Revealed: first DNA profiles of ancient people who roamed a lush Sahara

The genomes of two women who lived 7,000 years ago in the Sahara when it was a green savannah reveal a remarkably isolated population

Green oasis: during a time known as the African Humid Period, it’s thought that the Sahara was a lush savannah.Credit: Henrik Karlsson/Getty

The Sahara Desert has not always been the arid, inhospitable landscape we know today. Between 14,500 and 5,000 years ago, the area was unrecognizable, transformed into a lush savannah by an unusually wet interval called the African Humid Period. People roamed this green landscape for thousands of years before it was again lost to sand.

Ancient DNA extracted from two women who died in what is now Libya around 7,000 years ago is now helping researchers to reconstruct the origins of these early Saharans. The women’s DNA profiles, described in a study published on 2 April in Nature¹, represent the first full Saharan genomes from the African Humid Period — and reveal that the people were remarkably isolated from other African populations.

“The prehistory of North Africa is a big puzzle, and we only have a few pieces available,” says Rosa Fregel, a geneticist at the University of La Laguna in San Cristobal, Spain, who was not involved in the research. The work is “a significant contribution to the palaeogenomics of North Africa”, she says.

Precious genomes

Ancient genomes from North Africa are hard to come by. Almost all palaeogenetic work is concentrated in Europe and Asia. Ancient DNA is especially rare in the Sahara, where high temperatures and strong ultraviolet light quickly degrade genetic material in remains.

The Takarkori rock shelter in Libya, where the remains were unearthed.Credit: University of Rome La Sapienza

That’s why it’s important to explore sites that are protected from the elements, says Nada Salem, an archaeologist at the Max Plank Institute for Evolutionary Anthropology in Leipzig, Germany.

One such site is the Takarkori rock shelter in southwestern Libya. Between 2003 and 2007, archaeologists uncovered the remains of 15 people who were buried between 8,900 and 4,800 years ago at Takarkori. Two of the corpses — both belonging to women who lived between 7,000 and 6,000 years ago — had naturally mummified.

Archaeological evidence at the site suggested that the Takarkori women belonged to a group of herders who appeared in the region around 8,000 years ago. This marked a major transition in the way of life of early Saharans, who had previously all been hunter-gatherers. Some researchers have suggested that Saharans learnt herding by intermarrying with people who were migrating into North Africa from the Levant.

To test this, Salem and her colleagues sequenced the Takarkori genomes and compared the DNA to that of around 800 modern humans and 117 ancient genomes from around Africa, southern Europe and the Middle East. The team found that the Takarkori women had only small traces of Levant ancestry — suggesting that any intermingling had happened long before the advent of herding in the region.

What’s more, the analysis struggled to connect these early Saharans to any other ancient group. “This was puzzling for us. How is it that this lineage has not spread either to the east or the west or to the south?” says Salem.