Archaeologists have debated whether people entered the Americas before, during, or after the Last Glacial Maximum (LGM). A new study of genetic evidence now suggests the group that gave rise to today’s Indigenous peoples migrated into the Americas no earlier than about 21,000 years ago, likely near the end of the LGM.
“The evidence points to the arrival of humans ancestral to contemporary Indigenous peoples likely near the end of the Last Glacial Maximum, but earlier migrations may also have occurred,” said study co‑authors Bethany Potter of the Kansas Geological Survey and Savannah Hay of the University of Kansas.
In a study published Sept. 23 in Current Opinion in Genetics & Development, the researchers examined three main archaeological models: entry before the LGM (>25,000 years ago), entry during the LGM (25,000–14,000 years ago), and entry after the LGM (<14,000 years ago, the Clovis First theory). Using genetic data from roughly 250 ancient whole genomes and genome‑wide data from about 1,200 individuals, they concluded that the earliest sampled genome (the 12,800‑year‑old Anzick‑1 child) points to an initial migration no earlier than 21,000 years ago.
“The reason this topic is so contentious among anthropologists is because not all archaeologists agree about which of the earliest sites are legitimate, and that influences which model they think is most accurate,” Potter and Hay explained. “We know that humans were definitely in the Americas by about 13,500 years ago. We still don’t know if they arrived earlier than that and, if so, how much earlier.”
Genetic evidence of the first peoples in the Americas is still sparse. The first ancient whole genome, from a 4,000‑year‑old individual in Greenland, was sequenced in 2010. Since then, scientists have published around 250 whole genomes and genome‑wide data from roughly 1,200 ancient Indigenous people.
These DNA studies reveal that during the LGM, around 25,000 years ago, a population living near Siberia or Beringia split into ancient Native Americans, ancient Beringians, and one or more “ghost” lineages. The groups moved quickly along the Pacific coast and may have divided again around 16,000 years ago into Northern and Southern Native American ancestors.
“Huge gaps in our genetic dataset”
Current genetic data align with archaeological evidence for entry at least 14,000 years ago and possibly as far back as 21,000 years ago, but more DNA evidence is needed to clarify timing and routes. “There are huge gaps in our genetic dataset,” Potter and Hay noted. “For example, there are still no published ancient genomes from the Great Plains.”
Human footprints at White Sands, New Mexico, dated to 23,000 years ago, suggest a pre‑LGM presence. While the Acoma Pueblo people recognize these as ancestral traces, genetic data from contemporary and ancient Indigenous peoples indicate that the White Sands population did not make a major genetic contribution to today’s Indigenous groups, though some lineage may remain undiscovered.
Several pre‑LGM migration scenarios remain possible, but assessing them requires broader geographic sampling. Expanding ancient DNA coverage, while maintaining ethical, community‑focused research practices, could fill these gaps and reshape our understanding of the early peopling of the Americas.
The exact timing of the first entry into the Americas remains unresolved. Continued ancient genomic work across the continent holds the promise of revealing missing pieces and refining the story of how humanity first settled the New World.
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