Erlandson, J.M., M.H. Graham, B.J. Borque, D. Corbett, J.A. Estes

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The Kelp Highway Hypothesis: Marine Ecology, the Coastal MigrationTheory, and the Peopling of the AmericasJon M. Erlandsona; Michael H. Grahamb; Bruce J. Bourquec; Debra Corbettd; James A. Estese; Robert S.Steneckf

a Museum of Natural and Cultural History, University of Oregon, Eugene, Oregon, USA b MossLanding Marine Laboratories, Moss Landing, California, USA c Department of Anthropology, BatesCollege, Lewiston, Maine, USA d US Fish and Wildlife Service, Anchorage, Alaska, USA e USGeological Survey, Long Marine Laboratory, University of California, Santa Cruz, California, USA f

School of Marine Sciences, University of Maine, Darling Marine Center, Walpole, Maine, USA

To cite this Article Erlandson, Jon M. , Graham, Michael H. , Bourque, Bruce J. , Corbett, Debra , Estes, James A. andSteneck, Robert S.(2007) 'The Kelp Highway Hypothesis: Marine Ecology, the Coastal Migration Theory, and thePeopling of the Americas', The Journal of Island and Coastal Archaeology, 2: 2, 161 — 174To link to this Article: DOI: 10.1080/15564890701628612URL: http://dx.doi.org/10.1080/15564890701628612

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Journal of Island & Coastal Archaeology, 2:161–174, 2007Copyright © 2007 Taylor & Francis Group, LLCISSN: 1556-4894 print / 1556-1828 onlineDOI:10.1080/15564890701628612

The Kelp HighwayHypothesis: MarineEcology, the CoastalMigration Theory, and thePeopling of the AmericasJon M. Erlandson,1 Michael H. Graham,2 Bruce J. Bourque,3

Debra Corbett,4 James A. Estes,5 and Robert S. Steneck6

1Museum of Natural and Cultural History, University of Oregon, Eugene,

Oregon, USA2Moss Landing Marine Laboratories, Moss Landing, California, USA3Department of Anthropology, Bates College, Lewiston, Maine, USA4US Fish and Wildlife Service, Anchorage, Alaska, USA5US Geological Survey, Long Marine Laboratory, University of California,

Santa Cruz, California, USA6School of Marine Sciences, University of Maine, Darling Marine Center,

Walpole, Maine, USA

ABSTRACT

In this article, a collaborative effort between archaeologists andmarine ecologists, we discuss the role kelp forest ecosystems mayhave played in facilitating the movement of maritime peoplesfrom Asia to the Americas near the end of the Pleistocene.Growing in cool nearshore waters along rocky coastlines, kelpforests offer some of the most productive habitats on earth, withhigh primary productivity, magnified secondary productivity,and three-dimensional habitat supporting a diverse array ofmarine organisms. Today, extensive kelp forests are found

Received 8 January 2007; accepted 29 June 2007.Address correspondence to Jon M. Erlandson, Department of Anthropology and Museum of Natural andCultural History, University of Oregon, Eugene, OR 97403-1224, USA. E-mail: [email protected]

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Jon M. Erlandson et al.

around the North Pacific from Japan to Baja California. Aftera break in the tropics—where nearshore mangrove forestsand coral reefs are highly productive—kelp forests are alsofound along the Andean Coast of South America. These PacificRim kelp forests support or shelter a wealth of shellfish, fish,marine mammals, seabirds, and seaweeds, resources heavilyused historically by coastal peoples. By about 16,000 yearsago, the North Pacific Coast offered a linear migration route,essentially unobstructed and entirely at sea level, from northeastAsia into the Americas. Recent reconstructions suggest thatrising sea levels early in the postglacial created a highlyconvoluted and island-rich coast along Beringia’s southernshore, conditions highly favorable to maritime hunter-gatherers.Along with the terrestrial resources available in adjacentlandscapes, kelp forests and other nearshore habitats shelteredsimilar suites of food resources that required minimal adap-tive adjustments for migrating coastal peoples. With reducedwave energy, holdfasts for boats, and productive fishing, theselinear kelp forest ecosystems may have provided a kind of“kelp highway” for early maritime peoples colonizing the NewWorld.

Keywords archaeology, marine ecology, kelp forests, maritime migrations, Pacific Rim

I can only compare these greataquatic forests . . . with the ter-restrial ones in the intertropicalforests. Yet if in any country,a forest was destroyed, I donot believe nearly so manyspecies of animals would per-ish as would here, from thedestruction of the kelp. Amidstthe leaves of this plant, numer-ous species of fish live, whichnowhere else could find foodor shelter; with their destruc-tion the numerous cormorantsand fishing birds, the otters,seals, and porpoise, would soonperish also; and lastly, theFuegian[s] . . . would . . . de-crease in numbers and perhapscease to exist. (Charles Darwin[1909:256–257]; 1 June 1834,Tierra del Fuego, Chile)

INTRODUCTION

Despite some important discussionsabout the feasibility of a coastal migra-tion route (e.g., Fladmark 1979; Mason1894), theories about the human col-onization of the Americas were dom-inated by terrestrial models for mostof the twentieth century. These terres-trial models generally involved huntingpeoples walking from northeast Asiaacross Beringia near the end of thePleistocene, passing through the fabled“ice-free corridor” and into the heartlandof North America. Only considerablylater, according to these models, did thedescendants of land-based Paleoindianssettle in coastal habitats and graduallyadapt to life by the sea. Some scholarswarned that the dearth of early coastalsites might be due to rising post-glacialsea levels, but numerous ∼13,000 year

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old (cal BP; all dates in this article areexpressed in calibrated calendar yearsbefore present) sites in interior regionsand a lack of coastal shell middensolder than about 10,000 years left thePacific Coast relatively peripheral todebate about how people got to the NewWorld.

During the last decade or so, despitethe effects of rising seas and marine ero-sion on the archaeological record, thecoastal migration theory has emergedas an increasingly viable alternative forthe peopling of the Americas (see Dixon1999, 2001; Erlandson 1994, 2002; Fedjeet al. 2004; Gruhn 1994; Jones et al.2002; Mandryk et al. 2001). The transfor-mation of the coastal migration theoryfrom marginal to mainstream is theresult of the gradual accumulation ofgeological and archaeological evidencefrom both coastal and interior regionsaround the Pacific Rim. Fluted Clovis-like points have now been found fromcoast to coast in North America, forinstance, and terminal Pleistocene siteshave been identified in several areasalong the Pacific Coast of North andSouth America (see Erlandson et al.1996; Keefer et al. 1998; Richardson1998; Sandweiss et al. 1998). Theseinclude shell middens or human skeletalremains found on islands in Alta andBaja California, sites that demonstratethat coastal Paleoindians had seaworthyboats and other maritime capabilitiesbetween about 13,000 and 11,500 calBP (Des Lauriers 2006; Erlandson 2007;Johnson et al. 2002; Rick et al. 2005).

Evidence for even earlier maritimevoyaging by anatomically modern hu-mans (Homo sapiens sapiens) hasemerged from islands of the westernPacific Rim, including the colonizationof Australia roughly 50,000 years agoand additional ocean voyaging to theislands of western Melanesia, the RyukyuArchipelago, and Japan between 40,000

and 30,000 years ago (see Erlandson2002; Fedje et al. 2004; with references).By the Last Glacial Maximum (LGM)these colonizing voyages placed mar-itime peoples near the base of the KurileIslands, which could have provided aseries of staging points for a maritime mi-gration to the Kamchatka Peninsula andthe south coast of Beringia (Erlandson1994:269).

While the feasibility of a coastalmigration route into the New Worldhas grown, recent geological and ar-chaeological evidence has clouded thepotential of an interior route to accountfor the earliest human colonization ofthe Americas. Recent geological studiessuggest that the ice-free corridor be-tween the Laurentide and Cordilleranice sheets only became passable about13,000 years ago (Burns 1996; Dixon1999:30; Jackson and Duk-Rodkin 1996;Mandryk et al. 2001), for instance, andthere is increasing interest in the hypoth-esis that humans colonized the Americasbefore that time (Madsen 2004; Mandryket al. 2001; Meltzer 2004). Although thesite remains controversial (see Fiedel1999), widespread scholarly acceptanceof debate about a 14,500 year old occu-pation of the Monte Verde site near thecoast of Chile (Dillehay 1997; Meltzeret al. 1997) has also contributed to abroader interest in the coastal migrationtheory by American archaeologists.

If a variety of evidence now sug-gests that a coastal migration aroundthe North Pacific may have contributedsignificantly to the peopling of theAmericas, relatively little is known aboutthe paleogeography and paleoecology ofNorth Pacific coastlines or their feasibil-ity as a late Pleistocene migration route.Our primary goal in this article is to helpfill that gap by discussing the natureand productivity of nearshore habitatsaround those portions of the Pacific Rimthat may have served as a migration

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route for early maritime peoples movingfrom East Asia into the Americas. Ourfocus is on the ecology and history ofkelp forests, which are present todayaround much of the Pacific Rim fromJapan to Baja California.

ECOLOGICAL CONTEXTS FOR THECOASTAL MIGRATION THEORY

In this section we examine some issuesrelated to coastal productivity, kelp for-est ecology, and the paleoecology ofNorth Pacific coastlines since the LastGlacial Maximum (LGM). These discus-sions provide a broader ecological con-text for understanding the habitats andresources early coastal peoples may haveencountered during a gradual migrationfrom Northeast Asia into the Americas.

Latitudinal Variation in CoastalProductivity

Anthropological characterizations ofmarine or aquatic productivity haveoften been relatively negative (e.g.,Osborn 1977; Washburn and Lancaster1968; Wilson 1981), but many coastalecosystems offer a diverse array ofboth marine and terrestrial resources forhuman foragers, especially those withefficient boats (Ames 2002; Bailey andMilner 2003; Erlandson 2001; Yesner1980). Not all coastal ecosystems areequally productive or accessible formaritime peoples, of course, and latitu-dinal variations in coastal productivityaround the Pacific Rim are significant,especially in considering the potentialfor human migrations around the NorthPacific. If such migrations occurred,they took place primarily in higherlatitudes (35–70◦N), where the coastaloceans are relatively productive andlarge-bodied prey species tend to beconcentrated. Freshwater ecosystems,in contrast, are generally more produc-

tive in lower latitudes, with numerousbiological consequences. Anadromousfish are found primarily in high latitudes,for instance, but catadromous speciesdominate at low latitudes, reflecting theselective advantage of adult life in food-rich environments (Gross et al. 1988).Similar patterns are seen in evolutionaryradiations among many aquatic mam-mals. Despite their nearly ubiquitousdistribution in freshwater habitats, forinstance, otters radiated into the sea onlyat higher latitudes, while small cetaceansradiated into freshwater habitats (riverdolphins) only at lower latitudes. Otherbiological manifestations of high-latitudemarine productivity are seen in rainbowtrout (Oncorhynchus mykiss) that growslowly in fresh water while anadromousconspecifics (steelhead) grow rapidly inthe sea. Coastal grizzly bears (Ursusarctos) also achieve a maximum adultbody mass two to three times greaterthan those in inland regions. These pat-terns suggest that the high productivityof northern coastal ecosystems—whereresources of both land and sea wereaccessible—would have been powerfulmagnets for early coastal or maritimepeoples migrating around the NorthPacific.

Marine Ecology of the CoastalMigration Route

During the Last Glacial Maximum,between about 25,000 and 20,000 yearsago, global sea levels were more than100 meters lower than today, exposinglarge expanses of the now submergedcontinental shelves around the PacificRim, including the broad and low-lying plains of Beringia that once con-nected Northeast Asia and NorthwestNorth America. Since the 1980s, sev-eral authors (e.g., Colinvaux and West1984; Elias et al. 1997; Guthrie 1989;Hopkins et al. 1982) have published ex-tensively on the nature and productivity

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of Beringia’s terrestrial environments,but descriptions of the potential pro-ductivity of coastal resources and theirpossible role in facilitating or inhibitingcoastal migrations around the NorthPacific have been comparatively vague(e.g., Hopkins et al. 1982; Mason 1894)and little was known about the specificnature of nearshore ecosystems.

Recent reconstructions of the post-glacial flooding of Beringia, however,suggest that its south coast was geo-morphically complex (Figure 1; Manley2002) with numerous bays, inlets, andislands that may have provided rich habi-tat for a variety of seals and cetaceans,walrus (Odobenus rosmarus), the mas-sive (and now extinct) Steller’s seacow (Hydrodamalis gigas), and otherrelatively large-bodied marine animals(Brigham-Grette et al. 2004:59). Dur-ing the summer months, such convo-luted coastlines—especially when com-bined with the low gradient of theBeringian platform—may have offeredbroad expanses of productive inter-tidal and nearshore habitats for earlymaritime peoples to hunt, forage, andgather in. As Ames (2002:38) illustrated,along such convoluted coastlines peoplein seaworthy boats can access muchlarger areas of nearshore habitat—andtransport much larger loads back toresidential bases—than those travelingon foot.

Much of the northern Pacific Rimis also characterized by marine up-welling or other forms of oceanic mixingthat fuel high plankton production incoastal zones, primary productivity thatis passed to higher trophic levels whereit is more available to humans. Anothermajor source of coastal productivityaround the North Pacific is found inextensive kelp forests that concentratebiomass, magnify secondary productiv-ity, subsidize terrestrial productivity,and support relatively complex food

webs in coastal ecosystems (see Dayton1985; Duggins et al. 1989; Graham 2004;Maron et al. 2006; Polis et al. 1997;Steneck et al. 2002).

Modern Kelp Forest Ecology

Around the Pacific Rim today, kelpforests dominate shallow rocky coasts incool and cold-water marine habitats. Thedistribution of kelp forests is physiolog-ically constrained by water temperature(generally <20◦C) and the availabilityof light, firm substrates, and nutrients(Mann 1973; North 1994; Steneck etal. 2002). Fast-growing and structurallycomplex, kelps are generally limited tonearshore waters less than about 30m deep (Dayton 1985; Graham et al.2003). Kelp forests are common fromJapan to the Aleutians and down thePacific Coast of North America intoBaja California (Figure 2). After a breakin the tropics—where productive coralreefs, mangrove swamps, estuaries, andother coastal habitats support similarsuites of marine fish, shellfish, and otheraquatic animals—kelp forests continuealong the Andean Coast, from Peru toTierra del Fuego.

The North Pacific has an especiallydiverse array of kelps, with at least21 species in the northeastern Pacificalone (Dayton 1985:235; Druehl 1970;Estes and Steinberg 1988). Large canopy-forming kelps dominate many PacificRim kelp forests, including the giantkelps (Macrocystis spp.) which growto heights of 45 m along the westcoasts of North and South America (Gra-ham et al. 2007). Smaller canopy kelps(e.g., Nereocystis luetkeana, Alaria fis-tulosa) reach heights up to 10 m andare common from central California toAlaska and from the Aleutians to north-east Asia, respectively (Druehl 1970).Stipitate kelps are smaller (< 5–10 mlong), but Laminaria dominates many




Figure 1. Manley’s reconstruction of the geography of the Bering Sea area and Beringia’s southcoast about 15,000 years ago (coastal conformation is approximate, not corrected fortectonic adjustments, offshore sediments, etc.; glaciers not depicted; adapted from Manley2002).

North Pacific kelp forests from Japan andnortheast Asia to coastal Alaska and thePacific Northwest (Druehl 1970).

Most Pacific kelps thrive along rockyshorelines in conditions of ample light,high nutrients, and moderate watertemperatures, but some varieties haveadapted to subarctic conditions withstrong seasonal fluctuations in lightlevels, nutrient availability, and watertemperatures—even surviving beneathwinter sea ice and blooming during alimited growing season (Dunton andDayton 1995). In the Sea of Okhotsk,for instance, kelp forests form an almostcontinuous belt along the coastline, pho-tosynthesizing during ice-free summers

and growing from carbohydrate storesduring ice-packed winters. As Dayton(1985:235) noted, some North Pacifickelps also exhibit considerable morpho-logical and ecological diversity depend-ing on local conditions, ranging fromperennial to annual and from floatingcanopies to short prostrate turfs. Underthe right conditions, however, kelpstend to grow relatively rapidly, enrichingcoastal ecosystems with organic produc-tion derived from their spores and plantdetritus (Graham et al. 2007).

Around the North Pacific, kelpforests historically supported or shel-tered a similar suite of animal andplant resources heavily exploited by

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Figure 2. General distribution of kelp forest ecosystems (hatched areas in white) of the PacificRim region today. Inset: shell midden on San Miguel Island, California, with highconcentration of abalone shells, sea urchin tests, and the remains of other kelp forestorganisms (figure drafted by M. Graham; inset photo by M. Moss).

coastal and maritime peoples withrelatively high population densities.These include sea mammals (sea otters,pinnipeds, etc.), a variety of marineshellfish (abalones, sea urchins, mus-sels, chitons, etc.) and fish, sea birds,and edible seaweeds. Many of theseresources—including numerous mem-bers of the same genus or species (e.g.,the sea otter, Enhydra lutris) found innearshore habitats around much of thenorthern Pacific Rim—were harvestedhistorically with relatively simple tech-nologies. Some species were availablein aggregations of highly vulnerableor behaviorally naive fauna (pinnipedrookeries, seabird colonies, and salmonruns, etc.) that could be captured inlarge numbers. For maritime peoples,along with providing a diverse array of

food resources, kelp forests also reducenearshore wave energy and provideholdfasts for boats.

Reconstructing Late Pleistocene KelpDistributions

For the broader Pacific Rim, thegeographic distribution and ecologicalproductivity of kelp forests near theend of the LGM are not well under-stood. Due to the clear parameters thatgovern their growth today, the distri-bution of kelp forests in the past canbe roughly approximated (see Kinlan etal. 2005), but direct evidence for theirgeographic distribution or productivityis limited (Graham et al. 2003). Basedon the diversity of North Pacific kelpspecies, as well as the organisms strongly




associated with kelp communities, Estesand Steinberg (1988; see also Estes etal. 1989) argued for a deep antiquityof kelp forests in the area. During thePleistocene, for instance, the massivesea cow ranged from Japan aroundthe North Pacific to central California,where it almost certainly fed primarilyon kelp (Clementz 2002). Kelp itselfdoes not preserve well in the fossilrecord (Estes et al. 2005:591; Graham etal. 2003) and virtually all late Pleistoceneshorelines where such fossils might befound have been submerged by risingpostglacial seas or lost to coastal erosion.The same can be said for most coastalarchaeological sites (see below) datingto the late Pleistocene, where we mighthope to find the remains of organ-isms such as large abalones (Haliotisspp.) and sea urchins (Strongylocentro-tus spp.) strongly associated with kelpforests (see Graham 2004). In the future,indirect evidence for the presence andproductivity of kelp may come fromisotopic or trace element studies of theorganic fractions of fossil organisms oreven seafloor sediments, but the base-line research to determine the feasibilityof such methods has not yet been done.For now, we are left with estimatingthe distribution of ancient kelp foreststhrough the use of bathymetric maps,sea level curves, and sea-surface temper-ature data.

Kinlan et al. (2005) modeled thechanging distribution of kelp forestsalong the California Coast during thepast 20,000 years, for instance, conclud-ing that kelp forests were significantlymore extensive and productive duringthe terminal Pleistocene than they aretoday. If this holds true for the broaderPacific Rim, rocky coastlines along muchof the North Pacific may have beeneven more attractive for early maritimepeoples than they were for the dense Na-tive American populations that occupied

much of the Pacific Coast at the timeof European contact. Moreover, the gen-erally cooler sea-surface temperaturesthat characterized the LGM in the NorthPacific may have shifted the boundariesof kelp forest ecosystems into somewhatlower latitudes than they are found intoday, possibly narrowing the tropicalgap in kelp forests in the eastern Pacific.

Today, the survival of productivekelp forests in the Sea of Okhotskalso suggests that kelp forests existedalong much of the North Pacific Coastthrough the LGM (Steneck et al. 2002).Kelps also survive under the coastal seaice of the arctic Beaufort Sea, wherethey have probably persisted since thebeginning of the Pleistocene (Vermeij1991). Given the apparent abundanceof complex rocky shorelines, sea sur-face temperatures consistent with kelpgrowth, seasonal sea ice cover, and thedearth of sediment-producing glaciersalong most of Beringia’s south coast,there is no reason to think productivekelp forests were not present. For muchof the period between about 18,200 and14,700 years ago, moreover, late-springto early-fall sea surface temperaturesappear to have warmed to 8–11◦C in thefar northwestern Pacific, when sea icecover may have been limited to aboutsix months per year (Sarnthein et al.2006:142–43) and kelp forests may havebeen even more productive.

Clearly, the south coast of Beringiawould have been highly dynamic dur-ing the early post-glacial period. Withthe possible exception of the YoungerDryas cold spell (∼13,000–12,000 calBP), this was a time of rapid sea levelrise and flooding of the Beringian plat-form. Coastal ecosystems are inherentlydynamic, however, and rocky intertidaland nearshore kelp forest communi-ties are full of organisms capable ofrapid recruitment and growth, suggest-ing that nearshore productivity would

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have continued to support the largerand more mobile organisms at highertrophic levels. Fueled by high primaryproductivity driven by a combination ofsummer plankton blooms and nearshorekelp growth, estuaries with freshwaterand terrigenous input, Beringia’s southcoast probably attracted a wealth oflarger animals (marine and terrestrial)that could have helped early coastal peo-ples expand their range from NortheastAsia into the Americas. Shortly after theLGM, populations of cetaceans and othersea mammals of the North Pacific mayalso have been relatively large, makingcoastal scavenging a highly productiveactivity.

KELP FORESTS AND NORTH PACIFICCOASTAL ARCHAEOLOGICAL SITES

From the indirect evidence of maritimeactivity in the Ryukyu Islands and Japandating to the late Pleistocene, a vastgeographic gap exists in coastal archae-ological records from Northeast Asiaand the now submerged south coastof Beringia. Only future archaeologicalinvestigations in the Kurile Islands andthe Kamchatka Peninsula will determineif evidence for Pleistocene maritimeactivity or coastal settlement is presentin these areas. Archaeological investiga-tions on the submerged southern shoreof Beringia itself would be extremelychallenging given the combination oflate glacial shorelines located far fromcurrent coastal ports, Holocene sedi-mentation, the expense of ship time, andthe logistics of cold water, deep diving,and high wave energy in the BeringSea.

Reconstructing the late Pleistocenecoastlines and human history of thePacific Coast of North America is alsofraught with difficulties, but much ofthe area has been more intensively

investigated by archaeologists and ge-ologists. This research has providedbaseline data that has helped scien-tists find increasingly early archaeolog-ical sites along the coastlines of thePacific Northwest, southern California,and Baja California. From Alaska to BajaCalifornia some of the earliest coastalarchaeological sites in North Americaare situated in island or mainland localesadjacent to highly productive kelp foresthabitats. These include terminal Pleis-tocene sites (>11,500 cal BP) at Arling-ton Springs, Daisy Cave, and CardwellBluffs on California’s Northern ChannelIslands, as well as on Cedros Is-land off Baja California. The Arling-ton Springs site (CA-SRI-173), datedto about 13,000 cal BP (Johnsonet al. 2002; Rick et al. 2005) containsonly scattered human remains and nofaunal remains or diagnostic artifacts. AtDaisy Cave (CA-SMI-261) and CardwellBluffs (CA-SMI-678), however, compo-nents dated between about 12,000 and11,500 cal BP contain the remains oflarge red abalones (Haliotis rufescens),black turban snails (Tegula funebralis),and other marine shellfish strongly asso-ciated with kelp forest habitats. At DaisyCave and other Channel Island sitesdated between about 10,200 and 9000cal BP, the remains of black abalones (H.cracherodii), black turban, sea urchin(Strongylocentrotus spp.), pinnipeds,sea otter, California sheephead (Semi-cossyphus pulcher), and other fish com-monly found in nearshore kelp forestshave all been recovered (see Erlandson,Braje, et al. 2005; Erlandson, Rick, et al.2005; Rick et al. 2001, 2005). At twosites on Cedros Island dated betweenabout 11,500 and 12,000 cal BP, DesLauriers (2006) has also documentedevidence for the exploitation of a varietyof marine resources (black abalones,sea otters, etc.) common in kelp forestcommunities.




Early coastal sites are rare from SanFrancisco Bay to Vancouver Island, prob-ably because of a history of subsidenceearthquakes and tsunamis associatedwith the Cascadia Subduction Zone (seeAtwater 1987; Darienzo and Peterson1990; Erlandson et al. 1998), but numer-ous sites dated between about 10,700and 9000 cal BP have been identifiedalong the coastlines of British Columbiaand Southeast Alaska (see Fedje etal. 2004). Most of these componentslack well-preserved faunal remains, butthe 10,600 year old Kilgi Gwaay siteproduced the remains of sea otters andother animals common in kelp foresthabitats (Fedje et al. 2005).

DISCUSSION AND CONCLUSIONS

In reviewing the evidence for associa-tions between early maritime peoplesand kelp forest communities, we are notsuggesting that all early Pacific Coastsites will be found adjacent to kelpforests or contain evidence for theirexploitation. Indeed, in many cases,estuaries, large salmon streams, pin-niped rookeries, and seabird coloniesmay have been equally attractive toearly maritime peoples. In other cases,following productive rivers inland fromthe coast—or hunting mammoths orelk in peri-coastal upland areas—mayhave been as tempting as following thecoast.

Clearly, there is much to be learnedabout the antiquity of human settlementand subsistence in various coastal areasfrom Japan to the Kurile Islands andKamchatka, and from the south coast ofBeringia to the southern tip of Tierra delFuego. There is also much to be learnedabout the distribution and productiv-ity of kelp forests, estuaries, mangroveforests, and coral reefs around the PacificRim in the past, as well as the degree

to which their productivity may haveinfluenced the antiquity, demography,and migrations of maritime peoples nearthe end of the Pleistocene.

Current evidence suggests, how-ever, that anatomically modern hu-mans had colonized or explored severalarchipelagos in the eastern Pacific by50,000 to 30,000 years ago, islands thatcould only be reached with seaworthyboats. During the LGM, maritime peo-ples living in the islands of Japan wouldhave been adapting to relatively coolwaters, potentially comparable to thosein parts of the Gulf of Alaska today.Between about 18,200 and 14,700 yearsago, three extended warming episodesin the northwestern Pacific may havereduced seasonal sea ice cover sig-nificantly, increased human access tointertidal and nearshore habitats, andfacilitated the migration of maritimepeoples from northeast Asia to Beringia(Sarnthein et al. 2006). By about 16,000to 15,000 years ago, a migration routefollowing the outer coast of northwest-ern North America appears to havebeen open and productive, providingan opportunity for maritime peoplesto migrate down the Pacific Coast intomore temperate climates.

Along with the relatively high pro-ductivity of kelp forests and othercoastal habitats, such a coastal migra-tion route had a number of advantagesover interior routes. Climatically, coast-lines are generally more equable thanadjacent interior regions, which canbe brutally cold or hot. Fresh watersources tend to be concentrated andeasily accessible in coastal zones (Faureet al. 2002) and coastlines also provideaccess to a diverse array of plant andanimal foods from both marine and ter-restrial ecosystems—resources that tendto be tightly packed in the relativelymountainous and steep coastlines thatcharacterize most of the Pacific Rim.

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By definition, a coastal route could alsohave been traversed by maritime peo-ples entirely at or near sea level, withno major geographic barriers after about15,000 years ago. The linear distributionof similar coastal habitats and resourcescould have provided expanding humanpopulations with an ecologically similarand easily followed migration corridorfrom northeast Asia to northwest NorthAmerica and beyond.

In contrast, terrestrial peoples mi-grating through the interior fromBeringia to southern South America atthe end of the Pleistocene would haveencountered numerous physical barriers(massive glaciers, large rivers, mountainranges and alpine passes, deserts, etc.)and a wide variety of terrestrial ecosys-tems: from Arctic tundra, to relativelysterile periglacial landscapes, boreal andrain forests, grasslands, deserts, andmore. As Madsen (2004:20–21) noted,foragers traversing these environmen-tal “megapatches” would have encoun-tered a wide variety of habitats, plants,and animals, some with very differentproperties or behaviors that requirednew technologies and knowledge tosuccessfully exploit.

A variety of archaeological, anthro-pological, genetic, and geological evi-dence provides growing support thatone or more coastal migrations con-tributed to the peopling of the Ameri-cas (Erlandson 2002; Fedje et al. 2004;Gruhn 1994; Kemp et al. 2007). Eco-logical data suggest that North Pacificcoastlines would have provided earlymaritime peoples numerous opportuni-ties to hunt, fish, and gather in juxta-posed marine and terrestrial habitats.Some of the most productive of thesecoastal ecosystems were kelp foreststhat are nearly ubiquitous along cool orcold-water rocky coastlines of the PacificRim. Characterized by relatively highprimary productivity and supporting

predictable aggregations of marine or-ganisms harvested and eaten by coastalpeoples for millennia, Pacific Rim kelpforests may have provided a linearand relatively homogenous ecologicalsetting through which early maritimepeoples could have migrated to the NewWorld.

Along the Pacific Coast of NorthAmerica, some of the earliest archae-ological sites are found in island ormainland coast settings adjacent to pro-ductive kelp forests. Where faunal re-mains are preserved, many of these sitescontain evidence for the harvest of shell-fish, fish, and sea mammals commonin kelp forests. Between about 18,000and 13,000 years ago, as glaciers andsea ice retreated from North Pacificcoastlines, a linear band of productivekelp forests may have extended discon-tinuously from Japan to Baja Califor-nia, providing a “kelp highway” thatcould have facilitated the migration ofmaritime peoples into the New World(Steneck et al. 2002:453).

Showing that a coastal migrationaround the North Pacific was possibleor even highly plausible is obviouslynot the same as demonstrating thatsuch a migration took place. Given therising seas, coastal erosion, and dramaticcoastal landscape changes that have oc-curred since the end of the LGM, provingthat such a coastal migration took placewill be extremely challenging. More ar-chaeological research is urgently neededon land and beneath the sea to helpsearch for late Pleistocene sites along thecoastlines of Japan, the Kurile Islands,Kamchatka, Beringia, and the PacificCoasts of North and South America.Additional research on the paleoecologyof North Pacific coastal ecosystems isalso needed to provide a better under-standing of the problems and potentialsposed by a coastal migration route fromAsia to the Americas.




ACKNOWLEDGEMENTS

Inspiration for the “Kelp Highway Hy-pothesis” emerged during kelp forestworking group meetings associatedwith the Long-Term Ecological Recordsof Marine Environments, Populations,and Communities Working Group,supported by the National Center forEcological Analysis and Synthesis andchaired by Jeremy Jackson. Our workwas supported by the National ScienceFoundation (Grant# DEB-0072909),the University of California, and ourhome institutions. We are indebted toMark Clementz, Michael Collins, PaulDayton, Jeremy Jackson, Brian Kinlan,Kent Lightfoot, Patricia Netherly, andan anonymous reviewer for their help-ful comments. Finally, we thank ScottFitzpatrick, Christine Armstrong, andthe editorial staff of JICA for help in therevision and production of this article.

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Erlandson, J.M., M.H. Graham, B.J. Borque, D. Corbett, J.A. Estes