Compared to the rest of the world, the American continent welcomed its first humans relatively late. You might think that this (relative) proximity to modern times should make it easier to study, but it seems the reality is not so simple. At least, that’s one conclusion of a recent review of genomic research on the arrival of humans in the Americas based on a collection of relevant articles and data sets. From the analysis, researchers at the University of Kansas (KU) outlined three migration models for when humans began to occupy the American continent: before, during or after the last glacial maximum, or LGM (which the authors date between 25,000 and 14,000 years ago, although it is commonly dated between 26,000 and 19,000 years ago). Evidence pointed to the arrival of man no earlier than 21,000 years ago (at the height of the last ice age), although archaeological evidence may be consistent with an earlier date. Based on this research, it appears that humans living in Siberia or Beringia split into different groups during the Last Glacial Maximum and possibly about 16,000 years ago. For context, the last ice age ended about 11,700 years ago. “The results of this genomic synthesis align closely with our most reliable archaeological evidence,” David Kilby, an archaeologist at Texas State University who was not involved in the new work, told Gizmodo. “This article is an excellent example of how that relationship [between archaeology and genomics] “It may work to resolve one of our most difficult questions: how and when the ancestors of contemporary Native Americans came to occupy these last uninhabited continents.” So which one is it? A map of archaeological sites with controversial claims of having the oldest evidence of humans in the Americas. © Pratyeka via Wikimedia Commons The debate over human arrival in the Americas has progressed over the years. According to the article, when the debate began in the 19th century, archaeologists could not agree on whether this migration occurred during the Pleistocene (from 2.58 million years ago to 11,700 years ago). But although it is now accepted that it occurred during the Pleistocene, the exact timing remains elusive. Over the past 16 years, scientists have published 257 complete genomes of ancient Americans, the team explained in the study. “That’s more than one a month for 16 years,” Jesse Tune, an archaeologist at the University of Mississippi who was not involved in the latest work, told Gizmodo. “During that time, 1,204 additional genome-wide data sets have been published. Incredible.” More to be desired But geneticists still see significant limits, as study co-authors Jennifer Raff, Savannah Hay, and Bethany Potter told Gizmodo in a joint response. For example, samples from “very old but (so far) well-validated sites” like White Sands date back 23,000 years. However, genetic data suggests that this population did not make as large a contribution to modern indigenous peoples, and relationships like these “complicate our understanding of the genetic data,” the researchers explained. Human footprints found at the White Sands site in New Mexico. © National Park Service via Wikimedia Commons To give another example, the oldest published genome in the Americas is that of the Anzick boy, dating back to about 12,800 years ago, but scientists can’t say whether the boy’s genome is representative of previous waves of migration, the team said. If the team’s estimate of 21,000 years is correct, the earlier populations would belong to an undiscovered or nearly decimated lineage or to a lineage that is rare among modern Native Americans. “This paper is a literature review, so rather than providing novel data, we compiled recent papers and considered their findings as a whole,” the researchers said, adding that overall, the geographic distribution of genetic data remains quite uneven. Related to this, the team decided to address three different models in the paper to reflect ongoing debates about the validity of certain sites dating back more than 13,000 years. One way of looking at things Of course, the last analysis is not necessarily an exhaustive description of the different interpretations that exist, which really speaks to the controversial nature of this topic. Ben Potter, an archaeologist at the University of Alaska Fairbanks who was not involved in the new work (and is not related to Bethany Potter), told Gizmodo that he found the analysis of the archaeological data and the paper’s consensus “less compelling” compared to the review of the genetic data. Potter suggested that reading the latest analysis alongside similar reviews can help provide a broader perspective. Map showing all published pre-contact whole genome data in the Americas, scaled by sample size. © Raff et al., 2026 “My sense is that this review provides a perspective on settlement, based largely on the interpretations of David Meltzer and Eske Willerslev, as well as a survey of some authors (and the exclusion of others),” Potter said. “To be transparent, most of my colleagues favor the post-LGM model, between 16,000 and 14,000 years ago, as do most archaeologists, in my experience. That said, I appreciate that the map provides some alternative models.” Meltzer is an archaeologist at Southern Methodist University and Willerslev is an evolutionary geneticist at the University of Cambridge in the United Kingdom, both specializing in the peopling of the Americas. Looking Ahead Still, others praised the study for its demonstration of how paleogenomics has contributed to archeology over the past two decades. Kilby said the genetic pattern “corresponds to a satisfactory degree with the currently known archaeological pattern: very few convincing sites older than 16,000 years, a small but growing number of sites dating between 14,000 and 16,000 years ago, and widespread occupation of the North American continent by 13,000 years ago.” “Genomic research is expanding rapidly and improving our understanding of human migrations,” Tune added. “As [the researchers] “The complex nature of this problem requires genomics and archeology to work together to fully understand how the pieces of the puzzle fit together.” “There is still a lot to learn and it is important to keep an open mind,” the KU team said. “Our biggest takeaway from this project is the need for additional data as we continue to explore the peopling of the Americas.”
