The oldest direct evidence of human presence in the Americas are likely fossilized human footprints found in New Mexico, challenging once-conventional wisdom regarding humans migrating to the New World from Russia roughly 15,000 years ago, new research confirms.

The new discovery suggests that the first people actually arrived in the Americas much earlier than previously believed.

According to research published Thursday in the journal Science, footprints discovered at the edge of an ancient lake bed in White Sands National Park date back to between 21,000 and 23,000 years ago.

The finding challenges what many archaeologists believed to be true, that humans did not reach the Americas until about 15,000 years ago when they crossed the Bering land bridge between Russia and Alaska — perhaps about 15,000 years ago.

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This undated photo made available by the National Park Service in September 2021 shows fossilized human footprints at the White Sands National Park in New Mexico.  (NPS via AP)

The estimated age of the footprints was first reported in Science in 2021, but Thomas Urban, an archaeological scientist at Cornell University, who was involved in the study, said there was controversy around the dates.

"This is a subject that’s always been controversial, because it’s so significant — it’s about how we understand the last chapter of the peopling of the world," said Urban, who was not involved in the new study affirming the dates.

After the results of the 2021 study were revealed, questions concerned whether the seeds of aquatic plants used for the original dating may have absorbed ancient carbon from the lake — which could have thrown off radiocarbon dating by thousands of years.

The new study looked to affirm the dates by presenting two additional lines of evidence for the older range.

This October 2023 photo made available by the National Park Service shows White Sands National Park Resource Program Manager David Bustos at the White Sands National Park in New Mexico. (NPS via AP)

The study published Thursday used two entirely different materials found at the site: ancient conifer pollen and quartz grains.

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The new study isolated about 75,000 grains of pure pollen from the same sedimentary layer that contained the footprints.

"Dating pollen is arduous and nail-biting," said Kathleen Springer, a research geologist at the United States Geological Survey and a co-author of the new paper.

The researchers also studied accumulated damage in the crystal lattices of ancient quartz grains to produce an age estimate.

This October 2023 photo made available by the National Park Service shows human footprints infilled with white gypsum sand at the White Sands National Park in New Mexico. (NPS via AP)

While other archaeological sites in the Americas point to similar date ranges — including pendants carved from giant ground sloth remains in Brazil — scientists are not certain whether such materials really indicate human presence.

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"White Sands is unique, because there’s no question these footprints were left by people, it’s not ambiguous," said Jennifer Raff, an anthropological geneticist at the University of Kansas, who was not involved in the study.

Ancient footprints can provide archaeologists with a snapshot of how humans walked and interacted.

The Associated Press contributed to this report.