Our story – the story of humans – is still remarkably hazy. We're fairly certain that modern humans originated roughly 200,000 years ago in Africa. However, it’s long remained a mystery where exactly this momentous change took place.
A new study has now claimed that the ancestral homeland of all humans alive today can be found south of the Zambezi River in present-day Botswana, southern Africa.
Based on the oldest confirmed human skeletal remains, it was long thought that Homo sapiens emerged in the Horn of Africa, in the northeast of the continent. On the other hand, there's also been a competing school of thought that says modern humans first appeared in southern Africa. While it's still possible that anatomically modern humans emerged elsewhere and later went extinct, this new research argues that all human lineages alive today can be traced back to this basin of southern Africa. However, the findings have drawn skepticism from some other scientists in the field.
"As the data sits today – and the data is very thorough – it is pointing to southern Africa as the homeland of people living today," study author Professor Vannessa Hayes, of the Garvan Institute of Medical Research, said at a live-streamed press conference.
Reporting in the journal Nature, a team of Australian scientists traced back the human story by looking at mitochondrial DNA passed down the maternal line from mother to offspring. One of the oldest known lineages can be found in the haplogroup L0. The L0 lineage is still found today most commonly in sub-Saharan Africa with the highest frequency in the Khoisan, an indigenous population of hunter-gatherers living in regions of Botswana, Namibia, Angola, Zambia, Zimbabwe, Lesotho, and South Africa.
By looking for the lineages within the genetic code of mitochondria from 1,000 living southern Africans – together with a huge amount of linguistic, cultural, geographic, and archaeological data – the researchers honed in on where the base of the family tree emerged.
Through their analysis, they managed to pinpoint a region south of the Zambezi River, more specifically the Greater Zambezi River Basin region near the ancient Lake Makgadikgadi (map below). Today, this region is a harsh land of dry desert and salt plains. However, when our human ancestors were first emerging, it was a lush wetland surrounding a colossal body of water larger than Lake Victoria.
As per their findings, it's said that humans emerged, lived, and thrived here for some 70,000 years. Then, around 130,000 to 110,00 years ago, something big happened. The human population living near Lake Makgadikgadi suddenly embarked on two huge migrations due to changing climate conditions.
“Our simulations suggest that the slow wobble of Earth’s axis changes summer solar radiation in the Southern Hemisphere, leading to periodic shifts in rainfall across southern Africa,” study author Professor Axel Timmermann, director of the IBS Center for Climate Physics at Pusan National University, explained in a press release.
“These shifts in climate would have opened green, vegetated corridors, first 130,000 years ago to the northeast, and then around 110,000 years ago to the southwest, allowing our earliest ancestors to migrate away from the homeland for the first time.”
However, some scientists in the field have criticized the study's conclusions. Carina Schlebusch, a geneticist at Uppsala University who specializes in southern Africa, told The Atlantic: "The conclusions are far-fetched and very much overstated. It tells us very little about human origins as a whole. It only tells us about the origin of a very small part of the human genome, and nothing more.”
While undoubtedly an interesting piece of research, it looks like the story of our past remains as unsure and complex as ever.