Most people accept that anatomically modern humans first arose in Africa roughly 200,000 years ago, but the location where that monumental evolutionary event took place on the continent has been less certain. Now, a new study in the journal Nature purports to know the original, ancestral homeland of all humans roaming the planet today.
Vanessa Hayes and her colleagues used timeline, ethno-linguistic, and geographic frequency distribution data from more than 1,000 mitogenomes ( mitochondrial DNA ) from living southern Africans who have mostly lived in geographical isolation and combined that information with climatic reconstructions of the region south of the Zambezi River, in northern Botswana, from when anatomically modern humans (AMH) arose. They say the results of their study suggest that “the founder population of all modern humans possibly emerged in the Makgadikgadi–Okavango palaeo- wetland of southern Africa.”
And they are calling that the “ancestral homeland of all humans alive today.”
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Schematic map of southern Africa representing the AMH homeland and out of homeland migration and divergence. ( V. Hayes et al )
What is the Genetic Evidence They Used?
Although fossil finds often point to an eastern African origin for AMH, the researchers say that the area their genetic analyses suggest they should focus on is southern Africa.
In a press briefing on October 24, researchers said, “the mitochondrial DNA is all pointing to one region,” which they say the data suggests is south of the Zambezi river in Africa. They write in the Nature study that they have generated “one of the largest resources of the poorly represented and deepest-rooting maternal L0 mitochondrial DNA branch […] from contemporary southern Africans and show the geographical isolation of […] Khoesan descendants south of the Zambezi river in Africa.” And during the press briefing, researchers declared they “believe we were all Khoesan at one stage.”
"Khoisan engaged in roasting grasshoppers on grills" (1989 caption) 1805 aquatint by Samuel Daniell.
The genetic aspect of the study shows that the L0 lineage first arose in the Makgadikgadi–Okavango paleo-wetland of southern Africa approximately 240,000-165,000 years ago and remained in that area for about 70,000 years before migrating in the northeast and southwest directions.
Why Did We Leave Our ‘Ancestral Homeland’?
In their study, the researchers describe the current region of the living AMH “ancestral homeland” as an area “dominated by desert and salt pans.” But their computer model simulations of the region suggest that when the AMH ancestors lived in the area 200,000 years ago it was a vast wetland oasis, surrounded by a dry area, that hit it’s driest period roughly 180,00-160,000 years ago. Nonetheless, Axel Timmermann stated that their climatic reconstructions show that rivers were “still flowing into this vast terrain, still providing water resources for this early homeland and for hunter-gatherers to essentially look for their prey.”
Botswana Okavango Delta. (youngrobv/ CC BY NC 2.0 )
That environment is believed to have started to change about 130,000 years ago, so AMH decided it was time to explore and find some new places to live. The researchers’ reconstructions of the climate at that time show humidity levels increased and there were new green ‘corridors’ that emerged to entice people to explore new lands outside of the homeland – first to the northeast and then to the southwest. Essentially, the dry land barrier that was keeping people in the homeland was broken by these new ‘green corridors’, enabling the hunter-gatherers to spread out .
What About AMH Fossils Not Found in the Region?
It’s an interesting idea, but it has certainly created controversy. One of the big questions is related to all the prehistoric fossils found in other regions that may be early examples of AMH, such as the 300,000-year-old Homo sapiens remains that were discovered in Morocco in 2017. In light of these fossils, it makes sense that researchers will feel uneasy about the declaration that AMH have their ancestral homeland in Southern Africa.
And that’s where it’s important to note that the researchers haven’t stated that other AMH groups didn’t exist in other regions and possibly even before 200,000 years ago. In fact, they believe it’s possible other groups did exist, but their genes may not have survived. In a statement during the press briefing, it was made clear that the researchers’ focus was trying to find the ancestral homeland of “a founder population” for people who are walking the earth today.
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They also stated in the press briefing that it would be interesting to look into the genetic similarities and differences of their research with ancient fossils that have been found in areas like Morocco, in fact, Hayes stated that she would “love for someone to be able to get DNA from the skeleton to get a better picture of how people living today fit into the big picture.” Without having the genetic information of those remains, they cannot truly be certain if those remains are related to people living today or not.
‘The pan-African dawn of Homo sapiens’ CREDIT: (GRAPHIC) G. Grullón/Science ; (DATA) Smithsonian Human Origins Program; (PHOTOS, COUNTERCLOCKWISE FROM TOP LEFT) Ryan Somma/Wikimedia Commons; James Di Loreto & Donald H. Hurlbert/Smithsonian Institution/Wikimedia Commons; University of the Witwatersrand; Housed in National Museum of Ethiopia, Addis Ababa, Photo Donation: ©2001 David L. Brill, humanoriginsphotos.com
As this and other studies are being conducted and shared, we will certainly find more debate and controversy surrounding human evolution . These certainly are exciting times for discovering more about our ancient origins!