The prehistoric past of Africa is a complex, migratory mystery that has intrigued anthropologists for decades.
In a one-of-a-kind study, an international team of researchers reports that they have retrieved DNA from the bone fragments of 16 African individuals who lived up to 8,100 years ago.
Their findings, published in the journal Cell, unearth surprising details about Africa’s prehistoric past and the migrations that shaped the continent’s population today.
"The last few thousand years were an incredibly rich and formative period that is key to understanding how populations in Africa got to where they are today," said senior author David Reich, professor of genetics at Harvard Medical School, in a statement. "Ancestry during this time period is such an unexplored landscape that everything we learned was new."
The difficulty with this type of research is the climate – while the Siberian tundra preserves fossils well, the hot, humid climate of Africa quickly degrades genetic material.
Now, technological advances are breaking through this barrier and revealing a history more complex and compelling than previously believed.
"We are peeling back the first layers of the agricultural transition south of the Sahara," said Pontus Skoglund, a postdoctoral researcher in the Reich lab and first author of the study. "Already we can see that there was a whole different landscape of populations just 2,000 or 3,000 years ago."
The team was helped along by the fact that they searched for these skeletons not in the humid lowlands of Malawi, but in the cooler highlands where caves punctuate the landscape.
They also culled material from previous discoveries and museum collections to uncover a more sweeping tale.
Snapshot From Malawi Skeletons
Around half of the DNA the team analyzed came from skeletons in Malawi, including the oldest at 8,100 years. These samples were not taken from a single moment in time, but instead represent a genetic snapshot that spans thousands of years.
With the spread of agriculture, farmers and animal herders moved into new areas. This is as expected. However, it seems that once farmers reached Malawi, hunter-gatherers disappeared without an ancestral trace to the people who live there today.
"It looks like there was a complete population replacement," said Reich. "We haven't seen clear evidence for an event like this anywhere else."