Wednesday, July 19, 2017

The Cerutti Mastodon Site: Archaeological or Paleontological?

Eric Boëda, Christophe Griggo & Christelle Lahaye
Published online: 22 Jun 2017
(Link) pdf available at research gate

from the paper:

Once we have examined the appropriateness of the anthropogenic nature of the artifacts and the fact that we are confronted with a place of fracturing activity, it is obviously necessary to examine the chronological data which are crucial because they suggest that Cerutti is the oldest known site in the Americas. For this purpose, the lead author sought the advice of a specialist in the methods used (optically stimulated luminescence (OSL) and uranium-thorium (U-Th) dating), coauthor Lahaye. Indeed, without collagen the radiocarbon dates were immediately excluded from the methodological pool of dating. Instead, both dating methods used in this work converged on Pleistocene ages of the site. Quartz grains studied with OSL were too close to or beyond the limit of the method, so that only minimum ages could be deduced. They show the sediment surrounding the fossils of the Cerutti Mastodon site were not exposed to natural light for at least 60–70 ka. It can be deduced, if all the depositional and post-depositional phenomena are well understood, that the fossils enclosed in the site’s sediments are older than 60–70 ka. U-Th measurements on bones also can only be considered as minimum ages of bones’ burial. The results of analyses of different bones are consistent, giving an age of ca. 130.7 ± 9.4 ka. Combining OSL and U-Th results, in a well understood stratigraphic context, leads to the conclusion that the Cerutti mastodon dates to around 130 ka.

The resolution of the methods used does not allow a very precise chronological result (130.7 ± 9.4 ka), thus situating the site at the interface between the end of  the latest glacial (MIS 6), which is interpreted to have been a cold phase like the last glacial maximum and the beginning of the rapid warming which marked the beginning of the latest interglacial (MIS 5e). This chronological position makes it difficult to discuss the origins of this group of individuals and the process of their dispersal. For, assuming that they were newcomers, depending on the date taken into account, on the one hand they could have existed at the maximum extent of the glaciers blocking the land passage between Alaska and the Great Plains of North America, with the lowering of sea level more than 100 meters and the creation of a land bridge between Asia and North America. On the other hand, the alternative situation would have been characterized by a rise in sea level, which may have led to the closing of the land bridge but at the same time the opening of a corridor after the disappearance of glaciers, with the formation of large lakes as consequences. So, when in time are we situated, exactly? The fauna is not sufficiently informative to make us lean to one alternative or the other. Nonetheless, the coastal seaway remained a permanent solution whatever the climates.

Perhaps, however, these were not newcomers but instead descendants of generations already present in the Americas. But let us guard ourselves during this time of scientific upheaval to give priority to just those facts which alone have heuristic value. All the scenarios that we envisage must remain heuristic scenarios and not a paradigm, as we had with “Clovis first”.  Keep in mind that the facts once verified remain paramount.  We experienced this ourselves in Piauí in South America, where our successive and repeated discoveries in the same geographical area testified not to the presence of a “Robinson Crusoe” but to a large perennial population that existed for at least 5000 years between 35 and 40 ka (Boëda et al. 2016). This means that scientific research, finally rid of traditional ideological locks, can focus on the expansion of prospecting, taking into account the geomorphological changes of the Pleistocene. We have to look for the sites, in the places where they are likely to be, under water or under many meters of sediment.

We are left finally with one last problem: the creators of the Cerutti feature. Holen et al. (2017) provide a realistic picture of the situation in Asia. We have a fairly broad choice of candidates – late Homo erectus, Neanderthal, archaic Homo sapiens, or even Denisovan. In the absence of hominin remains, some researchers will consider these candidates’ respective cognitive aspects when making a taxonomic attribution. For our part, having experience across Asia from north to south, we would be suspicious of any specific biological/cultural fit. We are dealing with technical worlds quite different from our Western and African references. From experience, let us guard against prejudice and remain open to all possibilities.

To conclude, I endorse the last sentence of Holen et al.’s (2017) article by extending it to all of America:  this discovery calls for further archaeological investigation of the North and South American strata of early-late Pleistocene age.

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