Astudy that I have just come across (Del Papa M, De Los Reyes M, Poiré DG, Rascovan N, Jofré G, Delgado M (2024) Anthropic cut marks in extinct megafauna bones from the Pampean region (Argentina) close to the city of Buenos Aires, during the last glacial maximum. PLoS ONE 19(7): e0304956. https://doi.org/10.1371/journal.pone.0304956), reported bones with cut marks produced by humans that date back to roughly 20,000 years ago.
This pushes back the date of arrival of humans in South America, and may imply that the dates for humans crossing Beringia are too recent, and have to be revised.
"In this study, we present the analysis of fossil remains with cutmarks belonging to a specimen of Neosclerocalyptus (Xenarthra, Glyptodontidae), found on the banks of the Reconquista River, northeast of the Pampean region (Argentina), whose AMS 14C dating corresponds to the Last Glacial Maximum (21,090–20,811 cal YBP). Paleoenvironmental reconstructions, stratigraphic descriptions, absolute chronological dating of bone materials, and deposits suggest a relatively rapid burial event of the bone assemblage in a semi-dry climate during a wet season. Quantitative and qualitative analyses of the cut marks, reconstruction of butchering sequences, and assessments of the possible agents involved in the observed bone surface modifications indicate anthropic activities. Our results provide new elements for discussing the earliest peopling of southern South America and specifically for the interaction between humans and local megafauna in the Pampean region during the Last Glacial Maximum."
Map showing location of the site. Source
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Nicely done paper….The cut marks and other anthropic interactions on the bones of this extinct mammal seem to be clear and convincing, and plenty of considerations about the possibility of “equifinality” (that is; the feasibility of natural processes as being responsible for the bone modifications) were also included by the authors.
ReplyDeleteRespect to the datings, a conjunction of two methods was here utilized; a) AMS C14 dating on the carbonates that are present into the hydroxyapatite structure of the bones (an alternative approach when there is no collagen on them, as was this case), and b) geological analysis of facies; strongly based on a reliable model about sediments infilling of river valleys for the Pampean region, as is Toledo(2011)´s one. (Ref*).
Although AMS C14 on hydroxyapatite usually delivers a somewhat lower accuracy when compared with AMS C14 on collagen (and occasionally, it may be also objectionable)… the obtained results appear to be very consistent with the stratigraphic position of these remains, located within a well known MIS2 geological layer of fluvial origin, whose depositional ages span from 28/30 Ka to 16/17 Ka…So, I would say that this dating at 21 Ka seems to be sufficiently supported…
I believe this work is a pretty well documented research, that not only pushes the preexisting “barrier” for early peopling of the Pampean region of Argentina, from 14/15 Ka up to at least LGM (last glacial maximum) times, but (as you rightly point) also suggests that “certain readjustments” should be made on the up to now presumed dates for humans crossing Beringia…or perhaps, should be finally admitted the possibility of “several” crossings through Beringia, interleaved into the Pleistocene …an aspect that was also treated in your blog.
Best regards
Marcelo
Ref*: Toledo MJ. El legado lujanense de Ameghino: Revisión estratigráfica de los depósitos Pleistocenos-Holocenos del valle del Río Luján en su sección tipo. Registro paleoclimático en la Pampa de los estadios OIS 4 al OIS 1. Revista de la Asociación Geológica Argentina. 2011; 68:121–167.