Settlement of the Americas

Settlement of the Americas' is of intense interest to archaeologists and anthropologists. Modern biochemical techniques, as well as accumulation of archaeological and geological evidence, have shed progressively more light on the subject, however, significant questions remain unresolved.

Current understanding of human migration to and throughout the Americas derives from advances in four interrelated disciplines: archaeology, Pleistocene geology, physical anthropology, and DNA analysis. 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 Asia of the peoples who migrated to the Americas remain unclear. In recent years, researchers have sought to use familiar tools to validate or reject established theories, such as Clovis first. As new discoveries come to light, past hypotheses are reevaluated and new theories constructed. The archeological evidence suggests that the Paleo-Indians' first dispersal into the Americas occurred during the end of the last glacial period or, more specifically, what is known as the late glacial maximum (LGM), around 16,500â€"13,000 years ago.

The environment during the latest Pleistocene

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, varying portions of the Earth's water were stored as glacier ice in response to worldwide climate fluctuations. As water accumulated in glaciers, the volume of water in the oceans correspondingly decreased, resulting in lowering of the eustatic sea level. The variation of the eustatic sea level with time has been reconstructed using oxygen isotope analysis of deep sea cores, dating of marine terraces, and high resolution oxygen isotope sampling from ocean basins and modern ice caps. A drop of eustatic sea level from about 60M to about 120M lower than present-day levels, commencing around 30k years BP, caused the presence of Beringia as 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 again became 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 11k 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.

Glaciers

The onset of the LGM after 30k years BP saw expansion of alpine glaciers and continental ice sheets that blocked migration routes out of Beringia. By 21k 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 from the Saint Elias Range to the Alaskan Peninsula isolated the interior of eastern 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 15k ¹⁴C years BP (18k cal years BP). Coastal alpine glaciers started to retreat around 19k cal years BP while Cordilleran ice continued advancing in the Puget lowlands up to 14k ¹⁴C years BP (16.8k cal years BP) Even during the maximum extent of coastal ice, unglaciated refugia persisted on present-day islands, supporting terrestrial and marine mammals. As deglaciation occurred, refugia expanded until the coast became ice-free by 15k cal years BP. Retreat of glaciers on the Alaskan Peninsula provided access from Beringia to the Pacific coast by around 17k cal years BP. The ice barrier between interior Alaska and the Pacific coast broke up starting around 13.5k ¹⁴C years (16.2k cal years) BP. The ice-free corridor to interior North America opened between 13k and 12k 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

Paleoclimates and vegetation for eastern Siberia and Alaska during the Wisconsin glaciation have been deduced from high resolution oxygen isotope data and pollen stratigraphy. Prior to the LGM, 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. Abandonment of the northern regions of Siberia due to rapid cooling or 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, reflecting 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 LGM 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. Much of the coastal plain was covered with piedmont glaciers, however, 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. High coastal marine productivity due to kelp forests over rocky marine shallows has been proposed as an impetus for coastal migration of humans with the means to exploit offshore marine resources. 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. Estimates of a fully ice-free coast range 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-fee 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.

Competing theories

While the mainstream of the archaeological community is in general agreement that the Americas were settled by migrants sourced from northeastern Asian populations, uncertainties remain as to the chronology of the migrations, the source populations that contributed to the migrations, and the migration routes. The uncertainty is fed by a lack of archaeological evidence along migration routes dating to the periods when migrations are proposed to have occurred; uncertainties in the dating and interpretation of the oldest proposed archaeosites in the Americas; and uncertainties of assumptions underlying chronological and source models of migration derived from studies of modern Native American genetics.

Chronology

In the early 21st century, the chronology of migration models is divided into two general approaches. The first is the short chronology theory, based on the concept that the first migration into the New World occurred after the LGM, which went into decline after about 19k cal years BP, then was followed by successive waves of immigrants. The second is the long chronology theory, which proposes that the first group of people entered the Americas at a much earlier date, possibly 21kâ€"40k cal years BP. with a much later second wave of immigrants. Further controversy has been generated as age-dating of archaeosites in the Americas and the timing of the opening of the ice-free corridor have challenged the Clovis First theory, which dominated thinking on New World anthropology for much of the 20th Century.

Archaeological evidence

Pre-LGM migration across Beringia into the Americas has been proposed to explain purported pre-LGM ages of archaeosites in the Americas such as Bluefish Cave and Old Crow Flats in the Yukon Territory, and Meadowcroft Rock Shelter in Pennsylvania. The earlier ¹⁴C date from a bone artifact at the Old Crow Flats site has been supplanted by an Accelerator Mass Sectrometry ¹⁴C date indicating a Holocene age. The interpretations of butcher marks and geologic association of bones at the Bluefish Cave and Old Crow Flats sites have been called into question. The ages of the earliest positively identified artifacts at the Meadowcroft site are constrained by a compiled age estimate from ¹⁴C dates in the range of 12k-15k ¹⁴C years BP (13.8k-18.5k cal years BP). The Meadowcroft site and the Monte Verde site in southern Chile, with a date of 14.8k cal years BP, are the archaeosites in the Americas with the oldest dates that have gained broad acceptance.

The Yana Rhino Horn site has dated human occupation of eastern Arctic Siberia to 27k ¹⁴C years BP (31.3k cal years BP). The early date for humans at that location 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. A compilation of archaeosite dates throughout eastern Siberia is suggestive that the cooling period caused a retreat of humans towards refugia in southern Siberia. Pre-LGM lithic assemblages in Siberia indicate a geographically restricted lifestyle based on utilizing local resources, while post-LGM lithic assemblages indicate a more migratory lifestyle.

The oldest archaeosite dates on the Alaskan side of Beringia are around 12k ¹⁴C years BP (14k cal years BP). That does not preclude that a small founder population had entered Beringia before that time and that the appearance of an archaeological trace reflects population expansion rather than earliest migration. However, in the absence of dated archaeosites closer to the LGM on either the Siberian or the Alaskan side of Beringia, convincing evidence of pre-LGM migration into Beringia is lacking.

Genomic age estimates

Recent 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 are used to estimate the ages at which Native American DNA lineages branched off of their parent lineages in Asia and deduce the ages of demographic events. One model 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 (Figure 3) proposes that migration into Beringia occurred approximately 36k cal years BP, followed by 20k years of isolation in Beringia. Yet another model 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. The three Native American mtDNA evolution rate models all fall within the long chronology theory of migration into the Americas.

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.

Source populations

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. 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 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-LGM 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 a 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 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 with 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 Jomon 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.

HTLV-1 genomics

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 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.

Physical anthropology

Paleoamerican skeletons in the Americas such as Kennewick Man (Wahington State), Naia (Yucatan), Luzia Woman and other skulls from the Lago Santo site (Brazil), Buhl Woman (Idaho), Peñon Woman III, two skulls from the Tlapacoya site (Mexico City), and 33 skulls from Baja Californiahave 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 doliocephaly 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. Resolution of the issue awaits the identification of a Beringian phenotype among paleoamerican skulls or evidence of a genetic clustering among examples the Australoid phenotype.

Migration routes

A coastal east Asian source population is integral to the marine migration hypothesis. The problems associated with finding archaeological evidence for migration during a period of lowered sea level are well known. Sites related to the first migration are usually submerged, so the location of such sites is obscured. Certain types of evidence dependent on organic material, such as radiocarbon dating, may be destroyed by submergence. Wave action can destroy site structures and scatter artifacts along a prograding shoreline. Additionally, Pacific coastal conditions tend to be unstable due to steep unstable terrain, earthquakes, tsunamis, and volcanoes. 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. Otherwise, coastal archaeology is dependent on secondary evidence related to lifestyles and technologies of maritime peoples from sites similar to those that would be associated with the original migration.

Clovis culture

This big game-hunting culture has been labeled the Clovis culture, and is primarily identified by its artifacts of fluted projectile points. The culture received its name from artifacts found near Clovis, New Mexico, the first evidence of this tool complex, excavated in 1932. The Clovis culture ranged over much of North America and appeared in South America. The culture is identified by a distinctive Clovis point, a flaked flint spear-point with a notched flute by which it was inserted into a shaft. It could be removed from the shaft for traveling. This flute is one characteristic that defines the Clovis point complex.

Dating Clovis materials has been by association with animal bones and by carbon dating. Recent reexaminations of Clovis materials using improved carbon-dating methods produced results of 11,050 and 10,800 radiocarbon years B.P. (before present). This evidence suggests that the culture flowered somewhat later and for a shorter period of time than previously believed. Michael R. Waters of Texas A&M University in College Station and Thomas W. Stafford Jr., proprietor of a private-sector laboratory in Lafayette, Colorado and an expert in radiocarbon dating, attempted to determine the dates of the Clovis period. The heyday of Clovis technology has typically been set between 11,500 and 10,900 radiocarbon years B.P. (The radiocarbon calibration is disputed for this period, but the widely used IntCal04 calibration puts the dates at 13,300 to 12,800 calendar years B.P.). In a controversial move, Waters and Stafford conclude that no fewer than 11 of the 22 Clovis sites with radiocarbon dates are "problematic" and should be disregardedâ€"including the type site in Clovis, New Mexico. They argue that the datable samples could have been contaminated by earlier material. This contention was considered highly controversial by many in the archaeological community.

In 2014, the autosomal DNA of a 12,500+-year-old infant from Montana was sequenced. The DNA was taken from a skeleton referred to as Anzick-1, found in close association with several Clovis artifacts. Comparisons showed strong affinities with DNA from Siberian sites, and virtually ruled out any close affinity with European sources (the so-called "Solutrean hypothesis"). The DNA also showed strong affinities with all existing Native American populations, which indicated that all of them derive from an ancient population that lived in or near Siberia, the Upper Palaeolithic Mal'ta population. The data indicate that Anzick-1 is from a population directly ancestral to present South American and Central American Native American populations, ruling out hypotheses which posit that invasions subsequent to the Clovis culture overwhelmed or assimilated previous migrants into the Americas. Anzick-1 is less closely related to present North American Native American populations, suggesting an early divergence between North American and Central plus South American populations, with the North American populations being basal to the rest.

Problems with Clovis migration models

Discoveries in 2002 and 2003 of human coprolites (fossilized feces) as well as hunting tools found deeply buried in the Paisley Caves in Oregon indicate the presence of humans in North America as much as 1,200 years prior to the Clovis culture.

Y-DNA among South American and Alaskan natives

The micro-satellite diversity and distribution of a Y lineage specific to South America suggest that certain Amerindian populations became isolated after the initial colonization of their regions. The Na-Dené, Inuit and Indigenous Alaskan populations exhibit haplogroup Q (Y-DNA) mutations, but are distinct from other indigenous Amerindians with various mtDNA and autosomal DNA (atDNA) mutations. This suggests that the earliest migrants into the northern extremes of North America and Greenland derived from later migrant populations.

Watercraft migration theories

Earlier finds have led to a pre-Clovis culture theory encompassing different migration models with an expanded chronology to supersede the "Clovis-first" theory.

Pacific coastal models

Pacific models propose that people first reached the Americas via water travel, following coastlines from northeast Asia into the Americas. Coastlines are unusually productive environments because they provide humans with access to a diverse array of plants and animals from both terrestrial and marine ecosystems. While not exclusive of land-based migrations, the Pacific 'coastal migration theory' helps explain how early colonists reached areas extremely distant from the Bering Strait region, including sites such as Monte Verde in southern Chile and Taima-Taima in western Venezuela. Two cultural components were discovered at Monte Verde near the Pacific Coast of Chile. The youngest layer is radiocarbon dated at 12,500 radiocarbon years (~14,000 cal BP) and has produced the remains of several types of seaweeds collected from coastal habitats. The older and more controversial component may date back as far as 33,000 years, but few scholars currently accept this very early component.

Other coastal models, dealing specifically with the peopling of the Pacific Northwest and California coasts, have been advocated by archaeologists Knut Fladmark, Roy Carlson, James Dixon, Jon Erlandson, Ruth Gruhn, and Daryl Fedje. In a 2007 article in the Journal of Island and Coastal Archaeology, Erlandson and his colleagues proposed a corollary to the coastal migration theoryâ€"the "kelp highway hypothesis"â€"arguing that productive kelp forests supporting similar suites of plants and animals would have existed near the end of the Pleistocene around much of the Pacific Rim from Japan to Beringia, the Pacific Northwest, and California, as well 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 similar migration corridor, entirely at sea level, and essentially unobstructed.

East Asians: Paleoindians of the coast

The boat-builders from Southeast Asia may have been one of the earliest groups to reach the shores of North America. One theory suggests people in boats followed the coastline from the Kurile Islands to Alaska down the coasts of North and South America as far as Chile [2 62; 7 54, 57]. The Haida nation on the Queen Charlotte Islands off the coast of British Columbia may have originated from these early Asian mariners between 25,000 and 12,000. Early watercraft migration would also explain the habitation of coastal sites in South America such as Pikimachay Cave in Peru by 20,000 years ago and Monte Verde in Chile by 13,000 years ago [6 30; 8 383].

"'There was boat use in Japan 20,000 years ago,' says Jon Erlandson, a University of Oregon anthropologist. 'The Kurile Islands (north of Japan) are like stepping stones to Beringia,' the then continuous land bridging the Bering Strait. Migrants, he said, could have then skirted the tidewater glaciers in Canada right on down the coast." [7 64]'

Atlantic coastal model

Archaeologists Dennis Stanford and Bruce Bradley champion the coastal Atlantic route. Their Solutrean Hypothesis is also based on evidence from the Clovis complex, but instead traces the origins of the Clovis toolmaking style to the Solutrean culture of Ice Age Western Europe. The theory suggests that early European people (or peoples) may have been among the earliest settlers of the Americas. Citing evidence that the Solutrean culture of prehistoric Europe may have provided the basis for the tool-making of the Clovis culture in the Americas, the theory suggests that Ice Age Europeans migrated to North America by using skills similar to those possessed by the modern Inuit peoples and followed the edge of the ice sheet that spanned the Atlantic. The hypothesis rests upon particular similarities in Solutrean and Clovis technology that have no known counterparts in Eastern Asia, Siberia or Beringia, areas from which, or through which, early Americans are known to have migrated. Most professionals discount the theory for a variety of reasonsâ€"including the fact that the differences between the two tool-making traditions far outweigh the similarities, the several thousand miles of the Atlantic Ocean they would have had to cross, and the 5,000-year-span that separates the two cultures. Genetic studies of Native American populations have also shown that the Solutrean theory is unlikely, showing instead that the five main mtDNA haplogroups found in the Americas were all part of one gene pool migration from Asia.

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 of the biggest problems 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 difficultâ€"and systematic excavation of any sites found in deeper waters is challenging and expensive. 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 has been limited in South America related to the possibility of early coastal migrations.

Other hypotheses

The Solutrean hypothesis: Europe to America in the Paleolithic

Archaeologists Dennis Stanford and Bruce Bradley champion their Solutrean Hypothesis based on similarities between the Paleolithic Solutrean culture of Western Europe and the Clovis culture of the postglacial Americas. It hypothesizes the Solutrean culture of Western Europe as the source of the Clovis culture. The theory suggests that early European people (or peoples) may have been among the earliest settlers of the Americas. The theory suggests that late Pleistocene Europeans migrated to North America by using skills similar to those possessed by the modern Inuit peoples and followed the edge of the ice sheet that spanned the Atlantic. The hypothesis rests upon particular similarities in Solutrean and Clovis technology that have no known counterparts in Eastern Asia, Siberia or Beringia, areas from which, or through which, early Americans are known to have migrated. Most professionals discount the theory for a variety of reasonsâ€"including the fact that the differences between the two tool-making traditions far outweigh the similarities, the complete lack of evidence that Paleolithic Europeans had the means to cross an open ocean, and the 5,000-year-span that separates the two cultures. Genetic studies of Native American populations have also shown that the Solutrean theory is unlikely, showing instead that the five main mtDNA haplogroups found in the Americas were all part of one gene pool migration from Asia.

Pre-Columbian contact from other continents

Theories of pre-Columbian contact unrelated to the initial peopling of the Americas are not within the scope of this article, regardless of whether they are based on science or legend. The vast majority of pre-Columbian contact hypotheses are claims based on circumstantial or ambiguous evidence. The scientific responses to such pre-Columbian contact claims range from consideration in peer-reviewed publications to outright dismissal as fringe science or pseudoarcheology.

Notes and references

Bibliography

See also

• Early human migrations
• Origins of Paleoindians
• Denéâ€"Yeniseian languages, a proposed family of languages that are spoken by indigenous peoples of Asia and North America
• Historical migration
• Bluefish Caves
• History of Mesoamerica (Paleo-Indian)
• Paleo-Indians period (Canada)
• Norse colonization of the Americas
• Olmec alternative origin speculations
• Recent African origin of modern humans
• Pre-Columbian trans-oceanic contact
• List of countries and islands by first human settlement

External links

• "When Did Humans Come to the Americas?" - Smithsonian Magazine February 2013
• Ordering information and news items for The Deneâ€"Yeniseian Connection; the 2011 2nd printing has corriagenda for 14 articles in the 2010 ist printing
• Journey of Man: A Genetic Odyssey (movie) on YouTube - by Spencer Wells - PBS and National Geographic Channel, 2003 - 120 Minutes, UPC/EAN: 841887001267
• Atlas of the Human Journey, Genographic Project, National Geographic
• An mtDNA view of the peopling of the world by Homo sapiens Cambridge DNA's
• Journey of Mankind - Genetic Map â€" Bradshaw Foundation
• The Paleoindian Period â€" United States Department of the Interior, National Park Service
• Alabama Archaeology: Prehistoric Alabama â€" The University of Alabama, Department of Archaeology
• The Paleoindian Database â€" The University of Tennessee, Department of Anthropology.
• Paleoindians and the Great Pleistocene Die-Off â€" American Academy of Arts and Sciences, National Humanities Center