Humans reached Argentina by 20,000 years ago — and they may have survived by eating giant armadillos, study suggests

Ancient humans may have butchered and eaten a giant armadillo-like creature around 20,000 years ago in what is now Argentina, a new study finds. 

The discovery of the butchered bones supports a growing body of evidence that people spread throughout the Americas much earlier than previously assumed.

During the Late Pleistocene epoch (129,000 to 11,700 years ago), ice sheets and glaciers covered much of the planet, particularly during the Last Glacial Maximum, a period around 26,000 to 20,000 years ago when the ice age was at its height. While archaeologists previously thought that the first Americans arrived by journeying along a land bridge connecting Siberia with Alaska 13,000 years ago, archaeological sites discovered in North and South America in the last decade point to humans arriving in the region much earlier. 

In a new study published Wednesday (July 17) in the journal PLOS One, researchers revealed they found cut marks on the fossil remains of a glyptodont known as Neosclerocalyptus — a giant, extinct armadillo relative. These marked bones, found in the Pampean region of Argentina, may be among the earliest examples of humans interacting with megafauna in South America.

The incomplete animal skeleton, found along the banks of the Reconquista River on the outskirts of Buenos Aires, included parts of the pelvis and tail as well as a portion of the carapace — bony plates that covered the top of the animal's body. The researchers carbon-dated a fragment of pelvic bone to 21,090 to 20,811 years ago, which was consistent with the geological dates of the sediment in which the animal was found.

Related: How did humans first reach the Americas?

To determine whether the cut marks were human-made, the researchers photographed and created 3D scans of the animal bones. Some of the marks had a V-shaped cross-section, which the team believe is highly suggestive of stone tool butchering marks. In total, the researchers counted 32 cut marks across the animal's bones. Using a variety of statistical techniques to classify and compare the marks quantitatively, they concluded that the pattern could not have been random — the cuts were made by humans using tools.