America populated earlier than previously thought

The first humans to set foot on American soil were thought to have passed just east of the Rocky Mountains when a passage opened between the glaciers 15,000 years ago. But the discovery of footprints dating back more than 20,000 years in New Mexico shakes up this history.

Gypsum

White Sands National Park in New Mexico is famous for its white sand. It is a fine gypsum dust that gives the region a very interesting feature for paleontologists: the footprints left thousands, even tens of thousands of years ago, by the region’s first inhabitants. are preserved as if they had walked on fresh concrete.

“There were lakes with clay banks then,” says Kathleen Springer, a geologist at the United States Geological Survey (USGS), who is the lead author of a study published on the subject early October in the magazine Science.

Discovered in 2018, the footprints that are the subject of the study were found at different depths of up to one meter. “We first identified human and animal footprints on the surface,” says M.^me Springer. They were hunters tracking a tiger and a woman carrying a child being followed by another tiger. We did underground radar scans to discover other footprints. These are these buried footprints which date back between 21,000 and 23,000 years. »

Cabotage

When Christian Gates St-Pierre, an archaeologist at the University of Montreal, heard about these footprints from more than 20,000 years ago in a first publication in 2021, he was skeptical. “For a long time, the consensus was that the oldest human traces in America dated back 14,000, 15,000 years. There began to be older sites, but their dating was not unanimous. I think that with this new study, we can consider that these footprints in New Mexico are indeed older than 20,000 years. » There are now nearly a hundred human sites in America dating back more than 20,000 years, according to him.

This completely changes the assumptions of the path taken by the first humans to arrive in America. “20,000 years ago, there were glaciers from the Atlantic to the Pacific,” says Mr. Gates St-Pierre, specialist in the first settlements of Quebec.

In February, colleagues of M^me Springer published in the journal PNASmodeling indicating that a 2,500-year window, starting 24,500 years ago, was most likely for such an epic.

The human traces from 15,000 years ago are incidentally named “Clovis culture”, from the name of a village in New Mexico, located four hours north of White Sands Park, where were unearthed in the 1930s arrowheads characteristic of the people of that time.

Three dates

The works of M^me Springer and his team were interrupted by the pandemic. “We therefore published a first dating with a single method in 2021.” The study from early October presents the results of three other dating methods, all of which give results between 21,000 and 23,000 years ago.

“We also did six related checks,” says Jeff Pigati of the USGS, also a co-author. “For example, we verified that the ages are constant at different depths, that the type of pollen detected, from different conifers now present at altitude, indicates a cooler temperature. » Few sites have had such extensive research in terms of dating, according to Mr. Gates St-Pierre.

The critic

An Oregon State University paleontologist who criticized the 2021 study doubts the new data. “One of the additional dating techniques is done on a core taken two meters from the footprints,” observes Loren Davis, who himself has published several studies on sites dating back up to 15,000 years. “And I’m not convinced that the sediments at the underground footprints haven’t been contaminated by older material. » M^me Springer believes that Mr. Davis did not fully understand the methodology used.

And in Quebec?

The earlier arrival of the first humans in America, and by a coastal route rather than east of the Rockies, does not change much for Quebec. “The oldest human site in Quebec dates from 12,000 to 12,500 years ago, in Mégantic,” says Mr. Gates St-Pierre. Before, there was [sur le Québec] the Laurentian Glacier, which at its maximum descended to Manhattan. »

The Amazon

In the same issue of Science, a gathering of 230 paleontologists from the Old Continent and the New World announced that the Amazon contained between 10,000 and 24,000 pre-Columbian towns and villages potentially dating back 12,000 years. This conclusion, based on lidar data, a type of aerial radar, shows that the history of South America is very poorly known. So far, only 24 pre-Columbian Amazonian cities have been revealed using lidar. The most famous are those of the Casarab civilization, in northern Bolivia, which controlled 4,500 km^⁠2and were revealed by lidar in 2022.

“It shows that the Amazon was probably occupied more intensively than we thought in the past by indigenous populations,” says Mr. Gates St-Pierre.

Between -500 BC BC and 1000

First Iroquoian archaeological traces in Quebec, Ontario and northern New York State