A study provides a window into the first 100,000 years of the history of modern humans.

The real Garden Of Eden has been traced to the African nation of Botswana, according to a major study of DNA.

Scientists believe our ancestral homeland is south of the Zambezi River in the country's north.

The conclusion comes after the study of maternal genetic lineage of anatomically modern humans, finding it was closest to those living in the area, which includes northern Botswana, Namibia to the west and Zimbabwe to the east. Victoria Falls on the Zambezi River in Zimbabwe, Africa Image: The area includes northern Botswana, Namibia to the west and Zimbabwe to the east

For 70,000 years, our ancestors thrived in the area before changes in climate turned what was Africa's largest lake into what is now the Kalahari Desert.

This forced the population to migrate elsewhere between 130,000 and 110,000 years ago.

It also sparked the development of their genetic, ethnic and cultural diversity, the researchers said.

The first group to the northeast, the second to the southwest and the third remained in the area. More from Botswana

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The southwest group, in contrast to the northeast group, seemed to do well, possibly because they were able to adapt to marine foraging. A group of San Bushmen from the Khomani San community practice their hunter-gatherer craft in the Southern Kalahari desert on October 15, 2009 in the Kalahari, South Africa Image: The once verdant region is now part of the Kalahari Desert

The group that remained eventually adapted to the drier land and their maternal descendants can still be found in the Kalahari region today.

Professor Vanessa Hayes, from the Garvan Institute of Medical Research and University of Sydney, and extraordinary professor at the University of Pretoria, led the study.

She said blood samples from volunteers in South Africa and Namibia allowed researchers to compare the DNA code - mitogenome - which she described as "like a time capsule of our ancestral mothers, accumulating changes slowly over generations".

She added: "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."

The study is published in the journal Nature.