Hunter-gatherers pursuing big game and likely accompanied by dogs were the first known human settlers of the American Southeast, stone tools and the remains of a butchered mastodon show.

The findings, reported in the journal Science Advances, provide intriguing clues about the migration paths of the earliest Americans, how they lived, and what led to the extinction 12,600 years ago of several large native mammals.

The stone tools and mastodon remains date to about 14,600 years ago and were discovered in a Florida river at a site near Tallahassee called Page-Ladson, which is now one of the oldest radiocarbon-dated sites in the Americas.

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Navy Seal diver Buddy Page first spotted the underwater site on property owned by the Ladson family, hence the location's name. It predates the widespread Native American Clovis culture and is the same age as another pre-Clovis site, Monte Verde in Chile.

Florida and Chile are clearly a long way from Asia, where genetic testing suggests the first Americans came from via the Bering Land Bridge area of Alaska, but the researchers suggest a few possible migration routes.

"The only logical way people could have come to Florida by 14,600 years ago is if their ancestors entered the Americas by boat along the Pacific Coast," Michael Waters of Texas A&M; University told Discovery News. "They could have traveled by boat to central Mexico, crossed and come along the Gulf Coast. They could have entered the Americas via the Columbia River and then traveled inland to the Mississippi River and followed it down and entered the Gulf Coast, eventually making their way to Florida."

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Waters, Jessi Halligan of Florida State University, and their team worked in near zero visibility waters in Florida's murky Aucilla River over a two-year period to excavate animal remains and stone tools, which included a biface -- a knife used for cutting and butchering meat.

Deep, parallel linear grooves on the end of the mastodon's found tusk suggest that the animal was butchered or scavenged and literally eaten to the bone, with the hunters likely eating tender meat at the tusk's base.

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The geology of the site, as well as pollen and algae finds, suggest that the hunter-gatherers encountered the mastodon next to a small pond that both humans and animals used as a water source, the researchers believe.

Waters said that the prehistoric "people knew how to find game, fresh water and materials for making tools. These people were well adapted to this environment. The site is a slam-dunk pre-Clovis site with unequivocal artifacts, clear stratigraphy and thorough dating."

Ancient Humans, Dogs Hunted Mastodon in Florida: Page 2

Shown is a butchered mastodon tusk from the Page-Ladson site in Florida. The curvature is typical of an upper tusk from the left side of the animal.DC Fisher, University of Michigan Museum of Paleontology

Another research team previously excavated the site and found what they believed were dog remains, so dogs "would most likely have been associated with the early hunters," Waters said, indicating that the remains would be studied further. If confirmed, they could be the earliest known evidence for dogs in the Americas.

In terms of other animals, he said, "The animal bones from the site tell us that mastodon, sloth, giant armadillo, dire wolf, mammoth, horse, camel and giant bison were present. These and other animals became extinct by 12,600 years ago."

So humans co-existed with all of these animals for at least 2,000 years before they died out, Halligan said.

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Waters added, "The primary driver of extinction was likely climate and environmental changes that occurred at the end of the last ice age. However, if people were hunting these animals for 2,000 years prior to extinction, they must have made some impact."

Halligan suggested that the impact might have varied, depending on the location.

He explained, "We cannot expect that people in Chile, Oregon and Florida were facing the same challenges and living in exactly the same way."

David Anderson, professor and associate head of the University of Tennessee’s Department of Anthropology, told Discovery News, "The new artifacts, dates and other lines of evidence provide a compelling case for early human use of the site and, by extension, the region."