The Guardian Jennifer Raff
22 Feb 2018 04.26 EST
The recent release of The Ice Bridge, an episode in the Canadian Broadcasting Corporation series The Nature of Things has revived public discussion of a controversial idea about how the Americas were peopled known as the “Solutrean hypothesis.” This idea suggests a European origin for the peoples who made the Clovis tools, the first recognized stone tool tradition in the Americas...
First, in addition to the scientific problems with the Solutrean hypothesis which, it’s important to note that it has overt political & cultural implications in denying that Native Americans are the only indigenous peoples of the continents. The notion that the ancestors of Native Americans were not the first or only people on the continent has great popularity among white nationalists, who see it as a means of denying Native Americans an ancestral claim on their land. Indeed, although this particular iteration is new, the idea behind the Solutrean hypothesis is part of a long tradition of Europeans trying to insert themselves into American prehistory; justifying colonialism by claiming that Native Americans were not capable of creating the diverse & sophisticated material culture of the Americas. Unfortunately, the producers of the documentary deliberately chose not to address this issue head-on, nor did they include any critical perspectives from indigenous peoples...
Bruce Bradley & Dennis Stanford, proponents of the Solutrean hypothesis, base it on the claim that the North American Clovis stone spear points are the technological descendants of a subset of those made by the Upper Paleolithic southwestern European Solutrean peoples. Specifically they cite fact that both are made by a technique known as “overshot” flaking as evidence for their common origin. From this starting point, Bradley & Stanford propose a scenario in which a group of Solutreans migrated across the Atlantic Ocean to North America via an “ice bridge” approximately 20,000 years before present (YBP).
Although they don’t deny that the majority of Native American ancestry comes from a group of Siberians who lived in Beringia during the Last Glacial Maximum (~23,000 YBP-13,000 YBP), they claim that “great numbers” of Solutreans must also have migrated to North America. Archaeologists have...dismissed it on the basis of insufficient evidence...
1. There’s a serious time gap between when the Solutreans could have crossed the Atlantic via the ice bridge (~20,000 YBP) & when Clovis tools begin to show up in the archaeological record (~13,000 YBP). This means that they would have made the points in exactly the same way for 7,000 years. Nowhere else in the Americas do we see technologies & cultures existing unchanging for that length of time.
2. There is no evidence of boat use, or tools used for making boats at Solutrean sites. Although the Ice Bridge documentary makes much of an image of a fish & an auk in a French cave, it is a bit of a stretch to claim that this is sufficient to demonstrate a sophisticated seafaring culture, capable of crossing the Atlantic. The existence of a year-round “ice bridge” across the Atlantic during the Last Glacial Maximum is not supported by paleoclimate data. Instead, sea ice in the Atlantic would most likely have been seasonal, with a connection between North American & Europe only a few months out of the year.
3. The notion of overshot flaking technique as evidence of a link between Clovis & Solutrean has been challenged by many archaeologists, who think it far more plausible that the two cultures arrived at the same technology independently. As Strauss (2000) puts it, “One or two technical attributes are insufficient to establish a cultural link or long-distance interconnection.”
4. Radiocarbon dates of Clovis sites do not show a pattern one would expect if people diffused into North America from the east coast, as postulated by Stanford & Bradley.
Geneticists, too, have tested the Solutrean hypothesis. If it were true, we would expect to see ancestry from non-Siberian descended populations present in the genomes of ancient Native Americans. We don’t. All contemporary & ancient Native Americans, including the only known ancient individual buried in association with Clovis tools, show descent from an ancestral population with Siberian roots. There is a very clear pattern of evolutionary history recorded in ancient genomes from Siberia, Beringia, & North America, & no evidence for trans-Atlantic gene flow.
This is where the Ice Bridge documentary runs into great problems. It ignores all genomic evidence & instead relies upon an old idea that a particular mitochondrial haplogroup (a group of closely related maternal lineages) known as X shows a connection between North America & Europe. In the documentary, pediatrician/popular science writer Stephen Oppenheimer asserts that the presence of haplogroup X in an ancient North American population is a priori evidence for a European connection. The documentary makes this case persuasively with graphics & maps showing the presence of this haplogroup in both Europe & North America. But look below the surface & the entire argument falls apart. First of all, Standford, Bradley, & Oppenheimer simply assume that Solutreans would have had X because it’s seen in contemporary European populations. But in fact, the contemporary European gene pool was formed only within the last 8,000 years, & it’s unknown whether earlier peoples would have had haplogroup X in the same frequencies (or at all). No genomes from Solutren peoples have ever been sequenced...
Today, lineages of haplogroup X are found widely dispersed throughout Europe, Asia, North Africa, & North America. We can reconstruct their evolutionary relationships – much like you can reconstruct a family tree – by looking at patterns of shared & derived mutations. Lineages found in the Americas, X2a & X2g, are not descended from the lineages (X2b, X2d, & X2c) found in Europe. Instead, they share a very ancient common ancestor from Eurasia, X2...
X2a is of a comparable age to other indigenous American haplogroups (A,B,C,D), which would not be true if it was derived from a separate migration from Europe. Finally, the oldest lineage of X2a found in the Americas was recovered from the Ancient One (also known as Kennewick Man), an ancient individual dating to ~9,000 years ago & from the West Coast (not the East Coast as would be predicted from the Solutrean hypothesis). His entire genome has been sequenced & shows that he has no ancestry from European sources. There is no conceivable scenario under which Kennewick Man could have inherited just his mitochondrial genome from Solutreans but the rest of his genome from Beringians. Thus, without additional evidence, there is nothing to justify the assumption that X2a must have evolved in Europe.
The Ice Bridge unfortunately relied on cherry-picking of data to support the ideas of Bradley & Stanford...You must build your models based on evidence you have, not evidence you wish you had, & the Solutrean hypothesis is lacking sufficient evidence to be considered seriously.
References & further reading
Raff J, & Bolnick D. (2015) Does Mitochondrial Haplogroup X Indicate Ancient Trans-Atlantic Migration to the Americas? A Critical Re-Evaluation.
O’Brien, Michael J., Matthew T. Boulanger, Mark Collard, Briggs Buchanan, Lia Tarle, Lawrence G. Straus & Metin I. Eren (2014). “On thin ice: problems with Stanford & Bradley’s proposed Solutrean colonisation of North America”. Antiquity. 88: 606–624.
Stanford, Dennis J. & Bruce Bradley (2012). Across Atlantic Ice: The Origin of America’s Clovis Culture. Berkeley: University of California Press.
