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 relative of an Ice Age armadillo known as Neosclerocalyptus.
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A new study finds that more than 20,000 years ago in what is now Argentina, some of the first humans in the Americas encountered a giant armadillo-like creature and slaughtered it with stone tools.
The discovery, inferred from cut marks on the fossil remains of the Ice Age animal, is significant because it adds to a series of recent finds suggesting that the Americas were inhabited much earlier than archaeologists initially 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 up into a ball when threatened.
“The specimen we found belongs to one of the smallest species (of an extinct type of armadillo called Neosclerocalyptus),” Delgado said, noting that it weighed about 300 kilograms (660 pounds) and was 180 centimeters (nearly 6 feet) long, including its tail.
A bulldozer uncovered the animal’s fossil vertebrae and pelvis, which were found along the banks of the Reconquista River, near the town of Merlo in the Buenos Aires metropolitan area.
Carbon dating of bivalve bones and shells found in the same sediment layer revealed the armadillo remains were between 20,811 and 21,090 years old, according to the study published Wednesday in the journal PLOS One.
The cuts weren’t immediately obvious, but cleaning the fossils revealed 32 linear markings. After careful analysis, the team ruled out that the marks were made by rodents, carnivores that might have hunted the animals, or other factors such as trampling, Delgado said.
Miguel Eduardo Delgado et al.
In this illustration, the highlighted areas (in blue) indicate the fossilized bones of the Neosclerocalyptus specimen, which were unearthed during the excavations near the town of Merlo in Argentina.
Instead, the team found that the shape of the cut marks was consistent with that of stone tools. The placement of the marks suggested that the animals had been butchered for their meat with a deliberate series of cuts that targeted dense areas of the armadillo’s flesh, Delgado said.
“The cut wounds were not randomly distributed, but concentrated on those skeletal elements that housed large muscle packages, such as the pelvis and tail,” he said.
The authors provided “compelling evidence” that humans slaughtered this extinct armadillo 21,000 years ago, said paleoanthropologist Briana Pobiner, a researcher 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 analyses that the cut marks on the armadillo fossils were most likely human-made,” Pobiner, who was not involved in the study, said via email.
When and how early humans first migrated to North and South America, the last places humans settled after humans left Africa and spread throughout the world, has long been a matter of debate among experts and remains poorly understood.
Recent estimates place the first inhabitants around 13,000 years ago, but the oldest archaeological evidence for habitation in the region is scarce and often controversial.
The discovery of fossilized footprints in the mud in New Mexico dating from 21,000 to 23,000 years ago, described in a September 2021 study, is the most definitive in a series of recent evidence suggesting that the first inhabitants arrived much earlier than many scientists thought.
Miguel Eduardo Delgado et al.
Detailed examination of the cut marks on the fossils revealed that they were deliberately made in a specific sequence by stone tools.
At that time, the planet was in the grip of the Last Glacial Maximum, a period 19,000 to 26,000 years ago when two huge ice sheets covered the northern third of North America, extending as far as present-day New York City, Cincinnati, and Des Moines, Iowa.
The ice caps and 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 much earlier.
Along with three perforated giant sloth bones found in Brazil, which archaeologists think humans used as pendants 25,000 to 27,000 years ago, the butchered bones of an armadillo suggest humans were in South America a surprisingly long time ago.
The timing of the first human 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 indicated 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 occupation of the Americas, that is, the most likely date for the first human entry occurred between 21,000 and 25,000 years ago or even earlier.”