The "recent African origin" of modern humans means "single origin" (monogenism) and has been used in various contexts as an antonym to polygenism. The debate in anthropology had swung in favour of monogenism by the mid-20th century.OverviewThe recent African origin of modern humans or the "Out of Africa" theory (OOA) holds that present-day humans outside Africa descend mainly from a single expansion of ( "Recent African origin", or Out of Africa II, refers to the migration of () out of Africa after their emergence at c. 300,000 to 200,000 years ago, in contrast to "",. Beginning 135,000 years ago, tropical Africa experienced which drove humans from the land and towards the sea shores, and forced them to cross over to other continents.