In-depth genetic analysis challenges one of the simplest versions of the human origin story: the idea that all modern humans arose from a single ancestral population in Africa. Rather, the study points to a more complex beginning, with early human groups spreading across Africa and intermixing for long periods of time until some of their differences became visible in the DNA of people living today.
This study nature In 2023, they compared the genetic material of modern African populations with early fossil evidence. wise person population. The result is a model of human evolution that replaces a neat family tree with something like a network of deeply connected branches.
A more complex case begins in Africa
Scientists broadly agree that wise person Native to Africa. A more difficult question is how early human populations separated, moved, recombined, and shaped each other across continents.
Brenna Henn, a professor at the Anthropology and Genome Center at the University of California, Davis and corresponding author of the study, said the uncertainty comes from gaps in both fossil and ancient DNA.
“This uncertainty is due to the limited fossil and ancient genomic data and the fact that the fossil record does not always match expectations from models built using modern DNA,” she said. “This new study changes the origin of species.”
The study was co-led by Heng and Simon Gravel of McGill University. Their team tested several competing ideas about human evolution and migration in Africa, based on models proposed in paleoanthropology and genetics. The analysis included genomic data from southern, eastern, and western Africa.
Raw genome adds important clues
The bulk of the research was derived from 44 newly sequenced genomes of the modern Nama people of southern Africa. The Nama people are an indigenous people known for having unusually high levels of genetic diversity compared to many other biological groups.
Researchers collected saliva samples from villagers between 2012 and 2015 while participants went about their daily lives. These samples helped the team investigate whether human origins fit a single origin model or a broader, more interconnected model.
The best-fitting model suggested that the earliest population split between early humans still detectable in modern humans occurred approximately 120,000 to 135,000 years ago. Two or more weak differentiations before that split. homo Humans have been exchanging genes for hundreds of thousands of years.
After the split, migration and interbreeding between these early groups continued. The researchers describe this as a weak structural trunk, meaning that modern humans have roots in loosely connected groups with ongoing gene flow, rather than a single isolated population.
Network instead of one branch
The authors say models like this network may be able to explain human genetic diversity better than older models. This model shows how modern DNA patterns emerged from the structure of the ancestral human populations themselves, without having to assume a major contribution from unknown archaic human populations in Africa.
“We’re publishing something that people haven’t even tested before,” Heng said of the study. “This is a huge step forward for anthropology.”
Co-author Tim Weaver, a professor of anthropology at the University of California, Davis, who studies early human fossils, said the results change how scientists should think about old explanations.
“Previous, more complex models suggested a contribution from archaic humans, but this model shows otherwise,” he said.
Weaver lent his comparative fossil expertise to the study and helped connect genetic models to what early human remains looked like.
What this means for ancient fossils
This model also influences how scientists interpret the fossil record. According to the authors, only 1-4% of the genetic differentiation between living human populations can be traced to differences between these ancestral stem populations.
The early branches continued to intermingle, so they probably looked similar. It refers to fossils with very different physical characteristics (e.g. i was born a man) is unlikely to represent a lineage that directly contributed to the evolution of wise personsaid the authors.
In other words, the roots of humanity may have been geographically and genetically widespread, but they did not necessarily diverge into vastly different human forms. The deeper picture is one of movement, contact, and repeated mixing across Africa.
Subsequent research has further deepened the
Research published since the 2023 study continues to show how important Africa’s genomic diversity is to understanding human origins. 2024 natural ecology and evolution The study reports 9,000 years of genetic continuity in southernmost Africa, highlighting the region’s long and unusually deep human population history.
later nature The study analyzed the genomes of 28 ancient southern Africans from 10,200 to 150 years ago. The study found and identified that ancient southern Africans had genetic variations outside the range seen in modern humans. wise person Specific variants that may shed light on adaptation and evolution within Africa.
Taken together, these discoveries reinforce the larger message that humanity’s origins were not a single spark in one place. They were shaped by large populations, deep African diversity, and long-standing connections across the continent.
Additional co-authors of the 2023 study include Aaron Ragsdale of the University of Wisconsin-Madison; Elizabeth Atkinson, Baylor College of Medicine; Eileen Hoal and Marlo Möller from Stellenbosch University in South Africa;
