Miguel Eduardo Delgado et al.
Martin De Los Reyes (left) and Guillermo Jofré, two of the researchers involved in the study, discovered the fossil of an extinct Ice Age armadillo relative known as Neosclerocalyptus.
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More than 20,000 years ago in what is now Argentina, some of the first people in the Americas encountered a giant armadillo-like creature and killed it with stone tools, according to a new study.
The discovery, derived from cuts on the fossilized remains of an Ice Age creature, is significant because it adds to a flurry of recent findings that suggest the Americas were inhabited much earlier than archaeologists originally thought — perhaps more than 25,000 years ago.
“These animals are closely related to living armadillos,” 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 ability to curl into a ball when threatened.
“The specimen we found belongs to one of the smallest species (of an extinct species of armadillo called Neosclerocalyptus),” Delgado said, adding that it weighed about 300 kilograms (660 pounds) and was 180 centimeters (nearly 6 feet) long, including the tail .
A bulldozer revealed the animal’s fossilized vertebrae and pelvis, exposed along the banks of the Reconquista River near the town of Merlo in the Buenos Aires metropolitan area.
Radiocarbon data from bivalve bones and shells found in the same layer of sediment revealed that the armadillo’s remains were between 20,811 and 21,090 years old, according to a study published Wednesday in the journal PLOS One.
The cuts were not immediately obvious, but cleaning the fossils revealed 32 linear tracks. After careful analysis, the team ruled out that the marks were made by rodents, carnivores that may have hunted the animals, or 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 Neosclerocalyptus specimens discovered during excavations near the town of Merlo, Argentina.
Instead, the team found that the shape of the cut marks was consistent with those made by stone tools. The location of the marks indicated the animals were slaughtered for their meat with a deliberate sequence of cuts that focused on dense areas of the armadillo’s flesh, according to Delgado.
“The incision marks were not placed randomly, but focused on those skeletal elements that contained large muscle bundles, such as the pelvis and tail,” he said.
The authors provided “compelling evidence” that humans domesticated 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 good job of demonstrating through qualitative and quantitative analyzes that cut marks on armadillo fossils are most likely human-made,” Pobiner, who was not involved in the study, said via email.
When and how early humans first migrated to the Americas, the last places where people left Africa and spread around the world, has long been debated by experts and remains poorly understood.
Current estimates of the number of first inhabitants range from 13,000 years ago to more than 20,000 years ago, but the earliest archaeological evidence of settlement in the region is sparse and often controversial.
The discovery of fossilized footprints pressed into mud 21,000 to 23,000 years ago in New Mexico, described in a September 2021 study, is the most definitive of a string of recent evidence suggesting the arrival of the first inhabitants was much earlier than many scientists thought.
Miguel Eduardo Delgado et al.
Close examination of the cut marks on the fossils revealed that they were created by stone tools in a deliberate sequence.
During that time, the planet was in the grip of the Last Glacial Maximum, a period between 19,000 and 26,000 years ago when the northern third of North America was covered by two massive ice sheets that extended as far south as present-day New York, Cincinnati, and Des. Moines, Iowa.
The ice sheets and cold temperatures caused by the glaciers would have made travel between Asia and Alaska – the most likely route – impossible during that time, meaning the humans who made the tracks probably arrived much earlier.
Along with three perforated giant sloth bones found in Brazil, which archaeologists believe were used as pendants between 25,000 and 27,000 years ago, the butchered armadillo bones suggest that humans were in South America a surprisingly long time ago.
The timing of when humans first settled across the Americas, then home to many now-extinct Ice Age creatures, was “a hotly debated topic,” Delgado said.
“Until recently, the traditional model suggested that humans entered the continent 16,000 calendar years ago,” he said.
“Our results, combined with other evidence, suggest a different scenario for the first humans in the Americas, that is, the most likely date of the first human entry happened between 21,000 and 25,000 years ago or even earlier.”