The origin of modern humans appears to be far more complex than previously suggested by simplified evolutionary models. A large-scale genetic study is now challenging the idea of a single ancestral population.
Published in Nature in 2023, the research suggests that early populations of Homo sapiens emerged not from one isolated group, but from a network of populations spread across Africa, interacting and exchanging genes over long periods.
A more complex evolutionary picture
While scientists agree that Homo sapiens originated in Africa, the details of how early populations split, migrated, and reconnected remain unclear.
The study aims to bridge the gap between genetic data from modern populations and fossil evidence. According to Brenna Henn of University of California, Davis, limited fossil records and scarce ancient DNA have long complicated efforts to reconstruct human origins.
The research was co-authored by Simon Gravel of McGill University.
The importance of genetic diversity
The team analyzed genomic data from populations across southern, eastern, and western Africa, including new data from the Nama people, known for their high genetic diversity.
Their findings indicate that the earliest major population split occurred between 120,000 and 135,000 years ago. However, gene flow between groups continued both before and after this divergence.
In essence, human evolution appears to have been shaped by continuous interaction rather than isolation.
Rethinking fossil interpretation
The new model better explains present-day genetic diversity without requiring contributions from unknown archaic human species.
It also has implications for fossil interpretation. Researchers estimate that only a small fraction of genetic variation among modern humans can be traced back to differences between early populations.
This suggests those populations were not dramatically different in appearance, making it less likely that morphologically distinct species such as Homo naledi directly contributed to modern human evolution.
Supporting evidence from newer studies
Subsequent studies published in Nature Ecology & Evolution and Nature reinforce these conclusions, revealing deep genetic continuity and greater diversity across Africa.
Overall, the emerging picture is clear: human origins were not the result of a single event in one location, but a prolonged process shaped by migration, interaction, and genetic exchange across the continent.