Last year, Ardelean et al (2020) published a claim in Nature that they had recovered 30ky old archaeological material at Chiquihuite Cave in Mexico (I discussed the claim here). Now Chatters et al. (2021, the group includes my University of Alberta departmental colleague Margaret Spivey-Faulkner) have published a critique of the Adrelean et al. Nature piece, followed by a reply from Ardelean et al (2021), both in PaleoAmerica.

The original claim relies on the identification of objects found in a 30ky old contexts as stone tools. These would be by far the oldest securely dated archaeological objects in the Americas. The claimed stone tools are the only evidence presented in support of the conclusion that people lived in Chiquihuite Cave 30ky ago.

Not surprisingly, the critique focuses on whether the stone objects are tools or the product of non-human forces, and on the fact that there is no other evidence of humans. Spoiler alert: The critique concludes that there is no reason to suppose that the objects are stone tools made by humans. Even bigger spoiler: The response from the original authors reiterates that they are.

I won’t dwell on the critique here, because it is straightforward, solid, and unsurprising. In fact, my main reaction to the critique is to wonder why such a detailed statement of things that should be archaeologically evident is necessary at all.

Archaeologists have known for well over a century about the dangers of relying only on things that look like stone tools to make claims of ancient human activity. Early on, these potential tools, in deposits showing no other evidence of human presence, were known as Eoliths, and were eventually dismissed as evidence of human activity. Muthana and Ellen (2020) recently provided a good, updated history of the eolith controversy.

The main problem is that humans are not the only force that can produce individual objects that look like stone tools. There are a number of non-human mechanical forces that can do the same thing, from thermal changes, including natural fires, to impacts and pressure from rock slides and cave roof collapses.

In response, Ardelean et al. merely restate that some of the objects they found at Chiquihuite are indeed tools. Their critics simply “failed to recognize human-made stone items in the illustrations, as well as the concise descriptions we provided in our paper, of an assemblage whose traits would not occur naturally and under the circumstances alleged by our critics.” How we know that it would not occur naturally is not explained.

The examples they showed in their paper, to be identified as stone tools, “required a degree of expertise and familiarity with limestone technologies to recognize the artificiality of flakes, platforms, impact spots and bulbs, failed blows, blades, used edges, bifacial work, points, and biface preforms.” In other words, they rely on their authority as analysts to claim that these are tools.

By contrast, the critique relies on the same first principles that led to the rejection of eoliths as archaeological evidence a hundred years ago. It establishes that non-human forces can produce tool like objects. More significantly, it relies on the characteristics of the total assemblage rather than on the characteristics of a few objects within it.

This is because out of a large number of objects (potentially several tons at Chiquihuite cave), it isn’t surprising if a limited number of objects look more like tools than most of the others, and those can be found and plucked from the larger group. Even in a larger group that is more consistent with geological forces, a few objects can look remarkably like human productions.

Ardelean et al respond by focusing even more heavily on a few objects, which they claim in their reply, are even better examples of human-made tools found at the cave than the ones they originally reported. They seem to miss the point that in such a large assemblage, found in a high energy geological context (because of roof collapses, for example), it doesn’t matter how human-like some of the objects look, if the assemblage itself broadly has the characteristics of a on that is produced by geological forces. In fact, the larger the assemblage, the more likely it is that at least some of the objects will look like human-made tools.

No amount of focus on a few individual objects will make up for the fact that an assemblage overall looks more geologically than humanly produced, and that’s where the original authors and their critics differ significantly.

A secondary debate about the absence of evidence other than stone tools plays out in the back and forth, but it is definitely a sidelight. Ardelean et al. reasonably argue that the absence of human DNA, for example, doesn’t rule out the presence of humans. It doesn’t, however, it certainly doesn’t support it either.

More broadly, though, I worry that archaeology is developing a pattern of sensational claims published in high visibility journals such as Nature and Science, and widely covered in main stream media, but are then only examined and evaluated in more specialized and less accessible outlets like Paleoamerica, and a few obscure, out-of-the-way, backwater academic blogs. This is the pattern we find also in the Cerutti Mastodon saga and the Moralizing Gods debacle, although in this last case there was finally a resolution in Nature. But I will note that the resolution was not as widely covered and publicized as the initial claim.

There are two dangers here. One is that the public only sees the initial claim, and it becomes part of the public consciousness. The other is that high visibility outlets like Nature and Science will get burned one too many times and become even more hesitant to publish archaeology than they currently are.


Ciprian F. Ardelean, Mikkel W. Pedersen, Jean-Luc Schwenninger, Joaquín Arroyo-Cabrales, Devlin A. Gandy, Martin Sikora, Juan I. Macías-Quintero, Vladimir Huerta-Arellano, Jesús J. De La Rosa-Díaz, Yam Zul E. Ocampo-Díaz, Igor I. Rubio-Cisneros, Luis Barba-Pingarón, Agustín Ortíz-Butrón, Jorge Blancas-Vázquez, Corina Solís-Rosales, María Rodríguez-Ceja, Irán Rivera-González, Zamara Navarro-Gutiérrez, Alejandro López-Jiménez, Marco B. Marroquín-Fernández, Luis M. Martínez-Riojas & Eske Willerslev (2021) Chiquihuite Cave and America’s Hidden Limestone Industries: A Reply to Chatters et al., PaleoAmerica, DOI: 10.1080/20555563.2021.1985063

Ardelean, C. F., L. Becerra-Valdivia, M. W. Pedersen, J.-L. Schwenninger, C. G. Oviatt, J. I. Macías-Quintero, J. Arroyo-Cabrales, et al. 2020. “Evidence of Human Occupation in Mexico around the Last Glacial Maximum.” Nature 584: 87–92.

James C. Chatters, Ben A. Potter, Anna Marie Prentiss, Stuart J. Fiedel, Gary Haynes, Robert L. Kelly, J. David Kilby, François Lanoë, Jacob Holland-Lulewicz, D. Shane Miller, Juliet E. Morrow, Angela R. Perri, Kurt M. Rademaker, Joshua D. Reuther, Brandon T. Ritchison, Guadalupe Sanchez, Ismael Sánchez-Morales, S. Margaret Spivey-Faulkner, Jesse W. Tune & C. Vance Haynes (2021) Evaluating Claims of Early Human Occupation at Chiquihuite Cave, Mexico, PaleoAmerica, DOI: 10.1080/20555563.2021.1940441

Muthana A, R Ellen 2020. The Great Eolith Debate and the Anthropological Institute, Bulletin of the History of Archaeology.

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