Fig. 1.

Summary of inferred periods of archaic introgression between anatomically modern humans and archaic humans. Time is represented vertically (but not to scale), with the present time on top, and deep time roughly corresponding to the Holocene-Late Pleistocene, Late Pleistocene, and Middle Pleistocene. Anatomically modern human populations are represented in blue, two Neanderthal populations in red, two Denisovan populations in green, and superarchaic in yellow (this represents one or more populations of hominin that may have contributed to the genome ancestry of modern humans). Possible deep structure in African populations is represented in purple. Horizontal lines indicate gene flow between two populations, but may represent single or multiple gene flow events between the same two populations. Arrows indicate the scientific source which postulates each introgression event. The star notes that ancient African substructure and superarchaic introgression were postulated as alternative hypotheses to explain the same data pattern. It should be noted that in cases where older scientific articles postulated introgression from a population which later came to be understood as separate populations, we assigned the introgression to a specific population, such as European and Siberian Neanderthals, and Oceanian and Siberian Denisovans.