sentences:  The more western parts of the steppe host lakes of glacial origin and grades into barren mountains or cold temperate forests along valleys.Inhabited by hunter-gatherers since Pre-Hispanic times, the desert faced migration in the 19th century of Argentines, Welsh, and other European peoples, transforming it from a conflictive borderland zone to an integral part of Argentina, with cattle, sheep and horse husbandry being the primary land uses.The Patagonian Desert has existed since the Middle Miocene (14–12 million years ago) and came into existence as the Andes rose to the west.