The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa

We analyze the functional and spatiotemporal properties of 57 hard sweeps inferred in ancient human genomes to reconstruct human evolution during the poorly understood Out of Africa migration. Our analyses reveal a previously unsuspected extended period of genetic adaptation lasting ~30,000 y, potentially in Arabia or surrounding regions, prior to a rapid dispersal across the rest of Eurasia as far as Australia. Functional targets include multiple interacting loci involved in fat storage, neural development, skin physiology, and cilia function, with associations with multiple modern Western diseases. Similar adaptive signatures are also evident in introgressed archaic hominin loci and modern Arctic human groups, indicating that cold environments were a prominent historical selection pressure that potentially facilitated the successful peopling of Eurasia.