This map shows the paths our early ancestors and their descendants took out of Africa as they traveled to populate the rest of the world.

The following is from an IBM press release dated 2 Nov 2011:

Genographic Project Human Map
Through a new analytical method, IBM and the [National Geographic/]Genographic Project find new evidence to support a southern route of human migration from Africa via the Bab-el-Mandeb Strait in Arabia before any movement heading north, and suggest a special role for south Asia in the “out of Africa” expansion of modern humans.