Ancestral homeland of modern humans in Botswana, study finds

Region south of the Zambesi river was once home to a enormous lake, roughly twice the area of modern-day Lake Victoria.

    The sun rises behind a Baobab tree in northern Botswana. Researchers say they have traced the origin of modern humans back to an area in Botswana south of the Zambesi River. [File: Mike Hutchings/Reuters]
    The sun rises behind a Baobab tree in northern Botswana. Researchers say they have traced the origin of modern humans back to an area in Botswana south of the Zambesi River. [File: Mike Hutchings/Reuters]

    Scientists claim they have traced the homeland for all modern humans to a region of northern Botswana, south of the Zambezi River. 

    The area is now salt pans, but 200,000 years ago it was home to Homo Sapiens and hosted a population of modern humans for at least 70,000 years, according to a  study released in the scientific journal Nature on Monday.

    The group remained in the region until regional climate changes led them to migrate, roughly 130,000 years ago, first to the northeast then to the southwest.

    "We've known for a long time that modern humans originated in Africa roughly 200,000 years ago," Vanessa Hayes, from the Garvan Institute of Medical Research and the University of Sydney said.

    "But what we hadn't known until the study was where exactly this homeland was."

    The area identified in the study was called Makgadikgadi-Okavango, once home to an enormous lake, roughly twice the area of modern-day Lake Victoria.

    Genetic map 

    Scientists reached their conclusions after analysing DNA samples from 200 Khoisan people, an ethnic group living in modern-day South Africa and Namibia known to carry a high proportion of a branch of DNA known as L0.

    Researchers then combined the DNA samples with geographical distribution, archaeological and climate change data to come up with a genomic timeline that suggested a sustained lineage of L0 stretching back 200,000 years. 

    Their work created a kind of genetic map tracing L0 lineage to show that prehistoric humans lived in the region for about 70,000 years before they dispersed throughout the world.

    "Every time a new migration occurs, that migration event is recorded in our DNA as a time-stamp," Hayes told AFP news agency.

    "Over time our DNA naturally changes, it's the clock of our history."

    Botswana map
    Scientists say their work shows the origin of modern humans to Botswana, south of the Zambezi River. [Al Jazeera]

    Modern humans

    Although there have been humanoid fossil remains believed to pre-date the 200,000-year benchmark named in the study, the team said their study of L0 data allows us to trace our lineage directly back to the region south of the Zambezi river.

    "We're talking about anatomically modern humans, people living today," said Hayes.

    "Everyone walking around today... it does actually come back to L0 being the oldest, and it all comes back to this one (region)."

    The team said they wanted to collect more DNA samples to help refine their methods and better reconstruct the history of the first movements of our earliest ancestors.

    Doubts about study

    However, some researchers were not convinced by the study's findings.

    Chris Stringer, who researches human evolution at the Natural History Museum in the UK, says the study of human origins is complex.

    "I am very 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," he said in a statement posted on Twitter.

    "Moreover, 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," he said.

    He noted that other studies have suggested that our origins may be linked to West Africa and East Africa, not Southern Africa.

    SOURCE: Al Jazeera and news agencies