Paris | It is a real change for the world of archaeology: dating back to 30,000 years ago, the settlement of North America, the last continent to have been occupied by man, was more than twice as old as believed until now, revealed Wednesday the two studies.
In excavating the cave of Chiquihuite, in the north of Mexico, archaeologists have unearthed hundreds of stone tools and carved revealing a lithic industry still unknown, up to 33 000 years before our era.
They prove that this site, perched in altitude, was occupied for 20,000 years, according to two studies published in the journal Nature.
“Our research provide new evidence on a former presence of humans in the Americas”, the last continent to have been occupied by modern man, welcomed to the AFP, the archaeologist Ciprian Ardelean, lead author of one of the two studies.
The oldest specimens have been dated by radiocarbon (or carbon-14) over a range of between 33 000 and 31 000 years before our era. “They are few in number, but they are here”, commented the researcher from the Universidad autonoma de Zacatecas, Mexico.
They reveal a method of stone size, unique in north America, using cutting into thin strips – advanced technology that would be coming from elsewhere, according to the authors.
If any bones or DNA of humans have been found on the site, “it is likely that humans have used it as a base relatively fixed, probably during seasonal events recurring in the context of broader migration movements,” says the study.
The origins of the arrival of Homo sapiens in America – the last continent populated by our species – are hotly debated among anthropologists and archaeologists.
For decades, the thesis of the most commonly accepted was that of a settlement from eastern Siberia who crossed a land bridge – the current Bering strait – to land in Alaska, and then spread more to the south.
Archaeological evidence, including spear points used to kill the mammoths, have long suggested an old growth of 13 500 is associated with a culture known as Clovis – the name of a city in the State of New Mexico in the United States – regarded as the first american culture, from where the ancestors of the native americans.
This model of the “culture Clovis primitive” is called into question in the past 20 years, with new discoveries, which have declined in the age of early settlements. But only up to 16 000 years.
The results of this research are likely to be keenly contested. “This happens as soon as someone finds sites older than 16 000 years ago: the first reaction is either denial, or a strong approval”, according to the researcher who has started to excavate the cave in 2012.
“It is clear that the stands were in the Americas well before the development of the Clovis culture,” writes Ruth Gruhn, professor of anthropology at the University of Alberta, in a commentary accompanying the publications.
The second study, researchers were able to date samples from 42 sites across North America, using the dating by radiocarbon and luminescence.
Thanks to statistical models, they have demonstrated a breakdown of the human presence “before, during and immediately after the period of the last glacial maximum,” between 27 000 and 19 000 years.
This episode of glaciation is crucial, since it is commonly accepted that the ice caps covering at that time most of the north of the continent have made it impossible any migration of human came from Asia.
“So, if humans were there during this last ice age, this is necessarily because they were there before,” noted the Pr Ardelean.
The very presence of ancient populations across the continent also coincides with the disappearance of the megafauna of north america, including mammoths and other extinct species of camels and horses.
“Our analyses suggest that the widespread growth of men across North America has been a key factor in the extinction of large terrestrial mammals,” the study concludes.
Many questions remain unresolved, including that of the roads used by the early arrivals, either by the Bering strait, or, as suggested by recent discoveries along the pacific coast, on foot or by small boats.