Seedy footprints just added millennia to when humans first walked North America

The earliest known date of human habitation in North America has been pushed back thousands of years, after the discovery of much older footprints that upended common belief. The fossilized footprints were discovered at White Sands National Park in New Mexico, and will force scientists to rethink their understanding of just when in history human beings inhabited the continent.

Until now, the generally accepted assumption has been that humans migrated to North America sometime between 13,000 and 16,000 years ago. Previous research has claimed far greater dates, but generally been met with skepticism by other scientists.

This new data, from the United States Geological Survey, however, is being seen as far more reliable. They undertook geological work at White Sands National Park in New Mexico, discovering fossilized human footprints buried in multiple layers of sediment. Preserved seeds, embedded into the footprints themselves, were then radiocarbon dated.

The results date the footprints to around 23,000 to 21,000 years ago. That's at least 5,000 years older than the generally accepted timeline, and potentially as much as 10,000 years from some theories.

"The research dramatically extends the range for the coexistence of humans and Pleistocene (ice age) megafauna and confirms that humans were present in North America before the major glacial advances at the height of the last ice age closed migration routes from Asia," the US Geological Survey said. The findings were published this week in the journal Science.

Trying to figure out just how human beings colonized North America has been a longstanding topic of research and argument among archaeologists and other researchers. Not only is it unclear when they arrived on the continent, the route by which they migrated and where they originated is also uncertain. Footprints, being naturally delicate and vulnerable to age-related destruction, can be a problematic source of data, but the seeds trapped in this new discovery allowed for a far more precise conclusion.

"This timing coincided with a Northern Hemispheric abrupt warming event, Dansgaard-Oeschger event 2, which drew down lake levels and allowed humans and megafauna to walk on newly exposed surfaces, creating tracks that became preserved in the geologic record," the US Geological Survey team concludes.

The footprints themselves are believed to have been created by a group of people, and across a broader period of time than just one crossing. "This study demonstrates the process of science – new evidence can shift long held paradigms," USGS Acting Rocky Mountain Regional Director Allison Shipp said of the new research. The region has proved to be a treasure trove of archeological gems, including everything from Columbian mammoth tracks, evidence of saber-toothed cat, dire wolf, and other ice age animals tracks, and more.