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Africa is the cradle ofHomo sapiens and it harbors the greatest human genetic diversity than any other part of the planet. Studies ofAncient DNAof its archaeological sites can shed light on theoldest origins of mankind. However, they remain in short supply, in part due to the challenge of extracting DNA from degraded skeletons in tropical environments.
Now, an interdisciplinary and international team with the participation of the Institute of Evolutionary Biology (IBE), a joint center of the Higher Council for Scientific Research (CSIC) and the Pompeu Fabra University (UPF) in Barcelona, has rebuilt the complete ancient genome of four childrenburied in the rocky shelterShum LakainCameroon, between 8,000 years and 3,000 years ago, during the transition from the Stone Age to the Iron Age. This region is considered the cradle of the Bantu languages, the most diverse and extensive group of African languages.
The study, published in the journalNature and with the participation of the IBE researcher Carles Lalueza-Fox, it shows that there were at leastfour lineages important in the history of thehumanity, between 300,000 and 200,000 years ago. This branching had not been previously identified from genetic data.
The find reinforces the argument recently made by archaeologists and geneticists that human origins in Africa may have involveddeeply divergent populations and geographically separated.
The results suggest that the lineages leading to the hunter-gatherers of central Africa, those of southern Africa, and all other modern humans diverged in close succession around 250,000 and 200,000 years ago.
"Our analysis indicates the existence of at least four great deep human lineages that contributed to today's populations, and that diverged from each other about 250,000 to 200,000 years ago," he says.David reich from Harvard Medical School, responsible for the study.
The fourth lineage was a population "ghost"Previously unknown that contributed a small amount of ancestry to both West and East Africa. "This quadruple radiation, including the location of a deeply divided modern phantom human lineage, had not been identified before from DNA," Reich continues.
According to Carles Lalueza-Fox, the genomic analysis of ancient and current African populations denies the conclusions of previous works based solely on the analysis of mitochondrial DNA, and shows that the origin of our species was a much more complex phenomenon than we thought.
A rare lineage of paternal inheritance
In the region where the site is located, researchers suspect that the Bantu languages and cultures, the most widespread and diverse group of languages in Africa today. The spread of the Bantu languages and the groups that spoke them in the past 4,000 years are believed to explain why most people in Central, Eastern and Southern Africa are closely related to each other and to West and Central Africans.
While the findings of the work do not speak directly to the origins of the Bantu language, they do shed light on themultiple phases of historyoldest ofHomo sapiens. The researchers examined the DNA of children fromShum Laka along with the published DNA of ancientHunter-gatherersfrom eastern and southern Africa, as well as the DNA of many contemporary African groups. By combining these data sets, they were able to build a model of divergent lineages in the course of the human past.
Surprisingly, the sequenced ancient DNA of the four children reveals aancestryvery different from that of most Bantu speakers today. Instead, they are more similar to the hunter-gatherers of central Africa.
One of the individuals in the Shum Laka sample, amaleAs an adolescent, he carried a rare Y chromosome haplogroup (A00) that is found almost nowhere outside of western Cameroon today. A00 is best documented among the Mbo and Bangwa ethnic groups living near Shum Laka, and this is the first time it has been found in ancient DNA.
It's about ahaplogroupdeeply divergent, splitting from all other known human lineages around 300,000 years ago. This shows that this oldest known lineage of modern human males has been present in central and western Africa for more than 8,000 years, and perhaps much longer.
"This result suggests that the Bantu speakers living today in Cameroon and throughout Africa are not descended from the population to which the Shum Laka children belonged," he says.Mark Lipson from Harvard Medical School, lead author of the study. "This underscores the ancient genetic diversity in this region and points to a previously unknown population that contributed only small proportions of DNA to current African groups," he adds.
The spread of thefarmingand thegrazingin Africa, as in other parts of the world, it was accompanied by many population movements. "If you look back 5,000 years, practically all the inhabitants south of the Sahara were hunter-gatherers," the authors comment. "But if you look for them today, you will see that they are very few and scattered among them," they emphasize.
This study contributes to a growing body of ancient DNA research that could decipher ancient genetic diversity and the structure of populations that have been obliterated by the demographic changes that accompanied the spread of food production.
"The results highlight how the human landscape in Africa a few thousand years ago was profoundly different than it is today, and emphasize the power of ancient DNA to unravel the human past behind population movements," Reich concludes.
Mark Lipson, et. to the. "Ancient West African foragers in the context of African population history"Nature January 2020. DOI: 10.1038 / s41586-020-1929-1.