Here's why a butchered mastodon in a Florida swamp is rewriting American history

A butchered mastodon carcass found in a boggy Florida river is changing our views on which humans first got to the Americas.

For almost a century, the prevailing idea was that the first Americans were part of the Clovis, a group of Paleo-Indians first identified in 1930 near Clovis, New Mexico. They are thought to have crossed a now-submerged land bridge between Siberia and Alaska, passing through the ice-free corridor than ran through the middle of Canada, and rapidly populating much of the western hemisphere by about 13,000 years ago.

The Clovis were united by their trademark spearheads, which feature grooves on both edges of the weapon tips. These artifacts have been found as far north as Alberta, and as far south as northern South America.

But confidence in the "Clovis-First" theory has eroded in past decades, as a few isolated archaeological finds challenged the idea. However, supporters of Clovis-First were quick to point out that these finds could have been contaminated by more recent cultures — or represented settlements unrelated to the permanent American populations (like unconfirmed settlements of ocean-crossing Polynesians, which didn't last).

"It explained things so perfectly, and fit so perfectly, until it didn't," Jessi Halligan told Tech Insider.

Halligan, an underwater archaeologist at Florida State University coauthored the new study with fellow anthropologist Michael Waters of Texas A&M University.

Brendan Fenerty

Their new research, published in the journal Science Advances, confirms the suspicion that the long-defended theory doesn't hold up.

"Part of the reason Clovis made sense was that Clovis was known to be the oldest," Halligan said, "and we weren't looking in the [geological] layers that were 14, 15, 16 thousand years old."

That is, until divers found an ancient, submerged sinkhole in the Aucilla river on the Florida panhandle.

The stone tools and a mastodon carcass taken out of the site date back 14,550 years, which is considerably older than the Clovis.

What does it mean? If people back then were butchering animals with delicately-crafted tools as far southeast as Florida, it means the first Americans crossed the land bridge much earlier than previously thought.

Archaeological certainty is no small feat. One of the challenges of dating prehistoric artifacts is finding organic carbon material to radiocarbon date — you can't date stone spearheads alone.

A critical part of the evidence comes from the tusk of the butchered beast. The tusk features cut marks that would have been inside the skull of a living mastodon, suggesting that it was extracted by humans.

Excavating at the Page-Ladson site certainly has its challenges. Conducting archaeology underwater is considerably harder than digging in dry land.

"We can't have crews of 25 people digging at the same time," Halligan said. "At most, only half of your crew is underwater."

But Hannigan says the site yielded excellent archaeological finds, "because of the fabulous organic preservation that you can only find in a continuously underwater environment."

Without that preservation, we'd still be clutching to the wrong idea about the first Americans.

"If there was no organic preservation we'd only have about 5 stone tools," she said. "We wouldn't know that people had been there 14,000 years ago, just that people were there. The significance would have been lost if it wasn't underwater."

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