SAO PAULO: Sloths weren’t always slow-moving, cuddly tree dwellers. Their prehistoric ancestors were huge, up to 4 tons (3.6 metric tons) and, when startled, had enormous claws.
For a long time, scientists believed that the arrival of the first humans America Hunting soon killed these giant ground sloths, along with many other large animals such as mastodons, saber cats, and dire wolves that once roamed North and South America.
But new research from multiple sites is beginning to suggest that people came to the Americas earlier — perhaps much earlier — than once thought. The findings point to a significantly different life for these early Americans, who may have spent thousands of years sharing prehistoric savannas and wetlands with large carnivores.
“There was this idea that humans arrived and wiped out everything very quickly called ‘Pleistocene overkill,'” Daniel said. OdysseusArchaeologist at White Sands National Park in New Mexico. But the new findings show that “humans coexisted with these animals for at least 10,000 years without their extinction.”
Some of the most troubling clues come from an archaeological site in central Brazil called Santa Elena, where the bones of giant ground sloths show signs of manipulation by humans. Such sloths once lived from Alaska to Argentina, and some species had bony structures on their backs, called osteoderms—a bit like the plates of modern armadillos—which were probably used for decoration.
In a lab at the University of São Paulo, researcher Marian Pacheco holds a round, penny-sized sloth fossil in her palm. She notes that its surface is surprisingly smooth, that the edges appear to have been deliberately polished, and that there is a small hole near one edge.
“We believe it was deliberately altered and used by ancient people as ornaments or adornment.” The three similar “pendant” fossils are markedly different from the unworked osteoderms on the table – they are rough-surfaced and without pores.
These artifacts from Santa Elena are about 27,000 years old — more than 10,000 years before scientists once thought humans arrived in the Americas.
Originally, the researchers wondered if the artisans were working on fossils from before. But Pacheco’s research strongly suggests that ancient people were carving “fresh bones” from animals immediately after they died.
His findings, along with other recent discoveries, could help rewrite the story of when humans first arrived in the Americas—and what impact they had on the environment.
“There’s still a big debate to be had,” Pacheco said.
Scientists know that humans first emerged in Africa, then moved to Europe and the Asia-Pacific, before finally reaching the continent’s final frontier, the Americas. But questions remain about the final chapter of the human origin story.
Pacheco was taught the theory in high school that most archaeologists did during the 20th century. “What I learned in school was that Clovis was first,” she said.
Clovis is a site in New Mexico, where archaeologists in the 1920s and 1930s found distinctive projectile points and other artifacts dating back between 11,000 and 13,000 years ago.
This date coincides with the end of the last ice age, a time when an ice-free corridor likely emerged in North America – giving rise to the idea of how early humans crossed the Bering Land Bridge from Asia. Moved to the continent.
And because the fossil record shows that the widespread decline of American megafauna began around the same time—with North America losing 70 percent of its large mammals, and South America losing more than 80 percent— Many researchers hypothesized that the arrival of humans led to the mass extinction.
“It was a good story for a while, when all time stood together,” said Brianna Pobiner, a paleontologist at the Smithsonian Institution’s Human Origins Program. “But it doesn’t really work that well anymore.”
Over the past 30 years, new research methods – including ancient DNA analysis and new laboratory techniques – along with the examination of additional archaeological sites and the involvement of more diverse scholars across the Americas, have overturned the old narrative. And has raised new questions, especially about time. .
“Anything older than about 15,000 years still bears intense scrutiny,” said paleontologist Richard Farina of the University of the Republic in Montevideo, Uruguay. “But really compelling evidence continues to emerge from more and more ancient sites.”
In São Paulo and at the Federal University of São Carlos, Pacheco studies the chemical changes that occur when bone becomes a fossil. This allowed his team to analyze when sloth osteoderms were modified.
“We found that the osteoderms were carved before the fossilization process” into “fresh bones” — meaning anywhere from a few days to a few years after the sloths died, but not thousands of years later.
His team also tested and ruled out several natural processes, such as erosion and animal slaughter. The research was published last year in the journal Proceedings of the Royal Society B.
One of his colleagues, paleontologist Thais Pansani, recently based at the Smithsonian Institution, is analyzing whether similar sloth bones found at Santa Elena were burned by man-made fires, which Natural forest fires burn at different temperatures.
His preliminary findings suggest that fresh sloth bones were present in human camps — whether burned intentionally in cooking, or nearby, is unclear. She is also testing and ruling out other possible causes of dark marks, such as natural chemical pigmentation.
The site first accepted as being older than Clovis Monte VerdeChile
Buried under a peat bog, researchers discovered 14,500-year-old stone tools, fragments of preserved animal skins and various edible and medicinal plants.
“Monte Verde was a shock. You’re at the end of the world here, with all these organic things,” said an archaeologist at Vanderbilt University. Tom heart.a longtime researcher at Monte Verde.
Other archaeological sites suggest even earlier dates for human presence in the Americas.
Among the oldest sites is the Arroyo del Vizcaino in Uruguay, where researchers are studying human-made “cut marks” on animal bones dating back some 30,000 years.
In New Mexico’s White Sands, researchers have discovered human footprints dating from 21,000 to 23,000 years ago, as well as similarly aged tracks of giant mammals. But some archaeologists say it’s hard to imagine that humans would pass through a site repeatedly and not leave behind stone tools.
“They’ve made a strong case, but there are still some things about the site that bother me,” said David Meltzer, an archaeologist at Southern Methodist University. “Why would people leave footprints for a long time, but never a pattern?”
At White Sands, Odis said he expects and welcomes such challenges. “We didn’t set out to find the oldest thing — we really just followed the evidence where it led,” he said.
While the exact time of the arrival of humans in the Americas is contested — and may never be known — it seems clear that if the first humans arrived sooner than once thought, they would have quickly encountered these giant beasts. Did not finish those faced.
And footprints in the white sand preserve a few moments of their earliest interaction.
As Odysseus interprets them, a set of tracks reveals “a large ground sloth walking on all fours” when he encounters the footprints of a small human that has recently been covered. . The huge animal “stands on its hind legs and backs up, swings around, then goes the other way.”