THE MORRO BAY FAUNA: EVIDENCE FOR A MEDIEVAL DROUGHTSREFUGIUM ON THE CENTRAL CALIFORNIA COAST
Terry L. Jones, Deborah A. Jones, Kacey Hadick, Kenneth W. Gobalet, Judith F. Porcasi, andWilliam R. Hildebrandt
A robust collection of mammal, bird, fish, and shellfish remains from an 8,000-year residential sequence at Morro Bay, a small,isolated estuary on the central California coast, shows a strong focus on marine species during the Middle-Late Transitioncultural phase (950–700 cal B.P.), which largely coincides with the Medieval Climatic Anomaly (MCA). Previous studies haveprovided modest evidence for increased fishing and rabbit hunting during the MCA in adjacent regions, but the Morro Bayfindings suggest a distinctive marine-focused subsistence refugium during the period of drought. Specifically, the sequenceshows striking all-time peaks in marine and estuarine birds, fish NISP/m3, and fish/deer + rabbits during the MCA. Heavyexploitation of fish, aquatic birds, rabbits, and shellfish suggests that the bow and arrow, which seems to have arrived in thearea at this time, had little impact on local subsistence strategies.
La secuencia residencial de unos 8,000 años de duración procedente de Morro Bay (un pequeño estuario aislado en la costacentral de California, Estados Unidos) está compuesta por un gran conjunto faunístico que incluye restos de mamíferos,aves, peces y mariscos. Dicho conjunto faunístico indica una fuerte dependencia de las especies marinas durante la fasecultural de la Transición Media-Tardía (950–700 cal a.P.), la cual coincide plenamente con la anomalía climática medieval(MCA). Algunos estudios previos han mostrado modestas evidencias sobre el incremento de la pesca y la caza de lepóridosdurante la MCA en las regiones adyacentes. Sin embargo, en Morro Bay los hallazgos sugieren la presencia de un refugiobasado en los recursos marinos a nivel de subsistencia durante el periodo de sequía. Específicamente, la secuencia muestraunos picos nunca antes vistos en el número de especímenes identificados (NISP) por metro cúbico de restos de aves marinasy de estuario, mariscos y peces en proporción a la cantidad de cérvidos y lepóridos durante el MCA. La intensa explotaciónde la pesca, las aves acuáticas, los lepóridos y los mariscos sugieren que la llegada del arco y la flecha, coincidente con elmismo periodo, tuvo un impacto reducido en las estrategias de subsistencia locales.
One of the most long-standing issuesin the study of western North Ameri-can hunter-gatherer prehistory has been
the relative influence of paleoclimatic varia-tion on cultural change. Since at least the1940s, archaeologists have been interested in theeffects of prolonged periods of aridity on for-aging populations. Initially focused on the mid-Holocene warm period (known alternately as
Terry L. Jones Department of Social Sciences, California Polytechnic State University, San Luis Obispo, CA 93407,USA ([email protected], corresponding author)Deborah A. Jones Far Western Anthropological Research Group, 1725 Diablo Drive, San Luis Obispo, CA 93405,USAKacey Hadick and William R. Hildebrandt Far Western Anthropological Research Group, 2727 Del Rio Place, Suite A,Davis, CA 95618, USAKenneth W. Gobalet Department of Biology, Emeritus, California State University, Bakersfield, CA 93311 CurrentAddress: 625 Wisconsin St., San Francisco, CA 94107, USAJudith F. Porcasi Cotsen Institute of Archaeology, University of California, Los Angeles, CA 90095, USA
the Altithermal, Hypsithermal, or Xerothermic;Antevs 1948, 1955; Baumhoff and Heizer 1965;Byrne 1979; Currey and James 1982; Dean et al.1985; deMenocal 2001; Jennings 1964; Kennettet al. 2007; Moratto 1984:544–547; Moratto et al.1978), debate has since shifted to the MedievalClimatic Anomaly (MCA) of the late Holocene(Arnold 1992; Basgall 1999; Bettinger 1999;Boxt et al. 1999; Collins 2010; Cook et al.
2004; D’Oro 2009; Fischman 1996; Gamble2005; Herweijer et al. 2006; Johnson 2004; Joneset al. 1999; Jones and Brown 1999; Jones andSchwitalla 2008, 2012; Kennett 2005; Kennettand Kennett 2000; Lambert 1994; Raab andLarson 1997; Schwitalla 2012; Walker andLambert 1989). Stine (1994) defined the MCAas a period of prolonged and severe droughtsbetween ca. 1150 and 600 cal B.P. Originallyrecognized in the paleoclimatic records of bothCalifornia and Patagonia, the MCA is nowreasonably well accepted as a distinctive cli-matic interval, with recent studies confirming theoccurrence of epic droughts and elevated aridityin North America during medieval times (Cooket al. 2004; Graham et al. 2007, 2011; Graumlich1993; Mann et al. 2009), as well as correlationswith major cultural changes (including large-scale migrations and collapse; e.g., Benson andBerry 2009; Benson et al. 2007, 2009; Berry andBenson 2010; Billman et al. 2000).
In California, the effects of medieval droughtson native foraging populations have been debatedintensely for more than two decades (see reviewsby Schwitalla 2010; Schwitalla and Jones 2012).In most of this region, the cultural phase thatcoincides with the MCA is known as the Middle-Late Transition, dated ca. 950–700 cal B.P. Incentral and southern California, most scholarsaccept that changes in exchange (Arnold 1992;Gilreath 1995; Gilreath and Hildebrandt 1997;Jones et al. 1999; Jones and Schwitalla 2008),settlement patterns (Arnold 1992; Kennett 2005),regional abandonments, (Jones and Ferneau2002; Gardner 2006; Jones and Schwitalla 2008;Whitley et al. 2007), and disease and violence(Fischman 1996; Lambert 1994, 1997; Raab andLarson 1997; Walker and Lambert 1989; Weiss2002) during the Middle-Late Transition can beattributed to demographic stresses caused by pro-longed and severe droughts. However, some haveargued that the droughts were not severe enoughto cause major problems (Basgall 1999, 2008;Bettinger 1999) or that Native mechanisms forwater storage and resource redistribution weresophisticated enough to mitigate any serious,negative consequences (e.g., Gamble 2005) andthat, above all else, Native populations survived(Arnold and Walsh 2010:34). In this regard,findings from northern California have been
much less compelling in implicating drought asa primary agent of cultural change. Some studiesof the skeletal record from San Francisco Bayand the Sacramento-San Joaquin Valley (D’Oro2009; Pilloud 2006; Schwitalla et al. 2014) havenot found the same spike in violence duringthe MCA/Middle-Late Transition that Lambert(1994) documented in the Santa Barbara Chan-nel. Analysis of a metadata set of burials fromthe San Francisco Bay area confirmed a peakin projectile violence during the Middle-LateTransition, but also showed a concurrent peak indental carious lesions, which was attributed to aheavy reliance on acorn storage and consumption(Schwitalla and Jones 2012). The latter indicatesviability of the acorn crop during the droughtsin central California and some measure of areliable food base. Subsistence patterns basedon faunal remains from San Francisco Bay havealso more commonly been attributed to economicintensification (Broughton 1997, 1999) ratherthan climatically induced cultural change. Mostrecently, Bettinger (2015) suggested that themedieval droughts may have amplified processesthat were fundamentally historic/diffusionary innature, as the introduction of the bow and arrowinto California ultimately facilitated more inten-sive, privatized economic systems.
When Arnold (1992) first attributed settle-ment and social transitions on the southern Cali-fornia Islands during the Middle-Late Transition(MLT) to climatic changes, she suggested thatthe primary problem confronting these maritimehunter-gatherers was warm sea surface temper-atures that drastically reduced the productivityof the marine food base. Subsequent studies(Kennett and Kennett 2000) showed that sea sur-face temperatures were in fact cool and produc-tive during the MCA and that subsistence stresswas more a product of reduced precipitation anda resource-depleted terrestrial environment. Thenative response to the latter, which has beenfurther supported by subsequent paleoclimaticstudies (Barron et al. 2015), was an increasedfocus on marine resources during the droughts aswell as violent competition for limited resources(Kennett and Kennett 2000). The idea of a marinesubsistence focus during MCA subsequentlybecame common on the central California coast,and a number of scholars reported evidence for
Terry L. Jones et al.] 205THE MORRO BAY FAUNA
increased exploitation of fish, marine mammals,and/or shellfish during the MLT (e.g., Coddingand Jones 2007; Codding et al. 2010; Jones2003; Joslin 2010), but the collective empiricalevidence has not necessarily been compelling.Mikkelsen et al. (2000), for example, hypoth-esized that Morro Bay, a small estuary on thecentral coast, may have served as a refugiumduring the medieval droughts, but support forthe idea was not immediately forthcoming. Herewe affirm that hypothesis with a robust bodyof faunal evidence accumulated in the last 15years that clearly shows a heavy focus on marineresources along the shores of Morro Bay duringthe MCA. Frequencies of fish and marine birdremains from this setting are significantly higherduring the MLT than at any other period inthe 8,000-year occupational sequence, which weinterpret as evidence for an intense focus onmarine foods in the face of reduced terrestrialproductivity caused by drought. While the focuson fish and sea birds is logically consistent witha depleted terrestrial biome, the availability ofthese foods also suggests that, at least in thissetting, the effects of drought may not necessar-ily have been catastrophic. Further, the dietaryresponse evident at Morro Bay shows no obviousconsequences from introduction of the bow andarrow, which diffused into the area at about thesame time, and has been hypothesized as at least acontributing (Kennett 2005; Kennett and Kennett2000; Kennett et al. 2013; Lambert 1994), if notprimary, cause of cultural changes. This is notto say that the bow might not have been usedas a weapon in intergroup conflict and that itcould have led to increased violence, but it didnot contribute to subsistence change at this time.
Setting
Morro Bay is a shallow 8.1 km2 coastal estuarysituated on the central California coast in SanLuis Obispo County (Figure 1) that was occupiedby speakers of Obispeño or Northern Chumash atthe time of historic contact (Golla 2011:194). Thebay occupies the northern end of a southeastwardtrending depression that encompasses the LosOsos and San Luis valleys (Cooper 1967:74).Sand dunes surround the bay, and one arm ofthe dune system is a sand spit that serves as a
barrier between the estuary and the outer EsteroBay. Entrance to the bay from the open oceanwas significantly improved by construction ofbreakwaters in the 1940s by the U.S. ArmyCorp of Engineers. Prior to that construction, themouth of Morro Bay was open to surf action andwas unsuitable for ship portage.
Morro Bay’s Mediterranean climate is char-acterized by cool moist winters and warmdry summers, with frequent fog between Juneand September. Annual average precipitation is370 mm/yr, with a range from 152 to 610 mm(Gerdes and Browning 1974:21). Prior to exten-sive modern disturbance and development, thenatural vegetation fostered by the combinationof modest rainfall and dune soils was a coastalsagebrush shrub (Hoover 1970; Kuchler 1977;Ritter 2006). Common species include Californiasagebrush (Artemesia californica), coyote brush(Baccharis pilularis), poison oak (Toxicoden-dron diversilobum), and black sage (Salvia mel-lifera). Coast live oak forest is only a very smallcomponent of the vegetative landscape. Thisdiffers significantly from the open coast to thesouth (the Diablo Canyon or Pecho Coast), whereoak forest is much more extensive (Codding et al.2010; Hildebrandt et al. 2010; Jones and Codding2010; Jones et al. 2008).
Like most estuaries on the California coast,Morro Bay provides habitat for an extensive suiteof marine and terrestrial animals. In terms ofbirds, the bay is an integral part of the Pacificflyway and is visited by a myriad of migratoryspecies, particularly in the winter. CaliforniaFish and Game have identified no fewer than 75species that visit or reside year-round at MorroBay (Edell 2006; Gerdes and Browning 1974).The estuary attracts the snowy egret (Egrettathula), the great blue heron (Ardea herodias), anda variety of other waterfowl, shorebirds, and birdsof prey. Only four species of marine mammalsare known in the bay today: California sea lion(Zalophus californianus), harbor seals (Phocavitulina), Stellar’s sea lion (Eumetopias jubatus),and the sea otter (Enhydra lutris), but the archae-ological record indicates that elephant seals(Mirounga angustirostris) (Rick et al. 2012) andnorthern fur seals (Callorhinus ursinus) (Ricket al. 2009) were occasionally present nearshoreprior to historic times. Twenty-five species of
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Figure 1. Morro Bay, California, with archaeological sites discussed in text.
native terrestrial mammals were documentedaround the shores of Morro Bay in 1974 (Gerdesand Browning 1974). These include several smallburrowing species that are agents of bioturbationwithin local archaeological sites. The largestherbivore currently present is the black-taileddeer (Odocoileus hemionus), although tule elk(Cervus elaphus nannodes) remains are repre-sented in small amounts at a few archaeologicalsites (e.g., Mikkelsen et al. 2000). Cottontailand brush rabbits (Sylvilaus spp.) were commoninhabitants of the coastal scrub, along with jackrabbits (Lepus californicus). Historically, local
carnivores included brown bears (Ursus horri-bilis), mountain lions (Felis concolor), bobcats(Lynx rufus), gray foxes (Urocyon cinereoar-genteus), coyote (Canis latrans), and long-tailedweasels (Mustela frenata).
With respect to fishes, the California Depart-ment of Fish and Game identified 66 species(64 natives) within Morro Bay in 1966, whichwere subsequently confirmed by Fierstine et al.(1973). These surveys showed that three speciesaccounted for more than 50 percent of the fishin the bay by number caught: northern anchovy(Engraulis mordax), shiner perch (Cymatogaster
Terry L. Jones et al.] 207THE MORRO BAY FAUNA
Table 1. Morro Bay Study Sites.
Total Excavation Temporal ComponentsTrinomial Volume (m3) (Periods) Reference
CA-SLO-14 21.49 Middle Far Western Anthropological Research Group (2016)CA-SLO-23 92.39 Early, Late Far Western Anthropological Research Group (2016)CA-SLO-165 72.90 Millingstone/Lower Archaic, Mikkelsen et al. (2000)
Early, MiddleCA-SLO-215 5.00 Millingstone/Lower Archaic Jones et al. (2004)CA-SLO-457 27.70 Middle-Late Transition Far Western Anthropological Research Group (2016)CA-SLO-458 19.74 Early, Middle-Late Transition Far Western Anthropological Research Group (2016)CA-SLO-626 24.54 Late Far Western Anthropological Research Group (2016)CA-SLO-812 11.28 Millingstone/Lower Archaic, Far Western Anthropological Research Group (2016)
Early, MiddleCA-SLO-977 1.00 Early Dallas (1992)
Gobalet and Jones (1995)Total 276.04
aggregata), and black perch (Embiotoca jack-soni). At least 11 species, including black perch,shiner perch, lingcod (Ophiodon elongatus),Pacific staghorn sculpin (Leptocottus armatus),and starry flounder (Platichthys stellatus), areyear-round residents of the estuary. As many as29 other species are seasonal migrants (Gerdesand Browning 1974).
The history of research at Morro Bay reflectsthe relative isolation of the estuary away fromthe major centers of archaeological inquiry inCalifornia. While the San Francisco Bay shellmiddens began to be seriously investigated over100 years ago (Nelson 1909), the first sites atMorro Bay were not recorded until the late 1940s,the first excavation was not completed until1961 (Clemmer 1962), and the first radiocarbondates were not obtained until the late 1970s.Research on the prehistory of Morro Bay hastaken place wholly within the Cultural ResourceManagement (CRM) era. Lands surrounding thebay are held in private (small residential lots)and by California State Parks, and most of theearly CRM work on these properties was limitedto relatively small-scale survey and testing. Asof 2015, at least 50 sites had been tested, andradiocarbon dates are available from 28 of these,but most of these investigations, while accom-plishing the conservation objectives for whichthey were intended, did not produce substantivesamples of well-dated faunal remains and/orartifacts. In the last 15 years, there have beenseveral substantial investigations on the shore of
the estuary, along with serious attempts at syn-thesis (e.g., Bertrando 2000, 2004a, 2004b; Joneset al. 2004; Mikkelsen et al. 2000) highlighted bythe recent Los Osos Wastewater Project, whichyielded substantial artifact and faunal samplesfrom eight sites in the southern portion of the bay(Far Western Anthropological Research Group2016). The Los Osos findings, in conjunctionwith other local research, have established an8,000-year occupational history for Morro Baymarked by a substantial quantity of faunal data.Here we summarize the fish, mammal, bird, andshellfish remains from nine sites investigatedover the last two decades (Table 1, Figure 1),representing all periods in this sequence.
Methods
Field Recovery
The investigated sites were estuarine shell mid-dens marked by combinations of mammal, bird,and fish bone, shellfish remains, fire-affectedrock, flaked stone tools and debitage, groundstone, bone and shell tools, and occasional fea-tures including human burials. All investigationsat these deposits were completed between 1990and 2013 (Table 1). Two sites, CA-SLO-215and CA-SLO-977, were subjected to relativelymodest testing (1.0–5.0 m3) to evaluate the typeand distribution of materials present (Dallas1992; Jones et al. 2004). Larger samples wererecovered from CA-SLO-165 (Mikkelsen et al.
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2000), CA-SLO-14, CA-SLO-23, CA-SLO-457,CA-SLO-458, CA-SLO-626, and CA-SLO-812.Total recovery volume for these nine sites was276.04 m3 (Table 1). Excavators obtained mostsamples from these deposits via dry field screen-ing (3 mm mesh) from 1 × 2 m and/or 1 ×1 m units test units or trenches. Excavatorscollected vertebrate remains in unit-level lotsfrom all manually excavated units except in rapidrecovery units employed on a limited basis at onesite (CA-SLO-23 in 2013).
The abundance of fish and shell remains inthe deposits required a subsampling strategy.Control units and column samples providedthe assemblage of fish remains at most sites,while component-associated subsamples pro-vided samples at sites that produced extremelylarge numbers of fish bones. The latter includeda representative sample of control units (pro-cessed dry with 1/8 -inch mesh) and one-columnsample level (representing 20 × 20 × 10 cm)of recovery volume processed in the labora-tory with water through nested 1/8 - and 1/16 -inchmesh.1
Shellfish remains were, by far, the most abun-dant, visible cultural constituents in the deposits.Column samples provided a primary way ofrecovering a controlled representative sample ofshell remains from both feature and non-featuresite deposits. The shell column samples werelaboratory-processed with water through nested1/4 -, 1/8 -, and 1/16 -inch mesh, dried, catalogued byscreen size and unit provenience, and sorted forcultural and noncultural constituents. Analystsexamined the shell remains from 1/4 - and 1/8 -inchmesh samples.
Analysis
Using reference collections from the Los Ange-les County Museum of Natural History and theZooarchaeology Laboratory at the Cotsen Insti-tute of Archaeology at University of California,Los Angeles, Porcasi identified bird and mammalremains from all but one of the sites.2 Jamesonand Peeters (1988) and Peterson (1990) providedthe nomenclature and taxonomy for mammalsand birds, respectively. Porcasi identified allspecimens to the most discrete taxonomic levelpossible based on diagnostic features. In theabsence of such features, she assigned bones to
classes (i.e., Mammalia, Aves, etc.) and (for birdsand mammals) to size categories (small, medium,or large). In addition, she recorded to the degreepossible the element, part of element, side, age,number, weight, and evidence of modification(i.e., burned, gnawed, cut, or worked). The Mar-galef Index provided a measure of assemblagediversity to evaluate diet breadth and the Berger-Parker index (in reciprocal form) to evaluateevenness or relative specialization (Magurran1988).
Gobalet identified the element and taxonomiccategory of each fish specimen using referencematerials.3 Findings were summarized by thenumber of identified specimens (NISP). Thenomenclature and current taxonomy for fishesfollows Page et al. (2013). For this paper, wedefine “identified” as specimens assigned toat least a family. We excluded specimens thatwe could classify only as Elasmobrachiomorphi(sharks, skates, rays) or Actinoptergii4 (ray-finned fishes, 16,653 elements). Jones, Gob-alet, and Codding (2016) and Jones, Gobalet,Mikkelsen et al. (2016) discuss some aspects ofthe fish assemblages.
D. Jones and Hadick identified the shell-fish using reference collections at CaliforniaPolytechnic State University, San Luis Obispo,and Far Western Anthropological ResearchGroup, recording the weight of shell perspecies.
Based on these methodological protocols, thesample available from Morro Bay consists of2,247 bird and mammal bones from an ana-lytical volume of 141.60 m3, and 19,235 fishbones identified to a meaningful taxon (generallyfamily or better) from an analytical volume of127.1 m3. Shellfish remains represent a totalrecovery volume of 1.088 m3.
Chronology and Delineation of TemporalComponents
Radiocarbon dates (n = 80) and temporally diag-nostic shell beads and projectile points providedvertical and horizontal identification of compo-nents (Table 2). Seventy-eight of the dates werefrom single-shell samples, while the remainingtwo were from charred plant remains. All dateswere corrected for isotopic fractionization andcalibrated with Calib version 7.1 (Stuiver et al.
Terry L. Jones et al.] 209THE MORRO BAY FAUNA
Table 2. Summary of Morro Bay Temporal Components.
N Analytical Analytical AnalyticalN Temporally Age Span Excavation Volume Bird Volume Fish Volume Shell
Trinomial Temporal Radiocarbon Meaningful One-Sigma Volume and Mammal Remains RemainsCA-SLO- Perioda Dates Beads (cal B.P.) (m3) Remains (m3) (m3) (m3)
aLate = 700–180 cal B.P.; Middle-Late Transition = 950–700 cal B.P.; Middle = 2600–950 cal B.P.; Early = 5500–2600cal B.P.; Millingstone/Lower Archaic = 10,000–5500 cal B.P.∗Component based more on beads than radiocarbon.∗∗ Wet-screened recovery.
2016); a Delta R marine correction value of290 ± 35 years (Ingram and Southon 1996)was applied to the shell dates. Componentsexcluded portions of the excavation volumethat were disturbed or that exhibited excessivetemporal mixing so that the volumes associ-ated with the analytical samples are smallerthan the total recovery from the combined siteinvestigations.
Component Function
Interpretation of the Morro Bay fauna cannot bedisassociated from the role of sites in regionalsettlement systems, given that any change in thecharacter of site use could contribute to variationin the relative frequency of faunal species (Bin-ford 1978, 1980). We evaluated settlement func-
tion by considering the range and diversity of cul-tural materials recovered from each component,the presence/absence of burials or other features,the volumetric density of formal and informalartifacts, the ratios of flaked to ground stone, andthe evidence for seasonality (remains of migrat-ing animals [Figure 2] and seasonally availableplant foods). We evaluated assemblage diver-sity statistically using the Margolef DiversityIndex.
Results
Analysis identified 15 temporal componentsfrom the more substantive earlier excavationsat Morro Bay (CA-SLO-165, CA-SLO-215, andCA-SLO-977), and recent investigations for the
210 [Vol. 82, No. 2, 2017AMERICAN ANTIQUITY
Janu
ary
Febr
uary
Mar
ch
Apr
il
May
June
July
Aug
ust
Sept
embe
r
Oct
ober
Nov
embe
r
Dec
embe
r
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
Figure 2. Migratory species with seasonally restricted appearances at Morro Bay.
Los Osos Wastewater project. However, severalcomponents lacked adequate samples for certainconstituents, as specified below.
Birds and Mammals
Thirteen components provided the sample of birdand mammal remains (Supplemental Table 1).The Middle-period component from CA-SLO-165 produced very few bones, and the large verte-brate remains from CA-SLO-977 are unreported.The total from the remaining 13 componentsexcludes remains of all small burrowing animals(e.g., Botta’s pocket gopher [Thomomys bottae]and California ground squirrel [Spermophilusbeecheyi]), most of which are probably intru-sive. The sample includes 26 species of ducks,geese, and other aquatic birds; 18 species ofmarine birds; 6 terrestrial birds; 12 terrestrialmammals; and 6 marine mammals. Overall, the
birds and mammals are dominated by terrestrialmammals that account for 65.5 percent of NISP.Dominant species are rabbits (Sylvilagus spp.;NISP = 1075; 44.3 percent) and black-tailedjack rabbit (NISP = 196; 8.1 percent). Muledeer (Odocoileus hemionus), which was themost abundant species in the faunal collectionfrom Diablo Canyon and figured prominentlyin debates about large game hunting strategiesalong the central coast (Hildebrandt et al. 2010;Jones and Codding 2010), is decidedly lessabundant at Morro Bay, representing only sevenpercent (NISP = 170) of the bird and mammalinventory. The low frequency of deer and thelarge number of rabbits and hares almost cer-tainly reflect the abundance of sagebrush shrubvegetation at Morro Bay.
The number and diversity of bird remainsis a distinguishing feature of the Morro Bay
Terry L. Jones et al.] 211THE MORRO BAY FAUNA
fauna and reflects the importance of the estu-ary as a bird habitat. Ducks, geese, and otheraquatic species make up 19.4 percent (NISP =446) of the collection, followed by marine birds(NISP = 270; 11.1 percent). Most abundant aregrebes (Podiceps spp.; NISP = 144; 6 percent)and brown pelicans (Pelecanus occidentalis;NISP = 78; 3.2 percent). Fewer bird bones withless species diversity were reported from theexposed rocky coast at Diablo Canyon to thesouth (Jones et al. 2008)
Marine mammals, dominated by sea otter(NISP = 59; 0.4 percent), are relatively unim-portant in the Morro Bay collection, makingup less than 3 percent of NISP. This toocontrasts with the Diablo Canyon open coast,where marine mammals accounted for more than21 percent of the identified bird and mammalremains.
Of paramount importance, however, are pat-terns across time (Figure 3). Most striking inthis regard is variation in the relative importanceof terrestrial mammals. Throughout most of thesequence, terrestrial mammals, predominantlyrabbits and hares, account for no less than69 percent of the non-piscine vertebrate fauna.However, during the Middle-Late Transition, thisfigure plummets to only 14.2 percent, dominatedby cottontail rabbits (NISP = 44). At the sametime, deer reach a low of 1 percent (NISP = 5).Replacing terrestrial game in importance duringthis interval are aquatic and marine birds, whichtogether account for 84 percent of the non-piscineassemblage for Middle-Late Transition Period.This dearth of terrestrial mammals, combinedwith the high frequency of marine birds, rep-resents a profoundly different pattern than thatof any other interval in the 8,000-year sequence,with aquatic birds being three times more numer-ous than at any other time. Although marinemammals remained insignificant (1.5 percent),the non-piscine remains show a striking shifttoward marine species during the Middle-LateTransition. Following the end of this period,terrestrial species again dominate (70 percent),and marine/aquatic birds return to the low levelstypical for the rest of the sequence (25 percent).The heavy emphasis on aquatic birds and rabbits,which together account for 95 percent of theMiddle-Late Transition non-piscine vertebrate
remains, suggests little if any reliance onthe bow and arrow for hunting, given that theseanimals, especially the birds, were more likelytrapped or snared. Projectile point size profilesindicate, fairly convincingly, that the bow andarrow arrived to the central coast during theMiddle-Late Transition or slightly earlier (ca.1050 cal B.P.). This is confirmed at Morro Bay,where the same components that yielded the rab-bit and bird-dominated faunal assemblages alsoproduced arrow-sized projectile points, albeitin very small numbers (Far Western Anthro-pological Research Group 2016). While theappearance of the bow and arrow might have beenassociated with increased intergroup conflict(Kennett et al. 2013; Lambert 1994), it initiallyhad little effect on subsistence hunting strate-gies. This supports an idea advanced by Brill(2014) that the technology may have been usedmore for inter-human conflict than subsistencein southern California. However, there is nocomplementary burial record from Morro Bay orsurrounding areas robust enough to compare thefaunal record with skeletal evidence for projectileviolence.
Findings from another recently identifiedMiddle-Late Transition Period component pro-vide some support for the heavy representationof marine animals in faunal assemblages fromthis interval around Morro Bay. CA-SLO-239,near the current mouth of the bay, was excavatedin 1961 (Clemmer 1962), but its chronologywas unclear until the first radiocarbon datesfrom site materials were recently reported (Joneset al. 2017). Dates and temporal diagnosticsshow clearly that the site was inhabited duringthe early Middle and Middle-Late Transitionperiods. Faunal sampling strategies were not con-sistent with current standards, and componentdefinition is imprecise, but the faunal collectionis nonetheless dominated by marine mammals(NISP = 39; 78 percent), including Californiasea lions (Zalophus californianus; NISP = 13)and sea otters (Enhydra lutris; NISP = 13).Unfortunately, owing to the era during whichthe site was investigated, fish bones were notcollected, but the marine focus in the largevertebrates is consistent with findings from theother Middle-Late components in the currentstudy.
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(a) Percentage of Marine/Estuarine Birds
908070605040302010
0
Millingstone/Lower Archaic
Early Middle-LateMiddle Late
(b) Fish NISP/m³
1600140012001000
800600400200
0
Millingstone/Lower Archaic
Early Middle-LateMiddle Late
(c) Fish NISP/Deer + Rabbit NISP
Millingstone/Lower Archaic
Early Middle-LateMiddle Late
1600140012001000
800600400200
0
(d) Shellfish Weight (km)/m³
25
20
15
10
5
0Millingstone/
Lower ArchaicEarly Middle-LateMiddle Late
Figure 3. Key diachronic trends in faunal remains from Morro Bay, California: (a) percentage of marine/estuarinebirds, (b) fish NISP/m3, (c) fish NISP/(deer + rabbit NISP), (d) shellfish weight/m3.
Terry L. Jones et al.] 213THE MORRO BAY FAUNA
Fishes
Gobalet identified a total of 19,235 fish bones toa meaningful taxon (generally family or better)from an analytical volume of 127.1 m3 from15 components (Supplemental Tables 2 and 3).The only sample available for one component(the Middle-Late Transition at CA-SLO-458)was recovered via wet-screening, which typi-cally yields higher frequencies of fish remainsthan the dry-screening (Jones, Gobalet, andCodding 2016) used at all other sites. Threefamilies/species dominate the record throughoutthe sequence: surfperches, (Embiotocidae), her-rings (Clupeidae), and New World silversides(Atherinopsidae). Not surprisingly, these assem-blages vary considerably from those of DiabloCanyon to the south, which was dominatedby open rocky coast fishes (Fitch 1972; Joneset al. 2008). Surfperches include species thatcan be taken either with nets or as individualswith hooks/gorges. Herrings (including sardines)and silversides are small schooling fishes thatare much more commonly taken with nets, theformer often with the aid of watercraft and thelatter from shore (Boone 2012; Gause 2002; Love2011; Salls 1988). The dominance of silversidesand surfperches throughout the record suggeststhat fishing was undertaken with nets throughoutthe Holocene. This is similar to findings reportedby Rick and Erlandson (2000) for the SantaBarbara mainland to the south.
While this singular emphasis on nettingsmall schooling fish is apparent throughout thesequence, there is evidence for variation throughtime in the relative importance and intensityof fishing—again with a focus on the Middle-Late Transition Period. Volumetric densitiesof fish bone (NISP/m3) show relatively littlechange from the Millingstone/Lower Archaicthrough Middle periods (Table 3), but a majorincrease can be recognized during the Middle-Late Transition, followed by a decline duringthe Late period. Ratios of fish/(deer + rabbits)also show an all-time apex during the Middle-Late Transition. Together these indices suggesta major increase in the importance of fish inthe diet relative to terrestrial mammals dur-ing the Middle-Late Transition. Although thefish remains from one of the two components
that marks the Middle-Late Transition Periodwere recovered via wet-screening, both samplesexhibit high densities of fish bones with thedry-screened sample from CA-SLO-457 actuallyshowing the highest density.
Not included in the current study are fishremains recovered from 1/16-inch mesh wet-screened column samples. Reported elsewhere ina report exclusively on the piscine faunal remainsfrom Morro Bay, the column findings showconsistent recovery of tiny fish bones from allcomponents (Jones, Gobalet, and Codding 2016;Jones et al. 2016). This suggests that taphonomicpreservation issues are not a significant problemor influence on the assemblages.
Shellfish
Thirty-three species of shellfish from 14 compo-nents represent three habitats: estuary/bay, openrocky coast, and open sandy coast (SupplementalTable 4). Estuarine habitats were immediatelyadjacent to all sites and required minimal travel toexploit. Open rocky coast environment was avail-able at the mouth (Morro Rock) and outside ofthe bay and would have required modest trips of2–6 km (probably in balsa canoes). Open sandycoast habitat was available on the windward sideof the sand spit that separates the embaymentfrom the open waters of Estero Bay. In lightof these spatial distinctions, all of the com-ponents were dominated by estuarine species,specifically clams (littleneck clam [Leukomaspp.], Pacific gaper clam [Tresus nuttallii], Wash-ington clam [Saxidomus nuttalli], and macomaclam [Macoma spp.]), and the California oys-ter (Ostrea lurida). The relative abundance ofoysters within Morro Bay, especially during thelate Holocene, is a distinguishing feature of thisestuary relative to other similar environmentselsewhere in California. Also distinctive is theabsence of protected habitat mussels (Mytilustrossulus), which are common in less isolatedestuaries to the north and south. Mussel shellswere relatively abundant in some components,but all represented the exposed coast species,Mytilus californianus.
The molluscan remains exhibit complex vari-ation that reflects the evolution of the estu-ary, variation in foraging radii, and shifting
214 [Vol. 82, No. 2, 2017AMERICAN ANTIQUITY
Table 3. Faunal Indices from Morro Bay Temporal Components.
NISP N MargolefFish Birds Species Diversity Fish/ Shell
Site Fish NISP/ and Birds and Birds and NISP NISP Deer + wt (km)/CA-SLO- Period NISP m3 Mammals Mammals Mammals Deer Rabbit Rabbit m3
importance of shellfish in the diet over time.Millingstone/Lower Archaic–period people col-lected shellfish in modest amounts from rela-tively circumscribed foraging areas limited toestuarine habitats immediately adjacent to livingsites. In the northern reaches of the bay, wheresands had accumulated by 8,100 years ago,collection focused on white sand clams, whileto the south at CA-SLO-812, oysters dominatedthe earliest shell remains. Shellfish collectionincreased substantially at the onset of the Earlyperiod, when Morro Bay was larger than it istoday, prior to late Holocene infilling. Whilethe quantity of collected shell increased, oysterdeclined in importance in the south of the bay,and exploitation of rocky coast species increased.The latter suggests that the foraging radius forshellfish widened, while the decrease in oystersuggests ongoing accumulation of silty/muddysediments (not favored by oysters) within the
bay. Exploitation of shellfish decreased duringthe Middle period, at which time use of rockycoast species reached an all-time high at theexpense of estuarine species, which reacheda Holocene nadir. The Middle-Late Transitionshows a substantial increase in shellfish harvest,consistent with trends from the vertebrate faunaat that time. Oysters were again important at leastin the southern portion of the bay at CA-SLO-457. Unlike the vertebrates, shellfish increasedfurther during the Late period, even thoughsediments by that time had completely filled inand decreased the size of the estuary. Overall,the marked upturn in shellfish collection duringthe Middle-Late Transition is consistent withother faunal evidence for increased use of marinefoods during the time of the medieval droughts.It is important to recognize, however, that evengreater shellfish harvests were made after theMCA during the Late period, suggesting that
Terry L. Jones et al.] 215THE MORRO BAY FAUNA
marine subsistence was not necessarily at itsabsolute peak during the droughts interval.
Component Function
Sample sizes were too small to draw firm con-clusions about the function of the Early-periodcomponent at CA-SLO-977 or the Middle-periodcomponent at CA-SLO-165, but the 13 remain-ing components show diverse artifact assem-blages with similar frequencies of flaked stone,ground stone, and bone implements (Supplemen-tal Table 5). Flaked stone tool production wasevident for all components as well. Projectilepoints, ground stone, and bone tools show nomeaningful variation over time in their volumet-ric frequency. These similarities suggest that allof the components served as residential basesof some type throughout the sequence, althoughsome variation is apparent in the human burials,shell, and rock features, which were more com-mon at certain sites beginning in the Early period.The presence of these features suggests thatsome residential sites were occupied for greaterportions of the year from this point onward,and that the overall settlement strategy involvedlong-term and short-term residential sites (FarWestern Anthropological Research Group 2016).Nonetheless, the diverse assemblages at all studysites imply that the range of tasks pursued atlong-term and short-term residential sites wasfairly similar. There is nothing to suggest spe-cialized functions such as processing locations,stations, or caches. This is not to say that suchsite types were not used locally, as many havesuggested (e.g., Bertrando 2006; Farquhar 2003),but rather that these specialized functions arenot represented in the current sample. Ratios ofbifaces/groundstone suggest a modest increasein the importance of the latter late in timebut not enough to indicate wholesale changein site function. Beads also show a modestincrease beginning in the Middle-Late Transitionca. 1000 cal B.P., but there is little reason tothink that this alone represents major changein the residential nature of the occupations.Importantly, the absolute and relative frequenciesof ground stone implements, bone tools, shellbeads, features, and human burials from theMiddle-Late Transition component at CA-SLO-457 demonstrates the residential character of
this occupation. In sum, there is every reasonto believe that the components were similarenough that functional variation was not a majorcontributor to diachronic variability in the faunalassemblages.
Habitat Variability
The components with substantive faunal assem-blages are situated adjacent to a variety ofmicro-habitats within and around the Morro Bayestuary. In addition to varied molluscan habitatdiscussed above, Fierstine et al. (1973) definedat least four different fish habitats within thebay. Among the fish remains, findings fromCA-SLO-977 show frequencies of Pacificstaghorn sculpin and jacksmelt higher than anyother component in the sample. The prevalenceof these fishes almost certainly reflects the uniquelocation of CA-SLO-977 on the Morro Baysand spit (Jones, Gobalet, and Codding 2016;Jones et al. 2016). The possibility exists thatother habitat-related variability could contributeto the diachronic patterns in the faunal remains,particularly in light of the fact that the currentsample does not include components associatedwith all micro-habitats for all time periods. Whilesuch a possibility needs consideration in futurework, other reasons suggest that the diachronicpatterns delineated above reflect response toclimate change, not merely spatial variation. Fourof the sites that produced key components, CA-SLO-23, CA-SLO-457, CA-SLO-458, and CA-SLO-626 are located within 500 m of one anotheradjacent to the same part of the bay. CA-SLO-23 and CA-SLO-457 are separated by less than100 m, and produced similar residential toolassemblages. The three components at these twosites (Early, Middle-Late Transition, and Late)exhibit the strong shift to a marine resourcefocus that we believe was the general patternfor behavior around the bay during this interval.Furthermore, findings from other componentsshow uniformity across fish habitat zones. Forexample, the Early-period components from CA-SLO-165 at the mouth of the bay and CA-SLO-812 at the back of the bay are both heavilydominated by surfperches as is the Milling-stone/Lower Archaic component at CA-SLO-215, adjacent to a different habitat (Chorro Creekdelta).
216 [Vol. 82, No. 2, 2017AMERICAN ANTIQUITY
Seasonality
Remains of migratory animals suggest varia-tion generally consistent with component func-tions. High frequency of bat ray remains fromthe Millingstone/Lower Archaic component atCA-SLO-812 suggests that the short-term res-idential occupation here was focused on thesummer months (Table 4). Most sites occupiedafter that period show a broader seasonal rangeof occupation, although these indicators areabsent from CA-SLO-458, even though a rela-tively robust artifact assemblage was recoveredfrom that site. The Early-period components atCA-SLO-23 and CA-SLO-812 show four ofthe six winter migratory birds, but in relativelylow numbers (NISP = 11; 9.2 percent). Batrays are still dominant (NISP = 64), but theirrelative abundance decreases to 53.8 percent.Pile perch and marine mammals increase signifi-cantly (NISP = 44), representing 37.0 percent ofthe assemblage. The combined findings suggestthat occupation occurred during all seasons of theyear, which is consistent with the more robustnature of the artifact assemblages associatedwith the Early-period deposits at CA-SLO-23,CA-SLO-458, and CA-SLO-812 and the higherfrequency of features and burials. Multi-seasonoccupation is also apparent for the Middle-periodcomponents. The critical Middle-Late Transitioncomponent at CA-SLO-457 differs from othersin that it shows multi-season occupation, butalso a very heavy emphasis on fall, winter,and spring species. This is consistent with thegreater reliance on marine oriented birds. TheLate Period shows modest declines in fall-springindicators, which is consistent with decreasedemphasis on winter-migrating marine birds.
Conclusions
A robust collection of mammal, bird, fish, andshellfish remains from an 8,000-year residen-tial sequence at Morro Bay shows a decidedfocus on marine species during the Middle-LateTransition cultural phase (950–700 cal B.P.),which largely coincides with the Medieval Cli-matic Anomaly. This is consistent with find-ings from the Santa Barbara Channel 100 kmto the south, where research on the droughtshas a longer, more extensive history and where
Tabl
e4.
Freq
uenc
yof
Prim
ary
Ver
tebr
ate
Seas
onal
Indi
cato
rsov
erT
ime
from
Mor
roB
ay.
Mill
ings
tone
/M
iddl
e-L
ower
Lat
eA
rcha
icE
arly
Mid
dle
Tra
nsiti
onL
ate
Seas
onC
A-S
LO
-812
CA
-SL
O-2
3C
A-S
LO
-458
CA
-SL
O-8
12Su
btot
alC
A-S
LO
-14
CA
-SL
O-8
12Su
btot
alC
A-S
LO
-457
CA
-SL
O-2
3C
A-S
LO
-626
Subt
otal
Tota
l
Sum
mer
Bat
ray
1646
018
644
2024
2727
3461
192
Fall,
Win
ter,
Spri
ngPi
lepe
rch
138
00
3810
111
174
9094
184
408
Key
mig
ratin
g1
40
26
01
11
69
1524
mam
mal
s∗W
inte
rK
eyw
ater
fow
l1
80
311
31
439
2525
5010
5To
tal
1996
023
119
1723
4024
114
816
231
072
9
∗ Nor
ther
nfu
rse
alan
dC
alif
orni
ase
alio
n.∗∗
Gre
ater
whi
te-f
ront
edgo
ose,
redh
ead
duck
,red
neck
edgr
ebe,
blac
k-le
gged
kitti
wak
e,ea
red
greb
e,an
dca
nvas
back
.
Terry L. Jones et al.] 217THE MORRO BAY FAUNA
a heavy marine subsistence focus was firstrecognized as an apparent response to medievaldrought (Kennett and Kennett 2000). Previousfaunal studies from central coastal Californiaprovide modest evidence for increased fishing(Codding and Jones 2007; Joslin 2010) and amarked increase in rabbit exploitation (relativeto deer) during the Middle-Late Transition on theexposed coasts of central mainland California,but the Morro Bay findings indicate that thisestuarine setting served as a distinctive marine-focused subsistence refugium during the MCA.Due to a preponderance of shrub vegetation,rabbits dominate the entire 8,000-year MorroBay sequence, making the deer/rabbit ratio lesssensitive in this setting, although deer remainsdid reach a notable low (NISP = 7; 1.5 percent)during the MCA. More telling is an all-time peakin marine and estuarine birds, which is three-times higher during the Middle Late Transitionthan any other period in the sequence. Similarapices are apparent in fish NISP/m3 and fish/deer + rabbits, all of which are striking in theirdegree of variance and abundance during thiscritical interval of time. All of these indices alsoshow declines in marine focus during the ensuingLate Period, when climate ameliorated during thecolder, wetter Little Ice Age.
The heavy reliance on fish, aquatic birds,rabbits, and shellfish during the MCA suggeststhat use of the bow and arrow had little effect onthe pursuit of food, even though small numbersof arrow-sized projectile points appear in localmiddens for the first time around 1000 cal B.P.The technology might well have been involvedin intergroup conflict but, unlike areas to thenorth (Schwitalla et al. 2014) and south (Lambert1994), the Morro Bay area does not have askeletal record substantive enough to evaluatesuch a possibility.
Shellfish remains show a decided increaseduring the Middle-Late Transition, but, unlikethe vertebrate fauna, increase further after theMCA during the Late period. This suggests thatmarine foods were not tapped to the maximumduring the Medieval period and is further con-sistent with a recent evaluation of the regionalfishery that showed that it was never significantlyimpacted by regular Native harvest during theHolocene (Jones, Gobalet, and Codding 2016;
Jones et al. 2016). These findings indicate that,while drought influenced decision-making, sub-sistence economies in this setting had not reachedcrisis mode, at least not for the relatively largeblocks of time that can presently be distinguishedin the midden record. Nonetheless, the viabilityof the food base during the MCA is consistentwith the record of dental caries in the SanFrancisco Bay area (Schwitalla and Jones 2012),which suggests that people there weathered thedroughts through heavy reliance on stored foodsrich in carbohydrates, likely acorns. Continuedevaluation of the medieval droughts hypothesisneeds to critically examine evidence for thecharacter of actual responses and to sort out on aninterregional basis the degree to which the periodcan be accurately characterized as a time ofcrisis. Morro Bay, with a productive, sustainablemarine food base, was almost certainly not theonly such refugium; the presence and extentof others need to be carefully evaluated, as dopossible locations where food options were moreconstrained by drought and problems were moresevere.
Acknowledgments. We thank Nicole Birney for preparationof Figures 1 and 2. We also wish to thank Kate Ballantynefor her long, capable oversight of the Los Osos Wastewaterarchaeological project. The Spanish abstract was checked byAntonio Rodríguez-Hidalgo.
Supplemental Materials. Supplemental materials are linkedto the online version of the paper, accessible via the SAAmember login at https://doi.org/10.1017/aaq.2016.31.
Supplemental Table 1. Summary of Bird and MammalRemains from Morro Bay Sites.
Supplemental Table 2. Fish Remains (NISP) from MorroBay Components, Millingstone/Lower Archaic and EarlyPeriods.
Supplemental Table 3. Fish Remains (NISP) from MorroBay Components, Middle, Middle-Late Transition, and LatePeriods.
Supplemental Table 4. Shell Remains (Weight in grams)from Morro Bay Temporal Components.
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1. Only the control unit samples are considered here.For column sample results, see Far Western AnthropologicalResearch Group (2016).
2. Bird and mammal remains from CA-SLO-165 wereidentified by Tim Carpenter.
3. This reference collection was then housed at theDepartment of Biology, California State University, Bak-ersfield, and was subsequently donated to the California
Academy of Sciences Department of Ichthyology, SanFrancisco.
4. “Actinopterygii” is the chosen taxon here because itis more exclusive than “Osteichthytes,” which includes thelungfishes, coelacanths, bichirs, and their tetrapod descen-dants (Nelson 2006).
Submitted June 14, 2016; Revised October 2, 2016;Accepted October 3, 2016
