Ancient humans stayed isolated In Southern Africa for millennia, study finds

Jawbone of the Matjes River 1 woman, who lived 7,900 years ago in southern Africa. (Image: Mattias Jakobsson)

The silence of ancient landscapes holds many secrets. One such secret has emerged from southern Africa, where researchers say early humans lived in long isolation and developed unusual genetic patterns that differ greatly from people today.

What Did The Study Discover?

A new study in Nature reports that humans in southern Africa remained isolated for nearly 100,000 years. Their genetic traits sat outside the range seen in modern humans. Scientists sequenced genomes from 28 individuals dated between 225 and 10,275 years old. These remains came from regions south of the Limpopo River. Researchers then compared these genomes with data from ancient and present-day populations across global regions.

Why were these ancient Southern Africans so genetically distinct? Scientists found that people living there before about 1,400 years ago had very different genetic profiles. This suggested that the region stayed separate from wider human movements. The reasons for this long isolation remain unclear.

Why Were Humans Separated For So Long?

Study co author Mattias Jakobsson from Uppsala University said distance alone was not enough. He noted that people often travel across large areas. He suggested that regions around the Zambezi River might have been unsuitable for early communities. This combination of distance and harsh conditions could have kept the south isolated. Many individuals from 10,200 to 1,400 years ago fell beyond modern human genetic variation. They formed an extreme end of early human diversity.

Researchers named this unique pattern the ancient southern African ancestry component. They saw no strong evidence of outside mixing until about A.D. 550. These findings differ from earlier linguistic and archaeological theories suggesting ongoing contact between Africa’s regions.

How Large Was This Ancient Population?

Statistical modelling showed that the southern population stayed large until about 200,000 years ago. People may have moved north during favourable periods. The southern population began shrinking around 50,000 years ago. Farmers from the north later met and reproduced with southern foragers about 1,300 years ago.

What Do These Genetic Traits Reveal?

Jakobsson said this ancient group holds half of all human genetic variation. The rest of the world holds the other half. These genomes allowed scientists to examine key human variants. Several variants linked to kidney function were found. Some variants related to brain neuron growth also appeared. Kidney traits may have helped early humans manage water supplies. Neuron traits may relate to attention skills and mental capacity. These findings may help explain differences between humans and Neanderthals or Denisovans.

The researchers wrote that large amounts of genetic diversity remain unknown in ancient communities worldwide. Such variation helps reveal how Homo sapiens evolved. The presence of human-specific variants in ancient southern Africans supports a combinatorial model of evolution. Many variant combinations may have formed the basis of genetically modern humans.

Jakobsson said that humans may have evolved in several regions. He added that the way those regions shaped human traits remains an open question.