23,000-year-old footprints in New Mexico change scientists’ view of first Americans World News

For much of the twentieth century, the story of how humans arrived in North America seemed settled. They came from Siberia, crossed a land bridge called the Bering Land Bridge, migrated south as the ice caps receded, and gave rise to the Clovis culture about 13,000 years ago, the earliest widely accepted evidence of human presence on the African continent. This is a neat, well-argued consensus. Then, in 2019, archaeologists digging in the gypsum dunes of New Mexico’s White Sands National Park dug up something from the ground that consensus couldn’t assimilate: a set of ancient fossilized human footprints that had been pressed into the dirt at the height of the last Ice Age, before the land bridge these humans were supposedly still waiting to cross had yet to be opened.

How scientists date these footprints and why they’re controversial

The original 2021 study, published in the journal Science, dated the tracks through radiocarbon analysis of seeds of an aquatic plant called Ruppia cirrhosa found in layers of sediment just above and below them. The findings place the tracks between 21,000 and 23,000 years ago during the Last Glacial Maximum, the coldest and most extreme phase of the last ice age, when huge ice sheets covered much of the Northern Hemisphere.The date was immediately controversial. Critics argue that aquatic plant seeds are unreliable radiocarbon markers because they can absorb ancient dissolved carbon from groundwater, a phenomenon known as the reservoir effect, which can make materials appear older than they actually are. The substance of the debate is enough to cast real doubts about this landmark discovery.

How White Sand Footprints Preserved for 23,000 Years

White Sands National Park is located in the Tularosa Basin of southern New Mexico. Today the landscape is defined by rolling sand dunes of fine white gypsum and is one of the most visually striking geological features in North America. Beneath these dunes lies an entirely different world: the dry bed of an ancient lake called Lake Otero, which existed during the last Ice Age, when the region’s climate was wetter and cooler than today. It is along the muddy shoreline of that lost lake that the footprints are left and preserved.The tracks were excavated by a team from Bournemouth University in partnership with the US National Park Service. They were found buried in layers of sediment, pressed into ancient lakebed mud, left behind by people who walked, stood and moved along the shoreline tens of thousands of years ago. Many of the tracks were left by children and teenagers, a detail that strikes researchers as extraordinary as preserved evidence of young people living in a landscape that no longer exists.

Independent research on how to ultimately resolve arguments

The controversy prompted researchers to return to the site with a completely different approach to dating. A 2023 study published in the journal Science, led by Jeff Pigati of the U.S. Geological Survey, dated pollen grains and quartz crystals in the same sediment layer using two different techniques: light-stimulated luminescence and radiocarbon dating of the pollen itself. Both methods return dates between 20,000 and 23,000 years ago, statistically indistinguishable from the original seed-based results.

What footprints mean for Clovis’ first theory

The impact on the long-held Clovis-first model is significant and irreversible. The Clovis culture, named after a site near Clovis, New Mexico, where unique stone tools were discovered in the 1930s, has long been thought to represent the earliest known human presence in North America, dating back some 13,000 years. The footprints on the white sand are at least 8,000 years old than we thought.Even more striking is the geographical significance of this time. During the Last Glacial Maximum, the two main corridors through which humans are thought to have migrated to the Americas—the ice-free corridor east of the Rockies and the coastal route along the Pacific—were either blocked by ice sheets or not yet passable. If humans had reached New Mexico 23,000 years ago, they must have arrived before these routes closed, suggesting either much earlier than any existing models account for, or an alternative route into the continent that has not yet been identified.

What walked around white sand 23,000 years ago

Footprints do not exist alone. The white sand’s sediments also bear the tracks of the animals that shared the lake’s shores with these early humans: mammoths, giant ground sloths, and ancient camels, all of which are now extinct. The picture that emerges is of a functioning Ice Age ecosystem: a lake surrounded by meadows and wetlands, populated by megafauna that the humans who lived alongside them might have hunted.Vance Holliday, who has worked at White Sands since 2012, said the footprints were “very clearly” left by humans. The question has never been whether the footprints were left by humans. Exactly when. After four years of scientific debate, three independent dating methods and three separate studies all arriving at the same answer, the question appears to have finally been resolved.