Settlement of the Americas
The settlement of the Americas is widely accepted to have begun when Paleolithic hunter-gatherers entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the Last Glacial Maximum. These populations expanded south of the Laurentide Ice Sheet and spread rapidly throughout both North and South America, by 14,000 years ago. The earliest populations in the Americas, before roughly 10,000 years ago, are known as Paleo-Indians.
The peopling of the Americas is a long-standing open question, and while advances in archaeology, Pleistocene geology, physical anthropology, and DNA analysis have progressively shed more light on the subject, significant questions remain unresolved. While there is general agreement that the Americas were first settled from Asia, the pattern of migration, its timing, and the place(s) of origin in Eurasia of the peoples who migrated to the Americas remain unclear.
The prevalent migration models outline different time frames for the Asian migration from the Bering Straits and subsequent dispersal of the founding population throughout the continent. Indigenous peoples of the Americas have been linked to Siberian populations by linguistic factors, the distribution of blood types, and in genetic composition as reflected by molecular data, such as DNA.
The "Clovis first theory" refers to the 1950s hypothesis that the Clovis culture represents the earliest human presence in the Americas, beginning about 13,000 years ago; evidence of pre-Clovis cultures has accumulated since 2000, pushing back the possible date of the first peopling of the Americas to 33,000 years ago.
The environment during the latest glaciation
For an introduction to the radiocarbon dating techniques used by archaeologists and geologists, see radiocarbon dating.
Emergence and submergence of Beringia
During the Wisconsin glaciation, the Earth's ocean water was, to varying degrees over time, stored in glacier ice. As water accumulated in glaciers, the volume of water in the oceans correspondingly decreased, resulting in lowering of global sea level. The variation of sea level over time has been reconstructed using oxygen isotope analysis of deep sea cores, the dating of marine terraces, and high resolution oxygen isotope sampling from ocean basins and modern ice caps. A drop of eustatic sea level by about 60 to 120 metres (200 to 390 ft) from present-day levels, commencing around 30,000 years BP, created Beringia, a durable and extensive geographic feature connecting Siberia with Alaska. With the rise of sea level after the Last Glacial Maximum (LGM), the Beringian land bridge was again submerged. Estimates of the final re-submergence of the Beringian land bridge based purely on present bathymetry of the Bering Strait and eustatic sea level curve place the event around 11,000 years BP (Figure 1). Ongoing research reconstructing Beringian paleogeography during deglaciation could change that estimate and possible earlier submergence could further constrain models of human migration into North America.
The onset of the Last Glacial Maximum after 30,000 years BP saw the expansion of alpine glaciers and continental ice sheets that blocked migration routes out of Beringia. By 21,000 years BP, and possibly thousands of years earlier, the Cordilleran and Laurentide ice sheets coalesced east of the Rocky Mountains, closing off a potential migration route into the center of North America. Alpine glaciers in the coastal ranges and the Alaskan Peninsula isolated the interior of Beringia from the Pacific coast. Coastal alpine glaciers and lobes of Cordilleran ice coalesced into piedmont glaciers that covered large stretches of the coastline as far south as Vancouver Island and formed an ice lobe across the Straits of Juan de Fuca by 15,000 14C years BP (18,000 cal years BP). Coastal alpine glaciers started to retreat around 19,000 cal years BP while Cordilleran ice continued advancing in the Puget lowlands up to 14,000 14C years BP (16,800 cal years BP). Even during the maximum extent of coastal ice, unglaciated refugia persisted on present-day islands, that supported terrestrial and marine mammals. As deglaciation occurred, refugia expanded until the coast became ice-free by 15,000 cal years BP. The retreat of glaciers on the Alaskan Peninsula provided access from Beringia to the Pacific coast by around 17,000 cal years BP. The ice barrier between interior Alaska and the Pacific coast broke up starting around 13,500 14C years (16,200 cal years) BP. The ice-free corridor to the interior of North America opened between 13,000 and 12,000 cal years BP. Glaciation in eastern Siberia during the LGM was limited to alpine and valley glaciers in mountain ranges and did not block access between Siberia and Beringia.
Climate and biological environments
The paleoclimates and vegetation of eastern Siberia and Alaska during the Wisconsin glaciation have been deduced from high resolution oxygen isotope data and pollen stratigraphy. Prior to the Last Glacial Maximum, climates in eastern Siberia fluctuated between conditions approximating present day conditions and colder periods. The pre-LGM warm cycles in Arctic Siberia saw flourishes of megafaunas. The oxygen isotope record from the Greenland Ice Cap suggests that these cycles after about 45k years BP lasted anywhere from hundreds to between one and two thousand years, with greater duration of cold periods starting around 32k cal years BP. The pollen record from Elikchan Lake, north of the Sea of Okhotsk, shows a marked shift from tree and shrub pollen to herb pollen prior to 26k 14C years BP, as herb tundra replaced boreal forest and shrub steppe going into the LGM. A similar record of tree/shrub pollen being replaced with herb pollen as the LGM approached was recovered near the Kolyma River in Arctic Siberia. The abandonment of the northern regions of Siberia due to rapid cooling or the retreat of game species with the onset of the LGM has been proposed to explain the lack of archaeosites in that region dating to the LGM. The pollen record from the Alaskan side shows shifts between herb/shrub and shrub tundra prior to the LGM, suggesting less dramatic warming episodes than those that allowed forest colonization on the Siberian side. Diverse, though not necessarily plentiful, megafaunas were present in those environments. Herb tundra dominated during the LGM, due to cold and dry conditions.
Coastal environments during the Last Glacial Maximum were complex. The lowered sea level, and an isostatic bulge equilibrated with the depression beneath the Cordilleran Ice Sheet, exposed the continental shelf to form a coastal plain. While much of the coastal plain was covered with piedmont glaciers, unglaciated refugia supporting terrestrial mammals have been identified on Haida Gwaii, Prince of Wales Island, and outer islands of the Alexander Archipelago. The now-submerged coastal plain has potential for more refugia. Pollen data indicate mostly herb/shrub tundra vegetation in unglaciated areas, with some boreal forest towards the southern end of the range of Cordilleran ice. The coastal marine environment remained productive, as indicated by fossils of pinnipeds. The highly productive kelp forests over rocky marine shallows may have been a lure for coastal migration. Reconstruction of the southern Beringian coastline also suggests potential for a highly productive coastal marine environment.
Environmental changes during deglaciation
Pollen data indicate a warm period culminating between 14k and 11k 14C years BP (17k-13k cal years BP) followed by cooling between 11k-10k 14C years BP (13k-11.5k cal years BP). Coastal areas deglaciated rapidly as coastal alpine glaciers, then lobes of Cordilleran ice, retreated. The retreat was accelerated as sea levels rose and floated glacial termini. It has been estimated that the coast range was fully ice-free between 16k and 15k cal years BP. Littoral marine organisms colonized shorelines as ocean water replaced glacial meltwater. Replacement of herb/shrub tundra by coniferous forests was underway by 12.4k 14C years BP (15k cal years BP) north of Haida Gwaii. Eustatic sea level rise caused flooding, which accelerated as the rate grew more rapid.
The inland Cordilleran and Laurentide ice sheets retreated more slowly than did the coastal glaciers. Opening of an ice-free corridor did not occur until after 13k to 12k cal years BP. The early environment of the ice-free corridor was dominated by glacial outwash and meltwater, with ice-dammed lakes and periodic flooding from the release of ice-dammed meltwater. Biological productivity of the deglaciated landscape was gained slowly. The earliest possible viability of the ice-free corridor as a human migration route has been estimated at 11.5k cal years BP.
Birch forests were advancing across former herb tundra in Beringia by 14.3ka 14C years BP (17k cal years BP) in response to climatic amelioration, indicating increased productivity of the landscape.
Analyses of biomarkers and microfossils preserved in sediments from Lake E5 and Burial Lake in northern Alaska suggest early humans burned Beringian landscapes as early as 34,000 years ago. The authors of these studies suggest that fire was used as means of hunting megafauna.
Chronology, reasons for, and sources of migration
The archaeological community is in general agreement that the ancestors of the Indigenous peoples of the Americas of historical record entered the Americas at the end of the Last Glacial Maximum (LGM), shortly after 20,000 years ago, with ascertained archaeological presence shortly after 16,000 years ago.
There remain uncertainties regarding the precise dating of individual sites and regarding conclusions drawn from population genetics studies of contemporary Native Americans. It is also an open question whether this post-LGM migration represented the first peopling of the Americas, or whether there had been an earlier, pre-LGM migration which had reached South America as early as 40,000 years ago.
The first is the short chronology theory, that the first migration occurred after the Last Glacial Maximum, which went into decline after about 19,000 years ago, and was then followed by successive waves of immigrants.
The second theory is the long chronology theory, which proposes that the first group of people entered the Americas at a much earlier date, possibly before 40,000 years ago, followed by a much later second wave of immigrants.
The Clovis First theory, which dominated thinking on New World anthropology for much of the 20th century, was challenged by the secure dating of archaeosites in the Americas to before 13,000 years ago in the 2000s. The "short chronology" scenario, in the light of this, refers to a peopling of the Americas shortly after 19,000 years ago, while the "long chronology" scenario permits pre-LGM presence, by around 40,000 years ago.
The archaeosites in the Americas with the oldest dates that have gained broad acceptance are all compatible with an age of about 15,000 years. This includes the Buttermilk Creek Complex in Texas, the Meadowcroft Rockshelter site in Pennsylvania and the Monte Verde site in southern Chile. Archaeological evidence of pre-Clovis people points to the South Carolina Topper Site being 16,000 years old, at a time when the glacial maximum would have theoretically allowed for lower coastlines.
It has often been suggested that an ice-free corridor, in what is now Western Canada, would have allowed migration before the beginning of the Holocene, but a 2016 study has argued against this, suggesting that the peopling of North America via such a corridor is unlikely to significantly pre-date the earliest Clovis sites. The study concludes that the ice-free corridor in what is now Alberta and British Columbia "was gradually taken over by a boreal forest dominated by spruce and pine trees" and that the "Clovis people likely came from the south, not the north, perhaps following wild animals such as bison". An alternative hypothesis for the peopling of America is coastal migration, which may have been feasible along the deglaciated (but now submerged) coastline of the Pacific Northwest from about 16,000 years ago.
Evidence for pre-LGM human presence
Pre-Last Glacial Maximum migration across Beringia into the Americas has been proposed to explain purported pre-LGM ages of archaeosites in the Americas such as Bluefish Caves and Old Crow Flats in the Yukon Territory, and Meadowcroft Rock Shelter in Pennsylvania.
At the Old Crow Flats, mammoth bones have been found that are broken in distinctive ways indicating human butchery. The radiocarbon dates on these vary between 25,000 and 40,000 years BP. Also, stone microflakes have been found in the area indicating tool production.
Previously, the interpretations of butcher marks and the geologic association of bones at the Bluefish Cave and Old Crow Flats sites, and the related Bonnet Plume site, have been called into question.
In addition to disputed archaeological sites, support for pre-LGM human presence has been found in lake sediment records of northern Alaska. Biomarker and microfossil analyses of sediments from Lake E5 and Burial Lake in suggest human presence in eastern Beringia as early as 34,000 years ago. These analyses are indeed compelling in that they corroborate the inferences made from the Bluefish Cave and Old Crow Flats sites.
In 2020, evidence emerged for a new pre-LGM site in North-Central Mexico. Chiquihuite cave, an archaeological site in Zacatecas State, has been dated to 26,000 years BP based on numerous lithic artefacts discovered there.
Pre-LGM human presence in South America rests partly on the chronology of the controversial Pedra Furada rock shelter in Piauí, Brazil. A 2003 study dated evidence for the controlled use of fire to before 40,000 years ago. Additional evidence has been adduced from the morphology of Luzia Woman fossil, which was described as Australoid. This interpretation was challenged in a 2003 review which concluded the features in question could also have arisen by genetic drift. In November 2018, scientists of the University of São Paulo and Harvard University released a study that contradicts the alleged Australo-Melanesian origin of Luzia. Using DNA sequencing, the results showed that Luzia was entirely Amerindian, genetically.
Stones described as probable tools, hammerstones and anvils, have been found in southern California, at the Cerutti Mastodon site, that are associated with a mastodon skeleton which appeared to have been processed by humans. The mastodon skeleton was dated by thorium-230/uranium radiometric analysis, using diffusion–adsorption–decay dating models, to 130.7 ± 9.4 thousand years ago. No human bones were found and expert reaction was mixed; claims of tools and bone processing were called "not plausible" by Prof. Tom Dillehay.
The Yana River Rhino Horn site (RHS) has dated human occupation of eastern Arctic Siberia to 27k 14C years BP (31.3k cal years BP). That date has been interpreted by some as evidence that migration into Beringia was imminent, lending credence to occupation of Beringia during the LGM. However, the Yana RHS date is from the beginning of the cooling period that led into the LGM. But, a compilation of archaeosite dates throughout eastern Siberia suggest that the cooling period caused a retreat of humans southwards. Pre-LGM lithic evidence in Siberia indicate a settled lifestyle that was based on local resources, while post-LGM lithic evidence indicate a more migratory lifestyle.
The oldest archaeosite on the Alaskan side of Beringia date to 12k 14C years BP (14k cal years BP). It is possible that a small founder population had entered Beringia before that time. However, archaeosites that date closer to the Last Glacial Maximum on either the Siberian or the Alaskan side of Beringia are lacking. Biomarker and microfossil analyses of sediments from Lake E5 and Burial Lake in northern Alaska suggest human presence in eastern Beringia as early as 34,000 years ago. These sedimentary analyses have been suggested to be the only possibly recoverable remnants of humans living Alaska during the last Glacial period.
Genomic age estimates
Studies of Amerindian genetics have used high resolution analytical techniques applied to DNA samples from modern Native Americans and Asian populations regarded as their source populations to reconstruct the development of human Y-chromosome DNA haplogroups (yDNA haplogroups) and human mitochondrial DNA haplogroups (mtDNA haplogroups) characteristic of Native American populations. Models of molecular evolution rates were used to estimate the ages at which Native American DNA lineages branched off from their parent lineages in Asia and to deduce the ages of demographic events. One model (Tammetal 2007) based on Native American mtDNA Haplotypes (Figure 2) proposes that migration into Beringia occurred between 30k and 25k cal years BP, with migration into the Americas occurring around 10k to 15k years after isolation of the small founding population. Another model (Kitchen et al. 2008) proposes that migration into Beringia occurred approximately 36k cal years BP, followed by 20k years of isolation in Beringia. A third model (Nomatto et al. 2009) proposes that migration into Beringia occurred between 40k and 30k cal years BP, with a pre-LGM migration into the Americas followed by isolation of the northern population following closure of the ice-free corridor. Evidence of Australo-Melanesians admixture in Amazonian populations was found by Skoglund and Reich (2016).
A study of the diversification of mtDNA Haplogroups C and D from southern Siberia and eastern Asia, respectively, suggests that the parent lineage (Subhaplogroup D4h) of Subhaplogroup D4h3, a lineage found among Native Americans and Han Chinese, emerged around 20k cal years BP, constraining the emergence of D4h3 to post-LGM. Age estimates based on Y-chromosome micro-satellite diversity place origin of the American Haplogroup Q1a3a (Y-DNA) at around 10k to 15k cal years BP. Greater consistency of DNA molecular evolution rate models with each other and with archaeological data may be gained by the use of dated fossil DNA to calibrate molecular evolution rates.
There is general agreement among anthropologists that the source populations for the migration into the Americas originated from an area somewhere east of the Yenisei River (Russian Far East). The common occurrence of the mtDNA Haplogroups A, B, C, and D among eastern Asian and Native American populations has long been recognized, along with the presence of haplogroup X. As a whole, the greatest frequency of the four Native American associated haplogroups occurs in the Altai-Baikal region of southern Siberia. Some subclades of C and D closer to the Native American subclades occur among Mongolian, Amur, Japanese, Korean, and Ainu populations.
Human genomic models
The development of high-resolution genomic analysis has provided opportunities to further define Native American subclades and narrow the range of Asian subclades that may be parent or sister subclades. For example, the broad geographic range of haplogroup X has been interpreted as allowing the possibility of a western Eurasian, or even a European source population for Native Americans, as in the Solutrean hypothesis, or suggesting a pre-Last Glacial Maximum migration into the Americas. The analysis of an ancient variant of haplogroup X among aboriginals of the Altai region indicates common ancestry with the European strain rather than descent from the European strain. Further division of X subclades has allowed identification of subhaplogroup X2a, which is regarded as specific to Native Americans. With further definition of subclades related to Native American populations, the requirements for sampling Asian populations to find the most closely related subclades grow more specific. Subhaplogroups D1 and D4h3 have been regarded as Native American specific based on their absence among a large sampling of populations regarded as potential descendants of source populations, over a wide area of Asia. Among the 3764 samples, the Sakhalin – lower Amur region was represented by 61 Oroks. In another study, Subhaplogroup D1a has been identified among the Ulchis of the lower Amur River region (4 among 87 sampled, or 4.6%), along with Subhaplogroup C1a (1 among 87, or 1.1%). Subhaplogroup C1a is regarded as a close sister clade of the Native American Subhaplogroup C1b.
Subhaplogroup D1a has also been found among ancient Jōmon skeletons from Hokkaido The modern Ainu are regarded as descendants of the Jōmon. The occurrence of the Subhaplogroups D1a and C1a in the lower Amur region suggests a source population from that region distinct from the Altai-Baikal source populations, where sampling did not reveal those two particular subclades. The conclusions regarding Subhaplogroup D1 indicating potential source populations in the lower Amur and Hokkaido areas stand in contrast to the single-source migration model.
Subhaplogroup D4h3 has been identified among Han Chinese. Subhaplogroup D4h3 from China does not have the same geographic implication as Subhaplotype D1a from Amur-Hokkaido, so its implications for source models are more speculative. Its parent lineage, Subhaplotype D4h, is believed to have emerged in east Asia, rather than Siberia, around 20k cal years BP. Subhaplogroup D4h2, a sister clade of D4h3, has also been found among Jōmon skeletons from Hokkaido. D4h3 has a coastal trace in the Americas.
The contrast between the genetic profiles of the Hokkaido Jōmon skeletons and the modern Ainu illustrates another uncertainty in source models derived from modern DNA samples:
However, probably due to the small sample size or close consanguinity among the members of the site, the frequencies of the haplogroups in Funadomari skeletons were quite different from any modern populations, including Hokkaido Ainu, who have been regarded as the direct descendant of the Hokkaido Jōmon people.
The descendants of source populations with the closest relationship to the genetic profile from the time when differentiation occurred are not obvious. Source population models can be expected to become more robust as more results are compiled, the heritage of modern proxy candidates becomes better understood, and fossil DNA in the regions of interest is found and considered.
The Human T cell Lymphotrophic Virus 1 (HTLV-1) is a virus transmitted through exchange of bodily fluids and from mother to child through breast milk. The mother-to-child transmission mimics a hereditary trait, although such transmission from maternal carriers is less than 100%. The HTLV virus genome has been mapped, allowing identification of four major strains and analysis of their antiquity through mutations. The highest geographic concentrations of the strain HLTV-1 are in sub-Saharan Africa and Japan. In Japan, it occurs in its highest concentration on Kyushu. It is also present among African descendants and native populations in the Caribbean region and South America. It is rare in Central America and North America. Its distribution in the Americas has been regarded as due to importation with the slave trade.
The Ainu have developed antibodies to HTLV-1, indicating its endemicity to the Ainu and its antiquity in Japan. A subtype "A" has been defined and identified among the Japanese (including Ainu), and among Caribbean and South American isolates. A subtype "B" has been identified in Japan and India. In 1995, Native Americans in coastal British Columbia were found to have both subtypes A and B. Bone marrow specimens from an Andean mummy about 1500 years old were reported to have shown the presence of the A subtype. The finding ignited controversy, with contention that the sample DNA was insufficiently complete for the conclusion and that the result reflected modern contamination. However, a re-analysis indicated that the DNA sequences were consistent with, but not definitely from, the "cosmopolitan clade" (subtype A). The presence of subtypes A and B in the Americas is suggestive of a Native American source population related to the Ainu ancestors, the Jōmon.
Paleoamerican skeletons in the Americas such as Kennewick Man (Washington State), Hoya Negro skeleton (Yucatán), Luzia Woman and other skulls from the Lagoa Santa site (Brazil), Buhl Woman (Idaho), Peñon Woman III, two skulls from the Tlapacoya site (Mexico City), and 33 skulls from Baja California have exhibited craniofacial traits distinct from most modern Native Americans, leading physical anthropologists to the opinion that some Paleoamericans were of an Australoid rather than Siberian origin. The most basic measured distinguishing trait is the dolichocephaly of the skull. Some modern isolates such as the Pericúes of Baja California and the Fuegians of Tierra del Fuego exhibit that same morphological trait. Other anthropologists advocate an alternative hypothesis that evolution of an original Beringian phenotype gave rise to a distinct morphology that was similar in all known Paleoamerican skulls, followed by later convergence towards the modern Native American phenotype. Genetic studies support an Australoid origin.
A report published in the American Journal of Physical Anthropology in January 2015 reviewed craniofacial variation focussing on differences between early and late Native Americans and explanations for these based on either skull morphology or molecular genetics. Arguments based on molecular genetics have in the main, according to the authors, accepted a single migration from Asia with a probable pause in Berengia, plus later bi-directional gene flow. Studies focusing on craniofacial morphology have argued that Paleoamerican remains have "been described as much closer to African and Australo-Melanesians populations than to the modern series of Native Americans", suggesting two entries into the Americas, an early one occurring before a distinctive East Asian morphology developed (referred to in the paper as the "Two Components Model". A third model, the "Recurrent Gene Flow" [RGF] model, attempts to reconcile the two, arguing that circumarctic gene flow after the initial migration could account for morphological changes. It specifically re-evaluates the original report on the Hoya Negro skeleton which supported the RGF model, the authors disagreed with the original conclusion which suggested that the skull shape did not match those of modern Native Americans, arguing that the "skull falls into a subregion of the morphospace occupied by both Paleoamericans and some modern Native Americans."
Stemmed points are a lithic technology distinct from Beringian and Clovis types. They have a distribution ranging from coastal east Asia to the Pacific coast of South America. The emergence of stemmed points has been traced to Korea during the upper Paleolithic. The origin and distribution of stemmed points have been interpreted as a cultural marker related to a source population from coastal east Asia.
Historically, theories about migration into the Americas have revolved around migration from Beringia through the interior of North America. The discovery of artifacts in association with Pleistocene faunal remains near Clovis, New Mexico in the early 1930s required extension of the timeframe for the settlement of North America to the period during which glaciers were still extensive. That led to the hypothesis of a migration route between the Laurentide and Cordilleran ice sheets to explain the early settlement. The Clovis site was host to a lithic technology characterized by spear points with an indentation, or flute, where the point was attached to the shaft. A lithic complex characterized by the Clovis Point technology was subsequently identified over much of North America and in South America. The association of Clovis complex technology with late Pleistocene faunal remains led to the theory that it marked the arrival of big game hunters that migrated out of Beringia then dispersed throughout the Americas, otherwise known as the Clovis First theory.
Recent radiocarbon dating of Clovis sites has yielded ages of 11.1k to 10.7k 14C years BP (13k to 12.6k cal years BP), somewhat later than dates derived from older techniques. The re-evaluation of earlier radiocarbon dates led to the conclusion that no fewer than 11 of the 22 Clovis sites with radiocarbon dates are "problematic" and should be disregarded, including the type site in Clovis, New Mexico. Numerical dating of Clovis sites has allowed comparison of Clovis dates with dates of other archaeosites throughout the Americas, and of the opening of the ice-free corridor. Both lead to significant challenges to the Clovis First theory. The Monte Verde site of Southern Chile has been dated at 14.8k cal years BP. The Paisley Cave site in eastern Oregon yielded a 14C date of 12.4k years (14.5k cal years) BP, on a coprolite with human DNA and 14C dates of 11.3k-11k (13.2k-12.9k cal years) BP on horizons containing western stemmed points. Artifact horizons with non-Clovis lithic assemblages and pre-Clovis ages occur in eastern North America, although the maximum ages tend to be poorly constrained.
Geological findings on the timing of the ice-free corridor also challenge the notion that Clovis and pre-Clovis human occupation of the Americas was a result of migration through that route following the Last Glacial Maximum. Pre-LGM closing of the corridor may approach 30k cal years BP and estimates of ice retreat from the corridor are in the range of 12 to 13k cal years BP. Viability of the corridor as a human migration route has been estimated at 11.5k cal years BP, later than the ages of the Clovis and pre-Clovis sites. Dated Clovis archaeosites suggest a south-to-north spread of the Clovis culture.
Pre-Last Glacial Maximum migration into the interior has been proposed to explain pre-Clovis ages for archaeosites in the Americas, although pre-Clovis sites such as Meadowcroft Rock Shelter, Monte Verde, and Paisley Cave have not yielded confirmed pre-LGM ages.
Dené–Yeniseian language family proposal
A relationship between the Na-Dené languages of North America (such as Navajo and Apache), and the Yeniseian languages of Siberia was first proposed as early as 1923, and developed further by others. A detailed study was done by Edward Vajda and published in 2010. This theory received support from many linguists, with archaeological and genetic studies providing it with further support.
The Arctic Small Tool tradition of Alaska and the Canadian Arctic may have originated in East Siberia about 5,000 years ago. This is connected with the ancient Paleo-Eskimo peoples of the Arctic, the culture that developed by 2500 BCE.
Nevertheless, some scholars suggest that the ancestors of western North Americans speaking Na-Dene languages made a coastal migration by boat.
Pacific coastal route
The Pacific coastal migration theory proposes that people first reached the Americas via water travel, following coastlines from northeast Asia into the Americas, originally proposed in 1979 by Knute Fladmark as an alternative to the hypothetical migration through an ice-free inland corridor. This model would help to explain the rapid spread to coastal sites extremely distant from the Bering Strait region, including sites such as Monte Verde in southern Chile and Taima-Taima in western Venezuela.
The very similar marine migration hypothesis is a variant of coastal migration; essentially its only difference is that it postulates that boats were the principle means of travel. The proposed use of boats adds a measure of flexibility to the chronology of coastal migration, because a continuous ice-free coast (16–15,000 calibrated years BP) would then not be required: Migrants in boats could have easily bypassed ice barriers and settled in scattered coastal refugia, before the deglaciation of the coastal land route was complete. A maritime-competent source population in coastal east-Asia is an essential part of the marine migration hypothesis.
A 2007 article in the Journal of Island and Coastal Archaeology proposed a "kelp highway hypothesis", a variant of coastal migration based on the exploitation of kelp forests along much of the Pacific Rim from Japan to Beringia, the Pacific Northwest, and California, and as far as the Andean Coast of South America. Once the coastlines of Alaska and British Columbia had deglaciated about 16,000 years ago, these kelp forest (along with estuarine, mangrove, and coral reef) habitats would have provided an ecologically homogenous migration corridor, entirely at sea level, and essentially unobstructed. A 2016 DNA analysis of plants and animals suggest a coastal route was feasible.
Mitochondrial subhaplogroup D4h3a, a rare subclade of D4h3 occurring along the west coast of the Americas, has been identified as a clade associated with coastal migration. This haplogroup was found in a skeleton referred to as Anzick-1, found in Montana in close association with several Clovis artifacts, dated 12,500 years ago.
Problems with evaluating coastal migration models
The coastal migration models provide a different perspective on migration to the New World, but they are not without their own problems: One such problem is that global sea levels have risen over 120 metres (390 ft) since the end of the last glacial period, and this has submerged the ancient coastlines that maritime people would have followed into the Americas. Finding sites associated with early coastal migrations is extremely difficult — and systematic excavation of any sites found in deeper waters is challenging and expensive. Strategies for finding earliest migration sites include identifying potential sites on submerged paleoshorelines, seeking sites in areas uplifted either by tectonics or isostatic rebound, and looking for riverine sites in areas that may have attracted coastal migrants. On the other hand, there is evidence of marine technologies found in the hills of the Channel Islands of California, circa 10,000 BCE. If there was an early pre-Clovis coastal migration, there is always the possibility of a "failed colonization". Another problem that arises is the lack of hard evidence found for a "long chronology" theory. No sites have yet produced a consistent chronology older than about 12,500 radiocarbon years (~14,500 calendar years), but research in South America related to the possibility of early coastal migrations has been limited.
- Early human migrations
- List of first human settlements
- Genetic history of indigenous peoples of the Americas
- Pre-Columbian trans-oceanic contact theories
- Pringle, Heather (March 8, 2017). "What Happens When an Archaeologist Challenges Mainstream Scientific Thinking?". Smithsonian.
- Fagan, Brian M. & Durrani, Nadia (2016). World Prehistory: A Brief Introduction. Routledge. p. 124. ISBN 978-1-317-34244-1.
- Goebel, Ted; Waters, Michael R.; O'Rourke, Dennis H. (2008). "The Late Pleistocene dispersal of modern humans in the Americas" (PDF). Science. 319 (5869): 1497–1502. Bibcode:2008Sci...319.1497G. CiteSeerX 10.1.1.398.9315. doi:10.1126/science.1153569. PMID 18339930. S2CID 36149744. Archived from the original on 2014-01-02. Retrieved 2010-02-05.CS1 maint: bot: original URL status unknown (link)
- Zimmer, Carl (January 3, 2018). "In the Bones of a Buried Child, Signs of a Massive Human Migration to the Americas". The New York Times. Retrieved January 3, 2018.
- Moreno-Mayar, JV; Potter, BA; Vinner, L; et al. (2018). "Terminal Pleistocene Alaskan genome reveals first founding population of Native Americans" (PDF). Nature. 553 (7687): 203–207. Bibcode:2018Natur.553..203M. doi:10.1038/nature25173. PMID 29323294. S2CID 4454580.
- Waguespack, Nicole (2012). "Early Paleoindians, from Colonization to Folsom". In Timothy R. Pauketat (ed.). The Oxford Handbook of North American Archaeology. Oxford University Press. pp. 86–95. ISBN 978-0-19-538011-8.
- Kornfeld, Marcel & Politis, Gustavo G. (2014). "Into the Americas: The Earliest Hunter-Gatherers in an Empty Continent". In Vicki Cummings; Peter Jordan & Marek Zvelebil (eds.). The Oxford Handbook of the Archaeology and Anthropology of Hunter-Gatherers. Oxford University Press. p. 406. ISBN 978-0-19-102526-6.
- Ash, Patricia J. & Robinson, David J. (2011). The Emergence of Humans: An Exploration of the Evolutionary Timeline. John Wiley & Sons. p. 289. ISBN 978-1-119-96424-7.
- Roberts, Alice (2010). The Incredible Human Journey. A&C Black. pp. 101–103. ISBN 978-1-4088-1091-0.
- Ardelean, Ciprian F.; Becerra-Valdivia, Lorena; Pedersen, Mikkel Winther; Schwenninger, Jean-Luc; Oviatt, Charles G.; Macías-Quintero, Juan I.; Arroyo-Cabrales, Joaquin; Sikora, Martin; Ocampo-Díaz, Yam Zul E.; Rubio-Cisneros, Igor I.; Watling, Jennifer G.; De Medeiros, Vanda B.; De Oliveira, Paulo E.; Barba-Pingarón, Luis; Ortiz-Butrón, Agustín; Blancas-Vázquez, Jorge; Rivera-González, Irán; Solís-Rosales, Corina; Rodríguez-Ceja, María; Gandy, Devlin A.; Navarro-Gutierrez, Zamara; de la Rosa-Díaz, Jesús J.; Huerta-Arellano, Vladimir; Marroquín-Fernández, Marco B.; Martínez-Riojas, L. Martin; López-Jiménez, Alejandro; Higham, Thomas; Willerslev, Eske (2020). "Evidence of human occupation in Mexico around the Last Glacial Maximum". Nature. 584 (7819): 87–92. Bibcode:2020Natur.584...87A. doi:10.1038/s41586-020-2509-0. PMID 32699412. S2CID 220697089.
- Becerra-Valdivia, Lorena; Higham, Thomas (2020). "The timing and effect of the earliest human arrivals in North America". Nature. 584 (7819): 93–97. Bibcode:2020Natur.584...93B. doi:10.1038/s41586-020-2491-6. PMID 32699413. S2CID 220715918.
- Gruhn, Ruth (22 July 2020). "Evidence grows that peopling of the Americas began more than 20,000 years ago". Nature. 584 (7819): 47–48. Bibcode:2020Natur.584...47G. doi:10.1038/d41586-020-02137-3. PMID 32699366. S2CID 220717778. Retrieved 24 July 2020.
- Brigham-Grette, Julie; Lozhkin, Anatoly V.; Anderson, Patricia M. & Glushkova, Olga Y. (2004). "Paleoenvironmental Conditions in West Beringia Before the Last Glacial Maximum". In D.B. Madsen (ed.). Entering America: Northeast Asia and Beringia Before the Last Glacial Maximum. University of Utah Press. ISBN 978-0-87480-786-8.
- Jackson, Lionel E., Jr. & Wilson, Michael C. (February 2004). "The Ice-Free Corridor Revisited". Geotimes. American Geological Institute.
- Jackson, L.E. Jr.; Phillips, F.M.; Shimamura, K. & Little, E.C. (1997). "Cosmogenic 36Cl dating of the Foothills Erratics train, Alberta, Canada". Geology. 25 (3): 195–198. Bibcode:1997Geo....25..195J. doi:10.1130/0091-7613(1997)025<0195:ccdotf>2.3.co;2.
- Mandryk, Carole A.S.; Josenhans, Heiner; Fedje, Daryl W. & Mathewes, Rolf W. (January 2001). "Late Quaternary paleoenvironments of Northwestern North America: implications for inland versus coastal migration routes". Quaternary Science Reviews. 20 (1): 301–314. Bibcode:2001QSRv...20..301M. doi:10.1016/s0277-3791(00)00115-3.
- Dyke, A.S.; Moore, A. & Robertson, L. (2003). Deglaciation of North America (Report). Open File 1574. Geological Survey of Canada. doi:10.4095/214399.
- Booth, Derek B.; Troost, Kathy Goetz; Clague, John J. & Waitt, Richard B. (2003). "The Cordilleran Ice Sheet". The Quaternary Period in the United States. Developments in Quaternary Sciences. 1. pp. 17–43. doi:10.1016/S1571-0866(03)01002-9. ISBN 978-0-4445-1470-7.
- Blaise, B.; Clague, J.J. & Mathewes, R.W. (1990). "Time of maximum Late Wisconsin glaciation, west coast of Canada". Quaternary Research. 34 (3): 282–295. Bibcode:1990QuRes..34..282B. doi:10.1016/0033-5894(90)90041-i.
- Misarti, Nicole; Finney, Bruce P.; Jordan, James W.; et al. (10 August 2012). "Early retreat of the Alaska Peninsula Glacier Complex and the implications for coastal migrations of First Americans". Quaternary Science Reviews. 48: 1–6. Bibcode:2012QSRv...48....1M. doi:10.1016/j.quascirev.2012.05.014.
- Clague, John J.; Mathewes, Rolf W. & Ager, Thomas A. (2004). "Environments of Northwestern North America before the Last Glacial Maximum". In D.B. Madsen (ed.). Entering America: Northeast Asia and Beringia Before the Last Glacial Maximum. University of Utah Press. ISBN 978-0-87480-786-8.
- Vasil'ev, Sergey A.; Kuzmin, Yaroslav V.; Orlova, Lyubov A. & Dementiev, Vyacheslav N. (2002). "Radiocarbon-based chronology of the Paleolithic in Siberia and its relevance to the peopling of the New World". Radiocarbon. 44 (2): 503–530. doi:10.1017/s0033822200031878.
- Graf, Kelly E. (2009). "Modern human colonization of the mammoth steppe: a view from south-central Siberia" (PDF). In Marta Camps; Parth Chauhan (eds.). Sourcebook of Paleolithic Transitions. Springer. pp. 479–501. doi:10.1007/978-0-387-76487-0_32. ISBN 978-0-387-76478-8.
- Fedje, Daryl W.; Mackie, Quentin; Dixon, E. James & Heaton, Timothy H. (2004). "Late Wisconsin Environment and Archaeological Visibility along the Northern Northwest Coast". In D.B. Madsen (ed.). Entering America: Northeast Asia and Beringia Before the Last Glacial Maximum. University of Utah Press. ISBN 978-0-87480-786-8.
- Erlandson, Jon M. & Braje, Todd J. (2011). "From Asia to the Americas by boat? Paleogeography, paleoecology, and stemmed points of the northwest Pacific". Quaternary International. 239 (1–2): 28–37. Bibcode:2011QuInt.239...28E. doi:10.1016/j.quaint.2011.02.030.
- Erlandson, Jon M.; Graham, Michael H.; Bourque, Bruce J.; et al. (2007). "The Kelp highway hypothesis: marine ecology, the coastal migration theory, and the peopling of the Americas". The Journal of Island and Coastal Archaeology. 2 (2): 161–174. doi:10.1080/15564890701628612. S2CID 140188874.
- Vachula, R.S.; Huang, Y.; Russell, J. M.; et al. (20 May 2020). "Sedimentary biomarkers reaffirm human impacts on northern Beringian ecosystems during the Last Glacial period". Boreas. 49 (3): 514–525. doi:10.1111/bor.12449.
- Vachula, R.S.; Huang, Y.; Longo, W. M.; et al. (13 December 2018). "Evidence of Ice Age humans in eastern Beringia suggests early migration to North America". Quaternary Science Reviews. 205: 35–44. doi:10.1016/j.quascirev.2018.12.003.
- White, Phillip M. (2006). American Indian chronology: chronologies of the American mosaic. Greenwood. p. 1. ISBN 978-0-313-33820-5.
- Wells, Spencer & Read, Mark (2002). The Journey of Man - A Genetic Odyssey. Random House. pp. 138–140. ISBN 978-0-8129-7146-0.
- Lovgren, Stefan (March 13, 2008). "Americas Settled 15,000 Years Ago, Study Says". National Geographic.
- Bonatto, Sandro L. & Salzano, Francisco M. (1997). "A single and early migration for the peopling of the Americas supported by mitochondrial DNA sequence data". Proceedings of the National Academy of Sciences. 94 (5): 1866–1871. Bibcode:1997PNAS...94.1866B. doi:10.1073/pnas.94.5.1866. PMC 20009. PMID 9050871.
- Cinq-Mars, J. (1979). "Bluefish Cave 1: A Late Pleistocene Eastern Beringian Cave Deposit in the Northern Yukon". Canadian Journal of Archaeology (3): 1–32. JSTOR 41102194.
- Bonnichsen, Robson (1978). "Critical arguments for Pleistocene artifacts from the Old Crow basin, Yukon: a preliminary statement". In Alan L. Bryan (ed.). Early Man in America from a Circum-Pacific Perspective. Occasional Papers No. 1. Edmonton: Archaeological Researches International Department of Anthropology, University of Alberta. pp. 102–118. ISBN 9780888649997.
- Oppenheimer, Stephen. "Journey of mankind". Bradshaw Foundation.
- Goodyear, Albert C. (2005). "Evidence of Pre-Clovis sites in the eastern United States". In Robson Bonnichsen; et al. (eds.). Paleoamerican Origins: Beyond Clovis. Peopling of the Americas. Center for the Study of the First Americans, Texas A&M University. pp. 103–112. ISBN 978-1-60344-812-3.
- Dillehay, Thomas (2000). The Settlement of the Americas: A New Prehistory. New York: Basic Books. ISBN 978-0-465-07669-7.
- Kaplan, Sarah (October 24, 2018). "Continent's oldest spear points provide new clues about the first Americans". Washington Post.
- Pedersen, Mikkel W.; Ruter, Anthony; Schweger, Charles; et al. (August 10, 2016). "Postglacial viability and colonization in North America's ice-free corridor". Nature. 537 (7618): 45–49. Bibcode:2016Natur.537...45P. doi:10.1038/nature19085. PMID 27509852. S2CID 4450936.
- Chung, Emily (August 10, 2016). "Popular theory on how humans populated North America can't be right, study shows: Ice-free corridor through Alberta, B.C. not usable by humans until after Clovis people arrived". CBC News. Retrieved August 10, 2016.
- Figure 4 of Andrew, Kitchen (2008). "A Three-Stage Colonization Model for the Peopling of the Americas". PLOS ONE. 3 (2): e1596. Bibcode:2008PLoSO...3.1596K. doi:10.1371/journal.pone.0001596. PMC 2223069. PMID 18270583.
- Morlan, Richard E. (March 4, 2015). "Old Crow Basin". The Canadian Encyclopedia. Historica Canada.
- Bryant, Vaughn M., Jr. (1998). "Pre-Clovis". In Guy Gibbon; et al. (eds.). Archaeology of Prehistoric Native America: An Encyclopedia. Garland reference library of the humanities. 1537. pp. 682–683. ISBN 978-0-8153-0725-9.
- Handwerk, Brian (22 July 2020). "Discovery in Mexican Cave May Drastically Change the Known Timeline of Humans' Arrival to the Americas". Smithsonian Magazine.
- Santos, G.M; Bird, M.I; Parenti, F.; et al. (2003). "A revised chronology of the lowest occupation layer of Pedra Furada Rock Shelter, Piauı́, Brazil: The Pleistocene peopling of the Americas". Quaternary Science Reviews. 22 (21–22): 2303–2310. Bibcode:2003QSRv...22.2303S. doi:10.1016/S0277-3791(03)00205-1.
- van Vark, G.N.; Kuizenga, D. & Williams, F.L. (June 2003). "Kennewick and Luzia: lessons from the European Upper Paleolithic". American Journal of Physical Anthropology. 121 (2): 181–184, discussion 185–188. doi:10.1002/ajpa.10176. PMID 12740961.
• Fiedel, Stuart J. (2004). "The Kennewick Follies: 'New' Theories about the Peopling of the Americas". Journal of Anthropological Research. 60 (1): 75–110. doi:10.1086/jar.60.1.3631009. JSTOR 3631009. S2CID 163722475.
• González-José, R.; Bortolini, M.C.; Santos, F.R. & Bonatto, S.L. (October 2008). "The peopling of America: craniofacial shape variation on a continental scale and its interpretation from an interdisciplinary view". American Journal of Physical Anthropology. 137 (2): 175–187. doi:10.1002/ajpa.20854. PMID 18481303. S2CID 32748672.
- Moreno-Mayar, J. Víctor; Vinner, Lasse; de Barros Damgaard, Peter; de la Fuente, Constanza; et al. (7 December 2018). "Early human dispersals within the Americas". Science. 362 (6419): eaav2621. doi:10.1126/science.aav2621.
- Posth, Cosimo; Nakatsuka, Nathan; Lazaridis, Iosif; Skoglund, Pontus; et al. (15 November 2018). "Reconstructing the Deep Population History of Central and South America". Cell. 175 (5): 1185–1197.e22. doi:10.1016/j.cell.2018.10.027. ISSN 0092-8674.
- Adovasio, J. M; Donahue, J. & Stuckenrath, R. (1990). "The Meadowcroft Rockshelter Rasdiocarbon Chronology 1975–1990". American Antiquity. 55 (2): 348–354. doi:10.2307/281652. JSTOR 281652.
• Hirst, K. Kris (October 23, 2017). "What Does cal BP Mean?". Thoughtco.com. Retrieved October 30, 2018.
- Holen, Steven R.; Deméré, Thomas A.; Fisher, Daniel C.; et al. (2017). "A 130,000-year-old archaeological site in southern California, USA". Nature. 544 (7651): 479–483. Bibcode:2017Natur.544..479H. doi:10.1038/nature22065. PMID 28447646.
- Rincon, Paul (26 April 2017). "First Americans claim sparks controversy". BBC News. Retrieved 30 April 2017.
Michael R. Waters commented that "To demonstrate such early occupation of the Americas requires the presence of unequivocal stone artifacts. There are no unequivocal stone tools associated with the bones... this site is likely just an interesting paleontological locality." Chris Stringer said that "extraordinary claims require extraordinary evidence – each aspect requires the strongest scrutiny," adding that "High and concentrated forces must have been required to smash the thickest mastodon bones, and the low energy depositional environment seemingly provides no obvious alternative to humans using the heavy cobbles found with the bones.
- Pitulko, V.V.; Nikolsky, P.A.; Girya, E. Yu; et al. (2 January 2004). "The Yana RHS Site: Humans in the Arctic Before the Last Glacial Maximum". Science. 303 (5654): 52–56. Bibcode:2004Sci...303...52P. doi:10.1126/science.1085219. ISSN 0036-8075. PMID 14704419. S2CID 206507352.
- Tamm, Erika; Kivisild, Toomas; Reidla, Maere; et al. (2007). "Beringian Standstill and Spread of Native American Founders". PLOS ONE. 2 (9): e829. Bibcode:2007PLoSO...2..829T. doi:10.1371/journal.pone.0000829. PMC 1952074. PMID 17786201.
- Kitchen, Andrew; Miyamoto, Michal M. & Mulligan, Connie J. (2008). "A Three-Stage Colonization Model for the Peopling of the Americas". PLOS ONE. 3 (2): e1596. Bibcode:2008PLoSO...3.1596K. doi:10.1371/journal.pone.0001596. PMC 2223069. PMID 18270583.
- Goebel, Ted & Buvit, Ian (2011). From the Yenisei to the Yukon: Interpreting Lithic Assemblage Variability in Late Pleistocene/Early Holocene Beringia. Center for the Study of the First Americans, Texas A&M University Press. p. 5. ISBN 978-1-60344-384-5.
- Skoglund, Pontus & Reich, David (December 2016). "A genomic view of the peopling of the Americas" (PDF). Current Opinion in Genetics & Development. 41: 27–35. doi:10.1016/j.gde.2016.06.016. PMC 5161672. PMID 27507099.
Recently, we carried out a stringent test of the null hypothesis of a single founding population of Central and South Americans using genome-wide data from diverse Native Americans. We detected a statistically clear signal linking Native Americans in the Amazonian region of Brazil to present-day Australo-Melanesians and Andaman Islanders (‘Australasians’). Specifically, we found that Australasians share significantly more genetic variants with some Amazonian populations—including ones speaking Tupi languages—than they do with other Native Americans. We called this putative ancient Native American lineage “Population Y” after Ypykuéra, which means ‘ancestor’ in the Tupi language family.
- Kemp, Brian M.; Malhi, Ripan S.; McDonough, John; et al. (2007). "Genetic Analysis of Early Holocene Skeletal Remains From Alaska and its Implications for the Settlement of the Americas" (PDF). American Journal of Physical Anthropology. 132 (4): 605–621. CiteSeerX 10.1.1.576.7832. doi:10.1002/ajpa.20543. PMID 17243155.
- Perego, Ugo A.; Achilli, Alessandro; Angerhofer, Norman; et al. (2009). "Distinctive Paleo-Indian Migration Routes from Beringia Marked by Two Rare mtDNA Haplogroups". Current Biology. 19 (1): 1–8. doi:10.1016/j.cub.2008.11.058. PMID 19135370. S2CID 9729731.
- Derenko, Miroslava; Malyarchuk, Boris; Grzybowski, Tomasz; et al. (December 21, 2010). "Origin and Post-Glacial Dispersal of Mitochondrial DNA Haplogroups C and D in Northern Asia". PLOS ONE. 5 (12): e15214. Bibcode:2010PLoSO...515214D. doi:10.1371/journal.pone.0015214. PMC 3006427. PMID 21203537.
- Bortolini, Maria-Catira; Salzano, Francisco M.; Thomas, Mark G.; et al. (2003). "Y-chromosome evidence for differing ancient demographic histories in the Americas" (PDF). American Journal of Human Genetics. 73 (3): 524–539. doi:10.1086/377588. PMC 1180678. PMID 12900798.
- Schurr, Theodore G. (May 2000). "Mitochondrial DNA and the Peopling of the New World" (PDF). American Scientist. 88 (3): 246. Bibcode:2000AmSci..88..246S. doi:10.1511/2000.3.246.
- Zakharov, I.A.; Derenko, M.V.; Maliarchuk, B.A.; et al. (12 January 2006). "Mitochondrial DNA variation in the aboriginal populations of the Altai-Baikal region: implications for the genetic history of North Asia and America". Annals of the New York Academy of Sciences. 1011 (1): 21–35. Bibcode:2004NYASA1011...21Z. doi:10.1196/annals.1293.003. PMID 15126280. S2CID 37139929.
- Starikovskaya, Elena B.; Sukernik, Rem I.; Derbeneva, Olga A.; et al. (January 2005). "Mitochondrial DNA diversity in indigenous populations of the southern extent of Siberia, and the origins of Native American haplogroups". Annals of Human Genetics. 69 (Pt 1): 67–89. doi:10.1046/j.1529-8817.2003.00127.x. PMC 3905771. PMID 15638829.
- Sikora, Martin; Pitulko, Vladimir V.; Sousa, Vitor C.; et al. (2019). "The population history of northeastern Siberia since the Pleistocene" (PDF). Nature. 570 (7760): 182–188. Bibcode:2019Natur.570..182S. doi:10.1038/s41586-019-1279-z. PMID 31168093. S2CID 174809069.
- Adachi, Noboru; Shinoda, Ken‐ichi; Umetsu, Kazuo & Matsumura, Hirofumi (March 2009). "Mitochondrial DNA analysis of Jōmon skeletons from the Funadomari site, Hokkaido, and its implication for the origins of Native American". American Journal of Physical Anthropology. 138 (3): 255–265. doi:10.1002/ajpa.20923. PMID 18951391.
- Adachi, Noboru; Shinoda, Ken‐ichi; Umetsu, Kazuo; et al. (November 2011). "Mitochondrial DNA analysis of Hokkaido Jōmon skeletons: Remnants of archaic maternal lineages at the southwestern edge of former Beringia". American Journal of Physical Anthropology. 146 (3): 346–360. doi:10.1002/ajpa.21561. PMID 21953438.
- Li, Hong-Chuan; Biggar, Robert J.; Miley, Wendell J.; et al. (2004). "Provirus load in breast milk and risk of mother-to-child transmission of Human T Lymphotropic Virus Type I". The Journal of Infectious Diseases. 190 (7): 1275–1278. doi:10.1086/423941. PMID 15346338.
- Verdonck, K.; González, E.; Van Dooren, S.; et al. (April 2007). "Human T-lymphotropic virus 1: recent knowledge about an ancient infection". The Lancet Infectious Diseases. 7 (4): 266–281. doi:10.1016/S1473-3099(07)70081-6. PMID 17376384.
- Gessain, A.; Gallo, R.C. & Franchini, G. (April 1992). "Low degree of human T-cell leukemia/lymphoma virus type I genetic drift in vivo as a means of monitoring viral transmission and movement of ancient human populations". Journal of Virology. 66 (4): 2288–2295. doi:10.1128/JVI.66.4.2288-2295.1992. PMC 289023. PMID 1548762.
- Ishida, Takafumi; Yamamoto, Kohtaro; Omoto, Keiichi; et al. (September 1985). "Prevalence of a human retrovirus in native Japanese: evidence for a possible ancient origin". Journal of Infection. 11 (2): 153–157. doi:10.1016/s0163-4453(85)92099-7. PMID 2997332.
- Miura, T.; Fukunaga, T.; Igarashi, T.; et al. (February 1994). "Phylogenetic subtypes of human T-lymphotropic virus type I and their relations to the anthropological background". Proceedings of the National Academy of Sciences of the United States of America. 91 (3): 1124–1127. Bibcode:1994PNAS...91.1124M. doi:10.1073/pnas.91.3.1124. PMC 521466. PMID 8302841.
- Picard, F.J.; Coulthart, M.B.; Oger, J.; et al. (November 1995). "Human T-lymphotropic virus type 1 in coastal natives of British Columbia: phylogenetic affinities and possible origins". Journal of Virology. 69 (11): 7248–56. doi:10.1128/JVI.69.11.7248-7256.1995. PMC 189647. PMID 7474147.
- Li, Hong-Chuan; Fujiyoshi, Toshinobu; Lou, Hong; et al. (December 1999). "The presence of ancient human T-cell lymphotropic virus type I provirus DNA in an Andean mummy". Nature Medicine. 5 (12): 1428–1432. doi:10.1038/71006. PMID 10581088. S2CID 12893136.
- Coulthart, Michael B.; Posada, David; Crandall, Keith A. & Dekaband, Gregory A. (March 2006). "On the phylogenetic placement of human T cell leukemia virus type 1 sequences associated with an Andean mummy". Infection, Genetics and Evolution. 6 (2): 91–96. doi:10.1016/j.meegid.2005.02.001. PMC 1983367. PMID 16503510.
- Gonzaleza, Silvia; Huddart, David; Israde-Alcántara, Isabel; et al. (30 March 2015). "Paleoindian sites from the Basin of Mexico: Evidence from stratigraphy, tephrochronology and dating" (PDF). Quaternary International. 363: 4–19. Bibcode:2015QuInt.363....4G. doi:10.1016/j.quaint.2014.03.015.
- González-José, Rolando; González-Martín, Antonio; Hernández, Miquel; et al. (4 September 2003). "Craniometric evidence for Palaeoamerican survival in Baja California". Nature. 425 (6953): 62–65. Bibcode:2003Natur.425...62G. doi:10.1038/nature01816. PMID 12955139. S2CID 4423359.
- Dillehay, Thomas D. (4 September 2003). "Tracking the first Americans". Nature. 425 (6953): 23–24. doi:10.1038/425023a. PMID 12955120. S2CID 4421265.
- Fiedel, Stuart J. (Spring 2004). "The Kennewick follies: "new" theories about the peopling of the Americas". Journal of Anthropological Research. 60 (1): 75–110. doi:10.1086/jar.60.1.3631009. JSTOR 3631009. S2CID 163722475.
- Chatters, James C.; Kennett, Douglas J.; Asmerom, Yemane; et al. (16 May 2014). "Late Pleistocene Human Skeleton and mtDNA Link Paleoamericans and Modern Native Americans" (PDF). Science. 344 (6185): 750–754. Bibcode:2014Sci...344..750C. doi:10.1126/science.1252619. PMID 24833392. S2CID 206556297. Archived from the original (PDF) on 2015-07-13.
- de Azvedo, Soledad; Bortolini, Maria C.; Bonatto, Sandro L.; et al. (January 2015). "Ancient Remains and the First Peopling of the Americas: Reassessing the Hoyo Negro Skull". American Journal of Physical Anthropology. 148 (3): 514–521. doi:10.1002/ajpa.22801. PMID 26174009.
• Azevedo, Soledad de; Quinto-Sánchez, Mirsha; Paschetta, Carolina & González-José, Rolando (28 February 2017). ""The first human settlement of the New World " A closer look at craniofacial variation and evolution of early and late Holocene Native American groups". Quaternary International. 431 (part B): 152–167. Bibcode:2017QuInt.431..152D. doi:10.1016/j.quaint.2015.11.012.
- Seong, Chuntaek (December 2008). "Tanged points, microblades and late paleolithic hunting in Korea". Antiquity. 82 (318): 871–883. doi:10.1017/s0003598x00097647.
- Waters, Michael R. & Stafford, Thomas W. (23 February 2007). "Redefining the age of Clovis: implications for the peopling of the Americas". Science. 315 (5815): 1122–1126. Bibcode:2007Sci...315.1122W. doi:10.1126/science.1137166. PMID 17322060. S2CID 23205379.
- Jenkins, Dennis L.; Davis, Loren G.; Stafford, Thomas W., Jr; et al. (13 July 2012). "Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves". Science. 337 (6091): 223–228. Bibcode:2012Sci...337..223J. doi:10.1126/science.1218443. PMID 22798611. S2CID 40706795.
- Vajda, Edward J. (18 April 2017). "Dene-Yeniseian". Oxford Bibliographies Online. doi:10.1093/OBO/9780199772810-0064.
- Flegontov, Pavel; Altınışık, N. Ezgi; Changmai, Piya; et al. (October 13, 2017). "Paleo-Eskimo genetic legacy across North America". bioRxiv. doi:10.1101/203018. hdl:21.11116/0000-0004-5D08-C. S2CID 90288469.
• Flegontov, Pavel; Altınışık, N. Ezgi; Changmai, Piya; et al. (5 June 2019). "Palaeo-Eskimo genetic ancestry and the peopling of Chukotka and North America" (PDF). Nature. 570 (7760): 236–240. Bibcode:2019Natur.570..236F. doi:10.1038/s41586-019-1251-y. ISSN 0028-0836. PMC 6942545. PMID 31168094.
- Handwerk, Brian (February 12, 2010). "Face of Ancient Human Drawn From Hair's DNA; Genome paints picture of man from extinct Greenland culture". National Geographic News.
- Fladmark, Knute R. (January 1979). "Routes: alternate migration corridors for early man in North America". American Antiquity. 44 (1): 55–69. doi:10.2307/279189. JSTOR 279189.
- Callaway, Ewen (11 August 2016). "Plant and animal DNA suggests first Americans took the coastal route". Nature. 536 (7615): 138. Bibcode:2016Natur.536..138C. doi:10.1038/536138a. PMID 27510205.
- Summer, Thomas (10 August 2016). "Humans may have taken different path into Americas than thought Arctic passage wouldn't have provided enough food for the earliest Americans' journey". Science News.
- Rasmussen, Morten; Anzick, Sarah L.; Waters, Michael R.; Skoglund, Pontus; DeGiorgio, Michael; Stafford, Thomas W., Jr; et al. (February 2014). "The genome of a Late Pleistocene human from aClovis burial site in western Montana". Nature. 506 (7487): 225–229. Bibcode:2014Natur.506..225R. doi:10.1038/nature13025. PMC 4878442. PMID 24522598.
- Gornitz, Vivian (January 2007). "Sea Level Rise, After the Ice Melted and Today". Goddard Institute for Space Studies. NASA. Retrieved 23 April 2015.
- Hetherington, Renée; Barrie, J. Vaughn; MacLeod, Roger & Wilson, Michael (February 2004). "Quest for the Lost Land". Geotimes.
- "California islands give up evidence of early seafaring: Numerous artifacts found at late Pleistocene sites on the Channel Islands". Science Daily. University of Oregon. 3 March 2011.
- Bradley, Bruce & Stanford, Dennis J. (2004). "The North Atlantic ice-edge corridor: a possible Palaeolithic route to the New World". World Archaeology. 36 (4): 459–478. CiteSeerX 10.1.1.694.6801. doi:10.1080/0043824042000303656. S2CID 161534521.
- Bradley, Bruce & Stanford, Dennis J. (2006). "The Solutrean-Clovis connection: reply to Straus, Meltzer and Goebel". World Archaeology. 38 (4): 704–714. doi:10.1080/00438240601022001. JSTOR 40024066. S2CID 162205534.
- Stanford, Dennis J.; Bradley, Bruce (2012). Pre-Clovis First Americans: The Origin of America's Clovis Culture. University of California Press. ISBN 978-0-520-22783-5.
- Stanford, Dennis J. & Bradley, Bruce A. (2013). Across Atlantic Ice: The Origin of America's Clovis Culture. University of California Press. ISBN 978-0-520-27578-2.
- Dixon, E. James (1993). Quest for the Origins of the First Americans. University of New Mexico. ISBN 978-0-8263-1406-2.
- Dixon, E. James (1999). Bones, Boats & Bison: Archeology and the First Colonization of Western North America. University of New Mexico Press. ISBN 978-0-8263-2138-1.
- Erlandson, Jon M. (2013). Early Hunter-Gatherers of the California Coast. Springer Science & Business Media. ISBN 978-1-4757-5042-3.
- Erlandson, Jon M. (2001). "The Archaeology of Aquatic Adaptations: Paradigms for a New Millennium". Journal of Archaeological Research. 9 (4): 287–350. doi:10.1023/a:1013062712695. S2CID 11120840.
- Erlandson, Jon M. (2002). "Anatomically modern humans, maritime voyaging, and the Pleistocene colonization of the Americas". In Nina G. Jablonski (ed.). The First Americans: The Pleistocene Colonization of the New World. California Academy of Sciences. pp. 59–92. ISBN 978-0-940228-50-4.
- Erlandson, Jon. M.; Graham, M. H.; Bourque, Bruce J.; et al. (30 October 2007). "The Kelp Highway Hypothesis: Marine Ecology, The Coastal Migration Theory, and the Peopling of the Americas". Journal of Island and Coastal Archaeology. 2 (2): 161–174. doi:10.1080/15564890701628612. S2CID 140188874.
- Eshleman, Jason A.; Malhi, Ripan S. & Glenn Smith, David (2003). "Mitochondrial DNA Studies of Native Americans: Conceptions and Misconceptions of the Population Prehistory of the Americas". Evolutionary Anthropology. 12 (1): 7–18. doi:10.1002/evan.10048. S2CID 17049337.
- Fedje, Daryl W. & Christensen, Tina (October 1999). "Modeling Paleoshorelines and Locating Early Holocene Coastal Sites in Haida Gwaii". American Antiquity. 64 (4): 635–652. doi:10.2307/2694209. JSTOR 2694209.CS1 maint: date and year (link)
- Greenman, E.F. (February 1963). "The Upper Palaeolithic and the New World". Current Anthropology. 4 (1): 41–66. doi:10.1086/200337. JSTOR 2739818. S2CID 144250630.
- Hey, Jody (25 May 2005). "On the Number of New World Founders: A Population Genetic Portrait of the Peopling of the Americas". PLOS Biology. 3 (6): e193. doi:10.1371/journal.pbio.0030193. PMC 1131883. PMID 15898833.
- Jablonski, Nina G. (2002). The First Americans: The Pleistocene Colonization of the New World. California Academy of Sciences. ISBN 978-0-940228-50-4.
- Jones, Peter N. (2005). Respect for the Ancestors: American Indian Cultural Affiliation in the American West. Bauu Institute. ISBN 978-0-9721349-2-7.
- Korotayev, Andrey; Berezkin, Yuri E.; Borinskaya, Svetlana A.; Davletshin, Albert I.; Khaltourina, Daria A. (2017). "Which genes and myths did the different waves of the peopling of Americas bring to the New World?". In Leonid E. Grinin; Andrey V. Korotayev; Yuri E. Berezkin (eds.). History and Mathematics: Economy, Demography, Culture, and Cosmic Civilizations. pp. 9–77. ISBN 978-5-7057-5247-8.
- Lauber, Patricia (2003). Who Came First: New Clues to Prehistoric Americans. National Geographic Soc Childrens books. ISBN 978-0-7922-8228-0.
- Matson, R. G. & Coupland, Gary (2016). The Prehistory of the Northwest Coast. Taylor & Francis. ISBN 978-1-315-41739-4.
- Meltzer, David J. (2009). First Peoples in a New World: Colonizing Ice Age America. University of California Press. ISBN 978-0-520-94315-5.
- Snow, Dean R. (1996). "The First Americans and the Differentiation of Hunter-Gatherer Cultures". In Bruce G. Trigger; Wilcomb E. Washburn (eds.). The Cambridge History of the Native Peoples of the Americas: North America. Volume 1: Part 1. Cambridge University Press. pp. 125–199. ISBN 978-0-521-57392-4.
|volume=has extra text (help)
- Wells, Spencer (2002). The Journey of Man: A Genetic Odyssey. Princeton University Press. ISBN 0-691-11532-X.
|Wikimedia Commons has media related to Settlement of the Americas.|
- The Paleoindian Database – The University of Tennessee, Department of Anthropology.
- "The first Americans: How and when were the Americas populated?", Earth, January 2016
- "When Did Humans Come to the Americas?" – Smithsonian Magazine February 2013
- The Paleoindian Period – United States Department of the Interior, National Park Service
- Shepard Krech III, Paleoindians and the Great Pleistocene Die-Off – American Academy of Arts and Sciences, National Humanities Center, 2008.
- on YouTube – by Spencer Wells – PBS and National Geographic Channel, 2003 – 120 Minutes, UPC/EAN: 841887001267