The Nature of Things builds an Ice Bridge to nowhere

Like many Canadians my age, I grew up watching the Nature of Things on CBC. It was part of my education. Last week, I started seeing online chatter about the upcoming episode “Ice Bridge”, about the so-called Solutrean hypothesis, that the first occupants of the Americas followed the ice edge from Western Europe to the mid-Atlantic region of what is now the U.S. I watched the episode over the weekend.

The documentary presented is deeply problematic for a number of reasons. It gives an almost entirely uncritical view of an idea that currently has no evidence to support it. It leverages the public’s relative lack of understanding of standards of evidence in archaeology. It gives lip service to thoughtful critique by allowing critical scholars just enough screen time to state their opposition to the hypothesis, but not enough to explain their critique. It contributes to revisionist models of the occupation of the Americas that have a long history of legitimizing violence against indigenous peoples.

Similarity between stone tools as evidence of migration

The main evidence presented in the documentary is of the morphological similarity between stone tools (bifaces) found in 20 000 year old Upper Paleolithic archaeological sites in Western Europe and stone tools found in North America, notably those found by Stanford and Bradley (2012) in some sites in the Chesapeake Bay area. Significantly, the documentary does not specify the dates of North American bifaces, beyond making an unsupported statement that one of them was found “sticking out” of a 20 000 year old layer of sediment that was eroding into the sea. This can’t be considered a well dated find, and the team’s attempt to get more through a small excavation in the same spot yields nothing all.

But let’s imagine for a moment that there were Solutrean-like bifaces, found in North America, in securely dated 20 000 year old contexts. Would that be evidence of a Western European migration? That depends on whom you ask. There are two basic ways of explaining morphological similarity between objects found in different cultural or chronological contexts in archaeology: Cultural inheritance, and convergence.

Sometimes, the objects we find in different archaeological contexts, even ones that are geographically and/or chronologically distant from each other, are similar because the people who made them are culturally related and learned the same manufacturing techniques or designs from each other, or from common ancestors. In other words, they are the product of populations that are related, culturally and/or biologically, as is proposed in the case of a Solutrean migration to North America.

Sometimes, the objects we find in different archaeological contexts are similar because putting similar humans in similar environments, with similar resources and similar problems to solve, will yield similar solutions. Convergence, or structural similarities, are more likely to develop in applications that are tightly constrained by raw material or by purpose. Sometimes, there just aren’t many options for achieving a goal with a certain material. This is the case of highly curated tools such as very thin bifaces made of high quality stone. There aren’t many manufacturing techniques that will achieve the goal, and there isn’t a wide variety of shapes that can be produced.

Unfortunately, the documentary gives the example of pyramids in Egypt and Meso-America to argue that convergence yields a few general similarities (a rough pyramid shape) but many specific differences (steps vs smooth slope, platform at the top vs no platform, etc), whereas cultural relatedness is more likely to produce more identical results.

It should be clear to the viewer, and it should have been clear to the researchers in the documentary, that the makers of pyramids have many more stylistic options, and therefore many more possibilities to build varied products, than the makers of large, thin, sharp bifaces. It isn’t surprising that independently invented pyramids show wide variation in shape, just as it isn’t surprising that large stone bifaces invented independently are nearly identical.

The preference for explaining morphological similarity with cultural relatedness or convergence also depends on one’s assumptions about human creativity. If one assumes that humans are creative and that innovation is frequent, one is more likely to accept similarity as evidence of convergence. When confronted with a problem, people generally come up with a solution, rather than waiting for one to be inherited from distant relatives.

If one assumes that humans are not so creative and that innovation is rare, then one is likely to see similarity between tool types, for example, as clear evidence of cultural relatedness and perhaps even of outright migration. Notions of the passiveness or lack of creativity of American Indigenous populations are a sad legacy of a time when they were perceived by archaeologists as recipients of change brought by Europeans, rather than as actors in their own story. The Solutrean hypothesis perpetuates this.

The Solutrean hypothesis as presented in the documentary clearly underestimates the degree to which the technological production of stone tools is constrained by raw material availability and by intended purpose. It relies on the idea that humans, especially indigenous Americans, are not very creative, and that innovation is a rare phenomenon.

Finding similar looking tools in different regions or different time periods is not unusual at all in archaeology, and many of those similarities are clearly the result of convergence. An over-reliance on the assumptions behind the Solutrean hypothesis in archaeology’s past led directly to the theoretical excesses the hyperdiffusionists.

There is also the fact that deciding on which stone tools are similar to which involves more than standing around on a beach and looking at them, as is done in the documentary. There are well developed methods for measuring similarity in stone tools and stone tool assemblages. Studies (Buchanan and Collard 2007) using similarity in a much more systematic way, using cladistics and actual morphometric attributes of stone tools, rather than some impressionistic sense of likeness, point clearly to a Northwestern origin of the earliest well attested stone tool technologies in North America, and not a Northeastern origin, as the Solutrean hypothesis would demand.

The reality is that there are no securely dated solutrean-like remains, or any remains at all yet, that are older than about 14 000 years in the Americas. The documentary is based on claims made most recently by Stanford and Bradley (2012). They initially relied heavily on the Cinmar Biface, a solutrean-like stone tool reported to have been dredged up from the sea floor by the scallop trawler Cinmar in 1970, along with mastodon remains, and from a place that would have been land at the last glacial maximum (during the Solutrean period). If all that were true, it would be a pretty good start at establishing at the very least a human presence in North America 20 000 years ago. But given the above discussion about similarity in stone tools around the world, even that would not be a good indicator of contact with the European Paleolithic.

The rest of their claimed evidence is no stronger. O’Brien et al (2014) present a strong critique of the overall hypothesis. Stanford and Bradley (2014) provided a response, but I believe O’Brien et al have the stronger case.

Unfortunately, like many discoveries that are too good to be true because they fit very precisely into a major gap in the evidence, this one is likely false. Those interested in scientific detective stories will be not want to miss the work of Eren et al (2015), who have since shown that the Cinmar biface is most likely a hoax. A defense of the find by Lowery (n.d.) leaves enough questions unanswered that the Cinmar biface cannot at this point be considered a solid piece of evidence. Even if it is not an intentional hoax, it almost certainly did not come from a scallop net in 1970. It is disturbing that the documentary did not deal with this episode at all.

The X2a Haplogroup

The documentary makes much of the fact that haplogroup X2a is present in North American populations. It is true, as the film states, that the area of highest haplogroup X2 frequency that is geographically closest to the Chesapeake is in the Solutrean area. However, X2 has been known for a while now to be “widely spread throughout West Eurasia” (Reidla et al 2003), and is found “at low levels today throughout much of the world” (Raff and Bolnick 2015:298).

As I believe Jennifer Raff was attempting to explain in the documentary before she was edited out, frequency is the key concept here. Yes, X2 is more prevalent in certain areas than in others, but because early migrations typically involve small numbers, they can result in what is called a founder effect.

If we take a very small number of individuals from a large population in which there is a very low frequency of X2, it is possible that, simply by chance, the resulting group will have a higher frequency of X2 than the parent population. This is why it is so problematic to infer population relatedness based on a single marker. The notion of relatedness is a statistical one. We can estimate how likely it is that two populations are directly related, but that requires numbers.

In other words, a population entering North America through Beringia 15 000 years ago, could very well have had a relatively high frequency of the X2 haplotype, without having come straight from Southern France. This is at least as reasonable an explanation for the presence of X2a in the Americas as a Solutrean migration 20 000 years ago. In fact, it is a much better supported explanation, because we actually have well dated evidence of a Beringian migration after 15 000 years ago, whereas all we have to support the Solutrean explanation so far is the idea itself.

Why is the Western origin of the first Americans such a persistent idea?

The idea that the first occupants of the Americas came from Europe and were white is not new. It has been comforting settler descendants for centuries. In the 18^th Century, there was speculation that a Lost Tribe of Israel had colonized North America. In the 19^th Century, the impressive earthen architecture of sites like Cahokia was attributed to a vanished race of pre-Indians who had been the first occupants of the continent and had been displaced by the invading ancestors of current indigenous groups. Recently, Kennewick Man was held up as evidence that the first occupants of the Americas had “Caucasoid traits”.

It is easy to see why these ideas are so persistent. If the legitimacy of indigenous groups and their land claims are justified by priority of occupation, they can be invalidated by archaeological evidence that they weren’t the first occupants of the continent. This casts them as invaders and displacers, just like Europeans and their descendants. It justifies the dispossession of Indigenous groups. It alleviates some of the deep seated insecurity of recent settler populations whose privileges were established through violence and continue to be enforced through laws despite their self-evident unfairness.

The idea of a Solutrean migration to North America before the Beringian entry of the ancestors of indigenous populations belongs to that class of ideas, and it keeps coming up because it is attractive for the same reasons. Beyond the usual sin of archaeology’s telling of Indigenous history without Indigenous voices or participation, it is an attempt to actually remove these voices entirely from the story of the first occupation of the Americas by making them irrelevant. My UofA colleague Kisha Supernant discusses this in a recent interview with Muskrat Magazine. A quick search of Twitter and Facebook will reveal a number of other Indigenous reactions to the documentary. It is simply unacceptable that a documentary on the Solutrean hypothesis made in 2017 does not address this aspect of the controversy.

Bottom line

I don’t reject the Solutrean hypothesis out of hand. I find it an interesting possibility, like many others. However, there simply is no evidence to support it at the moment, and The Nature of Things spent an hour not changing that.

I have no problem with the idea of The Nature of Things presenting a documentary on the Solutrean hypothesis. A proper documentary would have been a wonderful opportunity to let the public see how archaeologists evaluate ideas, what evidence we use, and how we use it. It could have given people a clear sense of how archaeological ideas work in the present and how they interact with real-world politics and identity.

I have become used to the junk science being peddled by what still calls itself the History Channel, on shows like Ancient Aliens and The Curse of Oak Island. I am not even surprised by it anymore. But I expect more from the CBC.

References

Buchanan B and M Collard 2007. Investigating the peopling of North America through cladistic analyses of early Paleoindian projectile points. Journal of Anthropological Archaeology 26:366–393

Eren MI, MT Boulanger, MJ O’Brien 2015. The Cinmar discovery and the proposed pre-late glacial maximum occupation of North America.

Lowery D (n.d.) A response to the paper entitled “The Cinmar discovery and the proposed pre-Late Glacial Maximum occupation of North America” by three University of Missouri “scholars”.

https://www.academia.edu/12645256/A_Response_to_the_paper_entitled_The_CINMAR_discovery_and_the_proposed_pre-Late_Glacial_Maximum_occupation_of_North_America_by_Three_University_of_Missouri_Scholars_

O’Brien MJ, MT Boulanger, M Collard, B Buchanan 2014. On thin ice: problems with Stanford and Bradley’s proposed Solutrean colonisation of North America, Antiquity 88:606-613.

Raff JA and DA Bolnick 2015. Does mitochondrial haplogroup X indicated ancient trans-atlantic migration to the Americas? A critical re-evaluation, PaleoAmerica 1:297-304.

Reidla M et al 2003. Origin and diffusion of mtDNA Haplogroup X, American Journal of Human Genetics 73:1178-1190.

Stanford D and B Bradley 2012. Across Atlantic Ice: The origins of America’s Clovis culture, University of California Press, Berkeley.

Stanford D and B Bradley 2014. Reply to O’Brien et al, Antiquity 88:614-621.