Out of Africa and the evolution of human behavior

Twenty-one years ago, a landmark exploration of mitochondrial DNA diversity popularized the idea of a recent African origin for all living humans.1 The ancestral African population was estimated to have existed 200 ka (thousands of years ago) plus or minus a few tens of thousands of years. A corollary was that at some later date the fully modern African descendants of that population expanded to swamp or replace the Neanderthals and other nonmodern Eurasians. The basic concept soon became known as “Out of Africa,” after the Academy Award winning film (1985) that took its title, in turn, from Isak Dinesen's classic autobiography (1937). Many subsequent genetic analyses, including those of Ingman and coworkers2 and Underhill and coworkers,3 have reaffirmed the fundamental Out of Africa model. The fossil and archeological records also support it strongly. The fossil record implies that anatomically modern or near-modern humans were present in Africa by 150 ka; the fossil and archeological records together indicate that modern Africans expanded to Eurasia beginning about 50 ka.