The Sahara Desert hasn't always been the dry and arid landscape it is today. © Atosan/ Shutterstock
Today, the Sahara Desert is a hot and dry belt of sand stretching across much of northern Africa.
But between 15,000 and 5,000 years ago it would have been full of rivers, plants and people. New research is shedding light on the lives of these ancient humans.
Around 50,000 years ago, Homo sapiens made its main migration out of Africa. But what happened to the people who stayed behind?
New research, based on skeletons found in southwest Libya, is helping to answer this question. Ancient DNA from the Takarkori rock shelter has revealed an isolated group of humans who lived for tens of thousands of years in northern Africa.
While their relatives spread around the world and mixed with many different human populations and species, the people living at Takarkori remained isolated. It was not until the Sahara Desert became a green savannah 14,500 years ago that the group mixed with humans moving in from other regions of Africa and Asia.
PhD student Nada Salem, who led the study published in Nature, says that the legacy of this group lives on in modern north Africans today.
“Our research challenges previous assumptions about North African population history and highlights the existence of a deeply rooted and long-isolated genetic lineage,” Nada says. “This discovery reveals how pastoralism spread across the green Sahara, likely through cultural exchange rather than large-scale migration.”
Dr Savino di Lernia, the study’s senior author, adds, “the study highlights the importance of ancient DNA for reconstructing human history in regions like Central Northern Africa, providing independent support to archaeological hypotheses.”
The Takarkori rock shelter was used for ancient human burials for over 4,000 years. © Archaeological Mission in the Sahara, Sapienza University of Rome
The study of ancient DNA from prehistoric humans has revolutionised what we know about our past. It’s allowed researchers to better understand when and where our species evolved, as well as to identify our distant relatives.
Unfortunately, it has its limitations. One key issue is that DNA tends to break down faster in warmer regions. This makes it much less likely that any genetic material will be found in bones from deserts and rainforests.
But in the cool and dark places found in these regions, like caves and rock shelters, ancient DNA can survive. The Takarkori rock shelter in Sahara of southern Libya has preserved the graves of 15 women and children buried there between 8,900 and 4,800 years ago. This was towards the end of the period when the Sahara was flourishing with grasslands, woodlands and wetlands.
While previous research on these remains has focused on their mitochondrial DNA, which is passed down from mothers to their children, no one had yet looked at the nuclear DNA of each individual. This provides a much deeper insight into a person’s ancestry, as well as the population they were part of.
The skeletons at Takarkori still preserve DNA that can be studied by scientists. © Archaeological Mission in the Sahara, Sapienza University of Rome
The researchers managed to extract DNA from the teeth and bones from two of the burials. They found that as humans migrated out of Africa around 50,000 years ago, one population split off and became the ancestors of those now buried in the Takarkori rock shelter.
Over the following tens of thousands of years, the genetics of the Takarkori population show very little signs of change. During this time, the Sahara would have been similar to modern day areas like the Maasai Mara in Kenya. As a savannah criss-crossed with rivers, the Sahara would have been home to a wide variety of wildlife.
While it might be expected that this lush environment would have allowed humans living south of the Sahara to move north and mix with the Takarkori population, there’s no genetic evidence for this. Instead, their genetics only changed relatively recently.
It is thought that, around 8,000 years ago, herders descended from the out-of-Africa migration arrived back in the continent through the Sinai Peninsula, followed by early farmers from southwestern Europe around 1,000 years later. These people then mixed with the isolated Takarkori population, leaving their genetic signature behind.
This included small amounts of Neanderthal DNA, which their ancestors had inherited during the migration out of Africa. As a result, while other populations of African decent have little to no Neanderthal DNA, the Takarkori genome contains around 0.15%.
Other changes to the population are thought to have happened culturally rather than genetically. For example, the Takarkori people are believed to have practiced pastoralism, which is when large herds of animals are moved between different grazing areas across huge distances.
These practices arrived in the region from the eastern Mediterranean around 6,400 years ago. But as there is no simultaneous increase in the genetic signatures of Mediterranean farmers, it seems that these different populations exchanged ideas when they came into contact, rather than DNA.
As new fossils are found and genetic sequencing becomes more advanced, the scientists hope that they’ll be able to build up an even more detailed picture of ancient human life in Africa’s distant past. This could better explain our human origins, and narrow down key timings in the evolution of our species.
Museum science is helping to answer where, when and how humans evolved.
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