The first inhabitants of North America were small groups of hunter-gatherers who crossed from Siberia into the Americas at least 23,000 years ago, and possibly earlier. These people arrived during the last Ice Age, when massive glaciers locked up enough ocean water to expose a land connection between modern-day Russia and Alaska. For most of the twentieth century, scientists believed the first arrivals came roughly 13,000 years ago. That timeline has been dramatically rewritten by discoveries over the past few decades.
The Clovis-First Theory and Its Collapse
For generations, the standard story went like this: a small founding population of big-game hunters entered the Americas about 13,000 years ago by walking through an ice-free corridor that opened between two enormous glaciers covering Canada. These people left behind distinctive stone spear points, first found near Clovis, New Mexico, in the 1930s. The “Clovis-First” model held that these hunters spread rapidly across both continents, and that no one had been here before them.
That model began to crack as archaeologists found site after site with human activity below the Clovis layer. Meadowcroft Rockshelter in Pennsylvania, Cactus Hill in Virginia, and Monte Verde in Chile all contained tools and hearths older than any Clovis artifacts. Wilson Butte Cave in Idaho produced bone samples dating to before 13,000 years ago. At Oregon’s Paisley Caves, researchers found a completely different toolmaking tradition, called Western Stemmed, that overlapped with or even predated Clovis. The two traditions used fundamentally different approaches: Clovis toolmakers started with a large rock and reduced it considerably, thinning the base by removing a large flake, while Western Stemmed toolmakers shaped smaller flakes into points with narrow, constricted bases. The existence of two independent stone tool traditions strongly suggests Clovis people were not the sole founding population of the Americas.
How They Got Here
During the last Ice Age, sea levels dropped by roughly 300 feet, exposing a wide stretch of land between Siberia and Alaska known as Beringia. This wasn’t a narrow bridge but an expansive, habitable landscape that people likely lived on for thousands of years before moving into the rest of the continent.
The traditional idea was that people walked south through an ice-free corridor between the two great ice sheets covering Canada. But archaeological evidence now shows that humans were living south of those ice sheets before 15,000 years ago, which is before the corridor was passable. The timing simply doesn’t work. The more likely route, supported by a growing body of evidence, is coastal migration along the Pacific shoreline. People may have traveled by boat or on foot along the coast, following what researchers call the “kelp highway,” a chain of productive kelp forest ecosystems stretching from northeast Asia down the Pacific coast of the Americas. These coastal environments would have provided reliable food sources like fish, shellfish, and sea mammals, making it possible to move south even while the interior remained locked under ice.
The Oldest Evidence in the Americas
The most striking recent discovery comes from White Sands National Park in New Mexico, where dozens of human footprints were preserved in ancient lakebed sediments. Initial radiocarbon dating of seeds and pollen placed the footprints between 21,000 and 23,000 years old. Some scientists questioned whether the seed dates might be unreliable, so a team led by University of Arizona researchers returned in 2022 and 2023 to date the ancient lakebed mud itself. Two independent laboratories both reported the same range: 20,700 to 22,400 years ago. In total, scientists now have 55 radiocarbon dates on three different types of material, all pointing to the same time period. This is the strongest evidence that people were walking in North America during the height of the last Ice Age.
Farther north, Bluefish Caves in Canada’s Yukon Territory contain animal bones with cut marks made by stone tools. Researchers conducted a detailed analysis of the bones and identified fifteen specimens with marks confidently attributed to human activity, including evidence of skinning, dismembering, and defleshing. The oldest of these, a horse jawbone with cuts from tongue removal using a stone tool, dates to approximately 24,000 years ago. Other cut-marked bones from the caves range from 12,000 to 24,000 years old, showing that people used the site repeatedly over thousands of years during and after the peak of glaciation.
Where They Came From
Genetic studies trace the ancestry of the first Americans back to Siberia. Researchers analyzing mitochondrial DNA (genetic material passed down through mothers) have identified four major lineage groups, labeled A, B, C, and D, that are shared between Native Americans and indigenous Siberians. These lineages didn’t all come from one place. The founding versions of these lineage groups have been detected across a wide swath of Siberia: some trace to peoples of the Altai-Sayan Upland (a mountainous region where Russia, Mongolia, China, and Kazakhstan meet), while others connect to the Lower Amur River region near the Sea of Okhotsk in Russia’s Far East. The Chukchi and Siberian Eskimos of northeastern Siberia carry three of these four lineage groups today.
Genomic studies estimate that the ancestors of Native Americans split from Siberian and East Asian populations roughly 23,000 to 25,000 years ago. This timing lines up remarkably well with the White Sands footprints and the Bluefish Caves evidence. It suggests that a population became genetically isolated, likely while living in Beringia, around the same time some of their members were already pushing into the continent.
The World They Entered
North America during the late Ice Age looked nothing like it does today. The southern portions of the continent, below the glaciers, resembled the savannas of modern Africa in terms of ecological richness. Herds of mammoths, mastodons, horses, camels, and giant ground sloths roamed grasslands and open woodlands. Multiple species of bison, much larger than modern bison, grazed alongside pronghorn and deer. Predators included two species of sabertooth cat, the American lion, and the dire wolf. The ecosystem supported a full range of specialized grazers and browsers feeding on different types of vegetation.
Most of these large animals went extinct by about 11,000 years ago, in a wave of disappearances that reshaped North American ecosystems. The surviving mammals shifted in unexpected ways. Deer actually grew larger after the extinctions, likely because they no longer competed with so many other browsing species. Bison shrank. The ecological web that had sustained the first inhabitants for thousands of years collapsed relatively quickly, forcing the people who remained to adapt to a fundamentally different landscape.
A More Controversial Claim
One site pushes the timeline far beyond what most scientists accept. The Cerutti Mastodon site in San Diego, California, contains mastodon bones and stones that some researchers argue show evidence of intentional smashing by tool-using beings roughly 130,000 years ago. Two stones found among the remains carry chemical residue matching bone, concentrated in areas showing signs of repeated hard impacts. Supporters argue the larger stone served as a platform on which bones were cracked open with the smaller stone, possibly to extract marrow. If true, this wouldn’t have been the work of modern humans, who hadn’t left Africa yet, but potentially Neandertals, Denisovans, or another hominin species.
Most archaeologists remain deeply skeptical. Critics point out that heavy truck traffic over the area during twentieth-century construction could have jostled buried stones against older fossilized bones, mimicking the damage pattern. One mastodon limb bone was shattered into several hundred pieces, consistent with the effects of trucks rumbling overhead. The bone residue on the stones also lacks collagen, which would be expected if fresh bones had been smashed. The site remains highly disputed, and the mainstream view still places the first arrival of any humans in the Americas no earlier than about 25,000 to 30,000 years ago.