Researchers have found evidence of butchery marks on the back of an ancient armadillo-like animal, suggesting that humans were in South America 20,000 years ago – earlier than many researchers had thought.
SCOTT DETROW, HOST:
When did people first arrive in South America? It’s a matter of some debate, but curious markings carved into an ancient shelled mammal suggest that humans may have roamed the continent thousands of years earlier than scientists once thought. Here’s science reporter Ari Daniel.
ARI DANIEL, BYLINE: The Reconquista River flows through the western outskirts of Buenos Aires. Back in 2016, a bulldozer had excavated the river bank to widen the channel. Shortly after completing this work, one of Miguel Delgado’s colleagues, a paleontologist, went for a walk there.
MIGUEL DELGADO: Walking along the banks of the river, I discovered the exposed fossil bones.
DANIEL: A handful of small, fossilized bones that belonged to an ancient armadillo-like mammal – something called a glyptodont.
DELGADO: This animal was heavily armored.
DANIEL: Delgado is an archaeologist at the National University of La Plata in Argentina. Anyway, his colleague was halfway through the walk, having just discovered these bones.
DELGADO: It was an accident.
DANIEL: But a very random accident, because when I looked closer, I saw something unexpected.
DELGADO: Different types of bone scars.
DANIEL: These marks may have been cut into the bones by rocks or other bones scraping against them, or maybe rodents or carnivores biting or scratching at them, or maybe prehistoric people doing something to them. To find out what, Delgado and his colleagues excavated part of the site and found various fossilized bones of the glyptodont, including parts of the hard outer shell…
DELGADO: The tail, the vertebrae and the pelvis.
DANIEL: Back in the lab, they analyzed the specimens and measured the cut marks in detail, making them as 3D models. The results, Delgado says, were unmistakable.
DELGADO: We found that actually the shape of these scars is quite similar to scars made experimentally by humans.
DANIEL: In other words, Delgado believes that the V-shaped cut marks were made on this animal when it was butchered with stone tools by ancient people.
DELGADO: The most important piece of evidence is the location of the scars themselves – in parts of the bones with denser flesh.
DANIEL: Would you like to cut the animal where there is a lot of flesh, cut it up to eat it?
DELGADO: Yes. yes That’s the idea.
DANIEL: This isn’t the first fossilized glyptodont to appear with such markings, but it’s certainly among the oldest. When the team dated the fossil, they found that this animal lived about 21,000 years ago. So if humans are responsible for the cuts, they must have been around then.
DELGADO: This is one of the oldest evidences of human presence here in South America.
DANIEL: That would be towards the end of the Pleistocene, when all kinds of large animals were tramping across a harsh and cold landscape.
DELGADO: There are giant sloths, mastodons, sabertooths too.
DANIEL: They all shared the land with humans until about 10,000 years ago. The findings are published in the journal PLOS One. Alia Lesnek is a geologist at CUNY Queens College who was not involved in the study.
ALIA LESNEK: I think it’s a really exciting step forward.
DANIEL: But she says there’s more work to be done to establish that people made these marks, including looking for artifacts along the riverbank.
LESNEK: You know, finding things like stone flakes or charcoal – really unequivocal indications that humans were present in addition to the cut marks.
DANIEL: Lesneck says this work joins a slowly growing body of evidence that humans inhabited South America earlier than we once thought. Not a settled issue at all. But if true, it would place humans in the Americas during the last glacial maximum, before the vast ice sheets began to retreat.
LESNEK: So it can tell us about the really long history that humans have with climate change.
DANIEL: And, she says, the resilience of people in the face of that change.
For NPR News, I’m Ari Daniel.
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