Human origins. Each panel shows a hypothesis for the evolutionary history of humans. The colored bars show the phylogenetic relationships between species, with each color representing a species and blue representing the ancestral hominin species. Arrows represent gene flow, or admixture, with question marks to indicate possible admixture from as yet undiscovered hominins. (a) The Out of Africa (OOA) hypothesis; (b) the multiregional hypothesis; (c) a modification of the OOA hypothesis to include the archaic admixture inferred from recent work.