Ancient seas left an expanse of rolling gypsum dunes known as White Sands in New Mexico, and within this surreal landscape lies evidence that humans have roamed the Americas for at least 20,000 years.
While most of White Sands is protected as a national park, the US army controls part of it as a missile range. It was within this section that researchers found clay footprints, preserved below the gypsum, that have rewritten the timeline of human presence in the Americas.
Previously, we thought humans arrived in North America around 13,200 to 15,500 years ago.
But a new study led by University of Arizona archeologist Vance Holliday combines evidence from mud, Ruppia seeds and pollen found in layers above and below the trace fossils, to date the footprints as being between 20,700 and 22,400 years old.
This means they were trod in the last Ice Age, by people crossing a floodplain on the margins of the extinct Lake Otero that once covered around 4,140 square kilometers (1,600 square miles) of the Tularosa Basin.
A vast layer of eolian gypsum sand gives White Sands its strange appearance. (Holliday et al., Science Advances, 2025)
“Pleistocene lakes and associated biological resources in western and southwestern North America must have attracted foragers, but archaeologists have surveyed few paleolake basins,” Holliday and his colleagues write.
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The footprints were first discovered in 2021, and were dated to between 21,000 and 23,000 years ago using embedded seeds and pollen. But critics questioned this method to determine the footprints’ age, since these lightweight biological materials can easily be moved in such a dynamic ecosystem. But the new paper found that analysis of mud layers backs up what the plant traces tell us.
“Most of this dating of organic matter from palustrine muds complement the dating of the seeds and pollen previously reported,” the authors report.
“It would be serendipity in the extreme to have all these dates giving you a consistent picture that’s in error,” says Holliday.
The research is published in Science Advances.
