Two pairs of children, who were buried in an ancient rock shelter known as Shum Laka in northwestern Cameroon some 3,000 and 8,000 years ago, have yielded the first ancient human genomic data from the region, where the hot and humid climate has limited the amount of ancient DNA that has survived to see modern sequencers. The results, published today (January 22) in Nature, generated several unexpected conclusions. For one, traditional hunter-gatherer people known as pygmies likely had an expansive range before the explosion of Bantu-speaking groups 3,000 years ago, and for another, modern African groups represent one of the most ancient surviving lineages, dating back to nearly a quarter of a million years ago.
Using samples taken from the inner ear bones of the ancient children, researchers at Harvard Medical School and their colleagues reconstructed two whole genomes and two partial genomes, which the team compared to genomes of living Africans as well as to the genome of 4,500-year-old remains found in a cave in Ethiopia. The data suggest that the children were most closely related to hunter-gatherers of western Central Africa, but carried DNA from other groups as well, including so-called ghost populations of modern humans who died out.
The study offers “a glimpse of a human landscape that is profoundly different than today,” coauthor David Reich, a population geneticist at Harvard, tells Science.
While the genomic information raises more questions than it answers, the researchers’ ability to recover whole genomes from human remains in Central Africa is a promising sign, Princeton University population geneticist Joshua Akey, who was not involved in the study, tells Science. “The future is not as bleak for ancient DNA in these regions [as once thought].”
Uppsala University evolutionary geneticist Carina Schlebusch agrees, telling National Geographic that the new genetic data are a “welcome addition” to the relatively small but growing database of African genomes. But she also emphasizes that the study leaves a lot of room for speculation about the relationships between different ancient and modern African groups. “I think we have a lot more to do, and I don’t think this should be a final verdict.”
Jef Akst is managing editor of The Scientist. Email her at firstname.lastname@example.org.