• Study: the first man to leave Africa

The arrival in America marks the last great expansion of Homo sapiens on the planet. For a long time the traditional view of archaeologists was that the first humans to reach the continent arrived there some 13,000 years ago. Those pioneers would be people belonging to the so-called Clovis culture, which includes the use of sophisticated spearheads, carved in stone with a very distinctive shape. The basis of this theory was a set of objects found in the 1930s in the Great Plains region, along with the bones of mammoths and a now-extinct bison species.

An important part of the researchers then assumed that the first inhabitants of America were these ca zadores specialized in large dams, which have spread rapidly north and center of the continent in the post - millennium upon arrival. That territorial expansion would coincide with the opening of a corridor in the Alaskan ice, which would have long blocked the passage. However, in recent decades different findings have been questioning this model and more and more researchers believe that there was a previous presence on the continent . However, the chronology and origin of these first settlers continues to be debated.

Two independent studies are published in this regard in the latest issue of Nature . The first, led by researchers from the Autonomous University of Zacatecas, describes the results of excavations in the Chiquihuite cave (Mexico). There, analysis of stone tools, plant debris, and environmental DNA (molecules extracted from the rock layers) suggest that the site was already occupied some 26,500 years ago .

The Mexican cave thus joins several sites in northeast and central Brazil that have provided evidence suggesting dates of human occupation between 20,000 and 30,000 years ago, although its dating remains controversial. "Although they have been excavated and analyzed by experts, they are commonly discussed or simply ignored by most archaeologists because they are considered too old to be real," says Ruth Gruhn , professor of anthropology at the University of Alberta, Canada, and author. from a comment in the same issue of Nature . "But the findings in the Chiquihuite cave force a reconsideration of the issue."

CIPRIAN ARDELEANNATURE

This first work is reinforced by a second article based on radiocarbon and luminescence dating from more than 40 deposits in Mexico, the United States, and Canada, to determine patterns of human dispersion across the north of the continent. In this case, the analysis, carried out by researchers at the University of New South Wales (Australia), has produced a statistical model consistent with a human presence prior to the Clovis culture . Specifically, such presence would date, at least, to the Last Glacial Maximum (a period that spans between 26,000 and 19,000 years ago).

The study concludes that the interior regions of Alaska, the Yukon in Canada, and the United States should already be widely populated long before that 13,000-year date. "Although it is true that they are less compared to the later cultures of Clovis, Western Stemmed and Beringia, we have shown that there are pre-clovis deposits throughout North America and in Beringia," says Lorena Becerra-Valdivia, first author of the article.

Unknowns

The findings also raise new unknowns. One is the route -or routes- that these ancient peoples followed in their expansion. The most obvious entry point from Northeast Asia is through the Bering Strait. But for a long interval (estimated to be between 34,000 and 11,000 years) the only way through the lowlands east of the Rocky Mountains was blocked by the fusion of two great masses of ice, the Cordillerano and the Laurentino.

An alternative is that populations adapted to life on the coast find a way along the coast.

"The arrival of these groups, like the one in Chiquihuite, must have occurred before the closure of the ice sheets in Canada," says Ciprian Ardelean, a researcher at the University of Zacatecas. "The possibility that there would be arrivals during the Last Glacial Maximum is difficult to sustain; I think we have to focus on immediately previous entries and reassess the timing of that opening of Beringia by land." An alternative is that populations adapted to life on the coast find a way along the coast. "It is a possibility that has gained strength as a result of increased archaeological research in coastal areas ," says Gruhn.

Another question that remains in the air is why no other archaeological site equivalent to Chiquihuite has been found in the continental United States. If humans entered the continent through the Bering Strait, they should have passed through that area and perhaps left a fossil record. However, with the entry model for a coastal route, the possibility remains that the first archaeological sites are now submerged by rising sea levels at the end of the last ice age. "Therefore, in light of these new findings, archaeological research from this period should be intensified," Gruhn concludes.

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