Abstract
Previous research has shown that modern Eurasians interbred with their Neanderthal and Denisovan predecessors. We show here that hundreds of thousands of years earlier, the ancestors of Neanderthals and Denisovans interbred with their own Eurasian predecessors—members of a “superarchaic” population that separated from other humans about 2 mya. The superarchaic population was large, with an effective size between 20 and 50 thousand individuals. We confirm previous findings that: (1) Denisovans also interbred with superarchaics, (2) Neanderthals and Denisovans separated early in the middle Pleistocene, (3) their ancestors endured a bottleneck of population size, and (4) the Neanderthal population was large at first but then declined in size. We provide qualified support for the view that (5) Neanderthals interbred with the ancestors of modern humans.
One-sentence summary We document the earliest known interbreeding between ancient human populations and an expansion out of Africa early in the middle Pleistocene.
Footnotes
We have re-done the entire analysis with more recent versions of the Altai Neanderthal and Denisovan genomes. The only appreciable change is that our estimate of the size of the superarchaic population is now even larger than before.
