This is the first time researchers have done an in-depth analysis of ancient DNA from western Central Africa.
During the Stone Age in what is now western Cameroon, four children who perished before their prime were buried in a natural rock shelter. Now, thousands of years later, an analysis of the ancient DNA found in their bones has revealed secrets about the people who lived there many millennia ago, according to a new study.
Perhaps the most surprising finding is that these children are not related to the modern-day Bantu-speaking cultures that reside in the region today, the researchers said. Rather, the Stone Age youngsters are genetically closer to the present-day hunter-gatherer groups of Central Africa, which are not closely related to Bantu speaking groups, the researchers found.
This realization and others, including that a previously unknown “ghost” population contributed genetically to the people who live in Africa today, is shedding light on what is still the most genetically diverse region for humans in the world today, the researchers said.
The genetic analyses revealed a handful of other findings about the ancient people of Cameroon. For instance, one of the boy’s genomes revealed that he had the oldest branch of the Y chromosome, which shows that the oldest lineage of human males was present in Cameroon for at least 8,000 years, and possibly much longer, the researchers said.
The children’s genomes also showed signs of admixture, suggesting that the children’s ancestors mated with people from different populations, the researchers found.
In addition, the analysis suggests that there are at least four major human lineages, which date to between 200,000 and 300,000 years ago. This realization is unique to this dataset, and hasn’t been found from previous genetic studies, the researchers said.
The scientists also found another set of four sub-branches of human lineages that date to between 60,000 and 80,000 years ago. This includes the lineage that gave rise to all modern non-Africans, the researchers said.
“It is a nice paper and it is a welcome addition to the growing aDNA [ancient DNA] database of Africa,” Schlebusch said. “It is especially valuable to get aDNA from West Africa, where it is well know[n] that the preservation of human remains [is] very bad due to the acidic soils.”
That said, the researchers could have done even more with their unique dataset, she said. For instance, they could have visualized effective population sizes over time, Schlebusch said. She added that “the findings regarding the deep African population structure are interesting, but we definitely need more testing of possible models and most probably more aDNA results before we will be able to disentangle signals.”
The study, led by scientists at Harvard Medical School, was published online today (Jan. 22) in the journal Nature.