Earliest Ever Human Footprint in the Americas Discovered, Dating Back 15,600 Years

Researchers have discovered a human footprint in southern Chile they say is the oldest ever found in the Americas.

According to a study published in the journal PLOS One, the footprint was likely made 15,600 years ago, meaning it is one of the earliest signs of human presence in the region.

The track was discovered by a team from the Austral University of Chile during excavations in 2011 at a site in the city of Osorno—which lies around 500 miles south of the country's capital, Santiago.

It took several years for the researchers to confirm that it was indeed a human footprint, and not that of an animal.

"To my knowledge, it is the oldest footprint found in the Americas," Karen Moreno, an author of the study, told Newsweek.

The team's analysis showed that the print at the Pilauco site was likely made by a barefooted adult human. They determined that it belongs to the "ichnospecies" Hominipes modernus, which is usually associated with Homo sapiens, or modern humans.

Scientists classify fossil tracks by designating them as so-called "ichnospecies" rather than the more familiar "species" to avoid confusion, according to researchers Allison Vitkus, Karen Chin, and Martin Lockley—who were not involved in the study—writing on the University of California Museum of Paleontology's website.

There are two reasons for this. The first is that one type of print could have been produced by many different species. The other is that one species is capable of making many different types of tracks. Thus, scientists classify tracks using the "ichnospecies" system.

"The scientific study of footprints is called ichnology and different homo [human] species—Homo sapiens, Homo neanderthalensis, etc.—can make similar footprints, which are all named Hominipes modernus. This Hominipes modernus footprint has very definitive characteristics—the shape of the largest toe, the lateral toes, a well-rounded heel, elevation of the arch."

The Chilean researchers came to their conclusions about the origin and age of the footprint by analyzing the sediment and organic plant material in which it was found—using techniques such as radiocarbon-dating—and conducting track-making experiments to show how the shape was made.

"It's a footprint that could have been made by any homo [human] species, Neanderthal for example," Moreno said. "But it's very unlikely that Neanderthals were here in South America because they were extinct before this time. In fact, the only homo species there 15,000 years ago was homo sapiens."

"We did the comparison with all sorts of shapes of different animals and it is very very different from birds, bears, or other animals that could have been there," she said. "It's a very characteristic shape that cannot be made by other animals other than humans."

The Pilauco site—where excavations have been ongoing since 2007—also contains the remains of ancient megafauna, such as mastodon and primitive elephants, as well as human tools.

Another archaeological site, known as Monte Verde, located around 60 miles away from Pilauco in Chilean northwestern Patagonia, also contains a human footprint—among other artifacts—that researchers estimate to have been made around 14,600 years ago—1,000 years later than the recent find.

Since its discovery in the mid-'70s, the Monte Verde site has helped to reshape the debate on the earliest peopling of the Americas, providing evidence of human settlement that may have pre-dated the so-called "Clovis culture"—which researchers had long-considered the first inhabitants in the region.

Thus, the latest findings, according to the Chilean team, might represent further evidence for the still-contested idea of a pre-Clovis South American colonization of northern Patagonia, as originally indicated by the Monte Verde site.

"Early human occupation in southern South America (Patagonia) has been the focus of intense debate over the recent years," the authors wrote in the study. "Current detailed chronologies show that human presence in the area can be traced back as far as roughly 15,000 years ago with around 3,500 years of coexistence with extinct megafauna. This suggests a complex dynamic between climatic and human-made environmental changes."

"The human trace finding in Pilauco adds a new and independent line of evidence on the colonization of northern Patagonia, as has been continuously defended for more than 40 years by now based on scientific findings from the neighboring Monte Verde site," they wrote.

According to Moreno, findings such as this lend more weight to the increasingly popular hypothesis that humans settled in the Americas earlier than previously thought.

"[These people] definitely came before the migration through the Bering Strait that we have previously heard about," she said. "That same route might have been done, but earlier, perhaps not leaving much evidence in North America because there were very large extensions of glaciers, and these destroyed all sorts of data when they moved and melted."

"The people might have used the coastline to come further south where the climate was a lot better and that's probably why we're finding this earlier evidence in South America," she said. "It's not that it doesn't exist in the north, they might have come through the north, but [evidence of] these migrations through the coast might be now covered by the sea that is higher now and is rising with climate warming."

Todd Braje, an anthropologist from the California Academy of Sciences who was not involved in the latest research, described the new discovery as "exciting," agreeing with Moreno that it supported the hypothesis of an earlier settlement of the Americas.

"Given the associated radiocarbon dates, the site stratigraphy [study of rock layers], and the artifact assemblage, this discovery provides additional support for a peopling of the Americas sometime prior to around 15,000 years ago," he told Newsweek.

"Other human footprints discovered in the Americas have been claimed to be older, but these are all very controversial," he said. "Based on the supporting evidence presented in this paper, however, the Pilauco footprint could prove to be the earliest such discovery in the Americas."

This article was updated to include comments from Karen Moreno and Todd Braje.