New Evidence Reveals Ancient Humans Coexisted with Giant Sloths and Mastodons in the Americas for Millennia

New archaeological discoveries from North and South America suggest that humans may have arrived in the Americas much earlier than previously believed, coexisting with giant ground sloths, mastodons, and other megafauna for thousands of years, ABC News reports.

These findings challenge the long-held belief that early human hunters quickly drove these large animals to extinction, instead pointing to a more complex and extended period of interaction.

For much of the 20th century, the dominant theory was that humans first arrived in the Americas around 13,000 years ago, linked to artifacts from the Clovis site in New Mexico. According to this narrative, humans crossed the Bering land bridge from Asia, migrated south through an ice-free corridor, and hunted large mammals to extinction in a process known as “Pleistocene overkill.”

However, recent discoveries from several archaeological sites suggest that humans may have arrived as early as 27,000 years ago, more than 10,000 years earlier than previously thought. This extended timeline implies that humans may have coexisted with large animals like mastodons, saber-toothed cats, and giant ground sloths for millennia — not merely a few hundred years before their extinction.

One of the most compelling sites is Santa Elina in central Brazil, where researchers found evidence of human interaction with giant ground sloths. Bones from these enormous creatures, which could weigh up to 4 tons, show signs of human modification. Some sloth bones known as osteoderms — bony plates embedded in their skin — were discovered with smooth surfaces, polished edges, and small holes.

Researcher Mírian Pacheco from the University of São Paulo analyzed the sloth fossils and concluded that they had been intentionally altered by ancient people, possibly to create jewelry or adornments. Her team ruled out natural erosion and animal activity, further supporting the idea that humans had a role in shaping these bones. The osteoderm artifacts are approximately 27,000 years old, pushing back the timeline of human activity in the region.

At White Sands National Park in New Mexico, researchers discovered a different kind of evidence: human footprints dated to between 21,000 and 23,000 years ago. The site also contains tracks of megafauna, including mammoths and giant ground sloths. One track sequence appears to show a ground sloth reacting to the presence of a human, standing upright and changing its path.

Other sites, like Monte Verde in Chile (dated to 14,500 years ago) and Arroyo del Vizcaíno in Uruguay (where potential human-made cut marks on bones are dated to 30,000 years ago), have contributed to the growing body of evidence that humans were present in the Americas far earlier than previously believed.

The idea of “Pleistocene overkill” — that humans quickly wiped out megafauna after arriving in the Americas — is losing support. Instead, researchers like Daniel Odess, an archaeologist at White Sands, propose that humans coexisted with these large animals for at least 10,000 years.

“We didn’t set out to find the oldest anything — we’ve really just followed the evidence where it leads,” Odess said.

This revised timeline suggests that humans and megafauna interacted in more complex ways than previously understood. While overhunting may have contributed to the eventual extinction of some species, it was likely not the sole factor. Climate change and habitat shifts at the end of the Ice Age may have played significant roles as well.

Advancements in archaeological techniques have played a crucial role in rewriting this story. New methods, such as ancient DNA analysis and chemical testing of bones, allow researchers to more accurately date artifacts and distinguish between human-made modifications and natural processes.

At Santa Elina, for example, Pacheco’s team used chemical analysis to determine that the osteoderms were carved before fossilization occurred. This indicates that ancient people worked with “fresh bones,” suggesting they had access to sloths shortly after the animals died.

Elsewhere, scientists are analyzing potential signs of fire on ancient bones. Paleontologist Thaís Pansani is investigating sloth bones from Santa Elina to determine if burn marks are the result of human-made fires. The specific burn patterns differ from those caused by wildfires, hinting at human involvement.

Despite the growing evidence, debate remains. Sites like White Sands and Arroyo del Vizcaíno are subject to intense scrutiny, as researchers seek to rule out natural explanations for artifacts and markings. Some archaeologists, like David Meltzer of Southern Methodist University, remain cautious.

“Why would people leave footprints over a long period of time, but never any artifacts?” he asked, referring to the White Sands site.

Nevertheless, as more discoveries come to light and analytical methods improve, the story of human arrival in the Americas continues to evolve. The notion of early humans as rapid megafauna hunters is giving way to a more nuanced view — one where humans and large animals shared the landscape for thousands of years, influencing each other’s lives in subtle but significant ways.