Bone fragments from seven horses and a camel suggest that the First Americans hunted and butchered these animals in North America at least 13,300 years ago after migrating from northeast Asia, hundreds of years earlier than previously thought.

According to a study published today in the Proceedings of the National Academy of Sciences, these bones suggest that people were active at the Wally’s Beach location near Calgary, Alberta. That’s about 300 years before the Clovis people emerged — a group of prehistoric humans who had been previously considered the first settlers of the Americas, having arrived 13,000 years ago.

This finding is consistent with the last decade of research into who were the real ancestors of the Native Americans, explained Michael Waters, an anthropologist from Texas A&M University and director for the Center for the Study of the First Americans.

“It represents to us just more evidence that people were in the Americas before Clovis and that these people had some kind of weaponry that we haven’t found yet,” Waters said. “From 15,000 years on, they were moving across the landscape, hunting horse, camel, mastodon and mammoth.”

When he first looked in to the site at Wally’s Beach, Waters wondered if the estimated dates of the animal remains, originally pinned at roughly 13,000 years ago, were wrong. He noted the absence of distinctive Clovis tools, such as flaked-off stone spearheads made at the end of the Ice Age, at the Wally’s Beach site.

Then, he took samples of bone fragments into a laboratory to test to determine the age of amino acids present in the animal bones and radiocarbon dating. These tiny clues helped scientists more accurately pinpoint the age of the bones that belonged to animals killed during the same time period before the end of the Ice Age 13,300 years ago, “give or take 15 years,” Waters said.

That degree of accuracy is “a blink of the eye in geologic time,” he explained.

Horses and camels became extinct in North America at the end of the Ice Age in part due to a changing climate, Waters said. However, they were not the only notable North American animals who later disappeared at roughly the same time. Megafauna such as mammoth, mastodons and even giant armadillo “the size of Volkswagons” roamed the continent before dying off about 12,800 years ago. Eventually, as the climate warmed, that placed stress on the animals, which had adapted for the Ice Age, Waters said. Paired with the introduction of humans, the animals faded away.

Apart from Wally’s Beach in Canada, Waters said there is other evidence of First Americans in caves in Oregon and even mammoth hunts in Florida. He said they most likely came along the Pacific coastline from Siberia and China, using the Columbia River as “the gateway to the continent.”