Trending Science: Is Botswana the birthplace of humanity?

Our origins can be traced back to the African continent. New research in the journal ‘Nature’ has pinpointed a large wetlands region that spans northern Botswana as the “homeland” of modern humans.

Ancestral home of all modern humans

“It has been clear for some time that anatomically modern humans appeared in Africa roughly 200,000 years ago,” study co-author Prof. Vanessa Hayes, a geneticist at the Garvan Institute of Medical Research in Australia, told the ‘BBC’. “What has been long debated is the exact location of this emergence and subsequent dispersal of our earliest ancestors.” This location is an area south of the Greater Zambezi River Basin that includes northern Botswana and parts of Namibia and Zimbabwe.

According to the paper, our ancestors thrived there for 70 000 years before climate change drove them out of Africa. The researchers collected blood samples from more than 1 200 study participants in Namibia and South Africa and examined their maternal DNA data.

To give a picture of what the African continent might have been like 200 000 years ago, they combined genetics with geology and climate computer model simulations. The research team studied the region itself by analysing the fossil and geologic record. The area held the largest lake system in Africa. These wetlands provided ancient humans with everything they needed to survive. “It’s an extremely large area, it would have been very wet, it would have been very lush,” said Prof. Hayes. “And it would have actually provided a suitable habitat for modern humans and wildlife to have lived.”

This stable environment remained sustainable for 70 000 years. People then moved on in waves between 130 000 and 110 000 years ago when green fertile land began opening up elsewhere. The first wave ventured north-east, while the second travelled south-west. A third population remains there until today. The researchers believe that those who migrated south-west flourished and experienced steady population growth.

“But what we hadn’t known until this study was where exactly this homeland was,” Prof. Hayes told ‘Reuters’. “Our study provides the first quantitative and well-dated evidence that astronomically driven climate changes in the past caused major human migration events, which then led to the development of genetic diversity and eventually cultural, ethnic and linguistic identity,” explained co-author Prof. Axel Timmermann, a climate physicist at Pusan National University in South Korea.

''Homeland'' insecurity

Some experts have raised doubts about the results based on DNA samples. “I’m definitely cautious about using modern genetic distributions to infer exactly where ancestral populations were living 200,000 years ago, particularly in a continent as large and complex as Africa,” Prof. Chris Stringer, who studies human origins at London’s Natural History Museum, told ‘The Guardian’. “Like so many studies that concentrate on one small bit of the genome, or one region, or one stone tool industry, or one ‘critical’ fossil, it cannot capture the full complexity of our mosaic origins, once other data are considered.”

“Drawing sweeping conclusions about places of origin from analyses of this tiny part of the modern genome is deeply problematic and outdated,” noted Prof. Rebecca Ackermann, an archaeologist at the University of Cape Town in South Africa.