The history of the southern central Andes, including the world's second largest plateau and adjacent intermontane basins and ranges of the Eastern Cordillera and the northern Sierras Pampeanas of Argentina and Bolivia, impressively documents the effects of tectonics and topography on atmospheric circulation patterns, the development of orographic barriers, and their influence on erosion and landscape evolution at various timescales. Protracted aridity in the orogen interior has facilitated the creation and maintenance of the Puna-Altiplano plateau. Contraction and range uplift, filling of basins, and possibly wholesale uplift of the plateau increased gravitational stresses in the orogen interior, which caused the eastward migration of deformation into the foreland and successive aridification. The uplift of the Andean orogen has also had a far-reaching influence on atmospheric and moisture-transport patterns in South America. This is documented by the onset of humid climate conditions on the eastern side of the Andes in late Miocene time, which was coupled with the establishment of dramatic precipitation gradients perpendicular to the orogen, and changes in tectonic processes in the Andean orogenic wedge.

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Lake sediments in 10 Ethiopian, Kenyan, and Tanzanian rift basins suggest that there were three humid periods at 2.7 to 2.5 million years ago (Ma), 1.9 to 1.7 Ma, and 1.1 to 0.9 Ma, superimposed on the longer-term aridification of East Africa. These humid periods correlate with increased aridity in northwest and northeast Africa and with substantial global climate transitions. These episodes could have had important impacts on the speciation and dispersal of mammals and hominins, because a number of key events, such as the origin of the genus Homo and the evolution of the species Homo erectus, took place in this region during that time.

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