A team of geneticists at the University of California, Davis says its new research upends the dominant scientific model of how modern humans emerged, concluding that Homo sapiens likely arose not from a single ancestral population in Africa but from several genetically connected groups spread across the continent over hundreds of thousands of years.

The finding, built on 44 newly sequenced genomes from the Nama people of southern Africa and extensive computer modeling, directly challenges what scientists have long called the "Out of Africa" framework. That model held, for decades, that one main ancestral group gave rise to every living human. The UC Davis team says the DNA tells a different story.

Brenna Henn, a professor of anthropology and the Genome Center at UC Davis and co-author of the study, put it bluntly in a statement:

"This new research changes the origin of species."

What the researchers found, and why it matters

For generations, the textbook version of human origins went roughly like this: a single population of early humans in Africa evolved into Homo sapiens, and descendants of that group eventually migrated out of the continent to populate the rest of the world. Fossil evidence and earlier genetic studies seemed to support the idea.

The UC Davis team tested that model against the actual DNA of living African populations, and found it wanting. When researchers ran their data through computer simulations, the genomes of modern Africans were better explained by a model in which two or more loosely differentiated human populations exchanged genes across Africa for hundreds of thousands of years before any major split occurred.

The earliest detectable divergence among those ancient populations happened roughly 120,000 to 135,000 years ago, the study found. But even after that split, the groups kept exchanging genes for thousands of generations. The genetic differentiation among all living human populations that traces back to variation between those ancestral stem groups amounts to just 1 to 4 percent.

Henn acknowledged the limits of the existing evidence:

"This uncertainty is due to limited fossil and ancient genomic data, and to the fact that the fossil record does not always align with expectations from models built using modern DNA."

That candor is worth noting. The researchers are not claiming certainty where none exists. They are saying the old model does not fit the data, and that no one had even tested the alternative until now.

The Nama genomes and how they were collected

Central to the study are 44 newly sequenced genomes from the Nama, an indigenous people of southern Africa whose genetic lineage stretches back an estimated 100,000 to 140,000 years. Researchers collected saliva samples between 2012 and 2015 from people in Nama villages as participants went about their daily lives.

The Nama's deep genetic roots make their DNA especially valuable for studying early human history. Their genomes carry signals of ancient population structure that have been diluted or lost in many other modern groups. That depth gave the UC Davis team a clearer window into the distant past than most available datasets could provide.

Henn described the significance of the approach in direct terms:

"We are presenting something that people had never even tested before."

Tim Weaver, a UC Davis professor of anthropology who studies early human fossils and co-authored the study, said the results also reshape how scientists should interpret older fossil-based explanations. He noted that previous, more complicated models had proposed genetic contributions from archaic hominins, earlier human-like species, but that this model points in a different direction.

"Previous, more complicated models proposed contributions from archaic hominins, but this model indicates otherwise."

Ancient DNA research keeps rewriting the timeline

The UC Davis findings land in a field already being transformed by rapid advances in ancient DNA analysis. Over the past decade, genetic sequencing has repeatedly forced scientists to revise assumptions about when and how early humans mixed with other populations, including Neanderthals.

Fox News reported on earlier research in which scientists sequenced DNA from a 45,000-year-old Siberian femur, at the time, the oldest modern human genome ever sequenced. That individual carried a level of Neanderthal ancestry similar to present-day Eurasians, and the study estimated that Neanderthals and modern humans interbred approximately 50,000 to 60,000 years ago. Janet Kelso, one of the researchers, called the specimen "the earliest directly dated modern human outside of Africa and the Middle East."

Scientific breakthroughs of this kind, from identifying the oldest known humpback whale song to mapping the genome of a prehistoric Siberian man, remind us how much we still don't know about the natural world and our own history.

Separate research has continued to refine the interbreeding timeline. The New York Post detailed how scientists used genetic material from the Zlatý kůň skull in the Czech Republic and early human remains from Ranis, Germany, to estimate that modern humans and Neanderthals interbred around 45,000 years ago. Priya Moorjani, a study co-author at the University of California Berkeley, said that "genetic data from these samples really helps us paint a picture in more and more detail."

Still other studies have identified Neanderthal genes tied to immunity and metabolism, traits that may have helped early humans adapt as they moved beyond Africa into new environments.

John Hawks, a paleoanthropologist at the University of Wisconsin, captured the broader stakes of ancient DNA work in comments reported by Newsmax:

"It's irreplaceable evidence of what once existed that we can't reconstruct from what people are now. It speaks to us with information about a time that's lost to us."

What we still don't know

For all its ambition, the UC Davis study leaves important questions open. The specific journal that published the research is not identified in available reporting. Nor is it clear how many total genomes were analyzed beyond the 44 Nama sequences, what other modern African populations were included, or what specific computer models the team employed.

The fossil record, as Henn herself noted, does not always line up with what DNA models predict. That gap is not a weakness unique to this study, it is a persistent challenge across the field. But it means the new model, however promising, will face scrutiny from paleontologists and geneticists alike.

The question of how science leadership handles these findings matters, too. Institutions from the CDC to university research labs shape public understanding of breakthroughs like this one. Whether the scientific establishment engages honestly with findings that challenge its own prior consensus, or circles the wagons, will say a lot about the health of the enterprise.

Rick Potts, director of the Smithsonian's Human Origins program, framed the larger question in terms anyone can appreciate: "Out of many really compelling areas of scientific investigation, one of them is: well, who are we?"

That question has driven human inquiry since long before anyone sequenced a genome. The UC Davis team's answer, that modern humans emerged not from a single tribe but from a web of connected populations trading genes across a vast continent, is humbling in its complexity. It suggests the story of our species is messier, older, and more interconnected than the neat narratives we prefer.

The research world, from genetics labs to doctoral programs at universities across the country, will be grappling with these implications for years. Henn herself seemed to understand the weight of the moment.

"This moves anthropological science significantly forward."

Good science follows the evidence wherever it leads, even when the evidence overturns what the textbooks said last semester. That principle deserves defending, no matter who finds it inconvenient.