And what's true for names is also true for genes, say geneticists.
Amos and Hoffman's study is a controversial one in a controversial field of study. Geneticists vary widely in their interpretation of when and how humans migrated out of Africa -- and exactly what happened once they did. Amos and Hoffman suggest that humans began an exodus from Africa and ran into a bottleneck as they diverged and colonized Europe and Asia.
Robert Eckhardt, a geneticist from Pennsylvania State University, subscribes to a competing theory posed by researcher Alan Templeton of Washington University in St. Louis. Templeton suggests humans moved out of Africa in several major, distinct waves.
This theory contradicts the findings of Amos and Hoffman, who believe that colonists diverged from a single wave of emigrants. According to Templeton, these successive waves mated with the descendants from previous waves, accounting for the loss of diversity.
Eckhardt disagrees with the implications of Amos' and Hoffman's African bottleneck study, though he doesn't dispute their Bering land bridge findings. He is, however, wary of the computer program and raw data used in the study.