The "Out of Africa" theory is used in paleoanthropology to explain the geographic origin of modern day humans, and it asserts that modern humans evolved recently in Africa and migrated out into Eurasia, replacing all the regions that were once populated by lineages connected to Homo erectus. In the mainstream press, this theory goes by the moniker the "recent out of Africa model," but in academic literature, it is usually referred to as "recent single-origin hypothesis," "replacement hypothesis," or the "recent African origin" model.
While the "Out of Africa" theory states that the Homo sapien species arose solely in the African continent and subsequently replaced the Homo erectus species, there are other competing theories, such as the multiregional continuity model. This model postulates that all living humans come from the Homo erectus species, where evidence suggests this species also migrated out of Africa millions of years ago. The multiregional model also believes that the rise of the Homo sapien species did not occur from one specific geographic region, such as Africa, but instead occurred everywhere through the process of gene flow and natural selection. It also believes that this is what contributed to the variations seen in the human race. However, the "Out of Africa" theory challenges that the modern human variation is a more recent phenomenon and cannot be explained by multiregional gene mixing.