Northeastern Asia humidification at the end of the Miocene drives the boost of mammalian dispersals from the Old to New World

Mammals have high dispersal ability, and many lineages can spread across the continents when a landbridge appears. Here, we summarize the dispersal of mammals between the Old and New World at the end of the Miocene. Our analysis suggested that the three phases of dispersal represented the largest dispersal tide during the Neogene, and the direction of dispersal is dominated by being from the Old to New World. Judging from the components that crossed the dispersal corridor, the Arctic environment near the Beringia corridor in the first phase(～7.5 Ma) is a mixed environment, and in the second phase(～6.5 Ma) is an open environment,and in the third phase(～5.8 Ma and continue to the Pliocene) is a wooded(closed) environment. A clear trend of eastern Asian humidification driven by Asian monsoon and the global C4 grassland expansion explain this dispersal pattern. The boost of mammalian dispersals is controlled by the heterogeneity of environmental changes in different continents.