The Solutrean hypothesis, first proposed in 1998, is a hypothesis about the settlement of the Americas that claims Europeans may have been among the earliest settlers of the Americas. Among its more notable proponents are Dennis Stanford of the Smithsonian Institution and Bruce Bradley of the University of Exeter. This is in contrast with accepted theories that the North American continent was first populated by people from Asia, either by the Bering land bridge (i.e. Beringia), by maritime travel along the Pacific coast or by both.
According to the Solutrean hypothesis, people of the Solutrean culture in Ice Age Europe migrated to North America, bringing their methods of making stone tools with them and providing the basis for the later Clovis technology that spread throughout North America. The hypothesis is based on proposed similarities between European Solutrean and early American pre-Clovis and Clovis lithic technologies.
Supporters of the Solutrean hypothesis refer to recent archaeological finds such as those at Cactus Hill in Virginia, Meadowcroft Rockshelter in Pennsylvania, Miles Point in Maryland and the Cinmar blade recovered from the waters off coastal Virginia as indicative of a transitional phase between Solutrean lithic technology and what was later to become Clovis technology.
The Solutrean hypothesis has generally not been well received or enjoyed wide acceptance. Many archaeologists have criticized the proposed similarities as insignificant and just as likely to be due to chance as to shared origins. As David Meltzer put it in 2009, "Few if any archaeologists—or, for that matter, geneticists, linguists, or physical anthropologists—take seriously the idea of a Solutrean colonization of America." Recent DNA studies serve to weaken the case that Haplogroup X2A migrated to the Americas by way of the Atlantic. The thesis was popularized by a 2005 Discovery Channel docudrama.
Solutrean culture was based in present-day France, Spain and Portugal, from roughly 21,000 to 17,000 years ago. The manufacture of stone tools from this period is distinguished by bifacial, percussion and pressure-flaked points. The Solutrean toolmaking industry disappeared almost completely from Europe around 15,000 years ago, replaced by the lithic technology of the Magdalenian culture.
Clovis tools are characterized by a distinctive type of spear point, known as the Clovis point. Solutrean and Clovis points do have common traits: the points are thin and bifacial, and both use the "outrepassé", or overshot flaking technique, that quickly reduces the thickness of a biface without reducing its width. The Clovis point differs from the Solutrean in that some of the former have bifacial fluting, referring to the long groove carved into the bottom edge of a point to help attach it to the head of a spear. Bifacial fluting describes blades on which this feature appears on both its sides.
Clovis toolmaking technology appears in the archaeological record in eastern North America roughly 13,500 years ago. Older blades with this attribute have yet to be discovered from sites in either Asia or Alaska.
The Solutrean hypothesis claims that Ice Age Europeans crossed the North Atlantic Ocean along the edge of pack ice that extended from the Atlantic coast of France to North America during the last glacial maximum. The model asserts these people made the crossing in small boats, using skills similar to those of the modern Inuit people: hauling out on ice floes at night; collecting fresh water from melting icebergs or the first-frozen parts of sea ice; hunting seals and fish for food; and using seal blubber as heating fuel. Among other evidence, they cite the discovery in the Solutrean toolkit of bone needles used for sewing waterproof clothing from animal hides similar to those still in use among modern Inuit. These bone needles could, in theory, have been used to make kayaks from hides.
Supporters of the Solutrean hypothesis had pointed to the presence of haplogroup X, the global distribution of which is strongest in Anatolia and the northeast of America, a pattern supposedly consistent with their position. Michael Brown in a 1998 article identified this as evidence of a possible Caucasian founder population of early Americans spreading from the northeast coast.
But a 2008 article in the American Journal of Human Genetics by researchers in Brazil took up the argument against the Solutrean hypothesis. "Our results strongly support the hypothesis that haplogroup X, together with the other four main mtDNA haplogroups, was part of the gene pool of a single Native American founding population; therefore they do not support models that propose haplogroup-independent migrations, such as the migration from Europe posed by the Solutrean hypothesis."
A 2011 article in the American Journal of Physical Anthropology tends to argue against the Solutrean theory on genetic grounds. Researchers in Italy argued that the distinctively Asian C4c and the disputed X2a had "parallel genetic histories." They note that "C4c is deeply rooted in the Asian portion of the mtDNA phylogeny and is indubitably of Asian origin."
An abstract in a 2012 issue of the American Journal of Physical Anthropology states that "The similarities in ages and geographical distributions for C4c and the previously analyzed X2a lineage provide support to the scenario of a dual origin for Paleo-Indians. Taking into account that C4c is deeply rooted in the Asian portion of the mtDNA phylogeny and is indubitably of Asian origin, the finding that C4c and X2a are characterized by parallel genetic histories definitively dismisses the controversial hypothesis of an Atlantic glacial entry route into North America."
A 2014 genetic analysis published in the journal Nature reported that the DNA from a 24,000 year-old skeleton excavated in Central Siberia provided mitochondrial, Y chromosomal, and autosomal genetic evidence that suggests 14 to 38% of Native American ancestry originates from an ancient Western Eurasian population. The Mal'ta era skeleton's mitochondrial genome belonged to mtDNA haplogroup U, which has also been found at high frequencies among Mesolithic European hunter-gatherers. The authors state that their findings have four implications, the third being that "such an easterly presence in Asia of a population related to contemporary western Eurasians provides a possibility that non-east Asian cranial characteristics of the First Americans derived from the Old World via migration through Beringia, rather than by a trans-Atlantic voyage from Iberia as proposed by the Solutrean hypothesis." 
Mal'ta boy had YDNA haplogroup R1* which is common to both Europeans and Native Americans. Haplogroup R1 (Y-DNA)) is the second most predominant Y haplotype found among indigenous Amerindians after Q (Y-DNA). The distribution of R1 is believed to be associated with the re-settlement of Eurasia following the last glacial maximum. One theory put forth is that it entered the Americas with the initial founding population. A second theory is that it was introduced during European colonization. R1 is very common throughout all of Eurasia except East Asia and Southeast Asia. R1 (M173) is found predominantly in North American groups like the Ojibwe (79%), Chipewyan (62%), Seminole (50%), Cherokee (47%), Dogrib (40%) and Tohono O'odham (Papago) (38%).
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 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.
Archaeological and oceanographic challenges and counterchallenges
Arthur J. Jelinek, an anthropologist who took note of (superficial) similarities between Solutrean and Clovis styles in a 1971 study, observed that the great geographical and temporal separation of the two cultures made a direct connection unlikely, since the dates of the proposed transitional sites and the Solutrean period in Europe only overlap at the extremes. He also argued that crossing the Atlantic with the means available at the time would have been difficult, if not impossible. The opinion is shared by Lawrence G. Straus, who wrote that "there are no representations of boats and no evidence whatsoever either of seafaring or of the ability to make a living mainly or solely from the ocean during the Solutrean." Straus excavated Solutrean artifacts along what is now a coastline in Cantabria, which was some ways inland during the Solutrean epoch. He found seashells and estuarine fish at the sites, but no evidence that deep sea resources had been exploited. However, holdouts in the Solutrean camp counter that evidence of Solutrean-era seafaring may have been obliterated or submerged, since the coastlines of western Europe and eastern North America during the Last Glacial Maximum are now under water.
Another challenge to the hypothesis involves the paucity of non-technological evidence of a kind we would expect to find transmitted from east to west; cave paintings of a kind associated with the Cave of Altamira in Spain, for instance, are without close parallel in the New World. In response, Bradley and Stanford contend that it was "a very specific subset of the Solutrean who formed the parent group that adapted to a maritime environment and eventually made it across the north Atlantic ice-front to colonize the east coast of the Americas" and that this group may not have exhibited the full range of Solutrean cultural traits. A carved piece of bone depicting a mammoth found near the Vero man site in Florida was dated between 20,000–13,000 BP. It is described as possibly being the oldest art object yet found in the Americas and may yet provide hope for the Solutrean hypothesis. Art historian Barbara Olins has compared the Vero carving to "Franco-Cantabrian" drawings and engravings of mammoths. She notes that the San of southern Africa developed a realistic manner of representing animals similar to the "Franco-Cantabrian" style, hinting that such a style could have evolved in North America independently.
A 2008 study of relevant oceanographic data from the time period in question, co-authored by Kieran Westley and Justin Dix, concluded, however, that "it is clear from the paleoceanographic and paleo-environmental data that the LGM in the North Atlantic does not fit the descriptions provided by the proponents of the Solutrean Atlantic Hypothesis. Although ice use and sea mammal hunting may have been important in other contexts, in this instance, the conditions militate against an ice-edge-following, maritime-adapted European population reaching the Americas." Relying on the location of the ice shelf at the time of the putative Atlantic crossing, they are skeptical that a transoceanic voyage to North America, even allowing for the judicious use of glaciers and ice floes as temporary stopping points and sources of fresh water, would have been feasible for people from the Solutrean era.
The 2012 book Across Atlantic Ice: The Origin of America's Clovis Culture  expands upon and revises earlier formulations of the Solutrean Hypothesis. The book received significant media attention, but was met with mixed reviews from professional archaeologists. O'Brien and colleagues  critically evaluate the evidence presented in Stanford and Bradley's book, and find it to be unconvincing. Stanford and Bradley use, for example, cluster analysis to support the claim of Solutrean ancestry to Clovis; however, cluster analysis is a statistical technique that reveals similarities in the selected traits. It does not reveal or inform on ancestry. Moreover, the radiocarbon dates from purported pre-Clovis archaeological sites presented by Stanford and Bradley are consistently earlier in North America—predating Solutrean culture in Europe by 5–10 thousand years.
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Recent analyses of mitochondrial genomes from Native Americans have brought the overall number of recognized maternal founding lineages from just four to a current count of 15. However, because of their relative low number, almost nothing is known about some of these lineages. This leaves a considerable void in understanding the events that led to the colonization of the Americas following the Last Glacial Maximum (LGM). In this study, we identified and completely sequenced 14 mitochondrial DNAs belonging to one extremely rare Native American lineage known as haplogroup C4c. Its age and geographical distribution raise the possibility that C4c marked the Paleo-Indian group(s) that entered North America from Beringia through the ice-free corridor between the Laurentide and Cordilleran ice sheets. The similarities in ages and geographical distributions for C4c and the previously analyzed X2a lineage provide support to the scenario of a dual origin for Paleo-Indians.(subscription required)
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- Stone Age sailors 'beat Columbus to America' (The Guardian, 1999)
- Coming into America: Tracing the Genes (PBS, 2004)
- Stone Age Columbus (BBC 2002)
- Ice Age Columbus: Who Were the First Americans? (Discovery Channel 2005)
- New evidence suggests stone age hunters from Europe discovered America (The Independent, 2012)