A sweeping new genetic analysis suggests that humans living in southern Africa spent roughly 100,000 years in isolation, long enough for their DNA to drift far beyond the range of genetic diversity seen in people today.The study strengthens the idea that “modern” Homo sapiens are not defined by one fixed genetic blueprint, but by many different combinations of traits, some of which no longer exist in living populations. Published on December 3 and available on the Nature website, the research is based on the genomes of 28 ancient individuals whose remains date from between 225 and 10,275 years old.All were recovered from sites south of the Limpopo river, which cuts across southern Africa before entering the Indian Ocean. Scientists compared these newly sequenced genomes with existing data from both ancient and modern populations across Africa and the rest of the world.Individuals who lived in southern Africa more than 1,400 years ago carried genetic signatures unlike anything seen in present-day humans. This suggests the region remained largely cut off from the rest of the continent until relatively recently, though researchers are still unsure why.Also Read: Ceramic jug with charred insects, fossilised faeces: Sudan’s site reveals forgotten burial traditions of an African kingdomStudy co-author Mattias Jakobsson of Uppsala University, Sweden, said geography alone doesn’t fully explain the isolation. While the region lies far to the south, distance has rarely stopped humans from migrating. Instead, he suggested that environmental conditions near the Zambezi river, just north of this population, may have been inhospitable, creating a natural barrier.“The combination of distance and unfavourable conditions might have isolated the south,” he told the Live Science website.Story continues below this adThe team noted that many ancient individuals, especially those dating from about 10,200 to 1,400 years ago, fall entirely outside the genetic range of modern humans and represent an end of human diversity. They classified this previously unknown genetic signature as the “ancient southern African ancestry component” and found no clear evidence of genetic mixing with outsiders until around AD 550.These findings challenge earlier linguistic and archaeological theories suggesting long-term links between eastern, western, and southern Africa. Instead, the new data points to a deep and prolonged genetic separation.Statistical modelling allowed researchers to reconstruct ancient population trends, revealing that southern Africa once supported a large population at least 200,000 years ago. During periods of favourable climate, some groups may have moved northward, spreading genes into other regions. But around 50,000 years ago, the population began to shrink. By roughly 1,300 years ago, northern farmers had begun to interact and intermix with the long-isolated southern foraging communities.This ancient genetic diversity offered scientists rare insight into which traits mattered most in human evolution. According to Jakobsson, southern Africans from this period contain half of all human genetic variation, with the rest of the world’s populations sharing the other half.Story continues below this adAlso Read | Ancient Chinese texts reveal new clues about first recorded solar eclipseSeveral of the Homo sapiens-specific DNA variants identified in the ancient samples included genes linked to kidney function and genes involved in neuron growth. The kidney-related variants may have helped early humans regulate water more effectively, while the neural variants could influence attention span, possibly giving Homo sapiens cognitive advantages over Neanderthals and Denisovans.The findings underscore how much genetic diversity from ancient indigenous populations around the world remains unstudied. Large gaps in the global ancient DNA record, the authors say, still limit our understanding of how human evolution unfolded.The presence of key human-specific variants in ancient southern Africans supports a “combinatorial” model of evolution, where many different combinations of genes eventually produced what we now consider genetically modern humans. Jakobsson says he remains open to the possibility that humans evolved, at least in part, in multiple regions rather than a single geographic cradle.