Humanity was born in a fertile river valley in northern Botswana. A new study published in the journal Nature reveals that the earliest anatomically modern humans (Homo sapiens) arose 200,000 years ago in a vast wetland south of the Zambezi river. It has been called by the team working on the project the "cradle of mankind."
The region – which also covered parts of Namibia and Zimbabwe – was home to an enormous lake which sustained our ancestors for 70,000 years.
“It has been clear for some time that anatomically modern humans appeared in Africa roughly 200,000 years ago. What has been long debated is the exact location of this emergence and subsequent dispersal of our earliest ancestors,” said Professor Vanessa Hayes, a geneticist at the Garvan Institute of Medical Research in Australia and the lead researcher on this project.
To determine the precise location, Professor Hayes and her colleagues collected blood samples from study participants in Namibia and South Africa and looked at their mitochondrial DNA (mtDNA). mtDNA is passed almost exclusively from mother to child through the egg cell and its sequence stays the same over generations, making it a useful tool for looking at ancestrial roots.
The team focused their research on the L0 lineage – modern human’s earliest known population – and compared the complete DNA code (mitogenome) from different individuals. The researchers then combined genetics with studies of geology and climate predictions to help create a picture of what the world looked like 200,000 years ago. Geological evidence suggests the region once housed Africa’s largest ever lake system, ideal for early survival. Eventually climate change made travel easier for early humans to trek farther away. Professor Axel Timmermann, a climate scientist at Pusan National University in South Korea, said: “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.”
Professor Hayes said: “We observed significant genetic divergence in the modern humans’ earliest maternal sub-lineages that indicates our ancestors migrated out of the homeland between 130,000 and 110,000 years ago.
“The first migrants ventured northeast, followed by a second wave of migrants who travelled southwest. A third population remained in the homeland until today.”