Africa’s Kalahari Desert, cradle of modern humans, Sydney scientists say
Professor Hayes was among the first team to sequence the complete DNA, known as the genome, of five native Africans.
“Europeans and Asians today are so connected to each other,” she says. “We went through such a big genetic bottleneck when we left Africa. All we did was study a very small branch of a very large genetic tree.
Following the publication of this work, Professor Hayes continued to sequence the DNA of indigenous groups in Africa, dividing her time between the Kalahari and its bases at the Garvan Institute in Australia and the University of Sydney.
She has followed the trail of mitochondrial DNA, which is passed on unchanged from mother to child, in the hope of tracing the thread back to our earliest female ancestors.
This led her first to the Kalahari Desert and then to the Khoesan (pronounced koh sahn) people, a group identified by their use of clickable language.
“They represent a lineage that has never left the homeland,” says Professor Hayes.
She spent time with a Khoesan group, the Ju / ‘hoansi. They live as hunter-gatherers, just like their ancestors.
When she told them their DNA suggested their people were the ancestors of modern humans, they weren’t surprised. Their oral histories record them alive in the region forever.
“They know they’ve always been there,” Professor Hayes says.
On the edge of the lake
Today the Kalahari is dry.
But hundreds of thousands of years ago, according to climate modeling, the area was lush, humid, and dominated by Lake Makgadikgadi, a giant lake twice the size of Lake Victoria in Africa.
As modern humans began to emerge, Makgadikgadi crumbled into a series of smaller wetlands that were said to be teeming with life; “A perfect oasis for modern humans,” says Professor Hayes.
Around the wetland, Africa was dry. But 130,000 years ago, changes in Earth’s climate would have brought heat and rain to a corridor that ran from the northeast wetland to the coast. This would have provided food and water for some members of the group to migrate.
These are the people who would learn to cross the water and later to sail to conquer the rest of the world.
It’s a neat and comprehensive origin story.
But Professor David Lambert, one of the leading researchers in human evolution and indigenous DNA at the Australian Research Center for Human Evolution, fears the evidence is not strong enough to support these claims.
“The authors analyzed the mitogenomic variation – a single genetic locus that is inherited only by the female line – in conjunction with the estimated mutation rates to then calculate the times of divergence between the lines,” he said. .
“However, there are many concerns about the quality of this approach to recover the pattern and timing of population movements over time.”
In a press release published with the study, Nature says the research identifies the ancestral homeland of all humans.
But the last paragraph of the article notes that the evidence cannot rule out the possibility that modern humans evolved at similar times in different places across Africa before interbreeding.
This would mean that the Kalahari is only one of many homelands.