Patagonian monsters: November 2021

Monday, November 22, 2021

Ancient Australasian signal found in South American natives

A paper published earlier this year(Deep genetic affinity between coastal Pacific and Amazonian natives evidenced by Australasian ancestry. Marcos Araújo Castro e Silva, et al. PNAS April 6, 2021 118 (14) e2025739118; https://doi.org/10.1073/pnas.2025739118), suggest that the very early or even the earliest people to reach South America carried a genetic component that is not found in North or Central America, and that is linked to a "Y Population" the genetic signal inherited from this group (called "Y" after "Ypikuéra" or "ancestral" in Tupi language") is only found among Australasian people.

The paper reports that the Y-population signal originally found among Amazonian Amerindians is also found in natives from other parts of Brazil, and also in the Pacific coastal population of South America.

The authors write: "The best-fitted model showed that the Pacific coast is a mixed group of South American ancestry and a small non-American contribution associated with a sister branch of Onge, as also observed for Karitiana and Suruí. They suggest that the presence of this signal on the Pacific coast suggests that the original population reached the area following a coastal route.

The Onge are people that live in the Andaman islands, in the Bay of Bengal, dark skinned isolated people... and they are linked to South American natives.

Did they land in North America and Mesoamerica and die out? Did they bypass the northern part of the Americas and settle in the South?. The lack of this signal in the northern part of the continent is not explained in the paper.

Friday, November 12, 2021

The windows for human arrival in America

Marine isotope stages (MIS) are periods that alternate hotter and colder climate. They have been identified by measuring the content of oxygen isotope ¹⁸O in ice cores.

They are numbered, and the MIS with even numbers represent glacial periods (and therefore lower sea levels as the ice packs have taken water out of the oceans), and the odd numbered stages represent warm interglacial periods (like the current one), with higher sea levels.

So for humans to cross Beringia and reach America, they'd have to do so during a cold even numbered MIS.

This is the list of cold MIS during the past million years:

MIS 2 – 29 ky
MIS 4 – 71 ky
MIS 6 – 191 ky
MIS 8 – 300 ky
MIS 10 – 374 ky
MIS 12 – 478 ky
MIS 14 – 563 ky
MIS 16 – 676 ky
MIS 18 – 761 ky
MIS 20 – 814 ky

So why did our human ancestors cross during the last possible stage? Why didn't Neanderthals do so during MIS 10? or Homo erectus during MIS 2O?

The following map, adapted from Nature shows that there were humans in Asia that could have crossed into America from MIS 8 onwards, and this does not contemplate H. erectus.

Potential migrants from Asia range: 152-300 kyr.

They lived in temperate to cold locations, why not follow the megafauna into Siberia and North America?

Thursday, November 11, 2021

24 kyr Stone Tools in Pedra Furada, Brazil

Earlier this year a paper by Eric Boëda ( Boëda E, Ramos M, Perez A, Hatté C, Lahaye C, Pino M, et al. (2021) 24.0 kyr cal BP stone artefact from Vale da Pedra Furada, Piauí, Brazil: Techno-functional analysis. PLoS ONE 16(3): e0247965. rRephttps://doi.org/10.1371/journal.pone.0247965) analyzed stone tools dated 24,000 years old, from Brazil. The interesting part is (see my previous post) that the authors acknowledge the conflict between orthodox scholars and those that support an early peopling of America.

They wrote: "The peopling of the Americas continues to be subject of intense debate, basically between two positions that often do not consider fully South American research: a Last Glacial Maximum (LGM sensu stricto, dated between 19–23 kyr BP) occupation (current consensus) and a pre-LGM occupation. In support of the latter, a growing body of evidence demonstrates a Late Pleistocene human presence (i.e. Paleoamerican) in South America well beyond 20 cal kyr BP"

The article then goes on to describe stone tools and one in particular (24 kya). What I found interesting is the authors' comment that the older layers have cobble type quarz tools (they look Oldowan to my layman eyes. See Fig. 5), and as you reach younger levels, the tools morph into bifacial tools (Fig. 7). Both are shown below:

Fig. 5 they look like Pebble tools (Oldowan)

Fig. 7, bifacial (Acheulean axes?)

Anyway, these findings show two things. One, evidence is mounting and it supports an earlier peopling of America and, two, that North American scientists wouldn't even see an ancient stone industry tool because they don't think there are any in the Americas. They will ignore it or consider it a geofact.

Older dates vs. a later peopling of America Round 1

Ben Potter and James Chatters don't like the proof that is slowly building up supporting an early peopling of America. They wrote two separate papers decrying two papers that support the notion of an early peopling of America.

One (Ben A. Potter, James C. Chatters, et al. (2021) Current Understanding of the Earliest Human Occupations in the Americas: Evaluation of Becerra-Valdivia and Higham (2020), PaleoAmerica, DOI: 10.1080/20555563.2021.1978721) questions the findings of Lorena Becerra and Thomas Valdivia (Becerra-Valdivia, L., Higham, T. The timing and effect of the earliest human arrivals in North America. Nature 584, 93–97 (2020). https://doi.org/10.1038/s41586-020-2491-6).

Becerra and Valdivia analyzed data regarding the date of human entry to America and concluded that "The data obtained show that humans were probably present before, during and immediately after the Last Glacial Maximum (about 26.5–19 thousand years ago)."

Becerra wrote a rebuttal countering Potter and Chatters stating that "it is clear that they (Potter & Chatters) do not understand fully the methodology...As radiocarbon dating experts, it is sadly not uncommon for us to encounter: (i) academics who dismiss dates they view as incongruent with their expectations..." and conclude that "we note with interest a recent publication that has found further robust evidence for human activity (well-dated footprints) in North America at the time of the LGM (Bennett et al. 2021). This fits well within the chronology-centered peopling model we proposed (Becerra-Valdivia and Higham 2020). In the future, we hypothesize that new discoveries such as this one will strengthen the > 16,000 cal yr BP cultural signal in the continent."

Potter and Chatters' second paper against an early peopling of America ( James C. Chatters, Ben A. Potter, et al. (2021) Evaluating Claims of Early Human Occupation at Chiquihuite Cave, Mexico, PaleoAmerica, DOI: 10.1080/20555563.2021.1940441) attacks the finding of ancient stone tools in a cave in Mexico, surmising that they are geofacts (not man made).

The authors of the original paper Ardelean, Ciprian F., Lorena Becerra-Valdivia, et al. 2020. “Evidence of Human Occupation in Mexico around the Last Glacial Maximum.” Nature 584: 87092. doi:https://doi.org/10.1038/s41586-020-2509-0.) promptly replied. And something that drew my attention was this article, that tells us that "It's important to point out that Chatters and his colleagues didn't inspect the items gathered in Chiquihuite Cave first-hand, and instead relied "on the evidence provided in the original article and supporting documentation"." sort of "armchair detective" science job!.

It will take a lot of effort to overcome the old-school orthodoxy, but new discoveries will silence this kind of opposition.