Fossil footprints show humans were in North America more than 21,000 years ago

Footprints at a site have been revealed to be the oldest known footprints and the oldest firm evidence of humans anywhere in the Americas, showing that people lived there 21,000 to 23,000 years ago, several thousand years earlier than scientists once believed.

“It’s the earliest unequivocal evidence of humans in the Americas,” said study lead author Matthew Bennett, a professor of environmental and geographic sciences at Bournemouth University in the United Kingdom.

Fossilized human footprints have been found throughout the east of the national park, where a now-dry “paleo-lake” bed supplies the gypsum-rich soil that is eroded by wind to create massive white dunes for which the region is famous.

Any traces of early human occupation had been questioned because they were based on what appeared to be stone tools that could have formed naturally, Bennett said, or on artifacts that could have been moved from their original stratigraphic layers.

The team has studied the footprints in White Sands National Park for years, digging trenches and following the tracks with ground-penetrating radar. NPS, USGS and Bournemouth University

“A footprint is a really good, unambiguous piece of information,” he said. “That’s the importance of this site: we know they were there.”

The footprints, in turn, would lend credibility to other evidence of early humans in the Americas.

“Now you can look at older sites and say, ‘We know they were there during the last glacial maximum,’ so maybe some of these older sites are reliable, too,” he said.

The term “Last Glacial Maximum” is how scientists refer to the height of the last ice age, about 20,000 to 26,000 years ago.

There has long been debate about whether humans reached the Americas by a northern route from Siberia before or after the Last Glacial Maximum, when vast ice sheets would have made migration along the Pacific coast or across western Canada impossible.

The ancient footprints at White Sands answer that question, suggesting they may have arrived as long as 30,000 years ago, thousands of years before the height of the Ice Age, Bennett said.

The location of the new excavations was on the edge of a wetland when the footprints were left between 21,000 and 23,000 years ago. Karen Carr

White Sands is now mostly desert, but it was a lush wetland at the time the tracks were left and was populated by mammoths, ground sloths, bovids (cattle), and wild camels, as well as the Stone Age humans who hunted them.

The footprints, which are interspersed with animal tracks, show that people must have lived there for at least 2,000 years, Cornell University archaeologist Thomas Urban, a co-author of the study, said in an email.

“There are multiple layers of footprints spanning a significant amount of time, suggesting a sustained human presence in the area during the Last Glacial Maximum, rather than a single event,” he said.

Urban developed the noninvasive use of ground-penetrating radar to reveal footprints beneath the surface and show researchers the best places to dig.

The smaller footprints left by adolescents and children outnumber those of adults, Urban said, possibly because they were engaged in tasks that involved simple labor, rather than skilled tasks like hunting.

New research into ancient footprints at White Sands National Park establishes that they are the oldest known evidence of humans in North America. NPS, USGS and Bournemouth University

“Their presence is simply part of everyday life and is to be expected,” he said. Their activities may have ranged from play to domestic tasks, such as gathering food, water and raw materials for their hunter-gatherer community.

Geologist Cynthia Liutkus-Pierce of Appalachian State University in North Carolina, who has studied ancient human footprints in Tanzania and was not involved in the White Sands research, said it was often difficult to date exactly when fossilized footprints were made, especially when they were pressed into layers of mud, as at White Sands, and not volcanic ash, which is easier to date.

“It’s great to see that this team was able to constrain the formation date of the footprint using radiocarbon dates from the top and bottom [layers],” he said in an email.

Unlike bones or artifacts, footprints are unique because they record fossilized behavior, and their analysis can yield clues about the imprinters.

“Human footprints give us insight into the lives of our ancestors and, in this case, provide detailed information about their daily activities and social dynamics,” Liutkus-Pierce said.