Human beings may have had a brush with extinction 70,000 years ago, an extensive genetic study suggests.
The human population at that time was reduced to small isolated groups in Africa, apparently because of drought, according to an analysis released Thursday.
The report notes that a separate study by researchers at Stanford University estimated that the number of early humans may have shrunk as low as 2,000 before numbers began to expand again in the early Stone Age.
"This study illustrates the extraordinary power of genetics to reveal insights into some of the key events in our species' history," said Spencer Wells, National Geographic Society explorer in residence.
"Tiny bands of early humans, forced apart by harsh environmental conditions, coming back from the brink to reunite and populate the world. Truly an epic drama, written in our DNA."
Wells is director of the Genographic Project, launched in 2005 to study anthropology using genetics. The report was published in the American Journal of Human Genetics.
Studies using mitochondrial DNA, which is passed down through mothers, have traced modern humans to a single "mitochondrial Eve," who lived in Africa about 200,000 years ago.