Miguel Eduardo Delgado et al.
Martin De Los Reyes (left) and Guillermo Jofré, two of the researchers involved in the study, excavate the fossil of an extinct Ice Age relative of the armadillo called Neosclerocalyptus.
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More than 20,000 years ago, some of the earliest people in the Americas encountered a giant armadillo-like creature in what is now Argentina and dismembered it with stone tools, according to a new study.
The discovery, deduced from cut marks on the Ice Age creature’s fossilized remains, is significant because it adds to a series of recent finds that suggest the Americas were inhabited much earlier than archaeologists first thought – possibly more than 25,000 years ago.
“These animals are closely related to armadillos still alive today,” said study co-author Miguel Delgado, a researcher at the National University of La Plata in Buenos Aires. The animals are known for their armored scales and their ability to roll into a ball when threatened.
“The specimen we found belongs to one of the smallest species (an extinct armadillo species called Neosclerocalyptus),” Delgado said, pointing out that it weighed about 300 kilograms (660 pounds) and was 180 centimeters (almost 6 feet) long, including the tail.
A bulldozer uncovered the animal’s fossilized vertebrae and pelvis, which were found on the banks of the Reconquista River near the city of Merlo in Greater Buenos Aires.
Radiocarbon dating of bones and shells found in the same sediment layer revealed that the armadillo’s remains are between 20,811 and 21,090 years old, according to the study published Wednesday in the journal PLOS One.
The cuts were not immediately visible, but cleaning the fossils revealed 32 linear tracks. After careful analysis, the team ruled out that the tracks were made by rodents or carnivores that might have hunted the animals, or by other factors such as trampling, Delgado said.
Miguel Eduardo Delgado et al.
In this image, the highlighted areas (in blue) identify the fossilized bones of the Neosclerocalyptus specimen excavated near the town of Merlo, Argentina.
Instead, the team found that the shape of the cut marks was consistent with those of stone tools. The placement of the marks suggested that the animals were slaughtered for their meat, with a targeted sequence of cuts focused on dense areas of the armadillo flesh, Delgado said.
“The cut marks were not randomly distributed, but were concentrated on those skeletal elements that housed large muscle packages, such as the pelvis and tail,” he said.
The authors have presented “compelling evidence” that humans dismembered this extinct armadillo 21,000 years ago, said paleoanthropologist Briana Pobiner, a scientist in the Human Origins Program at the Smithsonian National Museum of Natural History in Washington, DC.
“The authors have done a solid job of using qualitative and quantitative analysis to demonstrate that the cut marks on the armadillo fossils are most likely human-made,” Pobiner, who was not involved in the study, said by email.
When and how the first humans arrived in North and South America, the last settled areas after humans left Africa and spread throughout the world, has long been controversial among experts and is still largely misunderstood.
Current estimates suggest that the first settlers lived in the region between 13,000 and over 20,000 years ago. However, the earliest archaeological evidence of settlement in this region is sparse and often controversial.
The discovery of fossilized footprints imprinted in mud, dating back 21,000 to 23,000 years, described in a September 2021 study, is the clearest in a series of recent pieces of evidence suggesting that the arrival of the first inhabitants occurred much earlier than many scientists had thought.
Miguel Eduardo Delgado et al.
A detailed examination of the cutting marks on the fossils revealed that they had been created with stone tools in an intentional order.
At that time, the planet was in the grip of the last ice age, a period 19,000 to 26,000 years ago when two massive sheets of ice covered the northern third of North America and extended south to what is now New York City, Cincinnati, and Des Moines, Iowa.
The layers of ice and the cold temperatures caused by the glaciers made travel between Asia and Alaska – the most likely route – impossible at that time. This means that the people who left the footprints probably arrived there much earlier.
Together with three holed giant sloth bones found in Brazil that archaeologists believe humans used as pendants 25,000 to 27,000 years ago, the dissected armadillo bones suggest that humans lived in South America a surprisingly long time ago.
The timing of human first settlement in the Americas – then home to many now extinct Ice Age creatures – is a “hotly debated topic,” Delgado said.
“Until recently, the traditional model assumed that humans entered the continent 16,000 calendar years ago,” he said.
“Our results, combined with other evidence, suggest a clear scenario for the first human settlement of the Americas. That is, the most likely date for the first human settlement is between 21,000 and 25,000 years ago, or even earlier.”