The Morro Bay Fauna: Evidence for a Medieval Droughts Refugium on the Central California Coast

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THE

MORRO

BAY

FAUNA:

EVIDENCE

FOR

A

MEDIEVAL

DROUGHTS

REFUGIUM

ON

THE

CENTRAL

CALIFORNIA

COAST

TerryL.Jones,DeborahA.Jones,KaceyHadick,KennethW.Gobalet,JudithF.Porcasi,and

WilliamR.Hildebrandt

Arobustcollectionofmammal,bird,fish,andshellfishremainsfroman8,000-yearresidentialsequenceatMorroBay,asmall,

isolatedestuaryonthecentralCaliforniacoast,showsastrongfocusonmarinespeciesduringtheMiddle-LateTransition

culturalphase(950–700calB.P.),whichlargelycoincideswiththeMedievalClimaticAnomaly(MCA).Previousstudieshave

providedmodestevidenceforincreasedfishingandrabbithuntingduringtheMCAinadjacentregions,buttheMorroBay

findingssuggestadistinctivemarine-focusedsubsistencerefugiumduringtheperiodofdrought.Specifically,thesequence

showsstrikingall-timepeaksinmarineandestuarinebirds,fishNISP/m3,andfish/deer+rabbitsduringtheMCA.Heavy

exploitationoffish,aquaticbirds,rabbits,andshellfishsuggeststhatthebowandarrow,whichseemstohavearrivedinthe

areaatthistime,hadlittleimpactonlocalsubsistencestrategies.

Lasecuenciaresidencialdeunos8,000añosdeduraciónprocedentedeMorroBay(unpequeñoestuarioaisladoenlacosta

centraldeCalifornia,EstadosUnidos)estácompuestaporungranconjuntofaunísticoqueincluyerestosdemamíferos,

aves,pecesymariscos.Dichoconjuntofaunísticoindicaunafuertedependenciadelasespeciesmarinasdurantelafase

culturaldelaTransiciónMedia-Tardía(950–700cala.P.),lacualcoincideplenamenteconlaanomalíaclimáticamedieval

(MCA).Algunosestudiosprevioshanmostradomodestasevidenciassobreelincrementodelapescaylacazadelepóridos

durantelaMCAenlasregionesadyacentes.Sinembargo,enMorroBayloshallazgossugierenlapresenciadeunrefugio

basadoenlosrecursosmarinosaniveldesubsistenciaduranteelperiododesequía.Específicamente,lasecuenciamuestra

unospicosnuncaantesvistosenelnúmerodeespecímenesidentificados(NISP)pormetrocúbicoderestosdeavesmarinas

ydeestuario,mariscosypecesenproporciónalacantidaddecérvidosylepóridosduranteelMCA.Laintensaexplotación

delapesca,lasavesacuáticas,loslepóridosylosmariscossugierenquelallegadadelarcoylaflecha,coincidenteconel

mismoperiodo,tuvounimpactoreducidoenlasestrategiasdesubsistencialocales.

O

ne of the most long-standing issues

in the study of western North

Ameri-canhunter-gathererprehistoryhasbeen

the relative influence of paleoclimatic

varia-tion on cultural change. Since at least the

1940s,archaeologistshavebeeninterestedinthe effects of prolonged periods of aridity on for-agingpopulations.Initiallyfocusedonthe

mid-Holocene warm period (known alternately as

theAltithermal,Hypsithermal,orXerothermic;

Antevs 1948, 1955;BaumhoffandHeizer 1965; Byrne 1979;CurreyandJames 1982;Deanetal.

1985;deMenocal 2001;Jennings 1964;Kennett etal. 2007;Moratto1984:544–547;Morattoetal.

1978),debatehassinceshiftedtotheMedieval

ClimaticAnomaly(MCA)ofthelateHolocene

(Arnold 1992; Basgall 1999; Bettinger 1999;

Boxt et al. 1999; Collins 2010; Cook et al.

TerryL.Jones DepartmentofSocialSciences,CaliforniaPolytechnicStateUniversity,SanLuisObispo,CA93407,

USA(Tljones@calpoly.edu,correspondingauthor)

DeborahA.Jones FarWesternAnthropologicalResearchGroup,1725DiabloDrive,SanLuisObispo,CA93405, USA

KaceyHadickandWilliamR.Hildebrandt FarWesternAnthropologicalResearchGroup,2727DelRioPlace,SuiteA, Davis,CA95618,USA

KennethW.Gobalet DepartmentofBiology,Emeritus,CaliforniaStateUniversity,Bakersfield,CA93311Current Address:625WisconsinSt.,SanFrancisco,CA94107,USA

JudithF.Porcasi CotsenInstituteofArchaeology,UniversityofCalifornia,LosAngeles,CA90095,USA

AmericanAntiquity82(2),2017,pp.203–222

Copyright©2017bytheSocietyforAmericanArchaeology

doi:10.1017/aaq.2016.31

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2004; D’Oro 2009; Fischman 1996; Gamble

2005;Herweijeretal.2006;Johnson2004;Jones etal. 1999; Jones andBrown 1999; Jonesand Schwitalla 2008,2012; Kennett 2005; Kennett

and Kennett 2000; Lambert 1994; Raab and

Larson 1997; Schwitalla 2012; Walker and

Lambert 1989).Stine(1994) definedtheMCA

as a period of prolonged and severe droughts

between ca. 1150 and 600 cal B.P. Originally

recognizedinthepaleoclimaticrecordsof both

California and Patagonia, the MCA is now

reasonably well accepted as a distinctive

cli-maticinterval,withrecentstudiesconfirmingthe occurrenceofepicdroughtsandelevatedaridity

inNorthAmericaduringmedievaltimes(Cook

etal. 2004;Grahametal. 2007, 2011;Graumlich

1993;Mannetal. 2009),aswellascorrelations

with major cultural changes (including

large-scalemigrationsandcollapse;e.g.,Bensonand Berry 2009;Bensonetal. 2007, 2009;Berryand Benson 2010;Billmanetal. 2000).

InCalifornia,theeffectsofmedievaldroughts onnativeforagingpopulationshavebeendebated intenselyformorethantwodecades(seereviews bySchwitalla 2010;SchwitallaandJones 2012). In most of thisregion, the cultural phase that

coincideswiththeMCAisknownasthe

Middle-LateTransition, dated ca. 950–700 cal B.P. In

central and southern California, most scholars

acceptthatchangesinexchange(Arnold 1992; Gilreath 1995;Gilreath andHildebrandt 1997; Jones etal. 1999;Jones andSchwitalla 2008), settlementpatterns(Arnold1992;Kennett2005),

regional abandonments, (Jones and Ferneau

2002;Gardner 2006;JonesandSchwitalla 2008; Whitley etal.2007),anddiseaseandviolence (Fischman 1996;Lambert 1994, 1997;Raaband Larson 1997;WalkerandLambert 1989; Weiss

2002)duringtheMiddle-LateTransitioncanbe attributedtodemographicstressescausedby

pro-longedandseveredroughts.However,somehave

arguedthatthedroughtswerenotsevereenough

to causemajor problems(Basgall 1999,2008;

Bettinger 1999)or thatNative mechanismsfor

water storage and resourceredistribution were

sophisticated enough to mitigate any serious,

negativeconsequences(e.g.,Gamble 2005)and that,aboveallelse,Nativepopulationssurvived

(Arnold and Walsh 2010:34). In this regard,

findings from northern California have been

muchlesscompellinginimplicatingdroughtas

aprimaryagentofculturalchange.Somestudies

of the skeletal record fromSan Francisco Bay

andtheSacramento-SanJoaquinValley(D’Oro

2009;Pilloud 2006;Schwitallaetal. 2014) have

not found the same spike in violence during

the MCA/Middle-LateTransitionthat Lambert

(1994)documentedintheSantaBarbara

Chan-nel.Analysis ofametadatasetofburials from

the San Francisco Bay area confirmed a peak

in projectile violence during the Middle-Late

Transition,butalsoshowedaconcurrentpeakin dentalcariouslesions,whichwasattributedtoa heavyrelianceonacornstorageandconsumption (SchwitallaandJones 2012).Thelatterindicates viabilityof theacorn cropduringthe droughts

in central California and some measure of a

reliable food base. Subsistence patterns based

onfaunalremainsfromSanFranciscoBayhave

alsomorecommonlybeenattributedtoeconomic

intensification (Broughton 1997, 1999) rather

thanclimaticallyinducedculturalchange.Most recently, Bettinger (2015) suggested that the

medievaldroughtsmayhaveamplifiedprocesses

thatwerefundamentallyhistoric/diffusionaryin nature,astheintroductionofthebowandarrow intoCaliforniaultimatelyfacilitatedmore inten-sive,privatizedeconomicsystems.

When Arnold (1992) first attributed settle-mentandsocialtransitionsonthesouthern Cali-forniaIslandsduringtheMiddle-LateTransition

(MLT) toclimatic changes,she suggested that

theprimaryproblemconfrontingthesemaritime

hunter-gathererswaswarmseasurface

temper-aturesthat drasticallyreduced the productivity

of the marine food base. Subsequent studies

(KennettandKennett 2000)showedthatsea sur-facetemperatureswereinfactcooland produc-tiveduringtheMCAandthatsubsistencestress wasmoreaproductofreducedprecipitationand aresource-depletedterrestrialenvironment.The

native response to the latter, which has been

further supported by subsequent paleoclimatic

studies (Barron et al.2015), was an increased focusonmarineresourcesduringthedroughtsas wellasviolentcompetitionforlimitedresources (KennettandKennett 2000).Theideaofamarine

subsistence focus during MCA subsequently

becamecommononthecentralCaliforniacoast,

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increasedexploitationoffish,marinemammals,

and/orshellfishduringtheMLT(e.g., Codding

and Jones 2007; Codding et al. 2010; Jones

2003;Joslin 2010),butthecollective empirical

evidence has not necessarily been compelling.

Mikkelsen et al. (2000), for example,

hypoth-esized that Morro Bay,a small estuary on the

central coast, may have served as a refugium

during the medieval droughts, but support for

theideawasnotimmediatelyforthcoming.Here

we affirm that hypothesis with a robust body

of faunal evidence accumulated in the last 15

yearsthatclearlyshowsaheavyfocusonmarine

resourcesalongtheshoresofMorroBayduring

the MCA.Frequenciesof fishandmarine bird

remainsfromthissettingaresignificantlyhigher

during the MLT than at any other period in

the8,000-yearoccupationalsequence,whichwe

interpret as evidence for an intense focus on

marine foods in the face of reduced terrestrial productivitycausedbydrought.Whilethefocus onfishandseabirdsislogicallyconsistentwith a depletedterrestrial biome,the availability of these foods also suggests that, at least in this setting,theeffectsofdroughtmaynot necessar-ilyhavebeen catastrophic.Further, the dietary

responseevidentatMorroBayshowsnoobvious

consequencesfromintroductionofthebowand

arrow,whichdiffusedintotheareaataboutthe sametime,andhasbeenhypothesizedasatleasta contributing(Kennett 2005;KennettandKennett

2000;Kennettetal. 2013;Lambert 1994),ifnot primary, causeof culturalchanges. Thisisnot

to saythat the bow mightnot have been used

as a weapon in intergroup conflict and that it

couldhaveledtoincreasedviolence,butitdid notcontributetosubsistencechangeatthistime.

Setting

MorroBayisashallow8.1km2coastalestuary

situated on the central Californiacoast in San LuisObispoCounty(Figure1)thatwasoccupied

byspeakersofObispeñoorNorthernChumashat

thetimeofhistoriccontact(Golla2011:194).The bayoccupiesthenorthernendofasoutheastward

trending depression that encompasses the Los

Osos and San Luis valleys (Cooper 1967:74).

Sand dunes surround the bay, and onearm of

the dunesystemisasand spitthat serves asa

barrierbetweentheestuaryandtheouterEstero

Bay.Entrance tothe bayfrom theopen ocean

was significantly improved by construction of

breakwaters in the 1940s by the U.S. Army

CorpofEngineers.Priortothatconstruction,the

mouthofMorroBaywasopentosurfactionand

wasunsuitableforshipportage.

MorroBay’sMediterraneanclimateis

char-acterized by cool moist winters and warm

dry summers,with frequent fog betweenJune

andSeptember.Annualaverageprecipitationis

370 mm/yr,witharangefrom 152to610 mm

(GerdesandBrowning 1974:21).Priorto

exten-sive moderndisturbance anddevelopment, the

natural vegetationfostered bythe combination

ofmodestrainfallanddunesoilswasacoastal

sagebrushshrub (Hoover 1970; Kuchler 1977;

Ritter2006).CommonspeciesincludeCalifornia sagebrush(Artemesiacalifornica),coyotebrush (Baccharis pilularis), poison oak ( Toxicoden-drondiversilobum),andblacksage(Salvia mel-lifera).Coastliveoakforestisonlyaverysmall

component of the vegetative landscape. This

differssignificantlyfromthe opencoast tothe south(theDiabloCanyonorPechoCoast),where oakforestismuchmoreextensive(Coddingetal.

2010;Hildebrandtetal. 2010;JonesandCodding

2010;Jonesetal. 2008).

Likemost estuarieson theCaliforniacoast, MorroBayprovideshabitatforanextensivesuite

of marine and terrestrial animals. In terms of

birds,the bayisan integral part of thePacific

flywayandisvisitedbyamyriadof migratory

species, particularly in the winter. California

FishandGamehaveidentifiednofewerthan75

speciesthatvisitor resideyear-roundatMorro Bay(Edell 2006; GerdesandBrowning 1974).

The estuary attracts the snowy egret (Egretta

thula),thegreatblueheron(Ardeaherodias),and avarietyofotherwaterfowl,shorebirds,andbirds

ofprey. Onlyfourspecies ofmarine mammals

areknowninthebaytoday:Californiasealion (Zalophus californianus), harbor seals (Phoca vitulina),Stellar’ssealion(Eumetopiasjubatus), andtheseaotter(Enhydralutris),butthe

archae-ological record indicates that elephant seals

(Miroungaangustirostris)(Ricketal. 2012)and northern fur seals (Callorhinus ursinus) (Rick etal. 2009)wereoccasionallypresentnearshore

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Figure1.MorroBay,California,witharchaeologicalsitesdiscussedintext.

native terrestrial mammals were documented

aroundtheshoresofMorroBayin1974(Gerdes

andBrowning 1974).Theseincludeseveralsmall burrowingspeciesthatareagentsofbioturbation

within local archaeological sites. The largest

herbivore currently present is the black-tailed deer (Odocoileus hemionus),although tule elk (Cervus elaphus nannodes) remains are repre-sentedinsmallamountsatafewarchaeological sites (e.g., Mikkelsen et al. 2000). Cottontail andbrushrabbits(Sylvilausspp.)werecommon inhabitantsofthecoastalscrub,alongwithjack rabbits (Lepuscalifornicus). Historically, local

carnivoresincluded brown bears(Ursus

horri-bilis),mountainlions(Felisconcolor),bobcats (Lynx rufus), gray foxes (Urocyon cinereoar-genteus),coyote(Canislatrans),andlong-tailed weasels(Mustelafrenata).

Withrespecttofishes,theCalifornia

Depart-ment of Fish and Game identified 66 species

(64natives) withinMorro Bayin1966,which

weresubsequentlyconfirmedbyFierstineetal.

(1973).Thesesurveysshowedthatthreespecies

accountedformorethan50percentof thefish

inthebaybynumbercaught:northernanchovy

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Table1.MorroBayStudySites.

TotalExcavation TemporalComponents

Trinomial Volume(m3) (Periods) Reference

CA-SLO-14 21.49 Middle FarWesternAnthropologicalResearchGroup(2016)

CA-SLO-23 92.39 Early,Late FarWesternAnthropologicalResearchGroup(2016)

CA-SLO-165 72.90 Millingstone/LowerArchaic, Mikkelsenetal.(2000) Early,Middle

CA-SLO-215 5.00 Millingstone/LowerArchaic Jonesetal.(2004)

CA-SLO-457 27.70 Middle-LateTransition FarWesternAnthropologicalResearchGroup(2016) CA-SLO-458 19.74 Early,Middle-LateTransition FarWesternAnthropologicalResearchGroup(2016)

CA-SLO-626 24.54 Late FarWesternAnthropologicalResearchGroup(2016)

CA-SLO-812 11.28 Millingstone/LowerArchaic, FarWesternAnthropologicalResearchGroup(2016) Early,Middle

CA-SLO-977 1.00 Early Dallas(1992)

GobaletandJones(1995)

Total 276.04

aggregata), and black perch (Embiotoca jack-soni).Atleast11species,includingblackperch,

shiner perch, lingcod (Ophiodon elongatus),

Pacificstaghorn sculpin(Leptocottusarmatus), and starry flounder (Platichthys stellatus), are year-roundresidentsoftheestuary.Asmanyas

29otherspeciesareseasonalmigrants(Gerdes

andBrowning 1974).

ThehistoryofresearchatMorroBayreflects the relative isolation of the estuaryaway from

the major centers of archaeological inquiry in

California. While the San Francisco Bay shell

middensbegantobeseriouslyinvestigatedover 100 years ago(Nelson 1909), the first sitesat MorroBaywerenotrecordeduntilthelate1940s,

the first excavation was not completed until

1961(Clemmer 1962),andthefirstradiocarbon

dates were not obtained until the late 1970s.

Research on the prehistory of Morro Bay has

takenplacewhollywithintheCulturalResource

Management(CRM)era.Landssurroundingthe

bay are held in private (small residential lots)

andbyCaliforniaStateParks,andmostof the

earlyCRMworkonthesepropertieswaslimited

torelativelysmall-scalesurvey andtesting.As of 2015,at least 50 siteshadbeen tested,and radiocarbondatesareavailablefrom28ofthese,

butmost of theseinvestigations,while

accom-plishing the conservation objectives for which

theywereintended,didnotproducesubstantive

samples of well-dated faunal remains and/or

artifacts. In the last 15 years, there have been severalsubstantialinvestigationsontheshoreof

theestuary,alongwithseriousattemptsat syn-thesis(e.g.,Bertrando2000,2004a, 2004b;Jones etal. 2004;Mikkelsenetal. 2000)highlightedby

therecentLosOsosWastewaterProject,which

yielded substantial artifact andfaunal samples fromeightsitesinthesouthernportionofthebay

(FarWestern AnthropologicalResearch Group

2016). The Los Osos findings, in conjunction

with other local research, have established an

8,000-yearoccupational historyfor MorroBay

markedbyasubstantialquantityoffaunaldata.

Herewesummarizethefish,mammal,bird,and

shellfish remains from nine sites investigated

over the last two decades (Table1, Figure1), representingallperiodsinthissequence.

Methods

FieldRecovery

Theinvestigatedsiteswereestuarineshell

mid-densmarkedbycombinationsofmammal,bird,

and fish bone, shellfish remains, fire-affected

rock, flaked stone tools and debitage, ground

stone,boneandshelltools,andoccasional fea-turesincludinghumanburials.Allinvestigations

atthesedepositswerecompletedbetween1990

and 2013 (Table1). Two sites, CA-SLO-215

andCA-SLO-977, weresubjected torelatively

modesttesting(1.0–5.0m3)toevaluatethetype

and distribution of materials present (Dallas

1992; Joneset al.2004).Largersamples were

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2000),CA-SLO-14,CA-SLO-23,CA-SLO-457,

CA-SLO-458,CA-SLO-626,andCA-SLO-812.

Total recoveryvolumefortheseninesiteswas

276.04m3 (Table1).Excavatorsobtainedmost

samplesfromthesedepositsviadryfield

screen-ing (3 mm mesh) from 1 × 2 m and/or 1 ×

1 m units test units or trenches. Excavators

collected vertebrate remains in unit-level lots fromallmanuallyexcavatedunitsexceptinrapid recoveryunitsemployedonalimitedbasisatone

site(CA-SLO-23in2013).

The abundanceof fishand shell remainsin

the deposits required a subsampling strategy.

Control units and column samples provided

the assemblage of fish remains at most sites,

while component-associated subsamples

pro-videdsamples atsitesthat producedextremely

largenumbersoffishbones.Thelatterincluded

a representative sample of control units

(pro-cesseddrywith1/8-inchmesh)andone-column

sample level (representing 20 ×20 ×10 cm)

of recovery volume processed in the

labora-torywithwaterthrough nested1/8- and1/16-inch

mesh.1

Shellfishremainswere,byfar,themost abun-dant,visibleculturalconstituentsinthedeposits.

Column samples provided a primary way of

recoveringacontrolledrepresentativesampleof shellremainsfrombothfeatureandnon-feature

site deposits. The shell column samples were

laboratory-processedwithwaterthroughnested

1/4-,1/8-,and1/16-inchmesh,dried,cataloguedby

screensizeandunitprovenience,andsortedfor cultural andnoncultural constituents. Analysts examinedtheshellremainsfrom1/4- and1/8-inch

meshsamples.

Analysis

UsingreferencecollectionsfromtheLos

Ange-lesCountyMuseumofNaturalHistoryandthe

ZooarchaeologyLaboratoryattheCotsen

Insti-tuteofArchaeologyatUniversityofCalifornia,

LosAngeles,Porcasiidentifiedbirdandmammal

remainsfromallbutoneofthesites.2 Jameson andPeeters(1988)andPeterson(1990)provided

the nomenclature and taxonomyfor mammals

and birds, respectively. Porcasi identified all

specimenstothemostdiscretetaxonomiclevel

possible based on diagnostic features. In the

absenceofsuchfeatures,sheassignedbonesto

classes(i.e.,Mammalia,Aves,etc.)and(forbirds andmammals)tosizecategories(small,medium, orlarge).Inaddition,sherecordedtothedegree possibletheelement,partofelement,side,age,

number, weight, and evidence of modification

(i.e.,burned,gnawed,cut,orworked).The

Mar-galefIndexprovided ameasureof assemblage

diversitytoevaluatedietbreadthandthe

Berger-Parker index (in reciprocal form) to evaluate

evenness or relative specialization (Magurran

1988).

Gobaletidentifiedtheelementandtaxonomic

categoryof eachfishspecimenusingreference

materials.3 Findings were summarized by the

number of identified specimens (NISP). The

nomenclature and current taxonomyfor fishes

follows Pageet al. (2013). Forthis paper, we

define “identified” as specimens assigned to

at least a family. Weexcluded specimens that

wecouldclassifyonlyasElasmobrachiomorphi

(sharks, skates, rays) or Actinoptergii4

(ray-finned fishes, 16,653 elements). Jones,

Gob-alet, and Codding (2016) and Jones, Gobalet,

Mikkelsenetal.(2016)discusssomeaspectsof

thefishassemblages.

D. Jones and Hadick identified the

shell-fish using reference collections at California

PolytechnicStateUniversity,SanLuisObispo,

and Far Western Anthropological Research

Group, recording the weight of shell per

species.

Basedonthesemethodologicalprotocols,the

sample available from Morro Bay consists of

2,247 bird and mammal bones from an

ana-lytical volume of 141.60 m3, and 19,235 fish

bonesidentifiedtoameaningfultaxon(generally

familyor better) froman analyticalvolumeof

127.1 m3. Shellfish remains represent a total

recoveryvolumeof1.088m3.

ChronologyandDelineationofTemporal Components

Radiocarbondates(n=80)andtemporally diag-nosticshellbeadsandprojectilepointsprovided verticalandhorizontalidentificationof compo-nents(Table2).Seventy-eightofthedateswere

fromsingle-shellsamples,whiletheremaining

twowerefromcharredplantremains.Alldates

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Table2.SummaryofMorroBayTemporalComponents.

N Analytical Analytical Analytical

N Temporally AgeSpan Excavation VolumeBird VolumeFishVolumeShell Trinomial Temporal RadiocarbonMeaningfulOne-Sigma Volume andMammal Remains Remains

CA-SLO- Perioda Dates Beads (calB.P.) (m3) Remains(m3) (m3) (m3)

23 Late 4 73 700–250 17.90 17.90 10.50 0.025

626 Late 3 34 700–450 24.50 21.40 11.70 0.032

Subtotal 7 107 700–250 42.40 39.30 22.20 0.057

457 Middle-Late 4 65 900–700 27.10 3.21 5.20 0.052

Transition

458∗ Middle-Late 1 5 1050–450 1.87 1.60 0.07∗∗ 0.070

Transition

Subtotal 5 61 1050–450 28.90 4.81 5.20 0.122

14 Middle 4 8 2050–1850 21.49 21.49 18.40 0.056

165 Middle 6 1 2400–900 1.20 1.20 1.20 0.020

812 Middle 2 6 2300–1800 3.30 3.20 2.90 0.060

Subtotal 12 15 2400–900 25.99 25.89 22.50 0.136

23 Early 8 10 4800–3350 73.21 9.00 14.60 0.077

165 Early 27 4 5700–3400 37.20 37.20 37.20 0.148

458 Early 2 0 5000–4750 17.58 9.30 9.30 0.024

812 Early 1 2 4200–4000 2.50 2.40 2.40 0.060

977 Early 3 0 3900–2800 1.00 1.00 1.00 –

Subtotal 41 16 5700–2800 131.47 58.90 64.50 0.309

165 Millingstone/ 3 2 8200–7200 3.50 3.50 3.50 0.024

LowerArchaic

215 Millingstone/ 10 0 7800–6880 5.00 5.00 4.40 0.310

LowerArchaic

812 Millingstone/ 2 2 8000–7400 4.90 4.80 4.80 0.130

LowerArchaic

Subtotal 15 4 8200–6880 13.40 12.70 12.70 0.464

Grandtotal 80 203 242.25 141.60 127.1 1.088

aLate=700–180calB.P.;Middle-LateTransition=950–700calB.P.;Middle=2600–950calB.P.;Early=5500–2600

calB.P.;Millingstone/LowerArchaic=10,000–5500calB.P. ∗Componentbasedmoreonbeadsthanradiocarbon. ∗∗Wet-screenedrecovery.

2016); a Delta R marine correction value of

290 ± 35 years (Ingram and Southon 1996)

was applied to the shell dates. Components

excluded portions of the excavation volume

that were disturbedor that exhibited excessive

temporal mixing so that the volumes

associ-ated with the analytical samples are smaller

thanthe totalrecoveryfromthe combinedsite

investigations.

ComponentFunction

InterpretationoftheMorroBayfaunacannotbe disassociatedfrom the roleof sitesinregional settlementsystems,giventhatanychangeinthe characterofsiteusecouldcontributetovariation intherelativefrequencyoffaunalspecies (Bin-ford 1978, 1980).Weevaluatedsettlement

func-tionbyconsideringtherangeanddiversityof

cul-turalmaterialsrecoveredfromeachcomponent,

thepresence/absenceofburialsorotherfeatures,

the volumetric density of formal andinformal

artifacts,theratiosofflakedtogroundstone,and theevidenceforseasonality(remainsof migrat-inganimals[Figure2]andseasonallyavailable

plant foods). We evaluated assemblage

diver-sity statistically using the Margolef Diversity Index.

Results

Analysis identified 15 temporal components

from the more substantive earlier excavations

atMorroBay(CA-SLO-165,CA-SLO-215,and

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January February March April May June July August September October November December

AQUATIC BIRDS

Greater white fronted goose

Redhead duck

Rednecked grebe

Black-legged kittiwake

Eared grebe

Canvasback

FISH

Bat ray

Shiner perch

Striped seaperch

Pile perch

Pacific hake

Redtail surfperch

MARINE MAMMAL

Northern fur seal

California sea lion

Figure2.MigratoryspecieswithseasonallyrestrictedappearancesatMorroBay.

LosOsosWastewaterproject.However,several

componentslackedadequatesamplesforcertain

constituents,asspecifiedbelow.

BirdsandMammals

Thirteencomponentsprovidedthesampleofbird

and mammal remains (Supplemental Table 1).

The Middle-period component from

CA-SLO-165producedveryfewbones,andthelarge

verte-brateremainsfromCA-SLO-977areunreported.

The total from the remaining 13 components

excludesremainsofallsmallburrowinganimals (e.g.,Botta’spocketgopher[Thomomysbottae]

and California ground squirrel [Spermophilus

beecheyi]), most of which are probably

intru-sive.The sampleincludes26speciesofducks,

geese, and other aquatic birds; 18 species of

marine birds; 6 terrestrial birds; 12 terrestrial

mammals;and6marinemammals.Overall,the

birdsandmammalsaredominatedbyterrestrial

mammalsthataccountfor65.5percentofNISP.

Dominant species are rabbits (Sylvilagus spp.;

NISP = 1075; 44.3 percent) and black-tailed

jack rabbit (NISP = 196; 8.1 percent). Mule

deer (Odocoileus hemionus), which was the

most abundant species inthe faunal collection

from Diablo Canyon and figured prominently

indebates aboutlarge gamehunting strategies

alongthecentralcoast(Hildebrandtetal. 2010;

Jones and Codding 2010), is decidedly less

abundantatMorroBay,representingonlyseven

percent(NISP=170)ofthebirdandmammal

inventory. The low frequency of deer and the

large numberof rabbits andhares almost

cer-tainlyreflecttheabundanceofsagebrushshrub

vegetationatMorroBay.

The number and diversity of bird remains

(9)

fauna and reflects the importance of the

estu-ary as a bird habitat. Ducks, geese, andother

aquaticspeciesmakeup19.4percent(NISP=

446)ofthecollection,followedbymarinebirds

(NISP=270;11.1percent).Mostabundantare

grebes(Podicepsspp.;NISP=144;6percent)

and brown pelicans (Pelecanus occidentalis;

NISP=78;3.2percent).Fewerbirdboneswith

less species diversity were reported from the

exposed rocky coast at Diablo Canyon to the

south(Jonesetal. 2008)

Marine mammals, dominated by sea otter

(NISP =59;0.4percent),are relatively

unim-portant in the Morro Bay collection, making

up less than 3 percent of NISP. This too

contrasts with the Diablo Canyon open coast,

wheremarinemammalsaccountedformorethan

21 percent of the identified bird and mammal

remains.

Ofparamountimportance,however,are

pat-terns across time (Figure3). Most striking in thisregardisvariationintherelativeimportance

ofterrestrialmammals.Throughoutmostofthe

sequence, terrestrial mammals, predominantly

rabbits and hares, account for no less than

69percentof the non-piscinevertebrate fauna. However,duringtheMiddle-LateTransition,this

figureplummetstoonly14.2percent,dominated

bycottontailrabbits(NISP =44).Atthesame

time,deerreachalowof1percent(NISP=5). Replacingterrestrialgameinimportanceduring thisintervalareaquaticandmarinebirds,which togetheraccountfor84percentofthenon-piscine

assemblagefor Middle-Late TransitionPeriod.

This dearth of terrestrial mammals, combined

with the high frequency of marine birds,

rep-resents aprofoundlydifferent patternthan that ofanyotherintervalinthe8,000-yearsequence, withaquaticbirdsbeingthreetimesmore

numer-ous than at any other time. Although marine

mammals remainedinsignificant (1.5percent),

the non-piscine remains show a striking shift

toward marine species during the Middle-Late

Transition. Following the end of this period,

terrestrialspecies againdominate(70percent), andmarine/aquaticbirdsreturntothelowlevels typicalfortherestofthesequence(25percent). Theheavyemphasisonaquaticbirdsandrabbits,

which together account for 95 percent of the

Middle-Late Transition non-piscine vertebrate

remains, suggests little if any reliance on

thebowandarrowforhunting,giventhatthese animals,especiallythe birds,weremorelikely trappedorsnared.Projectile pointsizeprofiles indicate, fairly convincingly, that the bow and

arrow arrived to the central coast during the

Middle-Late Transition or slightly earlier (ca.

1050calB.P.).ThisisconfirmedatMorroBay,

wherethesamecomponentsthatyieldedthe

rab-bitandbird-dominatedfaunalassemblagesalso

produced arrow-sized projectile points, albeit

in very small numbers (Far Western

Anthro-pological Research Group 2016). While the

appearanceofthebowandarrowmighthavebeen

associated with increased intergroup conflict

(Kennettetal. 2013;Lambert 1994),itinitially had little effect on subsistence hunting

strate-gies. This supports an idea advanced by Brill

(2014)thatthetechnologymayhavebeenused

morefor inter-humanconflict thansubsistence

in southern California. However, there is no

complementaryburialrecordfromMorroBayor

surroundingareasrobustenoughtocomparethe

faunalrecordwithskeletalevidenceforprojectile violence.

Findings from another recently identified

Middle-LateTransitionPeriodcomponent

pro-videsomesupportfortheheavyrepresentation

of marine animals in faunal assemblagesfrom

thisinterval around Morro Bay. CA-SLO-239,

nearthecurrentmouthofthebay,wasexcavated

in 1961 (Clemmer 1962), but its chronology

was unclear until the first radiocarbon dates

fromsitematerialswererecentlyreported(Jones

et al. 2017). Dates and temporal diagnostics

showclearlythat thesitewasinhabitedduring

the early Middle and Middle-Late Transition

periods.Faunalsamplingstrategieswerenot

con-sistent with current standards, andcomponent

definitionisimprecise,butthefaunalcollection

is nonethelessdominated by marine mammals

(NISP =39; 78 percent),including California

sealions(Zalophuscalifornianus; NISP=13)

and sea otters (Enhydra lutris; NISP = 13).

Unfortunately, owing to the era during which

the site was investigated, fish bones were not

collected, but the marine focus in the large

vertebratesisconsistentwithfindings fromthe

other Middle-Late components in the current

(10)

(a) Percentage of Marine/Estuarine Birds

90 80 70 60 50 40 30 20 10 0

Millingstone/ Lower Archaic

(b) Fish NISP/m³

1600

1400 1200 1000

800 600

400 200 0

Millingstone/ Early Middle Middle-Late Late

Lower Archaic

(c) Fish NISP/Deer + Rabbit NISP

1600

1400

1200 1000

800

600

400

200 0

Millingstone/ Early Middle Middle-Late Late

Lower Archaic

(d) Shellfish Weight (km)/m³

25

20

15

10

5

0

Millingstone/ Early Middle Middle-Late Late

Lower Archaic

Early Middle Middle-Late Late

(11)

Fishes

Gobaletidentifiedatotalof19,235fishbonesto ameaningfultaxon(generallyfamilyorbetter)

from an analytical volume of 127.1 m3 from

15components(SupplementalTables2and3).

The only sample available for one component

(the Middle-Late Transition at CA-SLO-458)

was recovered via wet-screening, which

typi-cally yieldshigher frequenciesof fish remains

than the dry-screening (Jones, Gobalet, and

Codding 2016) used at all other sites. Three

families/speciesdominatetherecordthroughout thesequence:surfperches,(Embiotocidae),

her-rings (Clupeidae), and New World silversides

(Atherinopsidae).Notsurprisingly,these

assem-blages varyconsiderably from thoseof Diablo

Canyon to the south, which was dominated

by open rocky coastfishes (Fitch 1972; Jones

et al. 2008). Surfperches include species that canbe taken eitherwithnets or as individuals withhooks/gorges.Herrings(includingsardines)

and silversides are small schooling fishes that

aremuch morecommonlytakenwithnets,the

formeroftenwiththeaidof watercraftandthe latterfromshore(Boone2012;Gause2002;Love

2011;Salls 1988).Thedominanceofsilversides

andsurfperchesthroughouttherecordsuggests

thatfishingwasundertakenwithnetsthroughout theHolocene.Thisissimilartofindingsreported

by Rick and Erlandson (2000) for the Santa

Barbaramainlandtothesouth.

While this singular emphasis on netting

smallschoolingfishisapparentthroughoutthe

sequence,thereisevidenceforvariationthrough

time in the relative importance and intensity

of fishing—again withafocus on the

Middle-Late Transition Period. Volumetric densities

of fish bone (NISP/m3) show relatively little

change from the Millingstone/Lower Archaic

through Middle periods (Table3), but amajor

increasecanbe recognizedduringthe

Middle-Late Transition, followed by a decline during

theLateperiod.Ratiosof fish/(deer+rabbits)

alsoshow anall-time apex duringthe

Middle-LateTransition.Togethertheseindicessuggest

a major increase in the importance of fish in

the diet relative to terrestrial mammals

dur-ing the Middle-Late Transition. Although the

fish remains from one of the two components

that marks the Middle-Late Transition Period

wererecoveredviawet-screening,bothsamples

exhibit high densities of fish bones with the

dry-screenedsamplefromCA-SLO-457actually

showingthehighestdensity.

Not included in the current study are fish

remains recovered from 1/16-inch mesh

wet-screenedcolumnsamples.Reportedelsewherein

areportexclusivelyonthepiscinefaunalremains

from Morro Bay, the column findings show

consistentrecovery of tinyfish bonesfrom all

components(Jones,Gobalet,andCodding 2016; Jonesetal. 2016).Thissuggeststhattaphonomic preservationissuesarenotasignificantproblem

orinfluenceontheassemblages.

Shellfish

Thirty-threespeciesofshellfishfrom14 compo-nentsrepresentthreehabitats:estuary/bay,open rockycoast,andopensandycoast(Supplemental

Table 4). Estuarine habitats were immediately

adjacenttoallsitesandrequiredminimaltravelto exploit.Openrockycoastenvironmentwas

avail-ableatthemouth(MorroRock)andoutsideof

thebayandwouldhaverequiredmodesttripsof

2–6km(probablyinbalsacanoes).Opensandy

coasthabitatwasavailableonthewindwardside

of the sand spit that separates the embayment

from the open waters of Estero Bay. In light

of these spatial distinctions, all of the

com-ponents were dominated by estuarine species,

specifically clams (littleneck clam [Leukoma

spp.],Pacificgaperclam[Tresusnuttallii],

Wash-ingtonclam[Saxidomusnuttalli],andmacoma

clam [Macoma spp.]), andthe California oys-ter (Ostrea lurida). The relative abundanceof oysterswithinMorroBay,especiallyduringthe lateHolocene,isadistinguishingfeatureofthis

estuary relative to other similar environments

elsewhere inCalifornia. Also distinctiveis the

absence of protected habitat mussels (Mytilus

trossulus), which are common in less isolated estuaries tothe northandsouth.Mussel shells

were relativelyabundant in somecomponents,

but all represented the exposed coast species,

Mytiluscalifornianus.

Themolluscanremainsexhibitcomplex

vari-ation that reflects the evolution of the

(12)

Table3.FaunalIndicesfromMorroBayTemporalComponents.

NISP N Margolef

Fish Birds Species Diversity Fish/ Shell

Site Fish NISP/ and Birdsand Birdsand NISP NISP Deer+ wt(km)/

3 3

CA-SLO- Period NISP m Mammals Mammals Mammals Deer Rabbit Rabbit m

23 Late 3,907 372.0 405 43 6.833 46 158 19.15 26.4

626 Late 837 71.5 218 15 2.416 1 188 4.43 14.0

Subtotal/mean 4,744 213.6 623 46 6.994 47 346 12.07 19.5

457 Middle-Late 7,041 1,354.0 451 36 5.727 4 47 138.1 34.9

Transition

458 Middle-Late 9* 128.6 7* – ∗ ∗ ∗ ∗ 5.3

Transition

Subtotal/mean 7,050 1,337.8 458 36 5.727 4 47 138.1 17.9

14 Middle 2,294 124.7 487 21 3.232 12 439 5.08 3.5

165 Middle 25 20.8 ∗ ∗ ∗ ∗ ∗ ∗ 33.3

812 Middle 107 36.9 53 13 1.259 4 37 2.53 7.2

Subtotal/mean 2,426 60.8 540 28 4.291 17 476 5.09 9.5

23 Early 2,916 199.7 204 30 5.453 13 82 32.94 14.9

165 Early 588 16.7 262 23 3.951 56 117 3.58 77.9

458 Early 31 3.44 10 4 1.563 0 8 4.00 7.6

812 Early 142 67.5 73 12 3.729 16 35 3.17 7.4

977 Early 218 226 – – – – – – –

Subtotal/mean 3,895 102.7 549 44 6.816 85 242 11.9 16.5

165 Millingstone/ 404 4.9 25 9 2.486 2 5 9.57 69.3

LowerArchaic

215 Millingstone/ 603 137.0 148 16 3.001 7 135 4.24 7.6

LowerArchaic

812 Millingstone/ 113 27.3 84 12 2.483 12 57 1.63 10.8

LowerArchaic

Subtotal/mean 1,120 88.2 257 25 4.334 21 197 5.13 11.7

Grandtotal 19,235 2,427

Recoveredviawet-screening.

importance of shellfish in the diet over time.

Millingstone/LowerArchaic–periodpeople

col-lected shellfish in modest amounts from

rela-tively circumscribed foraging areas limited to

estuarinehabitatsimmediatelyadjacenttoliving sites.In thenorthernreachesofthebay, where

sands had accumulated by 8,100 years ago,

collection focused on white sand clams,while

tothesouthatCA-SLO-812,oystersdominated

the earliest shell remains. Shellfish collection increasedsubstantiallyattheonsetoftheEarly

period, when Morro Bay was larger than it is

today, prior to late Holocene infilling. While

thequantityofcollectedshellincreased,oyster declinedinimportance inthe southofthe bay, andexploitationofrockycoastspeciesincreased. The lattersuggeststhatthe foragingradiusfor

shellfishwidened, whilethe decrease inoyster

suggestsongoing accumulation of silty/muddy

sediments (not favored by oysters) within the

bay. Exploitation of shellfishdecreased during

the Middleperiod, atwhichtimeuseof rocky

coast species reached an all-time high at the

expense of estuarine species, which reached

a Holocene nadir. The Middle-Late Transition

showsasubstantialincreaseinshellfishharvest, consistentwithtrendsfromthevertebratefauna atthattime.Oysterswereagainimportantatleast

inthesouthernportion ofthebayat

CA-SLO-457.Unlikethe vertebrates,shellfishincreased

further during the Late period, even though

sedimentsbythattimehadcompletelyfilledin

anddecreased the size of the estuary.Overall, themarkedupturninshellfishcollectionduring

the Middle-Late Transition is consistent with

otherfaunalevidenceforincreaseduseofmarine foodsduringthetimeofthemedievaldroughts. Itisimportanttorecognize,however,thateven

greater shellfish harvests were made after the

(13)

marine subsistence was not necessarily at its absolutepeakduringthedroughtsinterval.

ComponentFunction

Samplesizesweretoosmalltodrawfirm

con-clusionsaboutthe functionoftheEarly-period

componentatCA-SLO-977ortheMiddle-period

componentatCA-SLO-165,butthe13

remain-ing components show diverse artifact

assem-blageswithsimilarfrequenciesofflakedstone,

groundstone,andboneimplements

(Supplemen-tal Table5). Flakedstone toolproduction was

evident for all components as well. Projectile

points, ground stone, and bone tools show no

meaningfulvariationovertimeintheir volumet-ricfrequency.Thesesimilaritiessuggestthatall

of the components served as residential bases

ofsometypethroughoutthesequence,although

somevariationisapparentinthehumanburials,

shell,androckfeatures,whichweremore

com-monatcertainsitesbeginningintheEarlyperiod.

The presence of these features suggests that

someresidentialsiteswereoccupiedforgreater

portions of the year from this point onward,

andthattheoverallsettlementstrategyinvolved long-term and short-term residential sites(Far

WesternAnthropologicalResearchGroup2016).

Nonetheless,thediverseassemblagesatallstudy

sites imply that the range of tasks pursued at

long-term and short-term residential sites was

fairly similar. Thereis nothingtosuggest spe-cializedfunctionssuchasprocessinglocations, stations,or caches.Thisisnottosaythat such

sitetypeswerenot used locally,as manyhave

suggested(e.g.,Bertrando2006;Farquhar2003), but rather that these specialized functions are notrepresentedinthecurrentsample.Ratiosof

bifaces/groundstone suggest amodest increase

in the importance of the latter late in time

but not enough to indicate wholesale change

in site function. Beads also show a modest

increasebeginningintheMiddle-LateTransition ca. 1000 cal B.P., but there is little reason to

think that this alone represents major change

in the residential nature of the occupations.

Importantly,theabsoluteandrelativefrequencies

of ground stone implements, bone tools, shell

beads, features, and human burials from the

Middle-LateTransitioncomponentat

CA-SLO-457 demonstrates the residential character of

this occupation. In sum, there is every reason

to believe that the components were similar

enoughthatfunctionalvariationwasnotamajor contributortodiachronicvariabilityinthefaunal assemblages.

HabitatVariability

Thecomponentswithsubstantivefaunal

assem-blages are situated adjacent to a variety of

micro-habitatswithinandaroundtheMorroBay

estuary.Inadditiontovariedmolluscanhabitat discussedabove,Fierstineetal.(1973)defined at least four different fish habitats within the

bay. Among the fish remains, findings from

CA-SLO-977 show frequencies of Pacific

staghornsculpinandjacksmelthigherthanany

othercomponentinthesample.Theprevalence

ofthesefishesalmostcertainlyreflectstheunique

location of CA-SLO-977 on the Morro Bay

sand spit (Jones, Gobalet, and Codding 2016;

Jones et al. 2016). The possibility exists that otherhabitat-relatedvariabilitycouldcontribute tothediachronicpatternsinthefaunalremains, particularlyinlight of the factthat the current

sampledoesnotincludecomponentsassociated

withallmicro-habitatsforalltimeperiods.While suchapossibilityneedsconsiderationinfuture work,otherreasonssuggestthatthediachronic

patterns delineated above reflect response to

climatechange,notmerelyspatialvariation.Four

ofthesitesthatproducedkeycomponents,

CA-SLO-23,CA-SLO-457,CA-SLO-458,and

CA-SLO-626arelocatedwithin500mofoneanother

adjacenttothe samepartof thebay.

CA-SLO-23andCA-SLO-457areseparatedbylessthan

100 m, and produced similar residential tool

assemblages.Thethreecomponentsatthesetwo

sites(Early, Middle-LateTransition,andLate)

exhibit the strong shift to a marine resource

focus that we believe was the general pattern

forbehavioraroundthebayduringthisinterval.

Furthermore, findings from other components

show uniformity acrossfish habitatzones.For

example,theEarly-periodcomponentsfrom

CA-SLO-165atthemouthofthebayand

CA-SLO-812 at the back of the bay are both heavily

dominated by surfperches as is the

Milling-stone/Lower Archaic component at

(14)

Seasonality

Remains of migratory animals suggest

varia-tiongenerallyconsistentwithcomponent

func-tions.High frequency of bat rayremains from

the Millingstone/Lower Archaic component at

CA-SLO-812 suggests that the short-term

res-idential occupation here was focused on the

summermonths (Table4).Mostsitesoccupied

afterthatperiodshowabroaderseasonalrange

of occupation, although these indicators are

absent fromCA-SLO-458,eventhough a

rela-tivelyrobustartifactassemblagewasrecovered

fromthatsite. TheEarly-periodcomponentsat

CA-SLO-23 and CA-SLO-812 show four of

thesix wintermigratorybirds,butinrelatively

low numbers (NISP = 11; 9.2 percent). Bat

rays are still dominant (NISP = 64),but their

relative abundance decreases to 53.8 percent.

Pileperchandmarinemammalsincrease

signifi-cantly(NISP=44),representing37.0percentof

theassemblage.Thecombinedfindingssuggest

thatoccupationoccurredduringallseasonsofthe

year, whichisconsistent withthe morerobust

nature of the artifact assemblages associated

with the Early-perioddeposits atCA-SLO-23,

CA-SLO-458,andCA-SLO-812andthehigher

frequencyof featuresandburials.Multi-season occupationisalsoapparentfortheMiddle-period components.ThecriticalMiddle-LateTransition

componentatCA-SLO-457differsfromothers

in that it shows multi-season occupation, but

also a very heavy emphasis on fall, winter,

andspring species.Thisis consistent withthe

greater reliance on marine oriented birds. The

LatePeriodshowsmodestdeclinesinfall-spring

indicators, which is consistent with decreased

emphasisonwinter-migratingmarinebirds.

Conclusions

Arobust collectionofmammal, bird,fish,and

shellfish remains from an 8,000-year

residen-tial sequence at Morro Bay shows a decided

focusonmarinespeciesduringtheMiddle-Late

Transition cultural phase (950–700 cal B.P.),

whichlargelycoincideswiththeMedieval

Cli-matic Anomaly. This is consistent with

find-ings from the Santa Barbara Channel 100 km

to the south, where research on the droughts

hasalonger,moreextensivehistoryandwhere

(15)

a heavy marine subsistence focus was first

recognizedasanapparentresponsetomedieval

drought (Kennett and Kennett 2000). Previous

faunal studies from central coastal California

provide modest evidence for increased fishing

(Codding and Jones 2007; Joslin 2010) anda

markedincreaseinrabbitexploitation (relative todeer)duringtheMiddle-LateTransitiononthe

exposed coastsof centralmainland California,

but the Morro Bay findings indicate that this

estuarinesettingservedasadistinctive

marine-focusedsubsistencerefugiumduringtheMCA.

Due to a preponderance of shrub vegetation,

rabbits dominate the entire 8,000-year Morro

Baysequence,makingthedeer/rabbitratioless sensitiveinthis setting,althoughdeer remains didreachanotablelow(NISP=7;1.5percent) duringtheMCA.Moretellingisanall-timepeak

in marine andestuarine birds,which is

three-timeshigherduringtheMiddleLateTransition

thanany otherperiod inthe sequence. Similar

apices are apparent in fish NISP/m3 and fish/

deer+rabbits,allofwhicharestrikingintheir

degree of variance and abundance during this

criticalintervaloftime.Alloftheseindicesalso showdeclinesinmarinefocusduringtheensuing LatePeriod,whenclimateamelioratedduringthe colder,wetterLittleIceAge.

The heavy reliance on fish, aquatic birds,

rabbits,andshellfishduringtheMCAsuggests

thatuseofthebowandarrowhadlittleeffecton

thepursuitoffood,eventhoughsmallnumbers

of arrow-sizedprojectile pointsappearinlocal

middensfor thefirsttimearound1000calB.P.

Thetechnology mightwellhavebeeninvolved

in intergroup conflict but, unlike areas to the

north(Schwitallaetal.2014)andsouth(Lambert

1994), the Morro Bay area does not have a

skeletal record substantive enough to evaluate

suchapossibility.

Shellfish remains show a decided increase

during the Middle-LateTransition, but, unlike

the vertebrate fauna, increase further after the

MCAduringtheLateperiod.Thissuggeststhat

marinefoodswerenottappedtothemaximum

duringthe Medievalperiodandis further

con-sistent witharecentevaluation of theregional fisherythatshowedthatitwasneversignificantly

impacted by regular Native harvest during the

Holocene (Jones, Gobalet, and Codding 2016;

Jonesetal. 2016).Thesefindingsindicatethat,

whiledroughtinfluenceddecision-making,

sub-sistenceeconomiesinthissettinghadnotreached crisismode,atleast notfortherelativelylarge blocksoftimethatcanpresentlybedistinguished inthemiddenrecord.Nonetheless,theviability

of thefood baseduringthe MCAisconsistent

with the record of dental caries in the San

FranciscoBayarea(SchwitallaandJones 2012),

whichsuggeststhat peoplethereweatheredthe

droughtsthroughheavyrelianceonstoredfoods richincarbohydrates, likelyacorns.Continued

evaluationof themedievaldroughtshypothesis

needs to critically examine evidence for the

characterofactualresponsesandtosortoutonan interregionalbasisthedegreetowhichtheperiod

can be accurately characterized as a time of

crisis.MorroBay,withaproductive,sustainable

marine foodbase,wasalmostcertainly notthe

only such refugium; the presence and extent

of othersneedtobe carefullyevaluated, as do possiblelocationswherefoodoptionsweremore

constrainedbydroughtandproblemsweremore

severe.

Acknowledgments. WethankNicoleBirneyforpreparation

ofFigures1and2.WealsowishtothankKateBallantyne

forherlong,capableoversightoftheLosOsosWastewater archaeologicalproject.TheSpanishabstractwascheckedby AntonioRodríguez-Hidalgo.

SupplementalMaterials. Supplementalmaterialsarelinked

totheonlineversionofthepaper,accessibleviatheSAA memberloginathttps://doi.org/10.1017/aaq.2016.31.

SupplementalTable1.SummaryofBirdandMammal RemainsfromMorroBaySites.

SupplementalTable2.FishRemains(NISP)fromMorro Bay Components, Millingstone/Lower Archaicand Early Periods.

SupplementalTable3.FishRemains(NISP)fromMorro BayComponents,Middle,Middle-LateTransition,andLate Periods.

SupplementalTable4.ShellRemains(Weightingrams) fromMorroBayTemporalComponents.

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