupon plant productivity are thusreduced.Agricultureis a set of integrated whichaffects theenvironment activities inhabited its lifecycle.Agribythedomesticated plantthroughout cultureservesto increasethe domesticity of the plant. However,it has major effectsupon the communityof plants that are utilizedin agriculturalsystems.It tends to increasethe average yield of domesticatedplants. Competitionwithina speciesof domesticatedplantstendsto selectthoseindividuals best adapted to agriculturalpractices.Competitionbetween species of domesticatedplants tends,in a similarmanner,to select forthosespecies best adapted to agriculturalpractices. Thus, over time,althoughyieldincreases,it comesfromfewer plant species. Localizationof agriculturalproduction,however,is accomforsurvivaland panied by convergencein the requirements reproductionin species of domesticatedplants. This convergenceand,indeed,thelocalizationofproductionitselfintroduce new instabilitiesinto agriculturalproduction:what is a bad year forany givenagricultural plant is likelyto be a bad year CURRENT ANTHROPOLOGY many by concentrating plants.Agriculture, forall agricultural plants in one area, may also encourageexcessivedamage by disease,insects,and herbivoresand thusdecreaseyield.Instaare expressedas periodsof greatlyrebilitiesin productivity duced yield. These crises cause the emigrationof the excess populationfromagriculturalsocieties.These emigrantpopulaforthedispersaloftheagriculturalway of tionsare responsible life. Selectionhas favoredthe spread of agriculturalsystems which maximizeinstabilityin production.Maximization of instabilitybringswithit maximizationof dispersals.Thus the mostsuccessfulagriculturalsystemshave been thosethat are, at least in the broadestsense,the least "adapted" agricultural systems. Rindos:ORIGINS AND SPREAD OF AGRICULTURE Hartzell (1967) has reportedon one particularant/acacia relationship.The ants inhabithollow,enlargedthornson the acacia and receivea sugaryexudatefromspecialfoliarnectaries at the base of the leaves. They also harvestmodifiedleaf tips calledBeltrambodies,whichare richin bothproteinsand lipids. Theseare usedto feedtheant larvae.The antspatrolthefoliage insects.Whenants were and removeand feeduponherbivorous experimentallyremoved from acacias, the plants were so and insectsthatall died within severelyattackedby herbivores a year.Otheracacias are protectedby theirants fromherbivore theplantis attackedand given predation;anyanimaldisturbing numerouspainfulbites (Hockeng 1975). The loss of chemicaldefensemechanismswithina speciesof DOMESTICATION AND SYMBIOSIS acacia involvedin a mutualisticrelationshipwithants is apparentlycommon.Ant-acaciaslack the biochemicaldefense ANIMAL-PLANT INTERACTIONS mechanismpresentin otheracacias (Rehr,Feeney,and Hanzen plantshave Domesticationis best understoodas an interaction 1973). In an analogousfashion,manyhuman-crop Coevolution. is exeggplant wild the systems: defense chemical lost their betweenman and theplantson whichhe feeds.2It wouldseem wild of flesh bitter the 1976:80); (Choudhury bitter tremely as an adaptaless thanaccurateto describesuchan interaction (1975) and Bemis for Whitaker is sufficient species Cucurbita tion of or by man to the demandsof continuedsurvival-we to postulatean originaldomesticationof thesefruitsfortheir may just as easily describethe processof adaptationof or by seeds; the domesticationof lettuce (Latuca sativa) has been the plant, forit too benefitsfromthe association.By placing in latex the emphasisupon theactionsof man we neglect fundamental accompaniedby a reductionofspininessand a decrease can oleraceae) (Brassica cabbage wild 1976:39); content (Ryder contribution made by the domesticatedplant to the developdanof bitter and quantity the much as four times as contain exist withcould not mentof agriculturalsystems.Agriculture gerousglucosimatesas cultivatedstrains(Josefsson,cited in out domesticatedplants. Domestication,as seen here, is a 1976:49); cassava (Manihot esculenta)has two Thompson natural evolutionaryprocessby means of whichanimalsand one poisonouswhen raw and the otherlacking highly forms, plantsare able to increasetheirfitness.Coevolution-a typeof of beingcooked and eaten withprelimiand capable poisons evolutioninvolvingtwo geneticallyunrelatedspecies-occurs of the organismspositively narytreatment-thepresenceof toxinsprobablybeing correwheneverthe interrelationship lated, at least in part,withmethodsof cultivationin differing affectstheir potential for survival. The relationshipwhich describedas a symbiosis. agriculturalsystems(Rogers and Appan 1973, Rogers 1965). resultsfromcoevolutionis frequently The hoardingof seeds is widespread Storageand harvesting. Coevolutionis widespreadin nature.Pollination,seed discan persal, and even predation frequentlyhave coevolutionary in theanimalkingdom,and, as it relatesto plantdispersal, of plants. history in the evolutionary significance be of major withinwhich aspects.Coevolutionprovidesa usefulframework Various birds,includingnutcrackers,jays, and woodpeckers, to observedomestication.By means of his interactionswith and mor- are knownto storeseeds of such plants as pine, beech, oak, plants,man inevitablyinfluencestheirdistribution phology.These changes,of course,do not occur by the direct chestnut,filbert,and variousPrunus species. Small mammals storeedibleseedsin their and chipmunks suchas mice,squirrels, influenceof man's activityon the plants. Rather,theyoccur 1972,Stebbins1971). der Pijl caches (van in special and nests over manygenerationsas certainplants-the morefit-leave dried made of grassesand weeds. up a hay and store guard Pikas greaternumbersofprogeny. Guardingof storesis also commonin various birds (Emlen The most strikingevidenceforthe coevolutionaryview of 1973:164). Janzen(1971) notesthatseedsofstoredspecies can and agriculturaloriginsis the existenceof widedomestication soils near be foundgrowingto adult statusin thenitrogen-rich spread nonhumanagriculturalsystems.Domesticatedplants were "lost" seeds these that assumed be It can nest entrances. have establishedrelationshipswithmany animals otherthan resource a useful provide these plants Clearly, or "rejected." man. In a fewinstances,theseotheranimalshave incorporated fortheinhabitantofthenest.Muskrattrappersin centralNew manipulationintotheirbehavioral techniquesofenvironmental rice and we may thereforecall the resultantsystems York reportthatlargestoresofarrowheadtubersand wild repertoires, dens. muskrat in found can be agricultural.Agriculturehas generallybeen characterizedby forour purposesis the phenomenonof Far moreinteresting such actions as sowing,protection,and harvestingor by the Harvesterants seed (myrmecochory). dispersal ant-mediated existenceofmorphologically distinctcultivatedplantswhichare have establisheda symbiosiswithspeciesof plants frommore None ofthese adapted to thebehaviorsinvolvedin agriculture. 63 familiesof flowering plants phenomenais restrictedto the human-plantinterrelationship. than 223 genera representing (Nesomn.d.). These ants collectand therebyoftendisseminate Whilenumerousexamplesofprotectionof plants Protection. theseedsoftheseplants.The antsare "apparentlyable to conby animalsmightbe given,I wouldlike to describeherea paroftheseedstheycollectand also exertcontrolthegermination ticularlycomplicatedformof protectionactivitywhich has on thevegetationin thevicinityofthenest" influence siderable evolvedin the behaviorof certainants. Here we finda highly (Hockeng1975:83). developedmutualisticrelationshipbetweenants and plants in Harvesterants have developedquite sophisticatedformsof whichthe plants providedomiciles,food,or both forthe ant. behaviorto protecttheirseed stores.At least some species of In "return,"theant protectstheplant. ants willremoveseeds thathave becomewetfromthenestand drythemin thesun.Many speciesoftheants "thresh"theseed 2 In this analysis I am restricting myselfto the originof planttheygather,and moundsof chaffmay be foundin the vicinity human relationships.To add an analysis of animal domestication of the nest.It appears that bothant and plant benefitby this would substantiallyextendthe lengthof thisessay. Furthermore, all agriculturalsystemsare ultimatelybased upon plant domestication; association(Hartzell 1967:127): human-animalrelationships lackingthiselementare generallytreated The anddrought. coldperiods Theantis assureda foodsupplyduring as a separate phenomenon(i.e., pastoralism).Finally, the treatment against and it is protected plantspeciesis aidedin its distribution hereis at least in part dictatedby my trainingas a botanist. Vol. 21 * No. 6 * December1980 and coldby beingstoredin theunderground galexcessive drought collecttheirfoodsupplyin leriesoftheants.Sincetheantsnormally thisis an important inthesurvival factor excessoftheirrequirements, of the plantspeciesduringclimaticchangesthatwouldnormally themaboveground. destroy is characterized Stebbins(1971:243) notesthatmyrmecochory modifications in the plant: by a wholeseriesof morphological to theirrelatives In comparison ... [these]plantshavethefollowing theflower stalksarerelatively characteristics: low,and thepeduncle whentheseedis ripeso thatthematurecapsuleis becomesrecurved closeto theground.The capsule... does notdehisceregularly by and overa relatively longperiodof valvesor pores,butirregularly time.... Thismakespossiblerepeatedvisitsbytheantsto thesame haveseveralmodifications. Sometimes plants.The seedsthemselves theyhave a specialoilyseedcoat; theantsremovethisafterthey have carriedthe seeds to theirnests,and thentheydiscardthe fat-bearing strippedseeds.Moreoften,each seed has a particular appendagewhichthe ant clipsoffwithits mandiblesand carries ofthe afterithas transported theseedsto thevicinity underground, nest. ofant-dispersed Changesin themorphology plantsare adaptaof the symbiosis.Traits of tionsnecessaryto the functioning domesticatedcropssuch as indehiscencemay be viewedin the same manner. Transportationof the seeds to the vicinityof the nest can of fairlylarge populationsof the allow forthe establishment plantin an area whereit mostbenefitstheants.Like theestablishmentoffoodplantsin thevicinityof mammaliannests,this formof ant dispersalbears strikingsimilarities to the "dumpheap" modelsfortheoriginofagriculture. Furthermore, myrmecochory may allow forthe survivalof otherwiseunadaptedorganisms.Handel (1978) has extensively studied the competitiverelationshipsof threecloselyrelated United speciesofsedges(Carex)whichgrowin thenortheastern and extensiveexperimental States.Bothfieldwork investigation have shownthat one ant-dispersed speciesis a relativelypoor competitor.It has survivedbecause it does not have to compete directlywiththe otherspecies.This is because it is dispersedintoa habitat (rottinglogs) whichis unavailableto the others.Antsnestingin rottinglogs dispersethe speciesin the vicinityof theirnestsand providea refugeforit. The sedge thususes theant as its dispersalagentin a race to keep ahead of the other,morecompetitivespecies.The ant-dispersed species mustmoveintonewhabitatsas theybecomeavailable,for oncethehabitatis no longera newhabitat(thatis,oncethetree is completelydecomposed)the plant will be replaced by its relatives. Typical of the syndromeof a weedycolonizingspecies,the ant-dispersed sedgehas evolvedseveralothertraitswhichcontributeto its successin thisrole.It has, on the average,twice the seed set of its relatives.It is also typifiedby immediate germinationof the seeds; the othertwo species requireoverwintering beforetheywill germinate.This is also probablyan adaptationto greaterseed productionand thusthe maximizationof the total seed crop duringthe relativelyshortlifespan ofthedisturbedhabitat.The weedycolonizingspeciesmustput a great deal of energyinto the productionof seeds. Only by maximizingthe potentialfordispersalcan this type of plant survive. are not limstorage,and controlovergermination harvesting, ited to the relationshipbetweenplants and man. Similarly, of the plant throughcultivationis modification morphological withman.Numerousspecies to plantsinteracting notrestricted of insectshave establishedsymbioticcultivationrelationships withfungi.More than40 speciesofbeetles,knownas "ambrosia beetles,"as wellas somewoodwaspscultivatefungusas sources of food.These insectsboreinto,but do not directlyeat, wood and otherplant tissue.Instead,theyinoculatetheplant tissue withsmallamountsoffungus.This fungusis usuallycarriedby the insectsto the hostplant in specializedorgans,mycetangia. organsin the various Mycetangiaare derivedfromdifferent groupsof ambrosiabeetles,and we may thusassume that the in originevenforthis habitoffunguscultivationis polyphyletic groupofinsects.In all cases,fungusservesas thechiefsourceof stagesoftheinsect. foodforall thedevelopmental The fungithat are cultivatedcome frommany different generabut can be broadlyclassifiedintotwo groups.Some are knownoutsideof the symbiosis,but the majorityare highly specializedand are not knownto existindependently(Baker 1963). These fungiare generallyhard to classifybecause they do nothave a truesexual cycle,insteadbeingadapted to vegetativedispersalsby theirrespectiveinsectvectors.3It is important to note that the funguswill not growin the host plant withoutthepresenceoftheinsect.The insectin factmaintains pure culturesof its associatedfungiby removingany competremoved,the fungus.If theinsectis experimentally ing,foreign site is usuallytakenoverby alien growth.The insectsalso frequentlypreparespecialbedsofwoodchipsand fecesto enhance the growthof the fungi(Francke-Grosman1967). Growing thesefungiunderlaboratoryconditionshas provento be exComplexmedia that includevitamins,lipids, tremelydifficult. and amino-acidsare required.It appearsthatmanyofthefungi are dependentuponinsectsecretionsforgrowth.Underlaboratoryculture,thefungusloses thegrowthpatternand morphologypresentin theambrosialstate. Antsand termiteshave also developedsophisticatedcultivationsymbiosiswithfungi,someofwhichare highlycoevolved. For example,manyspeciesoftropicaltermitesmaintainfungus "gardens" in theirnests. Unlike most termites,these species lack theintestinalmicroorganisms necessaryforthedigestionof cellulose.Instead,theircarefully nurtured fungusprovidestheir foodsupply (Trager 1970). It is again among ants, however, that we findthe mosthighlydevelopedcultivationanalogues (Weber1966,Hartzell1967,Hockeng1975,Trager1970). Cultivatorantspreparespecialbeds,generallyofplantdebris,cut-up in special chambersin the ant and excrement, leaves, flowers, nest.The ants are meticulousabout growthconditionswithin thechamber;numerousventilationpassagesare dug,and these and humidare openedor closedto regulateboth temperature ity.To constructthebeds,theants chewthesubstratematerial to make a pulpymass and depositit in layersin the chamber. The bed is thenplantedwithpropagulesfrompreviouslymaintainedbeds. Constantcare is giventhe beds. The ants remove alien fungiand add anal and salivary secretionswhich apon thegrowthofthefungi.These parentlyhave a positiveeffect cultivationactivitiesencouragetheproduction,by the fungus, ofsmallwhitishroundbodies,theso-calledkohlrabistructures. These structures are theprincipalfoodoftheant colony.While underthecare oftheants,thefungusproducesno sexualstage. mushroom If the ants are removed,however,the reproductive ofremovalof however,theeffect mayappear. More frequently, of the beds by alien fungiand other the ants is contamination organismsto thequickexclusionoftheant-fungus. It is clear thatagriculture way,be cannot,in any meaningful If we tryto findany interaction. restricted to thehuman-plant activityor collectionofactivitiesto definethe man-plantrela- The similarities betweentheant-dispersed colonizingspecies and the cultivatedplant are ratherstriking, but theyare not unexpectedifwe recognizethat theyare the resultsof a commonprocess.The problemsconfronted by the cultivatedplant identical duringtheearlyphasesofdomestication are essentially to thoseofany otherplantmaximizing itspotentialas a weedy colonizingspecies.Total crop of seeds must be maximizedto allow forthetransportofthe plant to a newlyopened habitat. However,the creationof a new habitat is diagnosticforadvanced agriculturalsystems.It is withinthis habitat that I It would be hard to hold that this is necessarilya resultof the actionssuchas weedingbecomeimportant. association;thereare numerousfunginot associatedwithinsectsthat Morphological changethrough cultivation. Clearly, protection, possessno sexual stage (the so-calledfungiimperfecti). 754 CURRENT ANTHROPOLOGY tionship,we are at the same timedefiningotheranimal-plant To say that man has a different relationships. attitudeor approachto the cultivatedplant seemsinsufficient to distinguish the human-plantrelationship fromtheseothers.Further,even if we grant a qualitative difference in agriculturalbehavior betweenman and otheranimals,it seemsunreasonableto assumethatman was necessarilyas consciousofthe evolutionof agriclultural systemsin the earlieststages of plant domesticationas he is today. THE EVOLUTION OF DOMESTICATED MORPHOLOGIES Thedomesticated plant.As we have just seen,domestication is a particulartype of plant-animalinteractionwhichfavorsthe evolutionof certainmorphologicalchangesin the plant. The is also characterized relationship by specificsetsofbehaviorby the animal. It is necessaryto stress,however,that domesticationdoes notevolveorthogenetically or inevitablyintoagriculture.Indeed, the degreeof developmentof the domestication relationshipmay vary amongstthe total set of plants with whichan animalmay be interacting. Differentdegreesof domesticationmay be seen in manyof thecropswhichare cultivatedby man. Sincedomestication is a naturalevolutionary process,thisis notsurprising; it is a functionofthefactthattheplantis notexperiencing selectivepressure onlyfromits relationship withman (foran extendeddiscussion,see Rindos n.d.). For example,certain varietiesof wheat currentlyundercultivationscattersome of theirseeds withoutrequiringthreshing. The rachisto whichthe seeds are attachedis said to be partiallydehiscent.Thus the seeds are capable of limiteddispersalwithoutthe intervention of man. This is especiallysignificant whenone considersthewidelyheld beliefthat the indehiscentrachis is the hallmarkof domesticated grains.Likewise,in manyvarietiesofoats thereis a tendencyforthe ripe grain to shatter.This is a major problem, sinceit reducesthetotalyieldwhichcan be recoveredat harvest (see Schwanitz1966:34-35). Despite millenniaof interaction betweenman and thesecrops,"wild" characteristics have not been completelyeliminated.In the same way, "natural" dispersal mechanismscharacterizemost of our cultivatedornamentalplants and many of our vegetable,forage,and fruit crops (Schwanitz1966:96). One way to understandthe great variationwhichmay be foundin cultivatedplantsis to lookto theevolutionary tendencies whichare favoredby varioustypesofinteractions between man and plant.Perhapstheeasiestway to approachthisproblem is to considerthe interactions fromthe perspectiveof the organsof theplant thatare utilizedby man. (These responses are not restricted to human-plantinteraction, but are possibilitiesin all herbivore-plant interactions.) Threemajorclassesof plant organsmay be recognized:vegetativestructures, reproductivepropagules,4 and vegetativestructurespossessingsecondaryadaptationsas dispersalpropagules. In one type of herbivore-plant interaction,the animal consumes vegetative structures of the plant: roots,stems,petioles, leaves,and flowers.(Flowers,whilestrictlysexual organs,may be consideredvegetativeorgans until the fruitripens.) The generalevolutionarytendencywhenan animal feedson these parts of a plant is towardsnonedibility; the potentialforthe developmentof a cultivationsymbiosisis ratherlimited.Typical evolutionary sequencesincludethedevelopment ofchemical defensessuch as poisons and tanninsand the elaborationof physical deterrentsagainst predation such as trichomes, sclerids,and thorns.Amongannual plants, a pressureexists towardsthe evolutionofprecociousflowering, whichdecreases the timeduringwhichthe plant existsand thusis susceptible to consumption.Anotherresponseof the plant is colonization I A propaguleis any plant organadapted to the sexual or vegetative reproductionof the motherplant. Vol. 21 N 6 * December No. 1980 Rindos:ORIGINS AND SPREAD OF AGRICULTURE in regionsof highlydiversified florasin whichthe individual plant becomesless conspicuous.It wouldthusseemreasonable to assume that plants whosevegetativeorgansare utilizedby man were domesticatedafterprotectivebehaviorshad begun to be practiced.At such a time,plants not possessingdefense mechanisms mightbe sparedbecauseoftheirdesirability, and it wouldbe possibleforthemto pass thenonprotected stateon to succeedinggenerations. Whenan animal feedsupon the reproductive propagulesof a plant,thepotentialforthe developmentofdomestication symbiosesis great.The plantmaybe able to utilizethepredatoras a dispersalagent.The developmentand elaborationof dispersal symbioseshas been extensivethroughout nature.Confirmation of the importantrole of the reproductivepropagule in the developmentof domesticationsymbiosesmay be seen in the typesofcropswhichman generallygrows.Thereare numerous plants whose vegetativeparts are highly defended,either mechanicallyor chemically,but whosereproductive propagules are edible.This edibilityis frequently advertisedby the developmentof conspicuouscolorationwhen the propaguleripens. Of course,as would be expected,this advertisingand defense syndromeis not restrictedto cultivatedplants. It is also extremelywidespreadin trulywildplants(thatis, thosethathave establishedrelationships withanimalsotherthanman). Thereare twobasic modesin whichplantsadapt to theproblemsand opportunities ofan animal-mediated dispersalsystem. The firstand mostcommoninvolvesthe elaborationof an attractiveaccessorystructurefor consumptionby the animal. The accessorystructureis "expendable"tissuewhichservesto attract the dispersalagent. The propaguleitselfis variously protectedand carriedpassivelywith the accessorystructure. Many of the propaguleswhichwe call "fruits"representthis modeofadaptation.The fleshofthefruitservesto attractand feedthe animal dispersalagent,whilethe actual reproductive unitsare inedibleand are discarded,and thusdispersed,after thefruitis consumed.The seedsin stonefruitssuchas cherries and plumsand the corewhichcontainsthe seed in apples and pears are dispersedin thisway. The abundanceof feralapple trees growingin hedgerowsthroughoutthe northernUnited States and the feralpeaches of the southare evidenceof the effectiveness ofthismodeofdispersal. The otherbasic mode of plant responseto potentialanimal distribution agentsmaybe describedas aggregation. It involves the collectionof propagulesinto a largerstructure.Here the propagulesthemselvesare consumed,and dispersaloccursdespitepartiallossesfromthetotalpropagulepopulation.The indehiscentrachisof the small grains,the ear of maize,and the heads producedby sorghumsmay all be seen as examplesof this type of attractiveaggregation.The developmentof large seed massesin the New Worldcucurbitsis a further example. Accordingto Whitakerand Bemis (1975), theseplants were originally valuedfortheirseeds.Selectionforhighseed number, and thusforlargerfruits,allows forsecondaryadaptationsby theplant.Anaccessorystructure-thefleshofthegourditselfbecomesthemeansby whichtheplant attractsman. Even the indehiscentlegumeof the cultivatedbean may be seen as an example of this tendencytowardsaggregationin cultivated plants. Aggregationand the developmentof accessorystructuresmay be describedas responsesto thepredatorybehavior ofanimals.Eithercan occurwithoutthepresenceofdeveloped agriculturalbehaviors. McKey (1975) has recentlyreviewedthe coevolutionof tropicalfrugivorous birdsand the plants on whichtheyfeed. These plantshave adapted to specializeddispersalby a limited numberof species of birds.Their fruitsare generallyhighin proteinsand lipidsand thusprovidea verynutritiousdiet for the birdswhichfeedupon them.It is assumedthat the birds provide the plant with a "higher-quality, more 'predictable' 755 dispersal."This seems reasonable,because only one or a few species may feed on any plant. Thus dispersalbehaviorwill show less variationthan the total set of dispersalbehaviors exhibitedby all speciesofbirds. The various morphologicalmodifications exhibitedby the birdsare interesting in and of fruitsdispersedby frugivorous themselves.They also show a type of adaptation which is of the evolutionof especiallyimportantforour understanding cultivatedplants. The fruitsdispersedby frugivorous birds generallypossess morphologicalor biochemicalmodifications whichpreventdispersalsby birdswhichhave not coevolvedto are most comfeed upon them.Morphologicalmodifications mon. Generallythe specializedfruitsare too large formost birds of the tropicshave birds to ingest.Many fruit-eating specializedguts whichare adapted to the handlingof these fruits large fruits.Other types of specialized bird-dispersed seedswhichare groundup in thegizzards produceintoxicating of most otherbirds,producinga negativeexperienceto disof the fruits.Thus not onlydoes couragefurther consumption whichencouragethe relationcoevolutioncause modifications ship betweentheplant and its dispersalagent,but othermorphologicaland chemical traits may develop which serve to excludedispersalsby otherthanthecoevolvedagent. Certaintraitsof cultivatedplants havinga symbioticrelationshipwithman mayhave originally arisen,and are certainly in part maintained,as means forthe exclusionof nonhuman dispersalagents.The largefruitsofthecultivatedapple,mango, and peach are effective meansforexcluding pear, watermelon, most dispersalagents otherthan man. Of course,birds may peck at apples or stonefruits,but theyare generallyincapable of carryingoffthe fruitand thus actually dispersingit. The indehiscentrachis of the small grainsand the cob of maize serveanalogousfunctions in discouraging nonhumandispersal agents. As was implicitin my remarksabout the chemically defendedfruitsof certainbird-dispersed speciesof the tropics, a certainamountof outsideinterference withthe systemmay occur,but overevolutionary timeits effects are minimal.Thus it maybe seenthatcertaintraitsofthecultivatedplantare not solelyforman'sbenefit, butalso servetheplantin itsdispersals. The major evolutionaryeffectof thistypeof specializationin the relationship betweenplant and animalis an intensification of thesymbioticrelationship. An animal's consumptionof asexual propagulesalso allows foran adaptive responseon the part of theplant. Analysisof this typeof symbiosis,however,presentsmoreproblemsthan the analysisof the evolutionof domesticatedplants whosereproductivepropagulesare consumed.The firstissue which must be clarifiedis the distinctionbetweenreproductiveand storageorgans.The domesticationof crops such as manioc, turnips,and carrotsis best consideredwithinthe schemepresentedearlierforthedomestication ofplantsin whichthevegetativestructureis consumed.These plantsare not propagated by the structuresthat are generallyconsumed.However,the potentialof the top of the carrotor turnipto continuegrowth and eventuallyproducea seed stalkcannotbe discounted.The growingpoint of these roots is generallydiscarded (at least today) in preparation.The discardingof thesevegetabletops on a rubbishheap mightallow forseed productionand thus colonizationofthearea by theplant. Plantssuchas thepotato,in whichtheorganconsumedhas a natural dispersalfunction,are capable of developinga symbioticdispersalrelationship. The gatheringof the tuberswith subsequentinadvertentlosses wouldpermitthoseplants producingthemostacceptablefoodto humansto spreadpreferentially.Since thepropagulesare asexual,and thusreproducethe parentalphenotype,desiredcharacteristics oftheplantswould be establishedin thecropmuchmorerapidlythanwhensexual propagulesare beingdispersed.Plantswhoseasexualpropagules are utilizedhave an advantage that is only approachedby plants whose sexual propagulesare apomictic:any particular 756 fixedifit is successfulin the formis immediately morphological is elimsymbiosis,since variationfromsexual recombination inated. terms,the mostlikelyresponseof a In generalevolutionary plantlike thepotato to thepredatoryactivitiesofan animalis ofsmalltuberswidelyspaced fromtheparenthedevelopment tal plant.Individualspossessinglargetuberslocatedcloseto the motherplants would be undera negativeselectionpressure, predatorcouldeasilyretrievethem.If we sincea nondispersing during assumethatno plantingbehaviorby man was occurring the early stages of potato utilization,it would seem that the "desirable"typesofpotato wouldexperiencea loweredchance of the naturaldispersalsof wild ofsurvival.An understanding the evolutionof the potatoes could help us in understanding possiblethatpotato tubers cultivatedplant.It is theoretically werealreadycoevolvedwithanotherdispersalagentand man was able to "steal" the cropfromthatanimal. The domesticationof the potato is furthercomplicatedby of potato plants also occurs the fact that sexual reproduction withgreat frequencyin the regionto whichtheyare native. Most of the potatoes growingin the Andes set fruitsabundantly.This may be more than a climatic response.Brush, Carney,and Huaman (1980) reportthatthepresenceofvolunteerand feralpotatoescontributesgreatlyto the diversityof thepotato genepool in its nativehabitat.Fruitingabilitymay selectionforthe trait,since fruitbe a resultof unintentional ing potatoesmay be morelikelyto colonizefields.This is because a seed willalmostcertainlybe overlooked,whilea tuber willlikelybe harvestedand thusbe unavailableforgrowththe nextseason. Fruitingabilitymay also be a relicofthe original domesticationof the crop. It is possiblethatpotatoesbearing desirabletuberswere originallycarefullydug and that reproduction of the desirable types occurredby the inadvertent plantingof the fruitsin disturbedgroundthat occurredas a activity.Sinceconsiderabledisturbance resultoftheharvesting ofthesoiloccursduringthisprocess,thefruitwouldbe situated in an ideal positionforfuturegrowth.Competitionfromother plants wouldalso be reducedbecause of thisdiggingactivity. theevolutionof in understanding An additionalcomplication cropslike the potato is the factthat theymay be reproduced froma portionof the tuber.Thus, as in the case ofthe carrot, thediscardingofa sectionofthetubercouldallowforcolonizaall ofthecomplicationofthecropin dumpheaps. Considering investigation tionspresentedby a croplike thepotato,further of the behaviorsof the plant in the wild and in its regionof of could do muchto advance our understanding domestication domesticationas an evolutionaryprocess.Such investigation ofthetypes couldbe especiallyimportantforan understanding of selectivepressurewhichmay have existedbeforeplanting behaviorsby man werewellestablished. Independentsupportfora coevoluWeedsand domestication. may be foundin theexistenceof tionaryviewofdomestication weeds specificallyadapted to the conditionsof cultivation. Weeds showmanyofthe traitsofcultivatedplantsdespitethe factthattheyare clearlynotbeingselectedconsciouslyby man forthesetraits.Weeds may be analyzedin thesame manneras thattheyare "paracultivatedplants,but withtherecognition sites" upon thehuman-plantsymbiosis. Wickler(1968) gives several examplesof the evolutionof weeds under cultivation.He notes that the weed Camelina sativahas divergedfromits nonweedancestorCamelinaglabra by virtueof the selectiveprocessesoperatingin flaxfields.C. The sativais largerthanC. glabraand generallynonbranching. to flaxleaves resemblance leaves ofC. sativaalso bear a striking in both shape and color. Clearly,this resemblanceserves to protecttheplant frombeingweededout of theflaxfields.The to fruitof the weed is also indehiscentand requiresthreshing separate the seed fromthe husk. While the seeds of C. sativa fromthoseofflaxin bothsize and weight,thecombination differ ofthesetwofactorsis such thattheycannotbe separatedfrom CURRENT ANTHROPOLOGY flaxseedsby winnowing. C. sativais, in essence,a mimicof flax in bothvegetativeand dispersalphases ofitslifecycle. In a similarmanner,theagriculturaltechniquesofman have selectedstrainsof dodder (Cuscutaepilinum),whose mimicry offlaxoccursonlyduringthedispersalstage.Weedystrainsof dodderproduce a double-seededfruitwhichapproximatesa flaxseed in size and weight."Wild" strainsof doddercan be but the weedy removedfromthe linseedcrop by winnowing, strainsare dispersedwiththe crop. Teosinte so mimicsthe vegetativestructureof maize that cannot distinguishbetweenthe plants native agriculturalists untiltheflowering stage.At thispoint,ofcourse,thelargesize oftheplantand thelate stagein thegrowingcyclepresentgood reasonsnot to botherremovingit; removalwouldbe pointless or perhapseven damagingto adjacent maizeplantsbecause of rootdisturbance.Thus teosintehas adapted in sucha way that man unintentionally protectsit. Many believethat maize and teosintehave a commonevolutionaryhistory(Galinat 1974, 1975,Doggett1965,Mangelsdorf1974). If thisis thecase, then we mayviewthehistoryofthesetwoplantsas one ofdivergent evolution.Two paths developedin a partiallysharedgenepool by adaptationto different aspectsofthehuman-plant relationship.Both teosinteand maize have takenadvantageofman as a protectiveagent.As longas thecropwas an incidentaldomesticate,man may have dispersedboth of them,but once maize became obligatelydispersedby man it was dispersedwithout theteosinteportionofthegenepool. Thus themaizecob served to allow maize to divergefromboth its originalhome and its closest relative,teosinte.In the area in which teosintewas incidentallydispersed,however,man continuedto protectit, eventhoughtheintentoftheprotection, at leastat a laterdate, was directedtowardsquitea different plant. Isolationand domestication. The divergenceof a cultivated plant fromits wild ancestorrequireseffective isolation.Introgressionbetweenthe wild and the domesticatedpopulation would continuallyoppose the developmentof the cultivated plant. Isolation throughthe activitiesof differing dispersal agentshas alreadybeenmentioned. I wouldnowliketo consider spatialisolation.In populationgeneticsthisprocessis generally referred to as allopatricspeciation. Strongevidenceexists that certaincultivatedplants have becomedomesticatedoutsideof the regionto whichtheyare indigenous.Two examplesare the sunflower and the tomato. The sunflower (Helianthusannuus) is almostcertainlya native ofthewesternUnitedStatesand providedan importantsource ofwildfoodto theearlyinhabitantsofthatregion."It has been postulatedthat,in time,thesunflower becamea camp-following weedand was introduced fromthewesternto thecentralUnited States. Somewherein the latterarea the sunflower appears to have been domesticatedand, as a domesticatedplant,was carried both eastwardsand to the southwest"(Heiser 1976:37). The tomatois apparentlydescendedfromwildspeciesofLycopersiconindigenousto theAndes.Yet withintheAndesthereis no evidencethatthetomatowas knownas a domesticated fruit. Instead,all of the evidence-linguistic,botanical,biochemical, and historical--pointsto the area of domesticationfor the tomato as having been Central America and Mexico (Rick 1958, 1978). Since in naturebothof thesecropsare stronglyoutcrossing, spatial isolationofthecultivatedpopulationwas a prerequisite formorphological divergence ofthecropfromthewildancestor. While the sunfloweris still stronglyoutcrossing,cultivated strainsof the tomatohave becomelargelyself-fertilizing. This enhancesthepotentialforthe evolutionof the cropas a cultivated plant,since variationis greatlylimitedin self-fertilizing plants.Self-fertilization as a meansofisolationfordomesticated plants is extremelycommon;it may be seen, forexample,in peas, beans,peppers,and certainofthesmallgrains. Nondomestication. Yet anotherindependent sourceofsupport forthecoevolutionary modelforagricultural originsis thenonVol. 21 * No. 6 * December1980 Rindos:ORIGINS AND SPREAD OF AGRICULTURE domestication of certainfoodplants. Clearly,manymorefood plantsare available to man thanhave beendomesticated.Why should certain crops become domesticatedwhile other, apparentlyequally valuable crops remainwild? As a paradigm forthisproblemI wouldliketo briefly considertheacorn. Acornshave been used as botha stapleand a majoralternative source of food by many culturesthroughoutthe world. While the acorn-basedculturesof the west coast of North Americaare perhaps the best-known, acorns have also been extensively utilizedas humanfoodand as fodderin bothEurope and theNear East. Indeed,it is likelythat theacornhas been utilizedwhereverit is present.It is a large,conspicuousfood sourceand one thatneedsonlyminorprocessing(suchas leaching) beforecooking.The acornsof certainspeciesof oaks are palatable withoutany processing.In manywaystheoak seems ideallysuitedto beingone of thebasic cropsofan agricultural civilization. Since theoak has a longlifecycle,and thusa longtimemust pass betweengenerations, it wouldseem thatit wouldbe difficultto domesticate:theresultsofselectionwouldbe too longin appearingto encouragefurtherconsciousselection.Othertree crops,however,suchas olives,thevarioustreefruits, dates,and numerouspalms,have developedinto domesticatedplants despite theirlong life cycles. Anotherreason which mightbe advanced for the oak's nondomestication is that, since it is capable of providinga large and reliableharvest,thereis no reasonto select"improved"cultivatedforms.Yet, wildstands ofwheatsin theNear East are quiteas productiveas theolder varietiesof wheat (Harlan 1967). Thus productivity does not seemto be necessarilya controlling variable. Within the contextof a coevolutionarymodel for plant domestication, however,we may considerthe possibilitythat thenondomestication oftheoak had littleto do withits potential as a food source forman. Looking at the relationships already existingbetween oaks and otherpotentialdispersal agents in the environment, we may hypothesizethat divergenceof the oak intowildand cultivatedpopulationswas preventedbypreexisting coevolvedrelationships betweenoaks and variousotheranimalssuch as squirrels.Squirrelsnot onlyharvest acorns,but also plant them.We may call the planting behaviorof squirrelshoardingand considerany plantingaccomplishedmerelyincidental,but as faras thepropagationof the oak is concernedthe distinctionis meaningless.It would have been verydifficult forman to upsetthesquirrel'sagriculturalrelationship withoaks. Furthermore, it is hardto imagine a morphologicalchange in oaks that would exclude squirrels fromfeedingupon the acornsand thus dispersingthe plants. Withoutexclusionof otherdispersalagents,domesticationdid not occur. AGRICULTURAL ORIGINS AND DISPERSALS INTRODUCTION TO THE MODEL Domestication,as viewedhere,is an evolutionary processthat is the result of predator/preyinteractions.Domestication oforganand distribution changesthemorphology, physiology, isms.It resultsin a mutualism-a relationshipwhichbenefits geneticallyunrelatedorganisms.It is, however,neitherineviThe treatment thatfollowsis proneto a tablenororthogenetic. fatalerrorin interpretation. I shall be providinga modelfora certainchangein subsistencepattern.The modelis a dynamic one and places great emphasison feedbackprocesses,but it shouldnot be read to condonethe view that theprocess,once begun, must proceed inexorablyto certain ends. There are numerouswaysin whichtheprocessesleadingto domestication and agriculture may be subverted. 757 In a Likewise,thismodeldoes notpretendto be all-inclusive. sense, I am tryingto followa particularthread of cultural developmentsbackwardin time; I am not attemptingto describethefabric.Thus, muchofthevariationwhichmayoccur Little in humanculturesmustbe excludedfromconsideration. attentioncan be givento societieswhichwereagriculturalor domesticatory at certaintimesbut laterabandonedthe behavior. Clearly,it would be extremelyusefuland interestingto deal with such phenomena,but it would go far beyond the boundsofthisessay. Finally,we mustbeginto refinetheconceptofdomestication advancedearlier.I have attemptedtoprovidean understanding so of whydomestication occurs,but the view of donmestication far presentedis so broad as to be, in the finalanalysis,uninteresting. Coevolutionary domestication is a processthathas occurredin almostall culturesat mostperiodsofhumanexiswith tence.It gains its significancefromits interrelationship agriculturalorigins. In orderto appreciatetheroleofdomestication inagricultural origins,it is necessaryto anticipatesomeofthelaterarguments and firstpresenta definitionfor agriculture:agricultureis characterizedby an integratedset ofactivitieswhichaffectthe environment inhabitedby the domesticatedplant throughout itslifecycle.As we shallsee,themajoreffect is to ofagriculture forthe doincreasethe carryingcapacity of the environment mesticatedplant, and this increasein plants and thus plant has majoreffects productivity upon humanpopulations. Agriculture is a level or type of behavior.Like manyother phenomena,it is frequently easier to recognizethan to define. To attemptto defineit solelyon thebasis ofa certaintechnique, such as plowingor weeding,tendsto createa falseimpression of the importanceof any particulartechniquewithinthe integrated schedule of activitiescomprisingagriculturalsubsistence.Frequentlythisleads us intobelievingthatculturessharinga particulartechnique,suchas theuse ofa diggingstick,or evenparticularplants,suchas wheat,musttherefore have had a commonorigin. of domestication. is an outgrowth Thus it is imAgriculture to definea momentoftransition. At an early possiblerigorously stagein thedevelopmentofagriculture, it would be impossible to identify theprotoagricultural confidently society.The interactions with domesticatedplants of the early agricultural fromthoseofthedomesticasocietywouldbe indistinguishable matorysociety.The significant techniquesof environmental nipulationmightnotbe beingperformed forconsciouslyagriculturalends.Firesencouraging thegrowthofdomesticated plants mightbe beingset to drivegame;forestsmightbe beingcleared to furnishbuildingmaterials.We could only be sure that we wereindeeddealingwitha protoagricultural societyifwe knew howtherelationship woulddevelopin thefuture.If we need to define,for any particularsociety,the momentof transition froma domesticatory to an agriculturalway of life,I would suggestthat it is the point at whichagriculturalinteractions became more importantto the society than domesticatory interactionswith plants. "Importance" may be read in two ways.We may considerit to representtherelativesignificance of agriculturalbehavior to the futuredevelopmentof the thateach form society.We mayalso viewit as thecontribution of behaviormakes to the overallsubsistenceof the societyat is of criticalimany givenmoment.This latterinterpretation theevolutionand subsequentspread portancein understanding ofagriculturalbehavior. 0~~~~~~ Population Solidline,totalfood; relationship. 1. The typicalpredator/prey broken line,yieldper predator;a, pointat whichcompensatory or all availableregions behaviorof predatorbecomesineffective ofpreyarefilled. togrowth favorable FIG. betweenpredapredatordecrease.In a mutualisticrelationship torand prey (fig.2), as the numberofpredatorsincreasesthe totalamountofavailablefoodalso increases.The energeticcost to thepreyinherentin providingsubsistenceto thepredatoris compensatedforby actions of the predatorthat provide inforthe survivalor dispersalof the prey. creasedopportunities Seen in otherterms,mutualismsserveto increasethe carrying forboththepredatorand theprey. capacityoftheenvironment The actionsof thepredatorwhichtendto increasethenumber of the prey indirectlypermita greaternumberof predators. Domesticationtendsto increasethe yieldofpreywithinthe area inhabitedby thepredator.Ofcourse,thistendencywillnot Numerousfactorsmay act to limitthe continueindefinitely. numberofpreyand thusofpredator.Eventuallythecompensaor all tory behaviorof the predatorwill become ineffective available regionsfavorableto the growthof the prey will becomefilled;thusthe yieldwilllevel offor even assumea negative slope. Yet thisstabilizationin yield,and thusin predator numbers,is also subjectto change.Most ofthefactorslimiting variablesand thesuccessofthepreyspeciesare environmental are thus external to the mutualisticrelationshipbetween predatorand prey. Since few,if any, species are naturally limitedin numbersby theirintrinsicrates of increase,any will permitincreasesin the "relaxation"of the environment numbersof the prey species. Changes in the environment for directlyincreasethe carryingcapacity of the environment permitgreaternumbersof predathepreyand thusindirectly tors. ofthepreyspeciesmay The changethatleads to proliferation / __ ~~~~~// / DOMESTICATORYRELATIONSHIPS Predator/prey i-nteraction. Mutualisticrelationships such as doPopulation mesticationhave thepotentialto changetherelationship which existsbetweenpredatorand prey.In thetypicalpredator/prey FIG. 2. A mutualistic Solid line,total relationship. predator/prey relationship(fig.1), as the total numberofpredatorsincreases food;broken change ofeffective b, moment line,yieldperpredator; ofthepreyspecies. leadingto proliferation both the total and relativeamountsof food available to the 758 CURRENT ANTHROPOLOGY be a changein the morphology ofthepreyor a modification of thebehaviorofitscoevolvedagent,includingchangein theway theagentrelatesto the environment. At a timebeforeagriculturalbehaviorswerewell established,changesin the morphologyofplantswereprobablyofmajorimportanceforthefurther developmentof the human-plantrelationship.Traits such as indehiscence,gigantism,and aggregationcould exclude previouslyeffective dispersalagentsand thus allow fora greater available yieldto humans.This changein theplants' morphology would enhance the developmentof the human-plant mutualism. As we have just seen,the Domesticates, yield,and instability. majoreffect ofthemutualismbetweenmanand plantis greater of the environment forman. This increaseis not, productivity however,based on equal increasesin productivityof all componentsof the environment (all potentialor actual preyspecies). Rather, a very small subset of potentialfood sources providesall of the increasein productivity.As domestication proceeds,so does man's relianceupon an eversmallersubsetof potentialfoodsources.Increasein theavailabilityofa resource is accompaniedby a corresponding increasein its utilization. The effectof thisdietaryshiftis a reductionin theimportance of nondomesticates. This simplification of the subsistencepatternhas majoreffects upon its stability. To understandtherelationship betweenyieldand instability in yield,we mayfirstconsidertherelationship betweenmanand any one domesticatedplant. The increasein yieldthat results is onlythe averageincreaseovertime,that fromdomestication is, as the mutualisticrelationshipdevelops.Any given plant whichis subjectto periodicand norgrowsin an environment and its yield will vary about the mean from mal fluctuation, Thus the contribution year to yearbecause of thisfluctuation. of any particularspeciesofplant to the totalplant foodavailable to man will vary in responseto environmental factors. Whileaverageyieldis increasingovertimebecause oftheelaboration of coevolutionarydomesticationrelationships,the absoluteyield at any given momentis a functionof specific environmental conditions. beforethedevelopDuringtheearlystagesofdomestication, mentof agriculturalsystems,this fluctuationin yield should have littleeffecton the total yieldavailable to man. The contributionof any givendomesticatedplant to the total subsistence patternwill be relativelysmall. Membersof any given domesticatedspeciesare likelyto be growingin any and all of the locationswhichare conduciveto theirgrowth.Also, the variousspeciesof plants withwhichman has establishedmutualisticrelationships are likelyto be fairlyuniformly distributed throughout the environment, no particularnichehaving establisheditselfas the principal one for all domesticated plants.Thus,whileenvironmental fluctuation willhave adverse effectson the yieldof any particularspecies,the overallyield will tend to remainreasonablyconstant.A bad year forone plant is likelyto be a good yearforanotherplantgrowingin a different habitat;a bad yearforonespeciesis likelyto be a good yearforanotherspecieswithdiffering edaphicand physiological This compensationin yield will permitproducrequirements. tivityto remainrelativelystablefromyearto year,muchas it does in any nondomesticatedecology.As we shall see, this standsin starkcontrastto theinteraction ofyieldand environmentwhichoccursin theagriculturalsetting. AGRICULTURAL ORIGINS tendencies. The primaryeffectof agricultureon a Evolutionary ofthedependenceofthatsocietyon societyis an intensification domesticatedplants.Highlydevelopedagricultural systemsare based upona limitednumberofcultivatedplantswhichprovide thebulk ofthesociety'sfood.Fromtheprecedingdiscussionit should be clear that this tendencytowardsa decreasein the number of niants nrovidinz subsistence is an ouutgrowth of the Vol. 21 * No. 6 * December1980 Rindos:ORIGINS AND SPREAD OF AGRICULTURE dynamicsof the mutualisticrelationship.There is a tendency towards increase in yield and concomitantdecrease in the numberofspeciesofdomesticatedplants providingthat yield. places the major It has also been notedthat the environment limitationupon thedevelopmentofthisrelationship. is composedof various niches forplant Any environment colonization.These nichesare welldefinedand relativelystable. Thus the potentialnumberof places in whichany givenplant oftheenvironby thecharacteristics mightgrowis determined ment. Clearly, any behavior by man that transcendsthese on plantgrowthwillbe accompanied limitations environmental by increasesin yield proportionalto the amount of "new" nichespace. At the same time,any behaviorincreasingniche size available forplant colonizationwillcause a corresponding forman. increasein the carryingcapacityof the environment changeswhich Any humanbehaviorcausingenvironmental successof the domesticated increasetheprobablereproductive plant, and thus its yield,will have importanteffectson the furtherevolutionof the domesticatedplant. Withinany locality,severaltendencieswill guidethe evolutionof the cultivated crop, among them (1) a reductionin diversity,both geneticand phenotypic,(2) a tendencytowardsincreasedproAt thesame time, and (3) autecologicalconvergence. ductivity, a seriesof tendencieswillbecomemanifestwithinthe total set thedomesticatedecology,amongthem(1) of cropscomprising a tendencytowardsreductionin the numberof species on whichman reliesforhis subsistence,(2) increasein total crop As we shallsee, these yields,and (3) autecologicalconvergence. tendencieswill formthe basis forthe elaboration interrelated systems. and dispersalofagricultural antdyield.Changesin thedirectionofplant diversity, Systems, modifiedecologyare evolutionwithinthe early agriculturally based on one rathersimplefactor:human agriculturaltechforplant growthand reproducnologycreatesan environment is structurally tion which, unlike the overall environment, and temporallystable. homogeneous As numerousauthorshave observed,agriculturalsystems ecologies:typicallythe agriculmay be describedas simplified turalplant is a "weedyheliophyte,"that is, a colonizerof disturbed habitats, and the agriculturalfield or garden is an in whichthe earlieststages of ecologicalsuccesenvironment ofthiscolonizersystem sionsare maintained.The predominance foragricultureis based upon the factthat thereare numerous ways in whicha disturbedhabitat can be createdby human behavior.Fires,disturbanceofthesoil,theclearingofforestsor the ringingof trees,and the creationof dump heaps are all routesby whicha disturbed,and thus open, habitat may be created. Early domesticatedplants preadaptedto this niche evolutionintoagricultural willthusbe favoredin theirfurther plants. Variousagriculturalbehaviorsserveto reducethe intensity ofplantsthatare necesof naturalselectionforcharacteristics saryforsurvivalin thewild.Irrigationreducesthenecessityfor plantsto maintainmechanismsforsurvivalduringperiodically droughts.Clearingof the land and weedingdecrease recurring the importanceof competitivemechanisms.Plantingencourages specificand uniformgerminationand seedlingphysioloultimatelyreducethevariagies.The techniquesofagriculture tion to be foundin a speciesof domesticatedplant. Both the wild and the early domesticatedplant had to maintainpleiotropicresponsesin the face of an unpredictableenvironment. With a reductionin overall environmentalunpredictability withinagriculturalsystems,thisvariabilityis no longerbeing maintainedby naturalselection.Physiologicaland autecologiplantswithinany also occursin all agricultural cal convergence givenlocality.As we shall see, thisdecreasein variabilityultimatelyyieldsan increasein vulnerability. At thesame time,theselectionforhigheryieldsjust discussed 759 will continueand even increase.Plants yieldingthe greatest numberof propagules-thoseplants best adapted to the agricultural environment-willbe most likely to survive and spread. The relaxationof selectionpressuresfortraitssuch as willalso bringabout a new way forplants to competitiveness increasetheiryield. Energythat was previouslydivertedto such tasks as protection,the manufactureof long internodes, and the like may now be utilizedfor perenniating structures, furtherincreasesin yield. Released fromthe requirementto the plant whichputs energyinto the possesssuch structures, productionofpropaguleswillbe themostfitwithinan agriculturalsystem. Processesanalogous to those occurringat the intraspecific levelwillalso occurat theinterspecific level.Those plantsbest withinthe agricultural adapted to survivaland reproduction ecologywill come to dominatethe system.Given the homogeneityand stabilityintroducedintothe environment by agriculturalbehavior,it is not unreasonableto expecta reduction in species diversity-an increasingreliance upon fewerand fewerspeciesto providethebasis forhumansubsistence. thistendencytowardsuniAnotherfactorwillalso reinforce of developingagriculturalsystems. and simplification formity As a food source becomes more common,feedingon it will increase.At firstthiswill be merelya functionof availability, but as timepasses techniquesof productionand consumption will tend to improve.Availabilityand efficiency interactin a positive-feedback manner,and furtherspecializationis likely. Specializationwillalso be encouragedby the localizationof agriculturalproduction.Reductionof usage will decreasethe probabilityoftheestablishment ofcoevolutionary relationships betweenhumansand new species of plants. As more time is man willcomeintoconspentin theagricultural environment, tact with fewerspecies of alternativefood sources. These changes in time allocation, generallyknown as scheduling changes,decreasetheimportanceofenterprises competingwith agriculture.Thus the establishmentof agriculturewithina society will intensifyand direct tendenciesalready existing underthedomesticatory way oflife. The development ecologies.Agriculture creates of agricultural a new type of climaxformation.The agriculturalfloratends towardsstabilityas longas humanbehavioris interfering with othersuccessionalprocesses.Many ofthespecieswhichinhabit the agriculturalclimaxare derivedfromplantsadapted to the earliest,colonizing,stage of ecologicalsuccession.Agricultural derivedfrom"weedy" plants that tend staplesare frequently to existonlyin newlydisturbedground.Anothercharacteristic of manyof the staple cropsof agricultureis that theyare descendedfromplantsthatdid not alreadyhave mutualisticdispersal systemswithany animal otherthan man. The agriculturalflorais a climaxformation composedofhighlyspecialized colonizerspecies.Many oftheplantsare descendedfromancestorshavinggeophysicalmodesofdispersal;secondarymodificationsare adaptationsto human-mediated dispersal.This striking combinationof geneticheritageand evolutionarysetting and goes farin helpingus to understandboththeproductivity thelimitedspeciesdiversitytypicalofagricultural systems. Whiletheagricultural ecologyis bothstableand simplecomparedwiththe overallecology,it nevertheless willshowchange overtime.Probablythemostimportantlong-term changethat occurs in agriculturalecologiesis the creationof new niches withinthe ecology.As timepasses and plants respondto the optionspresentedby the existenceof agriculturalareas, subdivisionof the existingspace will occur.This will permitthe entryof new, not necessarilydomesticated,plants into the ecology.For example,weedsmay evolveto utilizeagricultural fieldsduringfallowperiodsand then begin to be subject to manyof the same selectiveforcesexperiencedby the domesticates. The changesthat occur in agriculturalecologiesover time also allow us to understaind the evolutionof weedinessand the 760 entryof "secondary"domesticatesintothe system.Weeds are colonizersof thisnewagriculturalhabitatjust like agricultural betweenthemis in theattitudeman plants.The onlydifference has towardsthem.Vavilov (1926), amongothers,has pointed out that the distinctionbetweenweed and domesticateis at besta tenuousone. Secondarydomesticatesare plantsthatare capable of establishingthemselves,like weeds,in the agriculturalecologybut thatprovideman withusefulproducts.Prime amongtheseare plantswhoseutilityis foundin theirvegetative parts. Edible plantswhichcan establishthemselvesin the disturbedagriculturalecologyneed not developspecial coevolved in orderto survive.Theyneedonlyscatter meansofdistribution theirseed. However,since theyare growingin the same environmentwith otherearly agriculturalplants, they will be subject to the same selectionforhighpropaguleyield. They will also exhibitthe same tendencytowardsedaphicand autcrop.The secas any otheragricultural ecologicalconvergence ondarydomesticatewill evolve subject to the same selective pressuresas theprimarydomesticate:it is evolvingin thesame environment. The developmentof the agriculturalecologywill,because of the interactionbetweenit and thegeneralecology,have major effectson the divergenceof the cultivatedplant fromits progenitorspecies.While diversitywithinthe ecologicalniche is likelyto be, at least initially,less than that outsideof it, the of resultwill neverthelessbe an increasein the heterogeneity fordisthe entireregion.This will permitmoreopportunities thedivergenceof ruptiveselection(Thoday 1958) and intensify the agriculturalplant fromthe early domesticatedplant. Human interactionwith the originallydomesticatedtaxon will withtheagricultural decreaseas theinteraction plant develops. Relaxationof the amountof interactionbetweenman and his earliest domesticatedcrops will, in the presenceof highly developed agriculturalsystems,leave the early domesticate "stranded."The humanagent withwhichit had developeda coevolved dispersal or protectionsystemwill no longer be is as dispersalagentor protector, and its extinction functioning to almost inevitable.It is not surprisingthat it is so difficult species" forso manyofour important identifythe "progenitor forextinction have agricultural plants.Two majoropportunities occurredin the historyof all primarydomesticates:(1) The wild,uncoevolvedportionof theancestralgenepool mayhave becomeextinctduringthe long timeperiodduringwhichcoevolutionarydomesticationoccurred.(2) The portionof the genepool whichevolvedundertheconditionsofearlydomesticationmayhave becomeextinctduringtheperiodofintensified evolutionwhich led to the developmentof the agricultural plant. DISPERSAL OF AGRICULTURAL SYSTEMS We have alreadynoted andenvironmental instability. Agriculture thatincreasinghumanrelianceon cultivatedplantsbringswith it a relativedecreaseover timein the absolutenumberof taxa producingthe major portionof the society'ssubsistence;that fromyearto year; taxa varyinproductivity manydomesticated thatconvergence occursamongagricultural crops;and that,by limitationsupon the carrying removingcertainenvironmental fordomesticatedplants,agriculcapacity of the environment increasein potentialyield turalbehaviorpermitsa tremendous and thus in potentialhumanpopulation.I would now like to explorethe interactionof a contractingsubsistencebase, inan crease in carryingcapacity,and variationin productivity, have led to thespreadof effects interaction whosedemographic as a modeofhumansubsistence. agriculture We have discussedsomeof the consequencesof the developstableniche:thedivergence mentofagriculture as a temporally the evoluof agriculturaldomesticatesfromtheirprogenitors, tionofsecondarydomesticates, and theevolutionofagricultural weeds.Agricultural ecologiesalso have locationalstability.The CURRENT ANTHROPOLOGY ofagricultural concentration plantsin limitedregionsincreases yieldsby allowinga morecompleteharvest.At the same time, it intensifies thepotentialinstability ofthesystem,and thishas major effectsupon the demographyof the humanpopulation dependentupon agriculturalproduction.Locational stability intensifies instabilityin severalways. Prime among themare ofmicroenvironmental and microclimatic theeffects variation. A gardenarea thatoptimizesdrainageduringaverageyearswill be too wet duringperiods of highprecipitationand too dry duringperiodsof drought.Otherlocationaleffectsto be consideredlater includeconcentrationof resourcesand predation and edaphiceffects. Domesticatedand agricultural plantsbringabout an increase in thecarryingcapacityoftheenvironment contributed by domesticatedplants, hereafterreferredto as Kdom.5 While Kdom tendsto increasegreatlyovertime,forreasonsoutlinedabove, the changein Kdom is not alwayspositivefromone momentto another.The components oftheenvironment showseasonaland longer-term variation. Climate, for example,is not uniform fromyear to year, and over relativelyshortperiodsof time differing average climaticconditionswill prevail. Thus, yield willvaryin responseto theseconditions. In the later phases of nonagricultural there domestication, willbe somevariationin productivity overtime,but variability is restrainedby severalfactors.As we have alreadynoted,the early domesticatedplant is growingin a varietyof microenvironments. Thus any climaticchangeneednotaffectall ofthe microenvironments in thesame way. For example,domesticates growingin sitesthatare wetterthanoptimalwillprosperduring a period of reducedprecipitation.Nonagricultural domesticatorysocietiesalso tendto have a largernumberofspeciesconto Kdomthando agriculturalsocieties.Thus any given tributing changein the environment is not likelyto affectall speciesof domesticatesequally.Both oftheseintrinsic factorswilltendto reducetheeffects ofchangesin theenvironment on theproductivityofthedomesticatedecology.Perhapsthemostimportant factorlimitingtheeffectsofchangesin Kdom, however,is external to thedomestication symbiosis.The nonagricultural society is relyingupon domesticatedplants foronlypart of its total foodsupply.Thus it is possible to compensatefordeclinesin of the total Kdom by increasedrelianceupon othercomponents carryingcapacity (K). The failureof one domesticatedplant, or of one domesticatedspecies of plants,will be compensated for by increasedreliance upon other plants, both wild and domesticated. In a periodof earlyagriculture, the varianceof Kdom willbe greaterbecause of the evolutionof agriculturalecologies.The evolutionof the cultivatedplant in the agriculturalenvironmentincreasesnotonlyyield,but also thesusceptibility ofthat yieldto environmentally inducedcropfailure.The autecological convergence broughtabout by agricultural selectionbringswith it an increaseduniformity in theresponseofagricultural plants to environmental parameters.Thus a bad year forany given memberof a cultivatedspeciesis likelyto be bad forall membersofthatspecies.And sincetheconvergence is also occurring between,as well as amongst,plant species,bad years forany givenagriculturalstaple are likelyto be bad forotherstaples also. Increase in productivity has been boughtat the price of in responseto the environment. uniformity to and intensifying Contributing the effectsof autecological convergenceis the greaterlocational stabilityof agricultural ecologies.Localization intensifies the effectsof microclimatic effectsupon total yield.To take an extremeexample,a hailstormjust beforethe harvestseason willhave vastlydifferent effects upona societyifit fallsuponthecultivatedfieldsthanif it fallsin the woods. Since hail is frequently a highlylocalized 5K is widelyused to stand for"carryingcapacity." Kdommay thus be read as " that componentof K contributedby the yield of domesticatedplants." Vol. 21 * No. 6 * December1980 Rindos:ORIGINS AND SPREAD OF AGRICULTURE phenomenon,the effectof hailstormsupon the total available than it will be for yieldwill be far greaterforagriculturalists or a totallynondomesticatory society. eithera domesticatory ecologiesincreases Thus localizationofresourcesin agricultural the possibilitythat all of the resourcemay be lost to a catastrophe. Agriculturalsubsistenceis also accompaniedby a growing specializationin diet.Thus a decreasein theyieldfroma staple foodsupply, cropwillhave majoreffectson the total perceived and techas wellas theabsolutefoodsupply.Food preferences niques of preparationwill have placed certainfoodsourcesin positionsof prominence.Informationconcerningthe edibility and processingof alternativefoodsuppliesmay be lost. Thus decreasesin yield fromcultivatedplants may create the appearanceoffoodshortageeven thoughthe total available food supplyin theregionmaynothave fallento thepointwhereit is actuallylimitingsurvivalof the population.Animalsrespond to theperceivedfoodsupply,not to some "objective" measure of total available calories. The increasedsusceptibilityof the The basisfor instability. agriculturalecologyto the extremesof normalclimaticvariamanipulation tionmay be viewedas an effectofenvironmental manipulation itself.Many ofthesimplerformsofenvironmental controlrelativelyconstant,predictableparametersof the enthe effects of the vironment. They increaseKdom by mitigating on the carryingcapacity of the enfundamentalrestrictions vironmentforthe plant. Increasingcontrolover any limiting bringswithit, however,an increase aspect of the environment in the vulnerabilityof the newlyheightenedKdom to those leftunaffected by controlbehaviors. aspectsoftheenvironment As we have seen, forexample,localizationof productionincreases Kdom and thus allows fora largernumberof human of the systemto beings,but it also increasesthe susceptibility effects.The negative microclimaticand microenvironmental removalof any givenlimiton yieldallows other,uncontrolled limitsto becomeevident. Agriculturepermitspreviouslynonlimitingfactorsin the of plants to expressthemselves.For growthand productivity fromdroughtwill not have major example,a plant suffering by minorinsectinfestalimitationplaced upon itsproductivity tion. Correctionof the droughtconditionby irrigationwill conallow forthe expressionof the limitationon productivity tributedby the insectpredation.Thus techniquesof environto affectyield admental manipulationallow theenvironment in newways.At any giventime,techniquesof environversely mentalcontrolincreasethe negativeeffectsof conditionsthat cannotbe controlledby the system. new opportunities also createsentirely for limitaAgriculture ofa crop, The increasing geneticuniformity tionsonproductivity. reductionin species diversity,edaphic and ecologicalchanges of recreatedby agriculturalpractices,and the concentration sourcesin a limitedarea all contributeto new potentialinstabilitiesin productivity. of increasesthe susceptibility Increasinggeneticuniformity in the prothe crop to attacks by pathogens.Polymorphisms ductionofsecondarymetabolitesactingas biochemicaldefenses discouragethe evolutionof specializedpathogens.A reduction in thisdefensestrategyencouragesthe evolutionofpathogens whichmayseriouslydamagea plantspecies(Feeny 1973).This potentialsourceofdamageis especiallyclearwhenwe consider crops in whichsecondarymetabolitesdistastefulto man also serveto protecttheplantfromattackby otheranimals. ecology Reductionin speciesdiversitywithintheagricultural upon the susceptimay in and of itselfhave importanteffects bilityofthecropplant to pathogenattack.Escape frompredationmay be aided in manyplant communities by the associaplants;the plants"hide" frompotential tionofmanydifferent predatorsby beinghard to findin the mosaicof diverseplant 761 No to changes in the carryingcapacity of an environment. populationof animals is capable of instantaneouschange in numbersresponseto changein the carryingcapacity.Instead, nerability of crops to insect herbivores . . . may result from plantingin monoculture species whichhave evolved chemical thepotentialpopulationmust"track"thechangesin thecarrydefensesappropriateto communitiesin which the optimum ing capacity. It will be somewhatout of phase with those strategyis beinghard to find."Competitionbetweenagricul- changesbecause oflags in reproduction or behavioralresponse turalcropswhichresultsin tendenciestowardsboth increased to perceivedchangesin theenvironment. Changesovertimein yield and reductionin species diversitythus may work to Kdom willbe respondedto, in a delayedmanner,by changesin counteractdefensesacquiredduringthe evolutionof theplant the potentialpopulation.The average populationover long in the wild. to the effective periodsoftime,however,willtendto correspond The negativeeffectsof agriculturalpracticeson the land, minimalcarryingcapacity(Kdom) (fig.3). Part of the potential increasesinKdomcannot amongthemerosionand changesin soilstructureand drainage humanpopulationproducedbyrecurring patterns,are well documentedand will not be given further be maintainedduringperiodswhenKdomdropstoitslowestlevels. here.Less well studiedare the effects consideration of agricul- We may view this componentof the populationas agricultural systemson the feedingpatternsof animals other than turallyinduced "excess production"of people, hereafterreman. Agriculture, especiallyin its later phases, may signifi- ferredto as Pd. The amplitudeofPd is clearlydetermined by the cantly alter the local ecologysimplyby the replacementof interactionofa largenumberoffactors,includingthelengthof areas ofwildvegetationwithcultivatedfields.This destruction a generation, theamplitudeofKdom, therateof changeof Kdom, ofwildhabitatscreatesfoodshortagesforanimalsthatrequire the availabilityof alternativefood sources,and the way in plants growingin thesehabitats.Thus theymay turn,out of whichchangesin Kdom are tracked.Nevertheless,forour purnecessity,to feedinguponagricultural crops,eventhoughthese by the interactionof Kdom and poses treatingPd as determined plantsmaynotprovidefavoredsourcesoffood. heuristicvalue. Kdom has considerable Finally,theincreasingconcentration ofresourcesencourages of the demographiceffectsof Figure 3 is an interpretation predation.The sameconcentration ofresourceswhichfacilitates agriculturalinstabilitytakinginto account the trackingbehaharvestofthecropby humanswillfacilitateitsharvestby nonand viorof humanpopulations.The hypothetical productivity humanpredators.And whileman may delay consumptionof resultantdemographic by thisgraphreprechangesrepresented theplant to optimizeharvest,mostof thesepredatorswillnot sentconditionssuch as mighthave existedin an earlypristine be underthe same restraints.Thus theymay attack the field agriculturalsociety.Here we may note an averageincreasein beforethe cropripens.They may also be capable ofutilizinga minimalKdom and theeffective Kdom, thepotentialpopulations, crop at a period duringits life cycle whenit cannot be con(Kdom). The graphalso showsthreepoints(a, b, and c) at which sumedby man,forexample,duringearlyseedlingor vegetative the actual populationis greaterthan can be maintained.We stages.Thus loss of the total crop may occurbeforeany yield excessproductionof mustconsiderthefateof thistemporarily has been givento man. thefactor humanbeings.In essence,we are seekingto identify The fundamentalcause of agriculturalinstabilityis agricul- which acts to reduce the populationin a particularlocality tureitself.All ofthenewadverseeffects whichtheenvironment whenan environmental crisiscauses a suddendeclinein Kdommay have on agriculturalproductivity are inducedby agriculThe most frequentresponseof any animal populationto a turalpractices.Yet at thesame timeagricultureis responsible dropin thecarryingcapacityis emigration. Emigration(rather forgreatlyincreasedaverage yield and thus permitsgreatly than starvationor declinein per capita consumption)is espeelevatedhumanpopulationlevels.Overthelongterm,it would ciallylikelyif onlyone componentof the carryingcapacity is seemjustifiedto say that,despitethegreaterinstability ofagrisuddenlyreduced.Part of the animalpopulationwillleave the culturalproduction,this increasein populationlevels is eviarea in search of a place wherethe limitingresourceis more dence of "progress." abundant. However,the increasesin populationwhichaccompanyincreasesin Kdomoverlongperiodsoftimeare "successes"forthe systemonlyatthemoment ofchange.The agriculturally enhanced populationlevels now requirecontinuallyelevated levels of productionfortheirmaintenance.Further,overrelativelyshort periodsoftime,theenhancedpopulationlevelbecomesnothing morethan the "normal"populationlevel. Thus the increases in productivity broughtabout by agricultureare absorbedby a growingpopulation.Increasinglysophisticatedtechniquesof environmental manipulationare requiredforthe maintenance of the same rate of growthand, because of increasinginstability, oftenfor maintenanceof the same level of population. Human populationsgrowin proportionto the effectiveness of in raisingthe carryingcapacityof theenvironment agriculture forman. Yet, the moreeffective agriculturalproceduresare in reducingenvironmentallimitationsupon the productivityof y metiatdplnt Kdm) igte old in,miimmefeciea/ theagriculturalecology,themorelikelytheyare to createnew lat dmetiatd nirnmntcotrbuedb in cpait o te opportunitiesfor failuresof the system.And as agriculture idiat "exes" oplaio (Kom; roenlie,poultin.Arow createshigherand higherpopulationlevels,the effecton the (Pd) .~ ~ ~~~~ societyof the failuresof the systemwill becomeincreasingly tragic. Successfulagriculturalsystems require increasingly Timeabc successfultechniquesofenvironmental manipulationmerelyto maintainthe statusquo. andpopulation. between FIG. 3. The relationship Heavy productivitv Instabilityand dispersal.The interactionof increasein pro4iicrg ptfevn t tbd/ ductivityand increasein instabilityof productivity has been responsiblefor the tremendousspread of agriculturaltechniques.To understandthissomewhatparadoxicalsituation,it is species (Tahvanainen and Root 1972). As noted by Feeny to speculateas to whetherthevul(1973:14), "It is interesting necessarv to u,nderstand] how 762 anv animal nonaio,T1cn resnonAs CURRENT ANTHROPOLOGY a declinein foodsupplymaybe expectHumansexperiencing ed to respondin the same manner.A dropin Kd,,, willencourage part ofthepopulationto leave and establishitselfin a new area. A slowdeclinein relativeproductivity suchas thatoccurringat Pointa maybe due to ecologicalor edaphicdegradation becauseofagricultural occurring practices.Whilelargechanges in populationwill not necessarilyoccur,groupsmay leave in in whichto farm.Suddenand searchof "better"environments drasticdeclinesin relativeproductivity such as are shownat Pointsb and c willalso cause emigration. In thesecases we may assumethatemigration willbe encouragedby anotherfactorin additionto thesearchfora "better"agriculturalenvironment. If a drasticdrop in production(a famineor a sudden great scarcityofcultivatedfoods)occurs,it is likelythatthepopulation will returnto the exploitationof nondomesticated food sources.We have alreadynotedthatthefamineneed notbe an "objective"lack ofpotentialcaloriesin orderto be perceivedas one by thepopulation.However,sincean agriculturaleconomy can supporthigherpopulationlevelsthana gathering economy, and since at least certainnonagricultural domesticateshave beenlost,partofthepopulationwillbe forcedintonewareas in searchofwildresources.Thus a declinein Kdomwillbe especially noticeable to an agriculturalpopulation because of several interrelated factors:higherpopulationlevelsin any givenarea, losses of wild food sourcesand nonagricultural domesticates, and changesin theperceptionofwhatconstitutes foodscarcity. The onlyotherlikelyand effective responseofa societyto a dropin K(iomis increaseddemandforenvironmental control.If this occurs,however,it may simplybe incorporatedinto the graph by increasingthe amplitudeof the Kdom curve.In this modelincreasesin productivity alreadyincorporatetechniques of environmental control;thus theycannotbe reenteredas a newvariable.Also,as has been stressed,environmental control is intimatelytiedup withinstabilityin yield;decreasesin Kdom are inevitableeffectsof an agriculturalsystemexistingin a variable and evolvingenvironment.At best, environmental manipulation willdelaytheneedofthesocietyto finda solution to theproblemof theexcesspopulationinducedby theperiods of "successful"agriculturalproduction. It is importantto recognizethat theseemigrantgroupswill probablytake withtheman agriculturaltradition;theinstability created by agriculturalsubsistencewill bringabout the spreadofthesystem.Besides theconservatism inherentin any society,anotherfactorfacilitatestheemigration ofagricultural populationswithoutloss of agriculturaltechnology.The environmentalcontrolsinherentin agriculturalbehaviorpermit easy colonizationof new regions.Emigrantgroupsfrommost societiesrequirea definableset of preexisting nonagricultural conditionsiftheyare to maintaintheirmodeofsubsistence.Of course,agriculturalsocietiesrequiredefiniteecologicalconditionsalso, but the relativelyslow spreadof agriculturalsocieties, such as posited here,will allow time foradaptation by crops to gradientsin the environment. Secondarydomesticationwillpermitcolonizationof the fieldsand gardensby new, better-adaptedplants,and eventuallya wholenew ecological zone may open up to theagriculturalist. We mightalso briefly note that whilethe activitiesof most nonagricultural peoples do not interferewith subsequentutilizationof the land by agriculturalists, theconverseis farfromtrue. DISPERSAL AND INNOVATION Domesticatory and agricultural systems. We may summarizethe last sectionby sayingthatthedynamicinteraction betweenan increasingKdomand thePd places theagriculturalsocietyat an advantagerelativeto societieswithothermodesofsubsistence in termsofpotentialforgrowthand dispersal.Agriculture, by inducingenvironmental instability,creates the conditionsfavorableforits ownspread: theenvironmental controlinherent Vol 21 * No. 6 * December1980 Rindos:ORIGINS AND SPREAD OF AGRICULTURE notonlyspawnsnewpopulationsand sendsthem in agriculture but also allows themto continuein offintonewenvironments, the same subsistencepattern. manipulation The close connectionbetweenenvironmental and instabilitiesin productionwas of majorimportancein the evolutionof domesticatoryinteractionsinto genuineagricultural systems.Clearly,agriculturedid not springfullydevelopedfromthethighofculture.The earliesttypesofagricultural parts of existingsubsistence techniqueswere well-integrated strategies.Activitiesthat were performedfor other reasons The on the local environment. could not help but have effects the importanceoftheclearingofbrushforshelterconstruction, destructionof trees for defensiveor economicreasons, the burningofgrasslandsas an aid to hunting,theselectivepreserusefulplant or tree,and the creation vationofan immediately ofdumpheaps nearhumanhabitationsfortheevolutionof the techniquesof earlyagriculturalsystemshas been discussedat lengthin the literature.Preciselyhow theseactivitiesbrought about the transitionto a totallyagriculturalway of life has been less than clear. Especially confusingis the recognition thatmanyofthetechniquesmaybe knownto man withouthis necessarilyutilizingthemin a subsistencesystem.The model thus far developedfor the originand spread of agricultural systemsmay be extended,with certain qualification,to an interactionsevolvedinto of how domesticatory understanding agriculturalsystems. We mayfirstconsidera nullcase: A giventechniqueincreases fortheearlydomestithecarryingcapacityoftheenvironment an increasein cated plant (increasesKdwn)). There is therefore humanpopulationin the area. However,if onlythe carrying capacityof the regionforhumanswereto rise-that is, ifnow the same area could supporta greaternumberof humanstheinitial populationnumberswouldremainconstantfollowing resultantfromthis increase.However,the"culturalfecundity" change in techniquewould be extremelylow. If emigration capacity,thenemigrawerea fixedproportionof reproductive tionwouldonlyincreasein directproportionto the increasein population.If emigrationwere the resultof extrinsicfactors, rateswouldremainunchanged.If,however,another emigration formof behaviorwere to increaseboth carryingcapacityand ofthecarryingcapacity,we couldpositthesame theinstability sequence of eventsas in the dispersalof agriculturalpopulations.We have spokenof the "success" attendantupon techWe maynowmodifythe manipulation. niquesofenvironmental conceptof successto includethe probabilitythat certaintypes willprovidethecause of theirown dispersal.We may ofactivity potential"of a even speak, allegorically,of the "reproductive societypracticinga givenformofbehavior.The greatestreproductivepotentialwould arise when the relationshipbetween productivity(Kdom)and instability(expressedas Pd) is such that the emigrantpopulation,over time,wouldbe maximized. Theoretically,an increasein the reproductivepotentialof a societycould come about withoutincreasein absoluteproductivityifan increasein instabilityalone wereto occur.It seems unlikelythat thiswouldhave happenedin the developmentof because ofthepressures, alreadydiscussed,towards agriculture domestithe natural selectionof continuallyhigher-yielding cated plants,but it shouldbe recognizedas a possibility. We may restatethis insightby notingthat those systems Pd is thedirect whichmaximizePd willspreadmostsuccessfully. expressionof the interactionof Kdom and Kdom. Thus, fromthe behaviorswereappearing, veryfirststagesin whichagricultural of unstablesystemswas a tendencytowardsthe proliferation evident.Of course,thisis not to claim that Kdom, the average It is probably ofa system,is totallyunimportant. productivity at least today,whereperiodicshortagesin highlysignificant, one area are at least potentiallyamenableto solutionby the importof food fromotheragriculturalregions.However,the 763 ofKdomintoa modelforagricultural incorporation originsseems inappropriate. Theslowevolution ofdomesticatory systems. Perhapsthegreatest anomalyforthoseacceptingthe revolutionary viewofagriculturaloriginsis the observationin the archaeologicalrecord thatwell-domesticated plantsare foundin eventhemostprimitiveagriculturalcontexts.This is not in keepingwiththe view that earlyagriculturaltechniquesprovidedthe selectiveforces whichtransformed thewildplant intothedomesticate.If agriculturaltechniquesarose beforethe domesticatedplant, we wouldexpectto findnumerousintermediary formsshowingthe selectivepowerof agriculturaltechniqueson the evolutionof the domesticatedplant. Anotherhighlyconfusingissue for thosebelievingin a few"centers"of agriculturaloriginis the existenceofnumerousspeciesofplantsthatseemto have independentlyenteredagriculturalsystemsovervast areas. Both of theseproblemsare solvedif we accept the coevolutionaryinterpretation of the evolutionof the domesticated plant. As we have noted,domesticatory systems,especiallyto the extentthat theyare developinginto agriculturalsystems, will disperseinto new areas by means of the same instability maximizationprocessesjust discussed.This dispersalwill be accompaniedby opportunities fortheevolutionand acquisition ofnewdomesticates. New domesticatesmayevolve domesticationsymbiosiswithmanas he movesintonewareas. Also,since human-coevolved plants are not culturallybound,the movement of already coevolved domesticatesbetween coexisting domesticatory societieswillbe easy. This willpermita society to acquire new domesticatesand perhapsto move theminto new regions.Of course,not all domesticatory societiesneed developintoagriculturalsocieties,but thosethat do willbring withthemtheplantswithwhichtheyalreadyhave coevolved relationships.Thus "early agricultural societies" will be characterizedby well-developeddomesticatedplants coming fromseveraldifferent sources. Implicitin muchofthelogicthusfarhas beentheassumption that domesticatory societiesevolve moreslowlythan agricultural ones. This assumptiondeservessome comment."Pure" as we have alreadynoted,lack the domesticatory relationships, importantinstability presentin agriculturalsystems.Thus the spread of domesticatory societieswill be dependentupon factorsextrinsicto thedomesticatory It willbe much relationship. morelike that of nondomesticatory societies.Agricultural systems,in contrast,are literallydriveninto new localitiesby environment crises. periodicallyrecurrent Anotherimportantdistinctionbetweendomesticatory and agriculturalsystemsis related to anotheraspect of environmentalcontrol.Whileagriculture acts directlyupon the carryforthedomesticatedplant,the ingcapacityoftheenvironment purely domesticatorysociety must rely upon the inherent forits early coevolved carryingcapacity of the environment plants. Thus the populationlevel attainable by the purely fromthoseof domesticatory societyis, initially,littledifferent societies. nondomesticatory Finally, this hypothetical,purelydomesticatorysocietyis totallydependentupon natural,albeithuman-aided,dispersals of the domesticatedplant into new regions.This must of necessitybe a slowprocess.The numberofplaces available for colonizationby anyplantin a climaxecologyis bothstableand limited.As we ha...
Purchase answer to see full attachment
User generated content is uploaded by users for the purposes of learning and should be used following Studypool's honor code & terms of service.

Explanation & Answer

Attached.

Report: Discussion_Questions

Discussion_Questions
by HAL

General metrics
2,561

370

29

1 min 28 sec

2 min 50 sec

characters

words

sentences

reading
time

speaking
time

Score
99

Writing Issues
1

Issues left

1
Critical

Advanced

This text scores better than 99%
of all texts checked by Grammarly

Plagiarism
This text hasn’t been checked for plagiarism

Report was generated on Wednesday, Oct 7, 2020, 07:41 PM

Page 1 of 5

Report: Discussion_Questions

Writing Issues
1

Correctness

1

Improper formatting

Unique Words

54%

Measures vocabulary diversity by calculating the
percentage of words used only once in your
document

unique words

Rare Words

30%

Measures depth of vocabulary by identifying words
that are not among the 5,000 most common English
words.

rare words

Word Length

5.3

Measures average word length

characters per word

Sentence Length

12.8

Measures average sentence length

words per sentence

Report was generated on Wednesday, Oct 7, 2020, 07:41 PM

Page 2 of 5

Report: Discussion_Questions

Discussion_Questions
DISCUSSION QUESTION 2
Running Head: DISCUSSION QUESTION 1

Discussion
Student's Name:
Professor's Name:
Date:
What are the differences between primary sources and secondary sources?
Please provide some examples of primary and secondary sources from this
week's readings.
Primary sources are based on historical documents that are considered to have
facts on data. They hold real evidence over a particular subject that research
will use to refer to making studies. Some examples of primary data sources
that can be accessed include new articles, count records, property records,
diaries, military reports, personal journals, government records, among many
others (Sutton, 8). Secondary sources are those whose work is an interpretation
of other sources, issues, history, and concepts of a poor phenomenon. This
means it can have a series of data removed from its originality in the primary

Report was generated on Wednesday, Oct 7, 2020, 07:41 PM

Page 3 of ...


Anonymous
Awesome! Made my life easier.

Studypool
4.7
Trustpilot
4.5
Sitejabber
4.4

Similar Content

Related Tags