Ice-free Corridor Research Articles

The Search for the First Americans: Science, Power, Politics by Robert V. Davis

Reviewed by: The Search for the First Americans: Science, Power, Politics by Robert V. Davis G. Richard Scott The Search for the First Americans: Science, Power, Politics. By Robert V. Davis. Norman: University of Oklahoma Press, 2021. ix + 145 pp. Notes, bibliography. $45.00 cloth. Davis, a nonspecialist in the field of First American studies, breaks his book into three parts: (1) First American Theories, Myths, and Evidence, (2) First American Science, and (3) Community. Each part includes several chapters that cover a range of topics from American Indian creation myths and the Native American Graves Protection and Repatriation Act to how archaeologists, linguists, bioanthropologists, and geneticists address the issue of First Americans. On several occasions, Davis quotes Jim Adovasio, who says the basic problem is "who the hell are these people, where did they come from, and when did they get here" (ix). Davis adds that "Although much has been documented, science is no closer today to finding an answer than at any time since the arrival of Columbus. In short, it has been a failed endeavor" (ix). I have many colleagues who would take umbrage with such a pessimistic view of progress in the search for the First Americans. A short review cannot do justice to the strides made in this endeavor, and these strides are in every field Davis discusses, from archaeology and linguistics to dental anthropology and genetics. Perhaps Davis is thinking there should be a dramatic paradigm shift like plate tectonics in geology. The impact of genomics on this problem comes close and may reach that status at some point. Davis focuses attention on the Clovis culture, with special reference to Blackwater Draw in New Mexico, and how the technology of this culture with its distinctive lanceolate fluted points evolved to serve as the bellwether of First Americans. Following in the footsteps of Paul Martin and Vance Haynes, a Clovis-first position developed in the 1960s and hardened over several decades. I have known and worked with Clovis-first archaeologists, but they are not wedded to the "fact" that the Clovis tradition represented the earliest peoples in the Americas. They are "wedded" to the position of "show me the evidence." For many early claims of pre-Clovis, the evidence was questionable, and many sites were dismissed as pre-Clovis. In recent times, things have changed—there are now sites most agree are pre-Clovis, so the "Clovis police" is shrinking. Moreover, many scholars who thought First Americans arrived via the Bering Land Bridge and then traversed an ice-free corridor through Canada now acknowledge that a maritime route is likely given the late opening of the corridor. Granted, I am a First American scientist, but I appreciate the space Davis devotes to American Indian creation myths. Unfortunately, some pit these creation myths against science, but that is not a position with which I am familiar. Most of us in the field are anthropologists, so we understand the nature of creation myths. They are a cultural universal that meets a human need to know how everything was created, including specific groups of humans. They have no empirical basis and cannot be falsified, and none of us are in the business of doing that. As a nonspecialist, Davis does a good job summing up alternative viewpoints on the question of First Americans. His sections on history are useful and enlightening but his treatment of First American science is dated. He discusses mtDNA and Y chromosome variation, but these have been supplanted by genomic studies that analyze thousands of single nucleotide polymorphisms. The human footprints found at White Sands in New Mexico that are older than 20,000 years were reported after the book was published. I mention this because it adds another notch in the pre-Clovis belt [End Page 59] and generates a whole new set of questions on when and by what route the First Americans arrived in the "New World." For readers unfamiliar with the history of First American science and Native American creation myths, this book is a good starting point. Davis is to be commended for taking on such a thorny issue. It brings to the forefront the Native American position of...

Beringia and the peopling of the Western Hemisphere.

Did Beringian environments represent an ecological barrier to humans until less than 15 000 years ago or was access to the Americas controlled by the spatial-temporal distribution of North American ice sheets? Beringian environments varied with respect to climate and biota, especially in the two major areas of exposed continental shelf. The East Siberian Arctic Shelf ('Great Arctic Plain' (GAP)) supported a dry steppe-tundra biome inhabited by a diverse large-mammal community, while the southern Bering-Chukchi Platform ('Bering Land Bridge' (BLB)) supported mesic tundra and probably a lower large-mammal biomass. A human population with west Eurasian roots occupied the GAP before the Last Glacial Maximum (LGM) and may have accessed mid-latitude North America via an interior ice-free corridor. Re-opening of the corridor less than 14 000 years ago indicates that the primary ancestors of living First Peoples, who already had spread widely in the Americas at this time, probably dispersed from the NW Pacific coast. A genetic 'arctic signal' in non-arctic First Peoples suggests that their parent population inhabited the GAP during the LGM, before their split from the former. We infer a shift from GAP terrestrial to a subarctic maritime economy on the southern BLB coast before dispersal in the Americas from the NW Pacific coast.

The age of the opening of the Ice-Free Corridor and implications for the peopling of the Americas

SignificanceThe Ice-Free Corridor (IFC) has long played a key role in hypotheses about the peopling of the Americas. Earlier assessments of its age suggested that the IFC was available for a Clovis-first migration, but subsequent developments now suggest a pre-Clovis occupation of the Americas that occurred before the opening of the IFC, thus supporting a Pacific coastal migration route instead. However, large uncertainties in existing ages from the IFC cannot preclude its availability as a route for the first migrations. Resolving this debate over migration route is important for addressing the questions of when and how the first Americans arrived. We report cosmogenic nuclide exposure ages that show that the final opening of the IFC occurred well after pre-Clovis occupation.

Beringia and the Settlement of the Western Hemisphere

Previously, we addressed the problem of what variable(s) limited widespread human settlement of the Americas before ~15 ka. We concluded that while non-modern human taxa (e. g., Neanderthals) probably did not inhabit high-latitude environments (due to cold climate and/ or low plant and animal productivity) and thus could not disperse in the Western Hemispherevia Beringia, modern humans likely were denied access to mid-latitude North America >15 ka by coastal and interior ice sheets. Here we reexamine the problem with respect to modern humans in light of a revised chronology for glaciers and sea level, new research in paleo-genomics, and some new archaeological discoveries. During 35–30 ka, a lineage with west Eurasian roots occupied the Great Arctic Plain and may have expanded into eastern arctic Beringia and mid-latitude North America via an ice-free corridor. An East Asian lineage associated with microblade technology occupied the Lena Basin during the LGM and expanded onto the Great Arctic Plain >15 ka, possibly as early as the GI 2 interstadial (24–23 ka). Their immediate descendants probably occupied the southern Bering Land Bridge and Northwest Pacific coast >15 ka and dispersed widely in the Western Hemisphere during GI 1 (14.5–12.9 ka), primarily if not exclusively via a coastal route. The coalesced Laurentide and Cordilleran ice sheets blocked interior access to mid-latitude America until 13.8 ± 0.5 ka (and possibly later due to the length and narrow width of the ice-free corridor >13 ka).

Evidence for Pleistocene gene flow through the ice-free corridor from extinct horses and camels from Natural Trap Cave, Wyoming

Natural Trap Cave (Bighorn Mountains, Wyoming) preserves an abundance of fossil remains from extinct Late Pleistocene fauna and is situated near a past migration route that likely connected populations in Eastern Beringia and the contiguous US—the ice-free corridor between the Cordilleran and Laurentide icesheets. Some palaeontological evidence supports a correspondingly high affinity between fauna recorded in Natural Trap Cave and Eastern Beringia versus elsewhere in the contiguous US, but this hypothesis has not yet been extensively tested using genetic data. In the present study, we analysed 16 horse specimens and one camel specimen from Natural Trap Cave. Of the horse specimens we analysed, we obtained 10 unique and previously unreported mitochondrial haplotypes belonging to two distinct (extinct) genetic clades—two haplotypes corresponded to a caballine horse (Equus sp.) and eight corresponded to the stilt-legged horse (Haringtonhippus francisci). With only one exception, it appears these newly sequenced individuals all shared a common ancestor more recently with Eastern Beringian individuals than with others from the contiguous US. In addition, mitochondrial data from a specimen assigned to Camelops sp. revealed that it shares a closer affinity with specimens from the Yukon Territory than those from Idaho or Nevada, though all appear to belong to a single species (“yesterday's camel”; Camelops cf. hesternus). Together, these results are consistent with a high level of genetic connectivity between horse and camel populations in the Bighorn Mountains and Eastern Beringia during the Pleistocene.

The coastal migration theory: Formulation and testable hypotheses

The presence of well-documented sites in the Americas predating and south of the opening of an ice-free corridor in the North American ice sheets lends credence to a Pacific coastal migration theory (CMT) explaining the route for the initial peopling of the Americas. This theory has been informally discussed for more than 50 years, but until recently, has been largely ignored and never properly defined as a result. We provide a formal definition of the CMT which, briefly stated, is that Upper Paleolithic populations moved from Asia to coastal regions along the northwestern Pacific Rim between ∼45–30 ka. By ∼30 ka these coastal populations developed a mixed maritime, nearshore, and terrestrial adaptation involving the use of boats, shell fishhooks for deep-water fishing, and a stemmed point and macroblade core technology. About 25–24 ka a subset of these coastal populations became isolated somewhere in the vicinity of the Japan/Paleo-Hokkaido, Sahkalin, Kuril (PSHK) region, developing genetically into the ancient Native American (ANA) populations that eventually settled the Americas. Between ∼22–16 ka these ANA people began migrating by foot and boat along the southern Beringian coast and down the Alaskan and Canadian coastline into the Americas south of the continental ice sheets before eventually expanding inland. We develop a series of testable hypotheses through which the CMT can be examined.

Spatiotemporal analyses suggest the role of glacial history and the ice-free corridor in shaping American badger population genetic variation.

Recurring glacial cycles through the Quaternary period drastically altered the size and distribution of natural populations of North American flora and fauna. The “southerly refugia model” has been the longstanding framework for testing the effects of glaciation on contemporary genetic patterns; however, insights from ancient DNA have contributed to the reconstruction of more complex histories for some species. The American badger, Taxidea taxus, provides an interesting species for exploring the genetic legacy of glacial history, having been hypothesized to have postglacially emerged from a single, southerly refugium to recolonize northern latitudes. However, previous studies have lacked genetic sampling from areas where distinct glacial refugia have been hypothesized, including the Pacific Northwest and American Far North (Yukon, Alaska). In order to further investigate the phylogeographic history of American badgers, we collected mitochondrial DNA sequence data from ancient subfossil material collected within the historical range (Alaska, Yukon) and combined them with new and previously published data from across the species' contemporary distribution (n = 1,207). We reconstructed a mostly unresolved phylogenetic tree and star‐like haplotype network indicative of emergence from a largely panmictic glacial refugium and recent population expansion, the latter further punctuated by significantly negative Tajima's D and Fu's Fs values. Although directionality of migration cannot be unequivocally inferred, the moderate to high levels of genetic variation exhibited by American badgers, alongside the low frequency of haplotypes with indels in the Midwest, suggest a potential recolonization into central North America after the hypothesized ice‐free corridor reopened ~13,000 years ago. Overall, the expanded reconstruction of phylogeographic history of American badgers offers a broader understanding of contemporary range‐wide patterns and identifies unique genetic units that can likely be used to inform conservation of at‐risk populations at the northern periphery.

Fladmark + 40: What Have We Learned about a Potential Pacific Coast Peopling of the Americas?

Forty years ago, Knut Fladmark (1979) argued that the Pacific Coast offered a viable alternative to the ice-free corridor model for the initial peopling of the Americas—one of the first to support a “coastal migration theory” that remained marginal for decades. Today, the pre-Clovis occupation at the Monte Verde site is widely accepted, several other pre-Clovis sites are well documented, investigations of terminal Pleistocene subaerial and submerged Pacific Coast landscapes have increased, and multiple lines of evidence are helping decode the nature of early human dispersals into the Americas. Misconceptions remain, however, about the state of knowledge, productivity, and deglaciation chronology of Pleistocene coastlines and possible technological connections around the Pacific Rim. We review current evidence for several significant clusters of early Pacific Coast archaeological sites in North and South America that include sites as old or older than Clovis. We argue that stemmed points, foliate points, and crescents (lunates) found around the Pacific Rim may corroborate genomic studies that support an early Pacific Coast dispersal route into the Americas. Still, much remains to be learned about the Pleistocene colonization of the Americas, and multiple working hypotheses are warranted.

The early occupation of America

Archaeology The Cooper's Ferry archaeological site in western North America has provided evidence for the pattern and time course of the early peopling of the Americas. Davis et al. describe new evidence of human activity from this site, including stemmed projectile points. Radiocarbon dating and Bayesian analysis indicate an age between 16,560 and 15,280 years before present. Humans therefore arrived in the Americas before an inland ice-free corridor had opened, so a Pacific coastal route was the probable entry route. The stemmed projectile points closely resemble those found in Upper Paleolithic Japan, also supporting the hypothesis of a coastal route. Science , this issue p. [891][1] [1]: /lookup/doi/10.1126/science.aax9830

Late Upper Paleolithic occupation at Cooper’s Ferry, Idaho, USA, ~16,000 years ago

Radiocarbon dating of the earliest occupational phases at the Cooper's Ferry site in western Idaho indicates that people repeatedly occupied the Columbia River basin, starting between 16,560 and 15,280 calibrated years before the present (cal yr B.P.). Artifacts from these early occupations indicate the use of unfluted stemmed projectile point technologies before the appearance of the Clovis Paleoindian tradition and support early cultural connections with northeastern Asian Upper Paleolithic archaeological traditions. The Cooper's Ferry site was initially occupied during a time that predates the opening of an ice-free corridor (≤14,800 cal yr B.P.), which supports the hypothesis that initial human migration into the Americas occurred via a Pacific coastal route.

Initial peopling of North America: paleogeography and archaeology

The paper contains a summary of the new data relevant to the time and routes of the first peopling of the New World. The first unambiguous traces of humans are dated by the time span after the Last Glacial Maximum. The chronology and orientation of prehistoric migrations depended on the Late Pleistocene paleogeography. Instead of a postulated single wave of migration oriented from NW to SE from the Bering Land Bridge via the Mackenzie ice-free corridor to the territory lying southwards from the ice sheets we argue about a complicated picture of human movements of different age and direction. It seems that the earliest inhabitants penetrated from Beringia to the main area of North America following the Pacific coast and later dispersed to the east. The migration along the Mackenzie ice-free corridor should have place later. The Clovis culture seems to originate in the southeastern part of the USA territory then dispersing in northern and western directions along the whole continent. The Final Pleistocene saw the ‘inverse’ migration of the Paleoindians to the north, along the Mackenzie corridor to Beringia.

Beryllium-10 dating of the Foothills Erratics Train in Alberta, Canada, indicates detachment of the Laurentide Ice Sheet from the Rocky Mountains at ~15 ka

AbstractThe Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 10Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.

Confluences: Fluted Points in the Ice-Free Corridor

ABSTRACTWe undertake an expanded analysis of the Western Canadian Fluted Points database. Given clear evidence of biotic habitability along the entire Corridor by 13,000 years ago, fluted point spatial clusters likely reflect both Clovis contemporaneous and later fluted point instances. Points were overwhelmingly fashioned on local toolstones, featuring a bimodal length distribution (larger, relatively unaltered fluted points versus reworked, smaller fluted points at the end of their use life), mainly found in dispersed landscape settings rather than major kills or campsites. The temporal cline from older Clovis forms south of the ice masses to younger fluted points in Alaska suggests fluted point makers traversing the Corridor eventually met populations bearing eastern Beringian traditions. Corridor fluted point morphologies may indicate the degree to which diffusion or demic expansion mediated north-south interactions: deeper bases, parallel sides and multiple basal thinning flakes reflect intermediate forms similar to Younger Dryas-aged Alaskan fluted points.

Setting the Stage: The Late Pleistocene Colonization of North America

The timing of human entrance into North America has been a topic of debate that dates back to the late 19th century. Central to the modern discussion is not whether late Pleistocene-age populations were present on the continent, but the timing of their arrival. Key to the debate is the age of tools—bone rods, large prismatic stone blades, and bifacially chipped and fluted stone weapon tips—often found associated with the remains of late Pleistocene fauna. For decades, it was assumed that this techno-complex—termed “Clovis”—was left by the first humans in North America, who, by 11,000–12,000 years ago, made their way eastward across the Bering Land Bridge, or Beringia, and then turned south through a corridor that ran between the Cordilleran and Laurentide ice sheets, which blanketed the northern half of the continent. That scenario has been challenged by more-recent archaeological and archaeogenetic data that suggest populations entered North America as much as 15,300–14,300 years ago and moved south along the Pacific Coast and/or through the ice-free corridor, which apparently was open several thousand years earlier than initially thought. Evidence indicates that Clovis might date as early as 13,400 years ago, which means that it was not the first technology in North America. Given the lack of fluted projectile points in the Old World, it appears certain that the Clovis techno-complex, or at least major components of it, emerged in the New World.

Geographic patterns of Early Holocene New World dental morphological variation

Dental anthropology played a seminal role in early studies of the peopling of the New World, and was a foundation of the early three wave model proposed by Greenberg, Turner and Zegura. In recent years, however, developments in anthropological genetics, craniometry, and archaeological discoveries have largely omitted dental anthropology from debates regarding Native American origins. Here we consider this situation and reassert dental anthropology’s relevance to the topic by presenting an inter-individual analysis of Paleoindian and Paleoamer-ican dentitions. A small set of dental morphological variables was used to estimate Gower similarity coefficients between individual specimens. The resulting similarity matrix was ordinated using multidimensional scaling; all analyses were per-formed in Clustan v. 7.05. While results should be considered preliminary, patterns of variation suggest morphological similarity along both coasts of North and South America with a somewhat distinct grouping of North American Paleoindians deriving from more inland portions of the continent. This pattern is consistent with recent genetic scenarios, notably the bicoastal model presented by O’Rourke and Raff (2010), which indicates that Paleoindians may have taken multiple migration routes from Beringia, moving along both coasts as well as through the ice free corridor. Future studies may build on this work to reintegrate dental data and analysis into research concerning the peopling of the New World.

Peopling the Americas: Which way?

Anthropology For much of the 20th century, archaeologists firmly believed that the initial pathway into the Americas was via the “ice-free corridor,” a route from interior Alaska that snaked into the high plains of North America between two massive sheets of ice. Over the past 20 years, this consensus has been challenged and, for many, overturned, by data that support the “kelp highway” hypothesis—i.e., migration along the coastline of western North America. In a comprehensive review of genetic, archaeological, and paleoecological data, Potter et al. argue that both routes should be considered as viable pathways into the Americas. Sci. Adv. 10.1126/sciadv.aat5473 (2018).

Origins and spread of fluted-point technology in the Canadian Ice-Free Corridor and eastern Beringia

Fluted projectile points have long been recognized as the archaeological signature of early humans dispersing throughout the Western Hemisphere; however, we still lack a clear understanding of their appearance in the interior "Ice-Free Corridor" of western Canada and eastern Beringia. To solve this problem, we conducted a geometric morphometric shape analysis and a phylogenetic analysis of technological traits on fluted points from the archaeological records of northern Alaska and Yukon, in combination with artifacts from further south in Canada, the Great Plains, and eastern United States to investigate the plausibility of historical relatedness and evolutionary patterns in the spread of fluted-point technology in the latest Pleistocene and earliest Holocene. Results link morphologies and technologies of Clovis, certain western Canadian, and northern fluted points, suggesting that fluting technology arrived in the Arctic from a proximate source in the interior Ice-Free Corridor and ultimately from the earliest populations in temperate North America, complementing new genomic models explaining the peopling of the Americas.

Arrival routes of first Americans uncertain-Response.

In our Perspective, we argue that the earliest Americans followed a coastal migration route. Potter et al. counter that an inland, ice-free corridor route was more likely. The genetic and archaeological evidence that Potter et al. discuss support both the timing and coastal route for the peopling of

A coastal route to the Americas

Archaeology Archaeologists long thought that the first humans to arrive in the Americas were the Clovis people, who came via an ice-free corridor on the Beringia land bridge no more than 13,500 years ago. Since the early 2000s, evidence for older human sites has accumulated. In a Perspective, Braje et al. highlight recent suggestions that these earlier humans came via a “kelp highway” along the Pacific coasts of Asia and the Americas. However, because most pre-Clovis sites along the coast are likely to be submerged by today's higher sea levels, it will be difficult to find direct evidence for this route. Science , this issue p. [592][1] [1]: /lookup/doi/10.1126/science.aao5473

Session Rating of Perceived Exertion (sRPE), workload, and volume load relationships during off-season resistance training in NCAA division II baseball players: An exploratory analysis

Models of the first peopling of the Americas characterize arrival routes either along the coast or through the ice-free corridor following the Last Glacial Maximum. While the pendulum has currently swung somewhat towards the coastal route, archaeological evidence for either entry is lacking. In this paper we introduce a third option, an icy corridors entry route. We argue that the traditionally envisioned corridor is an unnecessary feature for the terrestrial arrival of Clovis or Clovis predecessors below the ice sheets. The recent genomic data is fully compatible with a re-envisioned peopling route.