New discovery could rewrite history of early Americans and the 4-ton sloths they lived with

Sloths weren’t necessarily slow-moving, furry, and tree-dwellers. Their prehistoric ancestors were huge, weighing up to 4 tons, and would swing their giant claws when startled.

For a long time, scientists believed that the first humans to arrive in the Americas quickly killed these giant ground sloths and many other giant animals by hunting. mastodonsaber-toothed cats and dire wolves that once roamed North and South America.

But new research from several sites is beginning to suggest that people came to the Americas earlier than previously thought, perhaps much earlier. These discoveries suggest that the lives of these early Americans were markedly different, and they may have spent thousands of years sharing prehistoric savannahs and wetlands with giant beasts.

“The idea was that as soon as humans arrived, they wiped out everything, what we call ‘Pleistocene overkill,'” said Daniel Odes, an archaeologist at White Sands National Park in New Mexico. But new discoveries suggest that humans have coexisted with these animals for at least 10,000 years without making them go extinct.

Some of the most fascinating clues come from an archaeological site in central Brazil called Santa Elina, where giant sloth bones show evidence of human manipulation. These sloths once lived from Alaska to Argentina, and some species have bone structures called osteoderms on their backs, which resemble the plates of modern armadillos and may have been used for decoration. There is a gender.

In her lab at the University of São Paulo, researcher Mirian Pacheco holds a penny-sized round sloth fossil in the palm of her hand. She noticed that its surface was surprisingly smooth, the edges seemed purposefully polished, and there was a small hole near one edge.

“We believe that ancient people intentionally manipulated it and used it as jewelry and ornaments,” she says. Three similar “pendant” fossils are clearly different from the unprocessed osteoderm on the table. They have a rough surface and no holes.

These artifacts from Santa Elina are approximately 27,000 years old, more than 10,000 years before scientists once thought humans arrived in the Americas.

At first, researchers wondered if the artisans were already working with old fossils. But Pacheco’s research strongly suggests that ancient humans were carving “fresh bones” immediately after animals died.

Her discovery, along with other recent discoveries, could help rewrite the story of when humans first arrived in the Americas and the impact they had on the environments they found.

“There’s still a big debate going on,” Pacheco said.

“Really convincing evidence”

Scientists know that the first humans emerged in Africa, then migrated to Europe and the Asia-Pacific, and finally reached the continent’s last frontier, the Americas. But questions remain about the final chapter of the human origin story.

In high school, Pacheco was taught a theory that most archaeologists believed throughout the 20th century. “What I learned in school was that Clovis was the first,” she said.

Clovis is an archaeological site in New Mexico where archaeologists in the 1920s and 1930s discovered distinctive projectile points and other artifacts dating from 11,000 to 13,000 years ago.

This date happens to coincide with the end of the last ice age, when an ice-free corridor is thought to have appeared in North America, and explains how early humans migrated from Asia across the Bering Land Bridge to the continent. An idea was born about what to do.

And since the fossil record shows that a widespread decline of America’s megafauna began around the same time, North America lost 70% of its large mammals, and South America lost more than 80%. , many researchers speculated that the arrival of humans may have led to a mass extinction.

“When all the timing aligned, it was a great story for a while,” said Brianna Pobiner, a paleoanthropologist with the Smithsonian Institution’s Human Origins Program. “But that doesn’t work very well anymore.”

Over the past 30 years, new research methods such as ancient DNA analysis and new experimental techniques, combined with the exploration of additional archaeological sites and the participation of more diverse scholars across the United States, are upending old narratives and raising new questions, especially about timing. caused. .

“Anything older than about 15,000 years is still subject to intense scrutiny,” said Richard Fariña, a paleontologist at the University of the Republic in Montevideo, Uruguay. “But really compelling evidence continues to emerge from more and more old sites.”

At São Paulo and the Federal University of São Carlos, Pacheco studies the chemical changes that occur when bones become fossilized. This allowed her team to analyze when sloth osteoderms may have been modified.

“Fresh bones” refers to days to years after the sloth has died, but not thousands of years later.

Her team also tested and ruled out several natural phenomena, such as erosion and animal bites. The study was published last year in the journal Proceedings of the Royal Society B.

One of her collaborators, paleontologist Tais Pansani, now based at the Smithsonian Institution, recently discovered that sloth bones of the same age found in Santa Elina were found at temperatures different from natural wildfires. It is being analyzed to see if it was scorched by a man-made fire.

Her preliminary results suggest that fresh sloth bones were present at the human campsite, but it’s unclear whether they were intentionally burned during cooking or simply nearby. Not. She also tests for and rules out other possible causes of black markings, such as natural chemical discoloration.

“Giant Sloth”

The first site widely accepted to be older than Clovis was at Monte Verde, Chile.

Researchers discovered 14,500-year-old stone tools, preserved animal skins and various edible and medicinal plants buried beneath the peat bog.

“Monte Verde was shocking. With all this preserved organic matter, you’re here at the end of the world,” said Vanderbilt University archaeologist and longtime Monte Verde researcher. Tom Dillehay said.

Other archaeological sites suggest that human presence in the Americas dates back even further.

Among the oldest sites is Uruguay’s Arroyo del Vizcaino, where researchers are studying what they believe to be human-made “cut marks” in animal bones some 30,000 years ago.

In White Sands, New Mexico, researchers found human footprints dating from 21,000 to 23,000 years ago, as well as giant mammal footprints from a similar age. But some archaeologists say it’s hard to imagine humans passing through the site repeatedly and leaving behind no stone tools.

“They made a strong case, but there are some things about the site that still baffle me,” said archaeologist David Meltzer of Southern Methodist University. “Why do people leave footprints over long periods of time but leave no artifacts behind?”

White Sands’ Mr Odes said he expected and welcomed such a challenge. “We didn’t set out to find the oldest one. We really just followed the evidence where it led,” he said.

Exactly when humans arrived in the Americas is still debated and may never be known, but even if the first humans arrived earlier than thought, they quickly wiped out the giant beasts they encountered. It seems clear that there was not.

And in the footsteps of the White Sands, moments of their early interactions are preserved.

One of the footprints, Odes interpreted, depicts a “giant sloth moving on all four legs” as it encounters the footprints of a small human who has recently run past. The giant animal “stops, stands up on its hind legs, and then limps away in a different direction.”

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