A jaw in a cave on Mount Carmel
In Misliya Cave, in present-day Israel, archaeologists found a partial upper jaw with teeth, together with burnt flint and other stone tools. Several dating methods placed it at roughly 177,000 to 194,000 years ago, and the 2018 report in Science argued it belonged to Homo sapiens. If that identification holds, modern-looking people were outside Africa far earlier than the figure of about 60,000 years that was long repeated. Researchers quoted in coverage were careful, though. One suggested the individual may belong to a lineage that left no descendants today, and another noted that finds cluster in Israel partly because that is where people have looked hardest.
That small disagreement contains the whole subject. “How humans spread across the planet” sounds like a single march. The evidence looks more like many movements, some of which may have faded out.
Not one exodus, but several attempts
The Smithsonian’s Human Origins program places the origin of our species in Africa about 300,000 years ago, with fossils such as Omo I and Singa among the early examples. The direct ancestor is still an open question. From there, the picture depends on which kind of evidence you trust most.
A 2024 study in Science by Liming Li and Joshua Akey searched Neanderthal genomes for DNA that came from early Homo sapiens. They inferred two episodes of gene flow, around 200,000 to 250,000 and around 100,000 to 120,000 years ago, and read this as a sign of earlier dispersals than the better-supported one 50,000 to 60,000 years ago. The result rests on only three Neanderthal genomes and on statistical modeling, and scientists not involved pointed out that early movements leave little DNA or bone behind.
- Find something. A jaw, a footprint trail, a hearth, a scatter of stone flakes.
- Date it. Radiocarbon, luminescence and other methods each have limits and can disagree.
- Decide what it is. Is the bone Homo sapiens? Are the stones tools or natural breaks?
- Add genetics. DNA from living and ancient people can suggest when groups split, but models carry assumptions.
- Revise. New sites, new methods and unsurveyed regions routinely change the map.
Crossing to Australia
At Madjedbebe, a rock shelter in Australia’s Northern Territory, researchers used radiocarbon and luminescence dating on the sediments around stone artifacts and reported human presence as early as about 65,000 years ago. The authors noted that this is close to some genetic estimates, which put first arrival near 70,000 years ago. Two cautions apply. “As early as” is a maximum, and the result comes from one site whose dated layers must be firmly tied to the artifacts. Also, reaching Australia is generally understood to have involved crossing stretches of open water, which makes the journey a story of seafaring skill as much as walking.
The Americas: a live argument
Few questions in this field are as unsettled as when people first reached the Americas. For much of the twentieth century, many archaeologists held that the Clovis culture, around 13,000 years ago, marked the earliest arrival. Sites such as Monte Verde in Chile and several in North America have since pushed accepted dates earlier, with figures around 14,000 to 16,000 years ago widely discussed. Each side has its disputed cases.
The older view
People arrive about 13,000 years ago, in a rapid spread associated with Clovis tools. Challenged by older sites from the 2000s onward.
The pre-Clovis view
People arrive by roughly 14,000 to 16,000 years ago or somewhat earlier, perhaps along the Pacific coast. Many researchers find this plausible, though individual sites are argued over.
The much-older claims
Footprints, tools and sediment evidence suggest 21,000 to 26,000 years or more. These are the most contested because dating methods and whether stones were shaped by people are both questioned.
Routes are argued too. One model has people walking through a gap between ice sheets in Canada, though geological work suggests the corridor may have opened late. Another has people moving along the Pacific coast, perhaps by boat, which fits the timing better but is hard to test because ancient shorelines are now under the sea. Different genetic studies estimate that the ancestors of Native Americans entered the Beringia region anywhere from roughly 40,000 to 25,000 years ago, and some propose a long pause there, a hypothesis that other lines of evidence do not fully support.
Why “spread” can mislead
Words like “conquest” or “settling the globe” suggest a purposeful march toward empty lands. The record shows something messier. Populations met other human groups, and genetic work indicates that interbreeding with Neanderthals went in both directions. Some researchers propose that Neanderthals were gradually absorbed rather than simply replaced, but that remains a hypothesis. Movements also stopped, reversed and restarted, and the people in them were adapting to coasts, deserts, forests and cold steppe, a theme explored in how humans adapt to extreme environments.
These journeys had costs we can only guess at, such as dangerous sea crossings, hunger in unfamiliar landscapes and the loss of whole lineages. Later chapters of the story, including the arrival of farming and the growth of cities, were built on knowledge carried across these landscapes. Migration did not end when the last continent was reached either. People are still moving, for reasons that range from opportunity to necessity.
