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. read more at edition.cnn.com