Forming a part of the Eastern Shoshone linguistic group in southeastern Wyoming who moved on to the buffalo Plains around AD 1500 (based on glottochronological estimations), proto-Comanche groups split off and moved south some time before AD 1700. The Shoshone migration to the Great Plains was apparently triggered by the Little Ice Age, which allowed bison herds to grow in population. It remains unclear why the proto-Comanches broke away from the main Plains Shoshones and migrated south. The desire for Spanish horses released by the Pueblo Revolt of 1680 may have inspired the move as much as pressures from other groups drawn to the Plains by the changing environment.