Researchers have long used stone tools and bones to determine when humans first arrived in the Americas. However, a recent genetic study offers a new perspective on this timeline. In a synthesis published in October 2026 in Current Opinion in Genetics & Development, archaeologist Ben Potter and geneticist Jennifer Raff analyzed hundreds of ancient genomes and compared them with remains found across the continent. Their findings suggest that the first humans arrived in the New World around 21,000 years ago, much earlier than previously thought. Some earlier discoveries, such as footprints dated to about 23,000 years ago, had hinted at an even earlier presence, but these new genetic insights are narrowing the timeline to the end of the last ice age, when large ice caps still limited southern migration routes. To trace this timeline, Potter and Raff did not excavate new sites but instead compiled all the ancient DNA data already available. Their research included 257 complete genomes of ancient Americans and genetic data from 1,204 other individuals, spanning from Alaska to Patagonia. A consistent signal emerged from this data: a founding population that began to diversify around 21,000 years ago, marking the earliest known genetic traces of the first arrivals. The oldest genome that has been fully sequenced comes from a child found at the Anzick site in Montana, who died 12,800 years ago. By analyzing the accumulated genetic mutations over generations, the researchers used a method called a molecular clock to estimate when different populations separated from each other. While bones and tools provide physical evidence of human presence, genetic data allows scientists to measure the time since a common ancestor. This study helps resolve a long-standing debate. For example, human footprints found in New Mexico, dated to 23,000 years ago, had suggested an early arrival during the height of the last ice age. However, the genetic data does not support the existence of a lineage that arrived in the Americas before 25,000 years ago. According to the researchers, a single ancestral population, isolated between Siberia and Alaska, gave rise to all indigenous groups in the Americas. This area, known as Beringia, was a vast land bridge that once connected Asia and the Americas when sea levels were much lower. The footprints in New Mexico are still considered real and well-dated, but Potter and Raff emphasize that a footprint only proves a presence, not a lasting genetic lineage. Humans may have ventured into the continent much earlier than previously thought, but without leaving descendants. The next step is to find even older genomes that could fill the gap between the time humans first entered Beringia and the oldest known bones. Until such DNA is discovered, the genetic timeline will remain the most accurate way to determine when the first Americans arrived.