Ice Age DNA Rewrites the Story of Who First Settled the Americas

A Long-Standing Mystery Gets a Clearer Answer

One of the most enduring mysteries in the history of the Americas is when the first people arrived — and despite decades of debate drawing on genetic, archaeological, and environmental evidence, no consensus has ever been reached. Now, a new review of ancient DNA is offering the most focused answer yet, and it points squarely to one of the most brutal chapters in Earth's climate history.

A new study of ancient DNA indicates that the ancestors of modern Native Americans first arrived in the New World no earlier than about 21,000 years ago, at the very end of the last Ice Age and the coldest period of Earth's history. Bethany Potter, Savannah Hay, Archana Singh, and Jennifer Raff of the Department of Anthropology at the University of Kansas tried to make sense of that longstanding disagreement in a review article published in Current Opinion in Genetics & Development.

Three Theories, One Winner

The three competing models propose that the ancestors of today's Indigenous Americans arrived before the Last Glacial Maximum — more than 25,000 years ago — during it, between 20,000 and 14,000 years ago, or after it ended, less than 14,000 years ago. To test these scenarios, the researchers evaluated how well each timeline fits three lines of evidence: findings from ancient DNA for genetic clues about when populations split, archaeological sites for evidence of human activity, and environmental data to see when ice sheets and climate conditions would have been favorable for travel.

The evidence best fits a timeline of 14,000 to 20,000 years ago for several reasons. Arriving after 14,000 years ago is at odds with most of the genetic evidence, which shows that key population lineages split well before a land path through the ice opened up — making it more likely that people had already entered the Americas by this point. Genetic data point to a population linked to ancient groups from northern Asia and Beringia, and during the Last Glacial Maximum, this population developed several distinct lineages, including Ancient Native Americans and Ancient Beringians.

The White Sands Problem

These findings sit in stark contrast to the 23,000-year-old human footprints at White Sands in New Mexico, which suggest that people might have already been in America before that wave of migration. The White Sands footprints contain no organic remains suitable for genetic analysis — meaning we may never know who made them. The researchers are candid about this gap. Potter and Hay told Live Science it is possible that descendants of the White Sands people simply haven't been sampled yet, or that "we've just not found DNA from the White Sands population yet."

"We know that humans were definitely in the Americas by about 13,500 years ago," Potter and Hay noted. "We still don't know if they arrived earlier than that and, if so, how much earlier." That kind of scientific honesty is refreshing — and it underscores just how much remains unknown despite the growing mountain of genomic data.

Big Data, Bigger Gaps

About 257 whole genomes and genome-wide data from 1,204 ancient individuals have now been published for the hemisphere — and the review is frank that this is still a thin and uneven sample. Potter and Hay acknowledge there are "huge gaps" in the genetic dataset — for example, there are still no published ancient genomes from the Great Plains — and these gaps could be hiding evidence of earlier migrations.

Potter and Hay emphasized that filling these gaps requires patience, noting that "many of us are intentionally slow with our ancient DNA approaches to ensure research relevant to descendant communities is ethical and collaborative." That balance between scientific urgency and cultural responsibility will shape how this story continues to unfold. The DNA evidence is converging on an answer — but the full picture of who the first Americans were, and exactly when they arrived, is still being written one genome at a time.