A study published in the prestigious scientific journal Nature earlier this week supposedly determined that a particular region of southern Africa gave rise to modern humans 200,000 years ago.
DNA mutates over time, and those changes build up at a predictable rate, so geneticists can compare genomes and calculate when they last shared a common ancestor.
The oldest mitochondrial lineage that we know of is called L0, and some of its oldest branches are now found mostly in people who live in southern Africa.
Chan and her colleagues used mtDNA genomes from about 1,200 people with the L0 lineage and used the results to build a "family tree."
Two hundred thousand years ago, paleoclimate records suggest that the area was a lush wetland mostly surrounded by less-inviting arid brushland.
People whose mtDNA belonged to the haplogroups that branched out 130,000 years ago mostly came from northeast of that region, and people with mtDNA from the 110,000-year-old haplogroups mostly came from southwest of the Zambezi basin, along the western coast of South Africa.