Researchers have found evidence of butchery marks on the backs of ancient armadillo-like animals, suggesting that humans were present in South America 20,000 years ago, earlier than many researchers thought.
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When did humans first arrive in South America? That’s up for debate, but strange prints on ancient shell-bearing mammals suggest humans may have roamed the continent thousands of years earlier than scientists once thought. Science reporter Ali Daniel reports.
ARI DANIEL: The Reconquista River flows through the western outskirts of Buenos Aires. In 2016, bulldozers dug up the riverbanks to widen the canal. Shortly after the work was finished, one of Miguel Delgado’s paleontologist colleagues took a walk there.
Miguel Delgado: I was walking along the riverbank and I found some exposed fossil bones.
Daniel: A handful of tiny fossilized bones from an ancient armadillo-like mammal called a Glyptodon.
DELGAD: This animal was heavily armored.
Daniel: Delgado is an archaeologist at the National University of La Plata in Argentina. Anyway, his colleague was out walking and just discovered these bones.
Delgado: It was an accident.
Daniel: But it was a very lucky coincidence, because upon closer inspection, he found something unexpected.
DELGAD: There are different kinds of marks on the bones.
Daniel: These marks could have been imprinted on the bones by rocks or other bones rubbing against them, or they could have been caused by a rodent or carnivore biting or scratching them, or they could have been caused by something prehistoric humans did. To find out, Delgado and his colleagues excavated part of the site and unearthed a variety of fossilized glyptodont bones, including fragments of their hard shells…
Delgado: The tail, the vertebrae, the pelvis.
DANIEL: Once back in the lab, they analyzed the specimen, taking detailed measurements of the cut marks and rendering them as a 3D model. The results, Delgado says, were unmistakable.
Delgado: In fact, we noticed that the shape of the marks was very similar to experimental incisions made by humans.
DANIEL: In other words, Delgado believes that the V-shaped cut was made when the animal was butchered by ancient humans with stone tools.
DELGAD: The most important piece of evidence is the location of the mark itself, in a fleshy part of the bone.
Daniel: Do you want to cut up a big piece of meat to eat?
Delgado: Right. Right. That’s the idea.
Daniel: This isn’t the first Glyptodon fossil to show these kinds of marks, but it is certainly one of the oldest. When the team dated the fossil, they found that the animal lived about 21,000 years ago, so if the cut marks are human, humans must have been present at the time.
DELGAD: So this is one of the oldest pieces of evidence of human presence in South America.
Daniel: This was towards the end of the Pleistocene epoch, when a wide variety of large animals roamed the harsh, frigid landscape.
Delgado: There are giant sloths, mastodons and sabre-toothed cats.
DANIEL: All of these shared the Earth with humans until about 10,000 years ago. The findings appear in the journal PLOS One. Aria Lesnek is a geologist at Queens College, City University of New York, who was not involved in the study.
Aria Lesnek: I think this is a really great step forward.
DANIEL: But she argues that more research is needed to really prove that humans made those incisions, including looking for artifacts along the riverbank.
Resneck: You see, they found stone fragments, charcoal, and other things, along with cut marks, and clear evidence of human presence.
Daniel: Resnek says this study adds to a growing body of evidence that suggests humans may have been settled in South America earlier than previously thought. It’s still an open question, but if it’s true, it would mean humans were there during the Last Glacial Maximum, before the vast ice sheets began to retreat.
RESNEK: So it tells us a very long history of humanity and climate change.
DANIEL: And she talks about the resilience of people in the face of that change.
For NPR News, I’m Ali Daniel.
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