Along the edges of a vanished ice age lake are the fossilized tracks of people who lived among the mammoths, giant ground sloths, and other Pleistocene mammals of ancient New Mexico. The footprints at New Mexico’s White Sands National Park are so old, they could upend past assumptions on when humans first ventured into North and South America.
The footprints look ordinary enough, like those left by a young barefoot teenager ambling about just moments ago – and while each and every footprint is well-defined – the tracks are not ordinary tourist tracks.
According to National Geographic, “These prints are among the oldest evidence of humans in the Americas, marking the latest addition to a growing body of evidence that challenges when and how people first ventured into this unexplored land.”
Interestingly, the seeds of a local plant called spiral ditch grass were pressed into the tracks, and these plant remnants are what has given archaeologists a possible time for when people lived here.
According to a paper published Thursday in the journal Science, the footprints were pressed into the mud near an ancient lake at White Sands between 21,000 and 23,000 years ago, a time when many scientists think that massive ice sheets walled-off human passage into North America.
Early footsteps in the Americas
In the first half of the 20th Century, a consensus emerged among North American archaeologists that the Clovis people had been the first to reach the Americas, about 11,500 years ago.
The ancestors of the Clovis people are believed to have crossed a land bridge linking Siberia to Alaska during the last ice age. That land bridge, known as Beringia, eventually disappeared underwater as the ice melted.
And while the idea of the Clovis people being the first inhabitants on the North American Continent was taking hold, archaeologists nearly stopped looking for earlier signs of habitation, however, in the 1970s, this consensus started being challenged.
In the 1980s, solid evidence for a 14,500-year-old human presence at Monte Verde, Chile, emerged. And by early 2000, other pre-Clovis sites had become widely accepted – Including a study published in 2011 about the 15,500-year-old Buttermilk Creek Complex in central Texas.
One thing is certain. While the White Sands discovery won’t close the book on the debate, it certainly leaves us with some compelling evidence.
“A discovery like this is very close to finding the Holy Grail,” says Ciprian Ardelean, an archaeologist with the Autonomous University of Zacatecas. Ardelean directs excavations at Mexico’s Chiquihuite Cave, where researchers believe they have evidence for human activity in the Americas as early as 30,000 years ago.
“I feel a healthy but profound envy—a good kind of jealousy—towards the team for finding such a thing.”
An ancient body of water reveals thousands of prints
About 2 to 3 million years ago, the Rio Grande River flowed along the southern edge of the Tularosa Basin. This river brought sediments and minerals downstream into the Tularosa Basin, and eventually blocked the basin’s outlet to the sea.
This blockage eventually formed Lake Otero, an ancient 1,600-square mile lake that covered much of the basin. Moving forward in time, to the last Ice Age, 40,000 to 12,000 years ago, the colder climate began to warm up.
By 11,000 years ago, rain and snowmelt carried dissolved gypsum from the surrounding mountain ranges into the basin, where it settled in the waters of Lake Otero. During this same period, Lake Otero began to evaporate, becoming a playa, or dry lake bed.
In the present-day White Sands National Park, besides the sites with hundreds of fossilized animal footprints, at least seven human footprint sites have been found, including one with 37 prints. Most are from smaller-statured people with foot anatomy just like that of modern humans.
Geologist Matthew Bennett of Bournemouth University in England and his co-authors hypothesize, that most of the tracks were left by adolescents and children, reports Scientific American.
Following an initial assessment in 2019, U.S. Geological Survey researchers Kathleen Springer and Jeff Pigati visited White Sands in 2020 to dig trenches through the lake sediments. Their main goal was to find a way to accurately date the footprints.
“Multiple footprint horizons were in place, in section, with seed layers smashed by footprints in some cases,” Springer says. These spiral ditch grass seeds were radiocarbon-dated, delivering the time range of 23,000 to 21,000 years ago at the center of the new study.
The older-than-expected age of the White Sands tracks raises a lot of questions about how the people who left them might have arrived in the Americas. The tracks’ time range falls within what archaeologists and paleontologists know as the last glacial maximum (LGM), the period when the world’s ice sheets were at their greatest extent.
Basically, this means that the people at White Sands had to have crossed the Beringia ice bridge before the ice expanded, traveled along the ice sheets’ coastal edges, or arrived by some other route.
“In truth, this site is a bombshell,” says University of Alberta anthropologist Ruth Gruhn, who was not involved in the new study. But one thing is for sure – the new research could spur archaeologists to take another look and reconsider how and when people arrived in the Americas.