South America was once home to some giant armadillo ancestors. About 20,000 years ago, these plated mammals called Glyptodonts skulked around present day Argentina. They varied in size from about 661 to over 4,000 pounds at 5.5 to 11 feet long. Glyptodonts went extinct about 6,000 to 7,000 years ago, but not before serving as a food source for some early humans. Cut marks on some recently uncovered Glyptodon fossils indicate that early humans may have butchered and eaten these bulky animals and are described in a study published July 17 in the open-access journal PLOS ONE.
The precise timing when early humans evolved in the Americas has been hotly debated since at least the 19th century.
“Until recently, the traditional model indicated that humans entered the continent 16,000 calendar years ago,” Miguel Eduardo Delgado, a study co-author and archeologist at Universidad Nacional de La Plata, in Buenos Aires, tells Popular Science.
[Related: What prehistoric poop reveals about extinct giant animals.]
More recent findings, including the White Sands Footprints, indicate an early human presence in the Americas more than 20,000 years ago. In present day Argentina, early hunter-gatherers were present during the Last Glacial Maximum (LGM), between 29,000 and 19,000 years ago.
“Since the LGM was a period where cold and dry environments predominated, this fact implies that humans adapted successfully to the harsh environments characterizing such a period,” says Delgado.
The role that human dispersal across the Americas played in the extinction of the large mammals like Glyptodonts is an enduring piece of this puzzle. These megafauna including mastodons, mammoths, enormous ground sloths, and giant beavers died at the end of the Pleistocene Epoch–around 11,700 years ago at the end of the last Ice Age. These include. North America saw the most dramatic drop in megafauna, where about 32 genera of large mammals disappeared over a period of 2,000 years. Further south, a lack of direct archaeological evidence of early humans in South America and how they interacted with animals has made studying this time period difficult.
In this new study, an international team of scientists examined some fossils that were recovered from a Glyptodont belonging to the genus Neosclerocalyptus.
“This animal was a large extinct heavily armored armadillo,” says Delgado. “They had a large, bony carapace that covered much of its torso, as well as smaller cephalic armor covering the roof of its head [and] a large and robust tail and short limbs.”
The team uncovered the fossils on the banks of the Reconquista River, northeast of the Pampean region in Argentina. The bones had evidence of butchery, including cut marks on parts of the animal’s tail, pelvis, and body armor that are consistent with known marks made by stone tools, according to the team’s statistical analysis of the fossils.
The placement of the marks is also consistent with a known butchering sequence that targets the areas of dense, meaty flesh. The fossils are roughly 21,000 years old and nearly 6,000 thousand years older than other known archaeological evidence found in southern South America. According to the team, this fits with the other findings that indicate an early human presence in the Americas over 20,000 years ago.
[Related: A new armadillo species was hiding in plain sight.]
“Our results in conjunction with other evidence that has been found in eastern South America (Brazil), but also in North America (Canada and USA), and Central America (Mexico) proposes a distinct scenario for the first human peopling of the American continent,” says Delgado. “The most likely date for the first human entry occurred between 21,000 and 25,000 years ago or even before. The interaction between humans and megafauna in southern South America occurred long before we thought.”
These fossils also represent some of the oldest evidence of human interaction with large mammals, not too long before many of these megafauna became extinct. Additional excavations at the site may, more analysis of the cut marks, and added radiocarbon dating of the fossils may offer better insights in the future.
