Ancient DNA reveals how early African foragers lived, travelled and created

Around 50,000 years ago, there was an explosion of artistry in Africa; beads, pigments and other symbolic art-forms were all widely produced. Scientists have long thought this profusion of art must reflect a shift in social networks, and perhaps even changes in population size – but before now, there was no genetic data to explain it. 

Now, a new genetic analysis of human remains buried on the continent over the last 18,000 years has demonstrated that 50,000 years ago, people began to move across the continent, developing regional networks and alliances – coinciding strikingly with the artistic bloom that happened at the time.

The research, published today by an international team of researchers in Nature, provides an unprecedented window into this ancient cultural golden-age. 

Ostrich eggshell beads. Image jpeg
Ostrich eggshell beads from Mlambalasi Rockshelter in Tanzania, where one of the individuals in the study was buried. Credit: Jennifer Miller.

The study involved an international team of 44 researchers, experts in both genetics and archaeology, who examined the miraculously well-preserved DNA of six individuals buried in Malawi, Tanzania and Zambia, who lived between 18,000 and 5,000 years ago.

“This more than doubles the antiquity of reported ancient DNA data from sub-Saharan Africa,” says David Reich, a professor at Harvard University and investigator at the Howard Hughes Medical Institute, whose lab generated the data in the paper. 

The study also reanalysed published data from 28 individuals buried across the continent. 

The result: an epic dataset of DNA from ancient foragers on the continent that reveals how they lived, moved and interacted over the last 80,000 years.

So, why do you need an 18,000-year-old skeleton to study a 50,000-year-old society?

To understand long-ago societal ebbs and flows, scientists had to look at ancient DNA, because present-day populations in Africa carry the impacts of more modern migrations and movements in their genes.

What did they find?

Around 50,000 years ago, people from different corners of the continent began to move and settle in other areas, build alliances and find partners through long-distance social networks. 

“We’ve never been able to directly explore these proposed demographic shifts, until now,” says study co-author Elizabeth Sawchuck, a professor at Stony Brook University and postdoctoral fellow at the University of Alberta, Canada. “It has been difficult to reconstruct events in our deeper past using the DNA of people living today, and artefacts like stone tools and beads can’t tell us the whole story. 

“Ancient DNA provides direct insight into the people themselves, which was the missing part of the puzzle.”

Mary Prendergast, a co-author and associate professor of anthropology at Rice University, US, says it’s possible this upsurge in movement and the establishment of long-distance trade networks might have helped people weather the last Ice Age.

“Humans began relying on each other in new ways,” she says. “And this creativity and innovation might be what allowed people to thrive.”

Mt. Hora in malawi. Image jpeg
Mt. Hora in Malawi, where recent excavations at Hora Rockshelter uncovered two of the individuals analyzed in a collaborative study of ancient DNA. Credit: Jacob Davis.

But the genes also signify another change: around 20,000 years ago, movement on the continent slowed dramatically.

“Maybe it was because by that point, previously established social networks allowed for the flow of information and technologies without people having to move,” Sawchuk suggests.

From then on, forager groups remained relatively stable genetically, and life become more local. 

“Our genetic study confirms an archaeological pattern of more local behavior in eastern Africa over time,” said Jessica Thompson, an assistant professor of anthropology at Yale University and author of the study, who helped uncover the remains. “At first people found reproductive partners from wide geographic and cultural pools. Later, they prioritised partners who lived closer, and who were potentially more culturally similar.” 

Potiphar Kaliba, director of research at the Malawi Department of Museums and Monuments and a co-author of the study, says some of the skeletons sampled were excavated fifty years ago, but their DNA was extraordinarily well-preserved despite the hot and humid conditions in the country.

“This work shows why it’s so important to invest in the stewardship of human remains and archaeological artefacts in African museums,” Kaliba says.

And Prendergast says the work goes some way to addressing a chronic imbalance in genetic research, a field that has tended to prioritise decoding ancient European genomes.

“There are around 30 times more published ancient DNA sequences from Europe than from Africa,” she says. “Given that Africa harbours the greatest human genetic diversity on the planet, we have much more to learn.”

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