WHITE SANDS, N.M. (KRQE) – New research reaffirms that fossil human footprints found in White Sands National Park in New Mexico date to the Last Glacial Maximum, placing humans in North America thousands of years earlier than once thought. 

In September 2021, U.S. Geological Survey (USGS) researchers and an international team of scientists announced that ancient human footprints discovered in White Sands National Park were between 21,000 and 23,000 years old. USGS said the footprints are the oldest ones that have been found in North America so far.

In that study, researchers used radiocarbon dating to study seeds from water plants found near the footprints. However, that report had some scientists questioning the accuracy of the dates.

“Sometimes we get old carbon in water for various reasons, and so sometimes aquatic material can give ages that are too old,” said Jeff Pigati, USGS research geologist and co-lead author of the newly published study. “This is a really well-known phenomenon in radiocarbon dating.”

In a follow-up study published Thursday, researchers used two new independent approaches to date the footprints, both of which resulted in the same age range as the original estimate, according to the news release by USGS.

“The immediate reaction in some circles of the archeological community was that the accuracy of our dating was insufficient to make the extraordinary claim that humans were present in North America during the Last Glacial Maximum. But our targeted methodology in this current research really paid off,” Pigati stated.

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For the follow-up study, the researchers focused on radiocarbon dating of conifer pollen, because it comes from terrestrial plants and avoids potential issues that arise when dating aquatic plants like Ruppia. The pollen samples were collected from the exact same layers as the original seeds, so a direct comparison could be made. In each case, the pollen age was statistically identical to the corresponding seed age, according to USGS.

“Just the date alone, this time stamp of White Sands National Park with these footprints, just opens up a huge can of worms about, again, ‘how did they get there,'” said Kathleen Springer, USGS research geologist and co-lead author of the study.

USGS said the team also used a different type of dating called optically stimulated luminescence, which dates the last time quartz grains were exposed to sunlight. Using this method, they found that quartz samples collected within the footprint-bearing layers had a minimum age of 21,500 years.

“Even as the original work was being published, we were forging ahead to test our results with multiple lines of evidence,” Springer stated. “We were confident in our original ages, as well as the strong geologic, hydrologic, and stratigraphic evidence, but we knew that independent chronologic control was critical.”

And their newest findings are just the beginning. “There’s other places to look, it’s a big, big area and so we’ve already kind of started looking into other spots in this national park,” Springer added.