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Matjes River Mandible 1 female, who lived 7,900 years ago in southern Africa. | Credit: Mattias Jakobsson
Humans were isolated in southern Africa for about 100,000 years, causing them to “fall outside the range of genetic variation” seen in modern humans, a new genetic study shows.
The finding supports the idea that “modern” A wise man it can have many different combinations of genetic characteristics, even those outside the norm.
In a study published Wednesday (December 3) in the journal Natureresearchers sequenced the genomes of 28 ancient individuals, whose remains were between 225 and 10,275 years old, from southern Africa south of the Limpopo River, which begins in South Africa and flows in an arc east through Mozambique to the ocean.
The team then compared the genomes of the skeletons with published data from ancient and modern Africans, Europeans, Asians, Americans and Oceanians.
Researchers have found that all humans who lived in southern Africa more than 1,400 years ago had dramatically different genetic makeups than humans today, indicating that relative isolation from the southern part of the continent until relatively recently.
Researchers still aren’t sure why people remained isolated in the region for so long.
“We can speculate that great geographic distance played a role in isolation, but this is not a very satisfactory speculation because humans have and often transcend large geographic areas,” the study co-author. Matthias Jakobssona human evolutionary biologist at Uppsala University in Sweden, told Live Science in an email. However, the geographical area around the Zambezi River, which lies just north of this isolated group, may not have been particularly suitable for ancient human habitation. “The combination of distance and adverse conditions could have isolated the south,” Jakobsson said.
Many of the ancient southern Africans, including those who lived between about 10,200 and 1,400 years ago, “fall outside the range of genetic variation among modern individuals,” the researchers wrote in the study, “and form an extreme end of human genetic variation.”
The researchers labeled this previously unknown suite of genetic variation the “Ancient South African Ancestral Component” and found that there was no clear indication of admixture – or foreigners sharing genes with the group – until around 550 AD.
“Our findings therefore contrast with linguistic, archaeological and some early genetic studies that point to a common ancestry or long-term interaction between East, West and South Africa,” the researchers wrote.
The population living in southern Africa was likely quite large until at least 200,000 years ago, the researchers determined using statistical models. Some people may have left the south in favorable climates, spreading their genes as they moved north. Then, about 50,000 years ago, the population of southern Africans began to decline, and about 1,300 years ago, farmers arriving from further north met and interbred with hunter-gatherers in southern Africa.
Study co-author Helena Malmström samples a skull at the Florisbad research station using the mobile cleaning lab. | Credit: Alexandra Coutinho
“Very important” genetic variants.
The unique genetics of ancient South Africans have provided researchers with other clues human evolution and variation.
The prehistoric population of South Africa contains half of all human genetic variation, while people spread around the rest of the world contain the other half, Jakobsson said in a statement. “Consequently, these genomes help us see which genetic variants were really important to human evolution,” he said.
When they investigated dozens of DNA variants that are unique to H. sapiensincluding in the ancient South African population, researchers have found some related to kidney function and some related to the growth of neurons in the brain. The kidney variants may have evolved to help humans retain or control water in their bodies, while the neuron variants may be linked to attention span, suggesting that humans had better mental capabilities than Neanderthals or Denisovan.
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The new analysis reveals that there is “vast yet unassessed genetic variation in ancient genomes from indigenous peoples globally,” the researchers wrote, which is important for understanding evolution. H. sapiens.
In particular, the presence of human-specific variants in ancient southern Africans lends support to a “combinatorial” genetic model of human evolution, the researchers noted, in which many possible combinations of genetic variants eventually led to “genetically modern” ones. H. sapiens.
“I think it’s certainly possible that humans evolved, at least in part, in multiple places,” Jakobsson said. “How — and if — such a process would have happened, and how it combined genetic variation in genetically modern humans, is an open question.”