Origins and spread of fluted-point technology in theCanadian Ice-Free Corridor and eastern BeringiaHeather L. Smitha,1 and Ted Goebelb

aDepartment of Anthropology and Applied Archaeology, Eastern New Mexico University, Portales, NM 88130; and bCenter for the Study of the FirstAmericans, Department of Anthropology, Texas A&M University, College Station, TX 77843

Edited by David J. Meltzer, Southern Methodist University, Dallas, TX, and approved March 5, 2018 (received for review January 25, 2018)

Fluted projectile points have long been recognized as the archae-ological signature of early humans dispersing throughout theWestern Hemisphere; however, we still lack a clear understandingof their appearance in the interior “Ice-Free Corridor” of westernCanada and eastern Beringia. To solve this problem, we conducteda geometric morphometric shape analysis and a phylogenetic anal-ysis of technological traits on fluted points from the archaeologicalrecords of northern Alaska and Yukon, in combination with arti-facts from further south in Canada, the Great Plains, and easternUnited States to investigate the plausibility of historical related-ness and evolutionary patterns in the spread of fluted-point tech-nology in the latest Pleistocene and earliest Holocene. Results linkmorphologies and technologies of Clovis, certain western Cana-dian, and northern fluted points, suggesting that fluting technol-ogy arrived in the Arctic from a proximate source in the interiorIce-Free Corridor and ultimately from the earliest populations intemperate North America, complementing new genomic modelsexplaining the peopling of the Americas.

peopling of the Americas | Paleoindian technology | Ice-Free Corridor |geometric morphometrics | cladistics

Evidence for the dispersal of modern humans throughout theAmericas has often been tied, archaeologically, to the

emergence and spread of fluted-point technology in the Paleo-indian era, as early as 13.4 thousand calendar years ago (ka) (1).Unique to the Americas, a flute removed from the base of astone projectile point in preparation for attachment to a haft canserve as a proxy for investigating transmission of technology andmaterial culture among the first Americans (2, 3). The earliestwell-dated fluted projectile-point form—Clovis—occurs pre-dominantly in the continental United States in contexts datingbetween 13.4 and 12.9 ka, coeval with rising temperatures of theAllerød interstadial (1, 4). By the onset of the Younger Dryascooling event (12.85 ka) fluted points had become prevalentthroughout the Western Hemisphere, in the process becomingvariable in morphology and technology, hypothetically theresult of technological adaptation to increasingly variable lo-cal ecological conditions, cultural drift, or both (5). Post-Clovis forms include Folsom in the Rocky Mountains andPlains, Barnes in the Great Lakes, Cumberland in theAmerican Southeast, and fluted Fishtail in South America (6–8). From eastern Beringia [i.e., Alaska and northern Yukon(Canada)] we can add northern fluted forms, now in-dependently dated to 12.7–10.7 ka at two archaeological sitesin northwest Alaska (9).Fluted-point forms vary considerably from north to south,

so that specific dispersal events within the hemisphere can beconsidered independently to develop a full understanding ofhow Paleoindian groups came to occupy the entire New Worldin a relatively short period. We focus on fluted points in theArctic because they are situated geographically in the rem-nants of the Bering Land Bridge, the presumed starting pointof the American dispersal, and because Arctic fluted formshave been hypothesized to share ancestral traits with earlyfluted points of the midcontinent. Accordingly they poten-tially represent a late Pleistocene social connection through

the western Canadian “Ice-Free Corridor” and the result ofnorthward human migration or cultural transmission, an un-tested hypothesis proposed more than a half-century ago (10).Alternative theories to explain the similarities in flutingtechnology north and south of the Canadian ice sheets in-clude an Arctic origin followed by southward movementthrough the Corridor, and even independent invention of thetechnologies (11). Until recently a lack of empirical evidencehas prevented testing of any of these theories. New researchinto the environmental viability of the Corridor suggests thata connection between midcontinent fluted-point producersand the Arctic was possible and, thus, a historical relation-ship between fluted-point technologies in the two regions isplausible (12, 13).Specifically, to explain the presence of fluting technology in

Arctic North America, we hypothesized that an evolutionaryrelationship between these fluted-point variants is implied bymorphological affinity in shape and indicated by patterns in thedistribution of ancestral and derived technological traits (fol-lowing ref. 14). We predicted that cladistic analysis would gen-erate phylogenetic trees showing a patterned distribution oftraits in which the northern fluted points and points from theCorridor are organized into clades, with Clovis positioned astheir most recent and common ancestor. Alternatively, if cla-distics produced trees upon which Clovis was not the most recentcommon ancestor of northern fluted and Corridor materials,then our hypothesis of an evolutionary relationship cannot besupported and any evidence of morphological affinity may beattributed to adaptive convergence. To test this hypothesis, wepresent a geometric morphometric and a phylogenetic analysis of

Significance

We report geometric morphometric and cladistic analyses ofarchaeological materials establishing early human interactionbetween the North American Arctic, western Canadian “Ice-Free Corridor,” and temperate North America prior to12,000 years ago, when the Corridor is inferred to have openedafter initial retreat of the continental ice sheets. The findingsinform a broad range of scientists engaged in genomic, evo-lutionary, ecological, climatological, geological, and anthropo-logical studies of the late Pleistocene, providing tangibleevidence of human dispersal through the Americas and placingthe archaeological record in the context of new genetic modelschronicling the initial migration into America, as well as pa-leoecological interpretations of the “opening” of interiorwestern Canada’s earliest habitable environments.

Author contributions: H.L.S. and T.G. designed research; H.L.S. performed research; H.L.S.analyzed data; and H.L.S. and T.G. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

Published under the PNAS license.1To whom correspondence should be addressed. Email: heather.l.smith@enmu.edu.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1800312115/-/DCSupplemental.

Published online April 2, 2018.

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fluted points from Alaska, northern Yukon, the Ice-Free Corri-dor, temperate Great Plains, and eastern United States andCanada. Evidence of affinity, and therefore cultural relatedness,in fluted-point morphologies and technologies (15) was evalu-ated by examining geographic and chronologic patterns in vari-ation that demonstrate evolution of point form and technologyand, ultimately, the direction of early human dispersal throughthe continent.In this paper we address two focal questions: Is there a strong

morphological and technological relationship between north-ern fluted points, Corridor points, and temperate NorthAmerican points, suggesting the potential for homology? And ifso, which of the temperate complexes best represent thenorthern fluted complex’s immediate and ultimate antecedents?We consider the ecologies and behaviors associated with thesefluted forms to establish the content and context that mayhave led to the northward spread of Paleoindian fluted-pointtechnology (16).Our evolutionary perspective considers morphological and

technological characteristics of stone tools to be cultural traits,the patterning of which may represent cultural descent withmodification when complemented by gradients of temporal andspatial archaeological context (3, 17, 18). This perspective in-forms our hypothesis of a phylogenetic relationship betweenArctic and midcontinent fluted-point traditions. To test for apatterned distribution of traits among the fluted specimens inour sample, we observed trends in two dimensions: (i) fluted-point basal morphology, identified in statistical analyses of shapedata generated using geometric morphometrics (GM); and (ii)technology and morphology, highlighted by eight specific traitsthat represent key characteristics of fluted-point variation, usingcladistics to test for homology among traits.GM data collection highlighted the basal portion of each

fluted point in the sample. Basal portions were designed in ad-vance of use to fit a predesigned haft, were the component mostresistant to alteration during resharpening and maintenance, andare the most readily identified fragment of broken points (19–24). Focusing on point bases also maximized the available sample.Although Paleoindians occasionally, and possibly intentionally,reworked bases (especially while recycling distal fluted-pointfragments) (21–23), previous analyses recognized little varia-tion in basal shape that could be attributed to original basingversus rebasing (23, 24). Major factors of variability in fluted-point morphology in the Alaskan, western Canadian, and tem-perate North American samples were evaluated using a GMdataset of 200 specimens representing forms from the northernfluted, Ice-Free Corridor, Northeast, and Great Lakes regions,Folsom in the Great Plains, and Clovis from across North America(Fig. S1). Principal component (PC) scores of shape variationgenerated in relative warp analysis were used to visualize shapecharacteristics representing major factors of variability in NorthAmerican fluted forms and in multivariate analysis of variance(MANOVA) (following ref. 25) to evaluate variance in shapeacross the continent and in discriminant function analysis (DFA)(following ref. 26) to heuristically examine morphologicalaffinity.We further evaluated trends in morphological affinity by

ordinally comparing frequencies of technological attributes thatbest characterized variant fluted-point manufacturing strategiesand, as a result, eight characters were found to generate thegreatest parsimony among 246 fluted specimens (i.e., the200 fluted points included in the GM dataset plus 46 that couldnot be included in the GM) (Figs. S3 and S4): average number offlutes on both faces, uniformity of number of flutes on bothfaces, basal retouch after fluting, lateral retouch after fluting,sequence of flute removals, basal shape (27), basal indentationlength, and fluted-area to basal-width ratio (see SupportingInformation for visual descriptions of characters) (Fig. S2).These eight traits were used in cladistic analyses based on theirability to reflect normative manufacturing choices and not

consequences of resharpening or rejuvenation [e.g., bladelength, face angle (21, 24)].

ResultsGM Analysis. For the entire dataset, more than 95% of vari-ability in basal shape was expressed in the first five PC axes(Fig. 1). See Supporting Information for descriptions of PC-axis shape characteristics and least-squares means of PCloadings for each complex/region (Fig. S5 and Table S2).MANOVA evaluated models of morphological affinity bytesting variation in shape and form among fluted points or-ganized by complex/region.For shape (in which size is used as a covariate to characterize

and control for linear allometry), F-statistics indicated significantvariation with regard to radiocarbon age, cultural complex/re-gion assignments, and size (Table 1). Considering latitude andlongitude, MANOVA did not identify significant variation inshape, indicating similarities exist along those gradients. Forform (which considers size in addition to shape), variation wasalso identified according to radiocarbon age and complex/region,but not in latitude and longitude (Table 1). Overall, geographicalpatterning suggests some morphological affinity exists interre-gionally along both gradients of latitude and longitude.As a heuristic investigation of shape organization, seven cat-

egories were considered in the DFA: Northern Fluted, Ice-FreeCorridor, Clovis, Clovis Caches, Folsom, Great Lakes, andNortheast (Figs. 2 and 3). DFA predictions (Dataset S1) led tomisclassifications of 38% of the dataset (Table 2). Clovis Cachepoints were the most accurately assigned with 91% classified asClovis Cache and the remaining 9% as Clovis. Northeast andFolsom points also classified well with 77% and 76% accuracy,respectively. These represent the three most homogeneousgroups in the dataset.Noncached Clovis and Great Lakes points were not so accu-

rately classified in the DFA. For Clovis, of which 60% classified

Fig. 1. Graphic depictions of the first five principal component axes gen-erated from the GM analysis.

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correctly, misclassifications were mostly assigned to Great Lakes(17%) and Clovis Cache (11%). The Clovis Cache assignmentsare not surprising, and the Great Lakes assignments likely reflectsome Clovis forms having pronounced basal concavities like thatregion’s Barnes points. For Great Lakes points, 52% wereassigned correctly, while most misclassified specimens wereassigned to Folsom (32%), presumably because some of thesepoints have angular basal concavities characteristic of the Fol-som complex points. Two points (8%, one from Parkhill and onefrom Thedford II) were misidentified as Clovis points, and an-other two Parkhill points (8%) were assigned to northern fluted,a potential product of their deeper V-shaped concavities andslightly flared basal corners.Northern fluted points were not well attributed in the DFA,

with only 42% classified correctly. Major shape characteristicsthat particularly describe these specimens are deep, curvilinear,and V-shaped basal concavities with straight lateral margins andslight proximal flaring (negative loadings of PCs 1–4). DFAassigned 31.5% of northern fluted points to Clovis, and theremaining 26% were dispersed fairly evenly (i.e., one or twopoints) among all categories except Clovis Cache, indicating at-tributes present on individual points are represented in multiple(noncached) fluted-point categories.Only 14% of the Ice-Free Corridor points were classified

correctly, indicating significant variability present in the sample.These specimens have variably shaped bases, with either deeplycurved basal concavities and straight lateral margins, or shallowbasal concavities and convex lateral margins (PC2 positiveloading; PC3 and PC4 negative loadings). Most Ice-Free Corri-dor points were classified as Clovis and Clovis Cache (41%),indicating the presence of morphologically Clovis-like points inrecently deglaciated western Canada. Another 23% wereassigned to the Great Lakes group, suggesting the additionalpresence of both Barnes and Crowfield-like forms in the Corri-dor. One point from Charlie Lake Cave and two points fromPink Mountain (14%) were assigned to the Northeast group as aresult of their common deep rounded basal concavities andslightly excurvate lateral margins (PC1 positive loading, PCs 2–4 negative loadings).In a DFA generated without points from the Ice-Free Corri-

dor only 31% of specimens misclassified (Table S3). Two Clovispoints previously assigned to the Ice-Free Corridor werereassigned to Clovis. Great Lakes points previously assigned tothe Ice-Free Corridor were instead misclassified as northernfluted. The sole northern fluted point previously misclassifiedto the Ice-Free Corridor was reassigned to the northern flutedcomplex.Overall, for every group, a percentage of points misclassified

as Clovis, a taxonomic pattern indicating Clovis morphology mayrepresent an ancestral state for all fluted-point variants (27). Themost robust classifications were in the Clovis Cache, Folsom,and Northeast groups, while DFA had themost difficulty distinguishing

northern fluted and Ice-Free Corridor points from Clovispoints, as well as Great Lakes points from Folsom.

Cladistic Analysis. The cladistic analysis consistently producedphylogenetic trees with similar patterning and retention indicesof 0.74 and 0.73 (Figs. S3 and S4), suggesting that a promisingdegree of phylogeny is represented (following ref. 28).In the trees rooted by a Clovis point from the Gault site, Texas

(Fig. 4; see also Fig. S3 for positions of individual points), severalingroup taxa consistently appear early, partitioned by nodes A–F,which produced four northern fluted points, two Corridorspecimens (from Sibbald Creek), two Clovis points (from Nacoand Cactus Hill), and two points from the Great Lakes region(Crowfield). The seventh node (G) connects a polytomy com-prising two clades, the first consisting of northern fluted (71%),Clovis (14%), and Folsom (14%) points; and the second, Clovis(34%), northern fluted (29%), Corridor (19%), Great Lakes(12%), Northeast (3%), and Folsom (3%) points; as well as theancestor of the clades in which the remaining taxa occur. NodesH–I partition four points from the Corridor, northern fluted, andGreat Lakes (Crowfield and Thedford II) groups. Node Jresulted in a polytomy where the frequencies of northern fluted(4%) and Clovis (7%) points are greatly diminished, whileNortheast (43%) and Great Lakes (25%) points dominate theclades, followed by Corridor (14%) and Folsom (7%) points.The remaining character-state changes further partition taxainto clades characterized by a majority of Folsom points (nodesL and M) or Great Lakes and Northeast points (node S), bothof which are joined by points from the Corridor that mayrepresent the presence of these forms at some point inwestern Canada.A similar pattern of taxon positioning occurs in the trees

rooted by a Clovis point from the Blackwater Draw site, NewMexico, presented in detail in the Supporting Information. Con-sistent with the Gault-rooted trees, ancestral nodes appearingearly in the trees form clades with high frequencies of northernfluted, Clovis, and Ice-Free Corridor points. Character-statechanges denoted later in the trees further partition taxa intoclades in which the majority of Northeast, Great Lakes, andFolsom points occur.

DiscussionContent: Morphology and Technology. Our analysis demonstratespatterned distribution of morphological and technologicalcharacteristics among fluted-point forms. The first five PCsgenerated for the GM dataset demonstrate a range of variabilitypresent in North American fluted-point basal morphology, andwhile MANOVA identified variation according to age, size, andcomplex, it suggested affinity in shape exists on a latitudinalgradient and less so according to longitude. This latitudinalpatterning in basal shape also appeared in the DFA results,

Table 1. MANOVA results for shape and form

Model F dfn/dfd P ηp2

ShapeRadiocarbon date 2.49 95/457 <0.0001 0.34Sites (complex) 2.12 130/759 <0.0001 0.27Latitude 1.33 5/153 0.2552 0.04Longitude 1.99 5/153 0.0838 0.06Latitude × Longitude 1.99 5/153 0.0828 0.06Size 90.16 5/153 <0.0001 0.75

FormRadiocarbon date 8.10 120/655 <0.0001 0.58Sites (complex) 3.70 156/958 <0.0001 0.38Latitude 1.38 6/159 0.2261 0.05Longitude 1.32 6/159 0.2522 0.05Latitude × Longitude 1.32 6/159 0.2504 0.05

Fig. 2. Fluted point examples included in the analysis: (A) the northernfluted complex, (B) Northeast, (C) Folsom, (D) Clovis and Clovis Caches, and(E) Great Lakes.

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demonstrating the greatest morphological affinity betweennorthern fluted points, a selection of fluted points from the Ice-Free Corridor (i.e., specific points from Sibbald Creek, LakeMinnewanka, Wally’s Beach, and additional isolated finds), andClovis. There were few misclassifications between northernfluted and Folsom, suggesting ancestral characteristics sharedbetween northern fluted and Clovis points were brought to theCanadian Plains and into the Ice-Free Corridor before the de-velopment of Folsom in the temperate Great Plains and RockyMountains. Additionally, Paleoindian groups of the northernGreat Lakes, likely representing Clovis descendants manufactur-ing Barnes points, may have initially dispersed along the edge ofthe retreating Laurentide ice sheet, also transmitting fluting infor-mation into the Corridor (Fig. 5). According to the shape analysis,however, while 23% of Corridor points were assigned to the GreatLakes group, none of the Great Lakes points were assigned to theCorridor, possibly suggesting unidirectional, westward transmission.These patterns in morphological affinity encouraged us to furthertest for evidence of homology by exploring for patterns in ancestraland derived technological characteristics.Cladistic analysis produced a pattern of character-trait distri-

butions that suggests northern fluted points and specific pointsfrom the Ice-Free Corridor share more common ancestral andderived traits with Clovis than either do with points representingthe Great Lakes, Northeast, or Folsom groups. Focusing onfrequencies of points (taxa) organized into each clade, two ad-ditional trends become clear. First, the occurrence of Clovispoints in all clades suggests that aspects of fluting technologypresent in the Clovis range of variation represent ancestral traitspresent in all variants of fluted points in this dataset (see also ref.27). Second, resulting cladograms did not perfectly partitionpoints into clades according to previously defined groups or ty-pologies. We interpret this reshuffling to represent noiseresulting from manufacturing reversals occurring at the individ-ual level, discrepancies in original typological assignments or, in

the case of the Corridor especially, the potential conflation ofvarious fluted-point industries present during the latest Pleisto-cene and early Holocene. Despite this, the geographic distribu-tion of points in the earliest clades supports the hypothesis thatClovis, early points from the Corridor, and northern flutedpoints share historical affinity and may represent either Clovisgroups moving north through the Ice-Free Corridor to northernYukon and Alaska, or the interaction of Clovis groups with hu-mans already present in the northwestern Subarctic and Arctic.Both of these processes of fluted-point transmission to the northare supported by latitudinal and chronological trends. Whilemany of the Corridor points are not associated with radiocarbondates, two sites, Charlie Lake Cave (12.7–11.3 ka) and LakeMinnewanka (13.1–11.3 ka) (12, 29), date to just before or coevalwith sites containing northern fluted points (9). The cladogramsalso suggest that many of the poorly dated Corridor points (30)have derived traits that better reflect different types from variousregions than they do a local type or set of types. This suggeststhat fluted-point users from numerous regions including thePlains, Great Lakes, Northeast, and potentially even the Arcticwere present in the Corridor at different points in time.

Ecological Context: The Potential for Information Transmission. En-vironmental context influences the type, distribution, and availabilityof floral, faunal, and lithic resources, as well as group-mobilitystrategies, creating the adaptive context that could host thespread of fluted-point technology northward into western Canadaand the Arctic. Fluting likely first appeared in the southern GreatPlains of temperate North America, in a diverse setting of openspruce parkland, piñon-juniper woodlands, and steppe dominatedby grasses with distinct riparian zones, which together supportedlarge grazers such as mammoth and bison, the remains of whichare often associated with Clovis sites (4). During the latest Pleis-tocene, elements of this mosaic became present in the Ice-FreeCorridor, which increasingly connected the western North Americaninterior to Beringia (31, 32). Environmental reorganization duringthe Younger Dryas (12.85–11.7 ka) across North America, how-ever, was variable in degree and schedule (33, 34), potentiallyinfluencing the diversification of Paleoindian fluted-point formsand adaptive behavior. Grassland expansion throughout the Plains,which supported large bison (Bison sp.) herds, led to distinctiveecological opportunities for later Paleoindians (i.e., Folsom),while the expansion of temperate deciduous forests of the Mid-west and eastern United States as well as the shrub-tundra innortheastern North America (5, 33, 35) likely facilitated the evo-lution of other, non-Folsom Paleoindian complexes, like Barnesand Crowfield in the Northeast and Great Lakes, and Redstoneand Cumberland in the Southeast (6).In the interior Northwest, Clovis, Ice-Free Corridor, and

Northern Fluted groups experienced similarly structured bioticenvironments supporting herds of bison and other megaherbivores.Some Clovis groups, or descendent Clovis groups, appear to havedispersed into the locally variable environments of westernCanada that formed during postglacial recovery (13). The pres-ence of these new landscapes potentially pulled Clovis groupsprogressively northward, eventually beyond the Plains’ grassland

Table 2. Results of DFA employing seven divisions of typological and regional categories: NFC, Clovis, Clovis Caches, Folsom, Ice-FreeCorridor, Great Lakes, and Northeast as grouping variables (38% misclassified, actual classifications are in rows and predictedclassifications are in columns)

Region Clovis Clovis Cache Ice-Free Corridor Northeast Great Lakes Folsom Northern Fluted Total

Clovis 21 4 2 1 6 1 0 35Clovis Cache 2 20 0 0 0 0 0 22Ice-Free Corridor 8 1 3 3 5 2 0 22Northeast 3 1 1 24 0 2 0 31Great Lakes 2 0 0 0 13 8 2 25Folsom 3 0 1 1 4 35 2 46Northern Fluted 6 0 1 1 2 1 8 19

Fig. 3. Examples of fluted points from the Ice-Free Corridor that wereassigned by DFA incorrectly to Clovis: (A and B) Sibbald Creek (EgPr2-8385,EgPr2-7229); (C and D) Lake Minnewanka (ROA1-863, ROA1-977); (E) Wally’sBeach (H99-22-4275); (F) DkPj38-170; (G) Hb7-354-4; (H and I) H06 (H06-17-2,H06-17-3); and correctly to the Ice-Free Corridor: (J) Lake Minnewanka(EhPu-1-144); (K) H90-142-1; (L) Clearwater Pass (1717R1A-1).

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(36) and into the Subarctic shrub-tundra (37). This process be-gan before the development of Folsom in the expanding grass-lands of the temperate Plains (12.8 ka) and Folsom’s eventualentrance into southcentral Canada (38).Bison were potentially integral to the adaptation of the

northward-dispersing fluted-point makers. During the last glacialmaximum (ca. 24 ka), bison clades of Beringia were geneticallydistinct from those living south of the ice sheets (32); however, by12.3–12 ka, a southern clade of bison had dispersed northwardinto the Ice-Free Corridor, reaching the Northwest Territoriesand becoming sympatric with the northern clade (12). Our re-sults suggest an analogous process of human dispersal or in-formation transmission, with humans from the southern Ice-FreeCorridor spreading north to Arctic Alaska. As fluting technologyspread northward, bison (Bison sp.) were still common in theCorridor, from Charlie Lake Cave in central British Columbia toEngigstciack in northern Yukon (32, 39). In Arctic Alaska,however, bison became locally extinct by 13.5 ka (12, 40), so thatfluted-point–using groups in the Far North had to adjust their

predatory focus to caribou (Rangifer tarandus), which were bettersuited to the region’s tussock-tundra communities (41). Notsurprisingly, faunal assemblages from the only buried and datedfluted-point sites in northwestern Alaska contain caribou, notbison (9). This shift toward caribou could have occurred in theCorridor, as fluted-point makers were pulled northward andeastward along the margin of the retreating Laurentide ice,resulting in high frequencies of ancestral traits shared by Clovis,the early Ice-Free Corridor, and Great Lakes point forms.The content and context of Clovis, Ice-Free Corridor, and

northern fluted groups discussed above suggest potential forhistorical relatedness in technology, leading to the followingconclusions: (i) northern fluted complex morphology and tech-nology was not independently invented in the north, but origi-nated proximately in the Ice-Free Corridor, and ultimately fromClovis in temperate North America; and (ii) different traitspresent in Clovis fluted-point technology were selected by hu-man groups in different ecological settings leading to regionalvariations in late Paleoindian projectile-point morphology andtechnology.Although with the evidence at hand we cannot unequivocally

determine whether the appearance of the northern fluted com-plex resulted from actual human dispersal and cultural drift or,alternatively, the transmission of cultural traits among preexist-ing peoples, emerging ancient genomic evidence supports thelikelihood of northward back-migrations of humans during themillennia following initial human dispersal into temperateAmerica (42, 43). Also unresolved is how the northern flutedcomplex relates to other end-Pleistocene Alaskan cultural tra-ditions, such as the “Mesa complex,” which is primarily charac-terized by unfluted lanceolate bifacial points but could stillrepresent the same northward spread from the temperate Plains(with the differences in point technology representing variabletool function) (9, 44). Interestingly, the people of the centralAlaskan “Denali complex,” with their radically different com-posite projectile technology of osseous points inset with stonemicroblades, may have escaped early interaction with the fluted-point makers, as suggested by the newly reported ancient ge-nome from the Upward Sun River site, which contained no

Fig. 5. Map showing extent of glacial ice at 12 ka and 11 ka, examples ofregional fluted-point forms, and inferred dispersal directions of fluted-pointtechnological groups from a Clovis “heartland” north into the Ice-FreeCorridor and Beringia, east to the northern Great Lakes and far Northeast,and back to the northwest along the southern edge of the Laurentide icesheet. Clovis existed in the American Southeast, too, but points from thisregion were not included in the present analysis.

Fig. 4. Phylogenetic tree (50% majority-rule consensus tree, RI = 0.74)rooted by a projectile point from the Gault site (4801-1). Proportions ofpoints partitioned into clades are shown in pies at Right (GL, Great Lakes;IFC, Ice-Free Corridor; NE, Northeast; NFC, northern fluted complex).

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evidence of interaction with Clovis descendants (43). Instead,microblade technology appears to have spread from Alaska intointerior western Canada a millennium or more later than theevents discussed here (45). Continued archaeological fieldworkand artifact analyses, incorporating both morphological andtechnological trait distributions coupled with ancient genomicstudies of human remains, are required to test these hypoth-eses and develop a complete portrayal of the peopling ofthe Americas.

Materials and MethodsAnalytical procedures are detailed in Supporting Information. We conducteda 2D landmark-based GM analysis of proximal-fragment shape using anapproach to produce horizontal alignment of segmented outlines in prep-aration for Procrustes superimposition, permitting a focus on basal mor-phology and inclusion of fragmented artifacts (n = 200) (23). Warp scoresresulting from Procrustes superimposition were subjected to PC analysis, andresulting PC scores summarizing 95.57% of total variation were used torepresent basal-fragment shape (25). PCs of shape variation were used tovisualize shape characteristics representing major factors of variability in thesample of North American fluted points and in MANOVA (following ref. 25)(of tool shape and form), which evaluated variability in shape for four mainmodels (chronology, size, complex/region, and geography), and in DFA(following ref. 26) and leave-one-out cross-validation, using JMP softwarev10 (SAS Institute) and R (v3.2.1), in which affinities between individual

points and regions were further explored. Effect strengths (ηp2) were cal-culated from E and H matrices of the JMP output.

Eight technologically based character traits were analyzed using a heuristicsearch in PAUP* 4.0a (46) to independently examine affinities in shape withpatterns in technology (n = 246). We used two different projectile points asoutgroups to root the resulting cladograms and generate 50% majority-ruleconsensus trees: a fluted point from the Gault site (4801-1) to root one set ofphylogenetic trees, and a fluted point from the Blackwater Draw site (1963-NB-A186) to root a second set of trees (see Supporting Information for ex-planation of point selection).

ACKNOWLEDGMENTS. We thank David Meltzer, Thomas DeWitt, Kelly Graf,Michael Waters, David Carlson, and two anonymous reviewers whose critiquessignificantly improved this research. Access to collections was graciouslyprovided by curators and professors at the University of Alaska-FairbanksMuseum of the North, Bureau of Land Management in Fairbanks, NationalPark Service in Fairbanks and Anchorage, Royal British Columbia Museum,Simon Fraser University Archaeology Department, Royal Alberta Museum,University of Alberta Anthropology Department, Parks Calgary, University ofWestern Ontario Anthropology Department, Museum of Ontario Archaeol-ogy, Canadian Museum of History, Smithsonian National Museum of NaturalHistory, Texas A&M University Center for the Study of the First Americans andAnthropology Department, University of Wyoming Frison Institute and An-thropology Department, and Eastern New Mexico University Department ofAnthropology and Applied Archaeology and Blackwater Draw National His-toric Landmark and Museum. The Arctic Social Sciences and Archaeology pro-grams of the US National Science Foundation (1204085 and 1019190)supported this project.

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