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Ancient footprints reshape scientists' understanding of early life in Americas

AccuWeather logo AccuWeather 9/28/2021 Monica Danielle

Incredible discoveries have been made in understanding when humans first migrated to North America. Researchers now believe ancient human footprints discovered in the ground at New Mexico's White Sands National Park date 23,000 years back to the Ice Age.

The unearthed footprints, discovered in 2009 and the subject of a study released in late September, have upended archaeologists' understanding of early life in North America and are being described as "unequivocal evidence" that human activity had been taking place in the Americas long before what was originally thought.

For decades it's been generally believed that humans first entered North America between 13,000 and 16,000 years ago - after the melting of the North American ice sheets opened up migration routes. These new findings, published in the journal Science, place human habitation in the Americas during the Last Glacial Maximum, a time when ice sheets covered much of North America and as much as 10,000 years earlier than evidence has so far suggested.

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Footprints found in White Sands National Park in New Mexico date to 23,000 years ago, making them the first 'unequivocal evidence' of human activity in North America. (National Park Service, USGS and Bournemouth University)

"I think this is probably the biggest discovery about the peopling of America in a hundred years," said Ciprian Ardelean, an archaeologist at Autonomous University of Zacatecas in Mexico, according to The New York Times.

Archaeologists have for decades debated when humans first arrived in the Americas as evidence of earlier dates is continually excavated. Most recently, a team of researchers, led by Matthew Bennett, a geographer from Bournemouth University in England, has determined a set of ancient human footprints in White Sands National Park are the earliest evidence of human activity in the Americas. The footprints were first discovered in 2009 by David Bustos, the park's resource program manager. Over the years, he has brought in teams of scientists to help understand the unearthed footprints.

Researchers said the footprints were made over a period of 2,000 years as people walked across soft mud at the edge of a shallow lake, which is a part of modern-day Alkali Flat in White Sands. As time passed, sediments, including grass seeds called ditch grass, an aquatic plant, filled in the prints and the ground hardened. More recently, erosion has caused the footprints to re-emerge.

Normally, rock layers are "a nightmare" to date, Bennett said. But two years ago, archaeologist and study co-author, David Bustos, discovered the ditch grass seeds co-mingling within the sediment layers above and below the footprints and realized he could carbon date the seeds.

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Excavations in White Sands National Park reveal human footprints at the base of a trench. (Photo credit: National Park Service, USGS and Bournemouth University)

The dates range in age and confirm human presence over at least two millennia with the oldest tracks dating from around 23,000 years ago, which corresponds to the height of the last glacial cycle. That makes the prints the oldest known human footprints in the Americas.

Reynolds told The Daily Mail that because researchers know the White Sands prints were made by homo sapiens, they can compare them to modern human sizes and estimate ages. "We can then compare the fossil foot size data and make an estimate based on the modern human ages for similar foot sizes."

The research team believes the tracks belonged to numerous people, mostly children and teenagers with some of the tracks left by adults. They also discovered tracks from mammoths, giant ground sloths and dire wolves.

The footprints found at White Sands are referred to as "ghost tracks," since they only appear when there are certain lighting and moisture conditions.

"The footprints left at White Sands give a picture of what was taking place, teenagers interacting with younger children and adults," Bennett said, according to the Cornell Chronicle. "'We can think of our ancestors as quite functional, hunting and surviving, but what we see here is also activity of play, and of different ages coming together ... A true insight into these early people."

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(Photo credit: National Park Service, USGS and Bournemouth University)

"The children tend to be more energetic," said Sally Reynolds, a paleontologist at Bournemouth University in England and a co-author of the study, told the Times. "They're a lot more playful, jumping up and down."

Dan Odess, a science advisor for the National Park Service and another of the study's authors, said the discovery at White Sands provides the first "unequivocal evidence" for human presence in the Americas during the Last Glacial Maximum.

"Not all archaeological sites contain such unequivocal evidence. One reason why this discovery is important is that it makes the idea that other purportedly ancient sites really are evidence for human presence that much more plausible, even if the evidence they contain is less unequivocal," Odess said. "This doesn't mean all of those sites are legitimate, but it means they cannot be dismissed out of hand."

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