Genetic evidence on modern human origins.

A review of genetic evidence leads to the following conclusions concerning human population history: (1) Between 33,000 and 150,000 years ago the human population expanded from an initial size of perhaps 10,000 breeding individuals, reaching a size of at least 300,000. (2) Although the initial population was small, it contained at least 1000 breeding individuals. (3) The human races separated several tens of thousands of years before their separate expansions. (4) Before their expansions the separate racial populations were small. These inferences are inconsistent with both the multiregional and the replacement models of modern human origins. They support the "weak Garden of Eden" hypothesis, which holds that the human populations separated some 100,000 years ago but did not expand until tens of thousands of years later.