Oldest fossil human footprints in North America are definitely older than thought

New research has confirmed that human footprints found in the southwestern US state of New Mexico date to the Last Glacial Maximum, about 20,000 years ago, far older than other human traces on the continent.

In September 2021, US Geological Survey (USGS) researchers and an international team of scientists announced that ancient human footprints discovered in White Sands National Park were dated between 21,000 and 23,000 years old, placing humans in North America thousands of years earlier than once thought.

New dating methods have added more evidence that these fossils date back to 23,000 years.

“Even as the original work was being published, we were forging ahead to test our results with multiple lines of evidence,” said Kathleen Springer, USGS research geologist and co-lead author on the current paper published in the journal Science.

“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,” Springer added.

For their follow-up study, the researchers focused on radiocarbon dating of conifer pollen, and a different type of dating called optically stimulated luminescence.

“With three separate lines of evidence pointing to the same approximate age, it is highly unlikely that they are all incorrect or biased and, taken together, provide strong support for the 21,000 to 23,000-year age range for the footprints,” it added.

Scientists have theorized that early humans crossed into North America via a Bering Strait land bridge that once existed, from modern-day northeastern Russia into what is now Alaska. But they have believed that the crossing came around 13,000 years ago, not the older date now being considered.