Stone tools at 15.5k at the Friedkin site : A definite maybe

Hot on the heels of the claim of a 16 000 year old human presence at the Gault site (Williams et al 2018) last August, Waters et al (2018) are claiming stone tools dated at 15 500 years at the nearby Friedkin site. Both of these are part of the pre-Clovis Buttermilk Creek complex. As I wrote in the wake of the most recent Gault site claim, I do think there is a convincing case that there is a pre-Clovis presence in the region. However, the case for a pre-14k presence is much weaker. This latest salvo doesn’t fix that.

Waters et al claim pre-Clovis projectile points at the Friedkin site “in the horizon dated between ~13.5 and ~15.5 ka ago”. Despite a quite close examination of the text and the figures both in the article and the supplemental materials, I can see no easy way to determine whether the projectile points in question are nearer the 13.5k or the 15.5k end of the range. While the headlines and media coverage that accompanied the release of the article emphasize the 15.5k age of the artifacts and the claim that they are the oldest known in North America, the article itself and its abstract are much more conservative. They emphasize the range of approximately 13.5 to 15.5k. The most chronologically precise claim is that of “a triangular lanceolate point form appearing ~14ka ago”. So the claim itself is not quite as sensational as would appear from the media coverage and does not break the current ceiling of 14k for well-dated finds in the Americas.

The authors do, slightly disingenuously I must say, label the Friedkin site as 15.5k years old in one of their map graphics. Everywhere else, they conservatively report the OSL range. Then again, the same graphic shows the very controversial Meadowcroft site as 14k years old. But they label the figure as “Proposed models”. The language in the figure’s caption, however is much less tentative and gives the impression that this is a conclusion supported by the article.

OSL dating and stratigraphy

The two main critiques leveled at the Buttermilk Creek Complex’s claim of antiquity are the uncertainty associated with OSL dating and the peculiar stratigraphy of the site. Morrow et al (2012) note the presence of vertisol at the sites, a type of stratigraphy in which there are vertical cracks in the soil extending downward. These cracks could allow younger archaeological material to fall down into older layers, and thus appear older than they really are. Figure 1c of the latest article shows these vertical cracks in terrifying detail for all those interested in the dating of the Friedkin artefacts.

Figure 1C of Waters et al (2018)

The nature of the stratigraphy certainly reduces my level of confidence in the claim. There may very well be artifacts in a layer dated to 15k, but I am not at all sure that the artifacts are of the same age. This is the sort of context in which I would very much like to see a direct association between dated material and a stone tool, such as directly dated organic residue, for example.

The problems about OSL noted in previous critiques are not addressed in this article. The OSL dating is simply taken at face value. The authors go into great detail about their methods, which is good, but they don’t try to reassure those who have concerns about the method itself. Williams et al (2018), last summer, clearly organized their article to address some of the main critiques of previous claims about Gault/Friedkin. Waters et al (2018) largely write as if those critiques don’t exist.

Implications of the claim

If accepted, the new Friedkin claim would make it the oldest known site in North America, and in the Americas in general, as far as I am concerned. There is an odd paragraph in the discussion section of the new paper that is worth quoting at length:

“As people occupied the coast, some began to move inland (Fig. 6A). By ~13.8 ka ago, they were on the Olympic Peninsula of Washington as witnessed by the Manis site. Traveling close to the ice margin, people are present in Wisconsin by ~14.8 and ~14.2 ka ago and in Pennsylvania by ~14 ka ago. By ~14.2 ka ago, people trekked into the northern Great Basin, as witnessed by Paisley Caves. Farther south, people made their way to the Valley of Mexico, as witnessed by the Iztapan Mammoth sites. Some people appear to have entered the Gulf of Mexico and made their way to Page-Ladson by ~14.6 ka ago. Others moved inland and discovered the Friedkin and Gault sites by ~15.5 ka ago. Some groups, carrying stemmed El Jobo points, continued south and reached the southern portion of South America by ~14.2 ka ago.”

Aside from the uncritical acceptance of highly critiquable dates all over the map, the paragraph is odd because it presents a NW to SE movement that somehow reaches SW area of Gault/Friedkin first, by way of Wisconsin. Even if one accepts all these dates, a more literal reading of the pattern would be a diffusion from of Gault/Friedkin outward to a starting point “By ~13.8ka ago…on the Olympic Peninsula of Washington”, which obviously does not make sense from an archaeological perspective. The model presented clearly does not match the dates reported.

I will repeat here my standard disclaimer that I have nothing in principle against the idea of a human presence in the Americas before about 14k years ago. As Jennifer Raff points out, other lines of evidence converge on earlier dates. I just haven’t seen convincing material evidence to support the claim so far. This latest report on the Gault/Friedkin complex does not change that. Even the article, in the final analysis, does not clearly claim to change that. If it did, the claim would be poorly supported by the evidence presented.

References

Morrow JE, Fiedel SJ, DL Johnson, K Kornfeld, M Rutledge, WR Woods 2012. Pre-Clovis in Texas? A critical assessment of the Buttermilk Creek Complex”, Journal of Archaeological Science 12: 3677-3682.

Waters MR, JL Keene, SL Forman, ER Prewitt, DL Carlson, JE Wiederhold 2018. Pre-clovis projectile points at the Debra L. Friedkin site, Texas, implications for the Late Pleistocene peopling of the Americas. Science Advances 4.

Williams TJ, MB Collins, K Rodrigues, WJ Rink, N Velchoff, A Keen-Zebert, A Gilmer, CD Frederick, SJ Ayala, ER Prewitt 2018. Evidence of an early projectile point technology in North America at the Gault Site, Texas, USA Science Advances 4.