Genetic Research Untangles Africa’s Human Evolutionary History
An international team of anthropologists, archaeologists, and genetic researchers that included 44 scientists from 12 countries has completed a new African genetic research study that reveals more details about the fascinating and complex evolutionary history of Homo sapiens, or modern man within the continent of Africa.
This study focused on ancient DNA of skeletal remains discovered in sub-Saharan Africa and included samples from people who lived as long ago as 18,000 years ago. This is somewhat of a change from the norm, as most previous research has concentrated on skeletal remains found outside Africa, tracing the travels of Homo sapiens as they migrated into Eurasia and other parts of the world between 60,000 and 80,000 years ago.
But the story of human evolution within Africa continued, even after their cousins had departed on their treacherous journeys to explore the rest of the world, as the researchers involved in this landmark African genetic research study just revealed in the Nature journal. The article discloses many enlightening details about the movements of people within Africa during the Upper Paleolithic period, which lasted from 50,000 to 12,000 years ago.
Mota Cave in Ethiopia, where a 4,500-year-old skeleton was discovered by University of South Florida researchers, who were part of the international team that published the African genetic research study in Nature. (University of South Florida)
African Genetic Research Reveals New Perspectives
Relying on an extensive databank of DNA data taken from individuals who lived in Africa in prehistoric times, the genetic scientists were able to detect major demographic shifts that occurred between 80,000 and 20,000 years ago.
By at least 50,000 BC, restless Africans began traveling across their vast continent of origin, seeking new places to explore and settle. This was going on throughout the sub-Saharan African region, causing a mixture of previously separated populations that shook up the gene pool in a dramatic way. This movement of peoples led to the development of new social, cultural, political, and economic alliances, creating diverse and complex cultures that became more active in trade and more interested in sharing ideas and technologies.
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“This pioneering research presents a new perspective on the ancient history of sub-Saharan Africa, allowing us to gain a more complete understanding of human interaction during this time,” said anthropologists and study participants Drs. Kathy and John Arthur, in a statement released by their home institution, the University of South Florida-St. Petersburg.
The latest African genetic research on what happened in Africa after modern man had entered Eurasia focused on remains and artifacts found at these sites in Sub-Saharan Africa. (Nature)
The Largest Database of African DNA Ever Studied
This exhaustive genetic study obtained new data from six individuals whose DNA had not been previously extracted and analyzed. The skeletal remains of these long-deceased men and women were recovered from archaeological sites in Malawi, Tanzania, and Zambia. Dating procedures determined they lived between 18,000 and 5,000 years ago.
Adding further to their database, the researchers retrieved data from other researchers who’d performed genetic tests on the remains of 28 ancient Africans who’d been found at different sites across the continent. Using more up-to-date methodologies, they were able to generate fresh and more comprehensive genetic information from 15 of these individuals.
At the end, the scientists were in possession of the largest DNA database ever assembled for prehistoric African hunter-gatherer populations.
“This more than doubles the antiquity of reported ancient DNA data from sub-Saharan Africa,” said Harvard University professor and co-author Dr. David Reich, in a press release issued by Rice University (Rice personnel contributed to this project). “The study is particularly exciting as a truly equal collaboration of archaeologists and geneticists.”
The DNA samples studied did not extend very far back into the Paleolithic past. But from a near Paleolithic starting point, the genetic experts who participated in this study were able to learn quite a lot about the genetic heritage of these individuals.
Beads made from ostrich eggshell were hot trade items in sub-Saharan Africa 50,000 years ago and were used in the study to show the extent of ancient social networks across the lower part of the continent. (Jennifer Miller / Nature)
About 50,000 years ago, the archaeological record had already made clear that a significant cultural change occurred in sub-Saharan Africa. Beads, pigments, and various types of symbolic art began to be created, and they could be found distributed across a relatively broad geographical space. Researchers had long suspected this was a consequence of mass population movements but had no way to prove it.
"We've never been able to directly explore these proposed demographic shifts, until now," said anthropologist Dr. Elizabeth Sawchuk, a study co-author from the University of Alberta. “It has been difficult to reconstruct events in our deeper past using the DNA of people living today, and artifacts 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.”
Dr. Mary Prendergrast, a Rice University anthropologist who collaborated in the study, links the survival of humans during the last Ice Age to the advantages of forming long-distance travel-and-trade networks.
"Humans began relying on each other in new ways," she noted. "And this creativity and innovation might be what allowed people to thrive."
Based on the patterns of genetic diversity found in the various DNA samples, the researchers were able to show that migrations between regions slowed dramatically starting about 20,000 years ago.
“Our genetic study confirms an archaeological pattern of more local behavior in eastern Africa over time,” said study co-author and Yale University anthropologist Dr. Jessica Thompson. “At first people found reproductive partners from wide geographic and cultural pools. Later, they prioritized partners who lived closer, and who were potentially more culturally similar.”
"Maybe it was because by that point, previously established social networks allowed for the flow of information and technologies without people having to move," Dr. Sawchuk speculated.
The latest study in Nature also revealed that the DNA diversity of sub-Saharan Africa divided into three at some point. (Mopic / Adobe Stock)
There Were Three Population Groups in Paleolithic Africa
There was one significant surprise that emerged from this deep genetics research project. That involved the separation of population groups in Africa during the Middle Paleolithic period.
Previous research had already shown that in the early stages of evolution, Homo sapiens populations in Africa split into two groups. One of these settled in the south of the continent, while the other settled in the east.
But this new study revealed a twist in the story. Genetic traces detected from 200,000 years ago proved that Africans actually split into three groups at this time, with the third settling in the central sub-Saharan region. These various groups became isolated from each other, creating a noticeable level of genetic divergence.
“That does not mean that there weren’t subsequent interactions,” explained Dr. Thompson. “It just wasn’t sufficient to merge the populations back into a homogenous population.”
Comparisons were done between ancient and modern African DNA, and this research confirmed the importance of this ancient separation of peoples.
“Geography is the best predictor of the relative proportions of eastern, central, and southern African ancestry,” Dr. Prendergast explained, in reference to the genetic heritage of current populations.
These three groups remained isolated from each other for more than 100,000 years, building diverse societies and cultures. And then around 50,000 years ago, or perhaps even earlier, they started to migrate between regions. This created a new genetic and cultural mixture, which complicated the picture but did not completely extinguish the differences between peoples who came from the three geographical areas.
Let the Learning Finally Begin
If researchers have their way, this exciting research project will be only a preview of things to come.
"By associating archaeological artifacts with ancient DNA, the researchers have created a remarkable framework for exploring the prehistory of humans in Africa," said Archaeology and Archaeometry program director John Yellen of the U.S. National Science Foundation, which helped fund this research. "This insight is charting a new way forward to understanding humanity and our complex shared history.”
Assuming this new way forward is followed in earnest, it could help correct unfortunate oversights that have left gaps in researchers’ understanding of human genetic diversity.
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“There are around 30 times more published ancient DNA sequences from Europe than from Africa,” Dr. Prendergast lamented. “Given that Africa harbors the greatest human genetic diversity on the planet, we have much more to learn.”
Top image: African genetic research has gone to a new level by looking at what happened in Africa after the Neanderthals and Homo sapiens migrated into Eurasia. Rock painting of humans and antelopes from the Drakensberg mountains, South Africa by the San bushman tribe. Source: EcoView / Adobe Stock
By Nathan Falde